Resolution of M43 lenses

Started Mar 31, 2013 | Discussions
MoreorLess Veteran Member • Posts: 4,648
Dropoff seems like a greater problem to me...

Anders W wrote:

On what grounds do you leap to the conclusion that designing lenses to be software-corrected in one specific regard (geometric distortion) is done only or primarily for the purpose of cutting costs? And what makes you think that the end results (after correction) must necessarily be worse than they would have been for a lens corrected by optical means only?

I find no reason to think along such lines. If the end results, after correction, are good, as they are for those MFT lenses with strong barrel distortion prior to correction that I own and use (12/2, 7-14/4, 14-45/3.5-5.6), what's wrong with it?

I think of this lens-design strategy as an asset rather than a liability for MFT and I am sure the main reason that some others refrain from taking advantage of it is that it runs into trouble with an optical viewfinder. When you compose, you want to know what you will get once the image is properly corrected. Possible with an EVF, not possible with an OVF.

I can definately understand the arguement with correction when it comes to distortion and CA but to me dropoff seems a little different. Your not losing resolution there your potentialy damaging the remaining resolution via recovery.

On the face of it the Panny zoom might not seem any worse than many other 2.8 normal zooms but I'd argue that the greater DOF your dealing with means that its much more likely to be used for scenes where the boarders of the picture are in focus and of interest.

Anders W Forum Pro • Posts: 21,468
Re: Dropoff seems like a greater problem to me...

MoreorLess wrote:

Anders W wrote:

On what grounds do you leap to the conclusion that designing lenses to be software-corrected in one specific regard (geometric distortion) is done only or primarily for the purpose of cutting costs? And what makes you think that the end results (after correction) must necessarily be worse than they would have been for a lens corrected by optical means only?

I find no reason to think along such lines. If the end results, after correction, are good, as they are for those MFT lenses with strong barrel distortion prior to correction that I own and use (12/2, 7-14/4, 14-45/3.5-5.6), what's wrong with it?

I think of this lens-design strategy as an asset rather than a liability for MFT and I am sure the main reason that some others refrain from taking advantage of it is that it runs into trouble with an optical viewfinder. When you compose, you want to know what you will get once the image is properly corrected. Possible with an EVF, not possible with an OVF.

I can definately understand the arguement with correction when it comes to distortion and CA but to me dropoff seems a little different. Your not losing resolution there your potentialy damaging the remaining resolution via recovery.

Not sure I follow your thoughts here. Yes, you lose a little bit of resolution by correcting distortion via software compared to what the resolution was like before the correction. But this before-after correction comparison is not very interesting from lens-design point of view. The interesting comparison is between the final (after correction) performance of a lens designed to be software corrected and one designed to be corrected by optical means only, with everything else held constant (cost of design and manufacture, size, and weight).

On the face of it the Panny zoom might not seem any worse than many other 2.8 normal zooms but I'd argue that the greater DOF your dealing with means that its much more likely to be used for scenes where the boarders of the picture are in focus and of interest.

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ptox Regular Member • Posts: 224
This always ends up as a faux-ethical argument

The argument that this lens, at this price, "should not" require so much software correction is specious: what other examples for this format are either a) cheaper or b) optically better? There are none; the word "should" carries no weight.

Compare against 35mm lenses all you like, but as the endless debates over physical/optical minutiae here attest--it's not that simple.

Dr_Jon Veteran Member • Posts: 5,811
Re: Dropoff seems like a greater problem to me...

Which is why I was disappointed with my fast Panasonic zooms over the results I get with my not-requiring-distortion-correction Canon lenses, which are generally noticeably sharper when looking at the final image at the same size. But allowing for the size-weight reduction I think the 35-100 is a pretty fair bit of kit and am happy with my purchase. I think the 12-35 should have been 12-50 for the performance it gives (meaning for that optical quality I would have preferred to be paying that much for a 4x zoom not a 3x). It is pleasantly light though.

However you are missing the point. He's talking about vignetting correction and if you have to boost the brightness you don't get an equivalent image as effectively that area has a much higher ISO (so more noise and less DR). This is also true of some of the Canon lenses I have, or of lenses generally unless you pay for one with an expanded image circle. (The Canon Tilt-Shift lenses are pretty good in the corners if you don't shift them much.)

I think the 12-35 vignetting is a little high, especially as the DR of the m43 sensors does disappear pretty quickly as ISO rises, but I wouldn't rate it as a design flaw, I think it's within acceptable limits even for a lens of that price. Actually what does surprise me is that quite a bit of the distortion and vignetting isn't fixed in the JPEGs but left in, which seems very odd to me. If I have JPEG vignetting correction on with my 5DmkII it fixes it, but the 12-25 seems to have 1-1.2 stops left, ditto with the distortion. I have no answer for this. (It is quite odd comparing DXO-processed raw files with the JPEGs, you start wondering if the camera wasn't correcting them at all...)

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Anders W Forum Pro • Posts: 21,468
Re: Dropoff seems like a greater problem to me...

Dr_Jon wrote:

Which is why I was disappointed with my fast Panasonic zooms over the results I get with my not-requiring-distortion-correction Canon lenses, which are generally noticeably sharper when looking at the final image at the same size. But allowing for the size-weight reduction I think the 35-100 is a pretty fair bit of kit and am happy with my purchase. I think the 12-35 should have been 12-50 for the performance it gives (meaning for that optical quality I would have preferred to be paying that much for a 4x zoom not a 3x). It is pleasantly light though.

However you are missing the point. He's talking about vignetting correction and if you have to boost the brightness you don't get an equivalent image as effectively that area has a much higher ISO (so more noise and less DR). This is also true of some of the Canon lenses I have, or of lenses generally unless you pay for one with an expanded image circle. (The Canon Tilt-Shift lenses are pretty good in the corners if you don't shift them much.)

I think the 12-35 vignetting is a little high, especially as the DR of the m43 sensors does disappear pretty quickly as ISO rises, but I wouldn't rate it as a design flaw, I think it's within acceptable limits even for a lens of that price. Actually what does surprise me is that quite a bit of the distortion and vignetting isn't fixed in the JPEGs but left in, which seems very odd to me. If I have JPEG vignetting correction on with my 5DmkII it fixes it, but the 12-25 seems to have 1-1.2 stops left, ditto with the distortion. I have no answer for this. (It is quite odd comparing DXO-processed raw files with the JPEGs, you start wondering if the camera wasn't correcting them at all...)

Vignetting correction (aka "shading compensation") is optional with MFT. It is not done by default. I think all Oly bodies might have the option and at least the more recent Panys.

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Dr_Jon Veteran Member • Posts: 5,811
Re: Dropoff seems like a greater problem to me...

The Photozone vignetting results are shown as "with correction" so I took my opinion from there. For the distortion I looked at a pic of my living room at 12mm - in the JPEG a picture on the wall is very distorted, in the DXO version it's rectangular.

Although on vignetting DXO produce a much wider FoV from the same shot, going much further into the corners and get vignetting to black with a 3mm filter attached, which is as thin as they get. The JPEG just chops this data off - so I wonder which is actually 12mm, hmmm, interesting, they can't both be. Opinions welcome!

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Dr_Jon Veteran Member • Posts: 5,811
Re: This always ends up as a faux-ethical argument

Since optical performance is only a minor driver of price in lenses (although build cost is a bigger one and you'd hope they are linked, quite a bit, fingers crossed) I think it is not unreasonable for people to say whether they think a lens is or is not worth the money.

For example is the Canon 24-70 f2.8 mk II worth £1700+, it's the best 24-70 out there (IMHO, tons of evidence available on that one, but I chose Canon not m43 to make it non-contentions here as it's an example not an argument) but do people care that much about absolutes or does value for money rear its head? (I'd say, and explain the reasoning, to get the 24-105 and pocket a grand, even more so on a FF body, unless you absolutely need the f2.8, others wouldn't...)

I'd certainly agree there isn't a "right" answer, but I'm cool with some debate if it's informed and reasonably conducted - though not do much with the tendency towards "this is the best and as I declare it to be the one true fact", but "my opinion is ... supported by this evidence ..." is okay with me. Not saying something's a personal opinion does annoy me a little though - that one doesn't need to be an opinion as it's a fact, although only about my thought processes! Then again maybe people are being handed engraved Marble tablets for real rather than just in their heads

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Anders W Forum Pro • Posts: 21,468
Re: Dropoff seems like a greater problem to me...
1

Dr_Jon wrote:

The Photozone vignetting results are shown as "with correction" so I took my opinion from there.

The Photozone results are with the vignetting correction you get as a by-product of distortion correction. When the distortion is corrected, the original corners are effectively cropped and vignetting thereby reduced. So their "with correction" label doesn't refer to the additional correction you can get by means of the "shading compensation" option.

For the distortion I looked at a pic of my living room at 12mm - in the JPEG a picture on the wall is very distorted, in the DXO version it's rectangular.

Not sure what you are referring to here. If it is barrel distortion you are talking about, it should certainly be corrected in the OOC jpegs. Don't know how DxO handles the instructions on distortion correction embedded in the RAWs. Commercial RAW converters would normally honor them but others might not.

But perhaps you are talking about something else. If the picture on the wall is located toward one corner/edge of the frame, it may look more "stretched" once the barrel distortion is corrected. If so, this is simply an effect of moving closer to the rectilinear projection any non-fisheye lens is designed to deliver, not an effect of software correction per se. A WA lens that is perfectly corrected for geometric distortion (barrel, pincushion) by purely optical means would show the same distortion (i.e., "stretching").

Although on vignetting DXO produce a much wider FoV from the same shot, going much further into the corners and get vignetting to black with a 3mm filter attached, which is as thin as they get. The JPEG just chops this data off - so I wonder which is actually 12mm, hmmm, interesting, they can't both be. Opinions welcome!

See here:

http://www.dpreview.com/forums/post/50747057

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Dr_Jon Veteran Member • Posts: 5,811
Re: Dropoff seems like a greater problem to me...

Yes, I'm talking about lens distortion not focal length effects.

DXO would profile the lens themselves and if available (it is for the 12-35) use that information, ignoring the much simpler data in the Raw file, they would also do selective sharpening based on the local lens sharpness. BTW they have different profiles for OOC JPEGs (which they can also handle) and Raw files, for kinda obvious reasons. (Although I would only feed it a JPEG if a Raw wasn't available and I had a problem - perhaps when I start doing time-lapses, but not to date.)

P.S. I must, as a matter of some urgency, see which FoV (JPEG or DXO processed Raw) agrees with the viewfinder. I'm assuming the former. It's quite a significant difference, both images are 4608 wide, but if I crop the DXO one to the FoV of the JPEG it ends up losing about 150 pixels from each side!

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Anders W Forum Pro • Posts: 21,468
Re: Dropoff seems like a greater problem to me...

Dr_Jon wrote:

Yes, I'm talking about lens distortion not focal length effects.

DXO would profile the lens themselves and if available (it is for the 12-35) use that information, ignoring the much simpler data in the Raw file, they would also do selective sharpening based on the local lens sharpness. BTW they have different profiles for OOC JPEGs (which they can also handle) and Raw files, for kinda obvious reasons. (Although I would only feed it a JPEG if a Raw wasn't available and I had a problem - perhaps when I start doing time-lapses, but not to date.)

Yes, I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

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Dr_Jon Veteran Member • Posts: 5,811
Re: Dropoff seems like a greater problem to me...

I'd need to shoot something a bit more diagnostically useful. I can certainly say it seems pretty clear to me they aren't using the same distortion correction as the JPEGs (plus frankly I wouldn't expect them to, they specialise in doing very exact distortion correction). There is a free trial of DXO so others can play too...

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Anders W Forum Pro • Posts: 21,468
Re: Dropoff seems like a greater problem to me...

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

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KenBalbari Regular Member • Posts: 276
Re: Resolution of M43 lenses

The photozone review looks pretty fair to me. If you are comparing to the Fuji XF 18-55, they graded that lens about the same overall, and noted many of the same weak points.  The lenses were nearly equal in the MTF charts, while the Fuji did very slightly better in uncorrected distortion, which they say isn't that important, but also did notably better on vignetting even after correction, and on uncorrected CA (with correction not available on Olympus cameras).  On the whole, they only graded the Fuji a half star better optically, while grading it a half star worse mechanically.

The other point is that the one lens sells for $600 less than the other.  Which is why one gets 4 stars for value (price/performance) while the other gets 3 stars.

Whatever the technical tradeoffs in lens design involved here, it seems to me the end result is a standard normal 2.9x zoom that wide open has slightly soft borders, and about a stop of vignetting, and for Olympus users at least a moderate problem with CA.  The trade off here is you can shoot f2.8, and the review also notes very little field curvature. People can decide for themselves whether that's worth the price.

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Detail Man
Detail Man Forum Pro • Posts: 17,020
Demonstration of Differences in DxO Geometric Corrections
2

Anders W wrote:

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

I can confirm that DxO Optics Pro geometric distortion corrections (in the case of my LX3 and GH2 RW2s) consistently have a visibly notably different appearance than the Panasonic OOC JPGs as well as the nature of the geometric corrections that can be performed using Lightroom or Silkypix.

After recently spending a lot of time when posting on the referenced thread trying to get RAW Therapee's (manual) geometric distortion correction to look like DxO's, I have concluded that DxO's geometric distortion corrections are based upon more than geometric corrections performed relative to a single point in the center of the image-frame (as Panasonic's image-file meta-data as well as RAW Therapee's appear to be) ... and are instead based upon geometric corrections performed relative to multiple points existing within the image-frame (how many I do not know).

It may be that a metric of residual geometric distortion based on evaluation referenced to a single reference-point existing at the center of an image-frame may not serve to adequately describe residual geometric distortion that is referenced to multiple points within an image-frame.

Here is a geometrically uncorrected LX3 wide-angle RW2 processed using DxO Optics Pro 7.23:

Uncorrected

.

Here is the (in-camera corrected) Panasonic OOC JPG:

Panasonic LX3 corrected in-camera OCC JPG

.

Here is the best that I was able to do using RAW Therapee 4.0.9.184's manual geometric distortion corrections. It has a simliar contour as the Panasonic in-camera corrected OOC JPG - a contour that appears to have a single correction reference located at the center of the image-frame:

RAW Therapee 4.0.9.184 manually corrected

.

Download the Original versions of either of the above displayed corrected images and view them in an image-viewer, switching back and forth with the DxO corrected image displayed below. Note that because the LX3 in-camera OOC JPG is chopping-off a lot of the perimeter, the existing differences are easier to view using the (similar to the OOC JPG) RAW Therapee corrected image.

DxO Optics Pro 7.23 automatically corrected (normal 4:3 aspect-ratio)

The differences between the nature of the DxO correction and other methods can be readily seen, showing the "flatter" contour of the DxO (evidently multiple reference-point) correction.

.

Here is a somewhat wider-angle version using the same automatic DxO Optics Pro 7.23 geometric distortion corrections, taking advantage of it's ability to present a larger FOV (in cases where rectilinear barrel distortion exists in the recorded image). The resulting aspect-ratio is 1.392.

DxO Optics Pro 7.23 automatically corrected (wider 1.392 aspect-ratio)

DM ...

sgoldswo
sgoldswo Veteran Member • Posts: 5,718
Re: Resolution of M43 lenses

zenpmd wrote:

I do not understand why photozone were a bit critical of the Pana 2.8 constant apeture zoom lens. They waxed lyrical about the Fuji zoom, but the pana resolves more detail - more so than the 1.8 Olympus.

Isnt that really impressive?

For what it's worth I agree with you. The Fuji 18-55 is very sharp but also suffers from distortion and is also corrected in software (to the extent it is the one lens I hate to process in Capture one). I do think (in its equivalent field of view) the 18-55 is slightly better optically and is more reasonable in price. However, the 12-35 is wider, weather sealed and in honesty the only thing wrong with the output is CA on Oly cameras. Anything else is just hyperbole.

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Anders W Forum Pro • Posts: 21,468
Re: Demonstration of Differences in DxO Geometric Corrections

Detail Man wrote:

Anders W wrote:

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

I can confirm that DxO Optics Pro geometric distortion corrections (in the case of my LX3 and GH2 RW2s) consistently have a visibly notably different appearance than the Panasonic OOC JPGs as well as the nature of the geometric corrections that can be performed using Lightroom or Silkypix.

After recently spending a lot of time when posting on the referenced thread trying to get RAW Therapee's (manual) geometric distortion correction to look like DxO's, I have concluded that DxO's geometric distortion corrections are based upon more than geometric corrections performed relative to a single point in the center of the image-frame (as Panasonic's image-file meta-data as well as RAW Therapee's appear to be) ... and are instead based upon geometric corrections performed relative to multiple points existing within the image-frame (how many I do not know).

It may be that a metric of residual geometric distortion based on evaluation referenced to a single reference-point existing at the center of an image-frame may not serve to adequately describe residual geometric distortion that is referenced to multiple points within an image-frame.

It may well be that DxO uses a different method. But aside from rescuing a greater portion of the uncorrected frame than the OOC jpeg (which RT does as well), is there a noticeable improvement in the quality of the correction? That's kind of hard to judge based on the examples you posted.

For more complicated forms of distortion, it is clear that more sophisticated methods are likely to yield noticeably better results. On the other hand, I wouldn't think it likely that the form of distortion generated by MFT lenses is as a rule very complex and haven't seen any sign of that with the MFT WAs I personally have/use. Complex forms of distortion are often the result of less than perfect attempts at optical correction and MFT lenses designed to be software-corrected for distortion are likely to avoid that particular problem.

Here is a geometrically uncorrected LX3 wide-angle RW2 processed using DxO Optics Pro 7.23:

Uncorrected

.

Here is the (in-camera corrected) Panasonic OOC JPG:

Panasonic LX3 corrected in-camera OCC JPG

.

Here is the best that I was able to do using RAW Therapee 4.0.9.184's manual geometric distortion corrections. It has a simliar contour as the Panasonic in-camera corrected OOC JPG - a contour that appears to have a single correction reference located at the center of the image-frame:

RAW Therapee 4.0.9.184 manually corrected

.

Download the Original versions of either of the above displayed corrected images and view them in an image-viewer, switching back and forth with the DxO corrected image displayed below. Note that because the LX3 in-camera OOC JPG is chopping-off a lot of the perimeter, the existing differences are easier to view using the (similar to the OOC JPG) RAW Therapee corrected image.

DxO Optics Pro 7.23 automatically corrected (normal 4:3 aspect-ratio)

The differences between the nature of the DxO correction and other methods can be readily seen, showing the "flatter" contour of the DxO (evidently multiple reference-point) correction.

.

Here is a somewhat wider-angle version using the same automatic DxO Optics Pro 7.23 geometric distortion corrections, taking advantage of it's ability to present a larger FOV (in cases where rectilinear barrel distortion exists in the recorded image). The resulting aspect-ratio is 1.392.

DxO Optics Pro 7.23 automatically corrected (wider 1.392 aspect-ratio)

DM ...

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Chez Wimpy
Chez Wimpy Veteran Member • Posts: 9,031
Re: Dropoff seems like a greater problem to me...

Dr_Jon wrote:

I think the 12-35 vignetting is a little high, especially as the DR of the m43 sensors does disappear pretty quickly as ISO rises, but I wouldn't rate it as a design flaw, I think it's within acceptable limits even for a lens of that price.

Post-shot vignetting correction is much worse on my 5D2 where any "DR" is crippled by pattern banding in the shadows.  The main issue I have with vignetting on m43 is that auto-correction is not built into ACR, and trying to work out the right inputs for radius and degree (stitched panoramas mostly) is somewhat trial and error. That, and residual barrel distortion.

As to distortion correction in lens vs in software, I find the 7-14 has about the same degree of sharpness in the corners as my "optically corrected" Sigma 12-24 for FF.  My 14-45 is as good as any 28-80ish I have ever seen (it looks like the new Canon 18-55 STM might be on this level at last) with much better corner resolution than my Canon gear in the past (17-40L, various 18-55 iterations).  So it seems in the case of a sharp distorted lens vs a soft rectilinear lens that results can favor the former over the later, with the added benefit of a reduction in size.

Taking some "moral offense" that $$$$ lenses use one form of correction over another when the image is all that matters (unless one is a Leica collector / optics aestheticist / mental masturbator) is, well.... about par for a gear forum I suppose.

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-CW

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Detail Man
Detail Man Forum Pro • Posts: 17,020
Re: Demonstration of Differences in DxO Geometric Corrections
1

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

I can confirm that DxO Optics Pro geometric distortion corrections (in the case of my LX3 and GH2 RW2s) consistently have a visibly notably different appearance than the Panasonic OOC JPGs as well as the nature of the geometric corrections that can be performed using Lightroom or Silkypix.

After recently spending a lot of time when posting on the referenced thread trying to get RAW Therapee's (manual) geometric distortion correction to look like DxO's, I have concluded that DxO's geometric distortion corrections are based upon more than geometric corrections performed relative to a single point in the center of the image-frame (as Panasonic's image-file meta-data as well as RAW Therapee's appear to be) ... and are instead based upon geometric corrections performed relative to multiple points existing within the image-frame (how many I do not know).

It may be that a metric of residual geometric distortion based on evaluation referenced to a single reference-point existing at the center of an image-frame may not serve to adequately describe residual geometric distortion that is referenced to multiple points within an image-frame.

It may well be that DxO uses a different method. But aside from rescuing a greater portion of the uncorrected frame than the OOC jpeg (which RT does as well), is there a noticeable improvement in the quality of the correction? That's kind of hard to judge based on the examples you posted.

The term "quality" may not be well addressed by numerical metrics here. It probably comes down to what various eyes see and minds perceive. That does not render the matter as "moot" - but it does involve subjective perceptions. To my eyes, DxO corrections always make the OOC JPG corrections (or single reference-point corrections performed by other RAW processors) looking bulbous and bloated at the center. Have not once found that I preferred such corrections to what DxO Optics Pro comes up with. DxO's always looks "flatter" and as a result more realistic to my eyes when viewing them. Thus, the differences are not (to me) insignificant at all.

Here is another LX3 wide-angle example for you. It involves crops that represent only part of the recorded image-frame, and subject matter that exists much closer to the camera lens. The two crops are not identical - so in viewing have a look at the general contour of the subject-matter.

LX3 in-camera distortion corrected JPG (cropped):

.

DxO Optics Pro corrected (cropped):

Do the same thing with these two Original images, and switch back and forth between them. A difference can be seen. Whether or not the aesthetics surrounding these visible differences constitute "meaningful" differences may be a matter of taste. The fact that one individual may prefer either one or the other correction method is valid - whether or not various metrics may or may not establish some kind of numerical "proof".

.

Then there exists an issue of corrections performed upon subject matter that exists far away from the center of the image-frame, and nearer to the edges or corners. In the following case (a somewhat cropped DMC-FZ28 RW2 image), I was able to accomplish geometric corrections using DxO 6.55's manual controls (processing an 8-bit TIF) that Lightroom 3.41 was unable to accomplish in RAW processing mode (using Panasonic image-file meta-data in conjunction with Lightroom 3.41's manual geometric distortion corrections).The differences seen are indeed significant to my own eyes.

Lightroom 3.41:

Lightroom 3.41 RAW geometric distortion (auto + manual) corrections

Download the Original and look in the upper left corner of the image-frame in an image-viewer.

.

Now, download this DxO Optics Pro 6.55 manual geometric correction of an 8-bit TIF of the same image. It can be seen that DxO Optics Pro is capable of extending it's useful geometric corrections farther out into the image-frame than Lightroom (or Silkypix, or the OOC JPG, I find).

DxO Optics Pro 6.55 8-bit TIF manual geometric distortion corrections

I myself prefer the DxO Optics Pro geometric correction functional capability. Lightroom (your 4.x, anyway) does do some things (in my view) better than DxO Optics Pro - but not this. Of course, our perceptions are not immune from being shaped by what are our chosen preferred applications. And, subjective individual perceptions of any single performance element may also vary between viewers.

For more complicated forms of distortion, it is clear that more sophisticated methods are likely to yield noticeably better results. On the other hand, I wouldn't think it likely that the form of distortion generated by MFT lenses is as a rule very complex and haven't seen any sign of that with the MFT WAs I personally have/use. Complex forms of distortion are often the result of less than perfect attempts at optical correction and MFT lenses designed to be software-corrected for distortion are likely to avoid that particular problem.

Here is a geometrically uncorrected LX3 wide-angle RW2 processed using DxO Optics Pro 7.23:

Uncorrected

.

Here is the (in-camera corrected) Panasonic OOC JPG:

Panasonic LX3 corrected in-camera OCC JPG

.

Here is the best that I was able to do using RAW Therapee 4.0.9.184's manual geometric distortion corrections. It has a simliar contour as the Panasonic in-camera corrected OOC JPG - a contour that appears to have a single correction reference located at the center of the image-frame:

RAW Therapee 4.0.9.184 manually corrected

.

Download the Original versions of either of the above displayed corrected images and view them in an image-viewer, switching back and forth with the DxO corrected image displayed below. Note that because the LX3 in-camera OOC JPG is chopping-off a lot of the perimeter, the existing differences are easier to view using the (similar to the OOC JPG) RAW Therapee corrected image.

DxO Optics Pro 7.23 automatically corrected (normal 4:3 aspect-ratio)

The differences between the nature of the DxO correction and other methods can be readily seen, showing the "flatter" contour of the DxO (evidently multiple reference-point) correction.

.

Here is a somewhat wider-angle version using the same automatic DxO Optics Pro 7.23 geometric distortion corrections, taking advantage of it's ability to present a larger FOV (in cases where rectilinear barrel distortion exists in the recorded image). The resulting aspect-ratio is 1.392.

DxO Optics Pro 7.23 automatically corrected (wider 1.392 aspect-ratio)

DM ...

Anders W Forum Pro • Posts: 21,468
Re: Demonstration of Differences in DxO Geometric Corrections

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

I can confirm that DxO Optics Pro geometric distortion corrections (in the case of my LX3 and GH2 RW2s) consistently have a visibly notably different appearance than the Panasonic OOC JPGs as well as the nature of the geometric corrections that can be performed using Lightroom or Silkypix.

After recently spending a lot of time when posting on the referenced thread trying to get RAW Therapee's (manual) geometric distortion correction to look like DxO's, I have concluded that DxO's geometric distortion corrections are based upon more than geometric corrections performed relative to a single point in the center of the image-frame (as Panasonic's image-file meta-data as well as RAW Therapee's appear to be) ... and are instead based upon geometric corrections performed relative to multiple points existing within the image-frame (how many I do not know).

It may be that a metric of residual geometric distortion based on evaluation referenced to a single reference-point existing at the center of an image-frame may not serve to adequately describe residual geometric distortion that is referenced to multiple points within an image-frame.

It may well be that DxO uses a different method. But aside from rescuing a greater portion of the uncorrected frame than the OOC jpeg (which RT does as well), is there a noticeable improvement in the quality of the correction? That's kind of hard to judge based on the examples you posted.

The term "quality" may not be well addressed by numerical metrics here. It probably comes down to what various eyes see and minds perceive. That does not render the matter as "moot" - but it does involve subjective perceptions. To my eyes, DxO corrections always make the OOC JPG corrections (or single reference-point corrections performed by other RAW processors) looking bulbous and bloated at the center. Have not once found that I preferred such corrections to what DxO Optics Pro comes up with. DxO's always looks "flatter" and as a result more realistic to my eyes when viewing them. Thus, the differences are not (to me) insignificant at all.

My problem here DM is that images like those you show are of a kind where geometric distortion probably wouldn't be much of an issue to my eyes even if it remained uncorrected altogether. I usually find geometric distortion (typically barrel distortion) problematic only if there are objects toward the edges of the frame that are known to be straight but aren't. For similar reasons, I have difficulties quite understanding in this case even what you mean by expressions such as "flatter" (do you simply mean that lines that should be straight are straightened out to a greater extent?), "bulbous and bloated", or "extending corrections farther out" (isn't it necessary for distortion correction to have a pretty significant impact on the corners in order to be at all successful?).

Here is another LX3 wide-angle example for you. It involves crops that represent only part of the recorded image-frame, and subject matter that exists much closer to the camera lens. The two crops are not identical - so in viewing have a look at the general contour of the subject-matter.

LX3 in-camera distortion corrected JPG (cropped):

.

DxO Optics Pro corrected (cropped):

Do the same thing with these two Original images, and switch back and forth between them. A difference can be seen. Whether or not the aesthetics surrounding these visible differences constitute "meaningful" differences may be a matter of taste. The fact that one individual may prefer either one or the other correction method is valid - whether or not various metrics may or may not establish some kind of numerical "proof".

.

Then there exists an issue of corrections performed upon subject matter that exists far away from the center of the image-frame and nearer to the edges or corners. In the following case (a somehwat cropped DMC-FZ28 RW2 image), I was able to accomplish geometric corrections using DxO 6.55's manual controls (processing an 8-bit TIF) that Lightroom 3.41 was unable to accomplish in RAW processing mode (using the Panasonic image-file meta-data in conjunction with Lightroom 3.41's manual geometric distortion corrections).The differences seen are significant to my own eyes.

Lightroom 3.41:

Lightroom 3.41 RAW geometric distortion (auto + manual) corrections

Download the Original and look in the upper left corner of the image-frame in an image-viewer.

.

Now, download this DxO Optics Pro 6.55 manual geometric correction of an 8-bit TIF of the same image. It can be seen that DxO Optics Pro is capable of extending it's useful geometric corrections farther out into the image-frame than Lightroom (or Silkypix, or the OOC JPG, I find).

DxO Optics Pro 6.55 8-bit TIF manual geometric distortion corrections

I myself prefer the DxO Optics Pro geometric correction functional capability. Lightroom (your 4.x, anyway) does do some things (in my view) better than DxO Optics Pro - but not this. Of course, our perceptions are not immune from being shaped by what are our chosen preferred applications. And, subjective individual perceptions of any single performance element may also vary between viewers.

For more complicated forms of distortion, it is clear that more sophisticated methods are likely to yield noticeably better results. On the other hand, I wouldn't think it likely that the form of distortion generated by MFT lenses is as a rule very complex and haven't seen any sign of that with the MFT WAs I personally have/use. Complex forms of distortion are often the result of less than perfect attempts at optical correction and MFT lenses designed to be software-corrected for distortion are likely to avoid that particular problem.

Here is a geometrically uncorrected LX3 wide-angle RW2 processed using DxO Optics Pro 7.23:

Uncorrected

.

Here is the (in-camera corrected) Panasonic OOC JPG:

Panasonic LX3 corrected in-camera OCC JPG

.

Here is the best that I was able to do using RAW Therapee 4.0.9.184's manual geometric distortion corrections. It has a simliar contour as the Panasonic in-camera corrected OOC JPG - a contour that appears to have a single correction reference located at the center of the image-frame:

RAW Therapee 4.0.9.184 manually corrected

.

Download the Original versions of either of the above displayed corrected images and view them in an image-viewer, switching back and forth with the DxO corrected image displayed below. Note that because the LX3 in-camera OOC JPG is chopping-off a lot of the perimeter, the existing differences are easier to view using the (similar to the OOC JPG) RAW Therapee corrected image.

DxO Optics Pro 7.23 automatically corrected (normal 4:3 aspect-ratio)

The differences between the nature of the DxO correction and other methods can be readily seen, showing the "flatter" contour of the DxO (evidently multiple reference-point) correction.

.

Here is a somewhat wider-angle version using the same automatic DxO Optics Pro 7.23 geometric distortion corrections, taking advantage of it's ability to present a larger FOV (in cases where rectilinear barrel distortion exists in the recorded image). The resulting aspect-ratio is 1.392.

DxO Optics Pro 7.23 automatically corrected (wider 1.392 aspect-ratio)

DM ...

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
Detail Man
Detail Man Forum Pro • Posts: 17,020
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Dr_Jon wrote:

I'd need to shoot something a bit more diagnostically useful. I can certainly say they aren't using the same distortion correction as the JPEGs. There is a free trial of DXO so others can play too...

I know DxO profile lenses themselves, e.g., for sharpening. But it would surprise me if what they do with regard to geometric distortion correction of RAWs from MFT equipment differs more than marginally, from what the in-camera jpeg engine or other RAW converters, e.g., LR would do. According to Lenstip, the in-camera jpeg engine leaves only -1.39 percent worth of barrel distortion from the 12-35/2.8 at 12 mm, which, as a rule, is barely visible. Your example sounded quite dramatic so could you please post the samples you were talking about and we'll have a look.

It could be that DxO tries to rescue more of the uncorrected frame than the jpeg engine or other RAW converters would. As you can see from the thread I linked to, it seems that the standard procedure is to chop off slightly more than would be required to get rid of the distortion. But I wouldn't think the distortion left behind by DxO is much different from that left behind by other processing alternatives for the simple reason that the latter get fairly close to the zero-distortion level.

I can confirm that DxO Optics Pro geometric distortion corrections (in the case of my LX3 and GH2 RW2s) consistently have a visibly notably different appearance than the Panasonic OOC JPGs as well as the nature of the geometric corrections that can be performed using Lightroom or Silkypix.

After recently spending a lot of time when posting on the referenced thread trying to get RAW Therapee's (manual) geometric distortion correction to look like DxO's, I have concluded that DxO's geometric distortion corrections are based upon more than geometric corrections performed relative to a single point in the center of the image-frame (as Panasonic's image-file meta-data as well as RAW Therapee's appear to be) ... and are instead based upon geometric corrections performed relative to multiple points existing within the image-frame (how many I do not know).

It may be that a metric of residual geometric distortion based on evaluation referenced to a single reference-point existing at the center of an image-frame may not serve to adequately describe residual geometric distortion that is referenced to multiple points within an image-frame.

It may well be that DxO uses a different method. But aside from rescuing a greater portion of the uncorrected frame than the OOC jpeg (which RT does as well), is there a noticeable improvement in the quality of the correction? That's kind of hard to judge based on the examples you posted.

The term "quality" may not be well addressed by numerical metrics here. It probably comes down to what various eyes see and minds perceive. That does not render the matter as "moot" - but it does involve subjective perceptions. To my eyes, DxO corrections always make the OOC JPG corrections (or single reference-point corrections performed by other RAW processors) looking bulbous and bloated at the center. Have not once found that I preferred such corrections to what DxO Optics Pro comes up with. DxO's always looks "flatter" and as a result more realistic to my eyes when viewing them. Thus, the differences are not (to me) insignificant at all.

My problem here DM is that images like those you show are of a kind where geometric distortion probably wouldn't be much of an issue to my eyes even if it remained uncorrected altogether. I usually find geometric distortion (typically barrel distortion) problematic only if there are objects toward the edges of the frame that are known to be straight but aren't.

Again, it comes down to personal perceptions here. Had I not compared DxO correction with other corrections, I would not be aware of the differences to my eyes. You may well see the same differences, and not consider them significant (or may yourself prefer the other one).

For similar reasons, I have difficulties quite understanding in this case even what you mean by expressions such as "flatter" (do you simply mean that lines that should be straight are straightened out to a greater extent?), ...

None of my examples are architectural photography. They are natural scenes where the eye has far less of any pre-conception of what something "should" look like. That can work both ways, then. It is indeed subjective. By "flatter" I mean less "raised towards the center" in areas nearer the center of the image-frame.

One cannot "take a measuring stick" to such natural scenes. DxO's corrections seem to please my eyes more - and (may) better comport with my visual memory. I cannot "prove" that - because my own visual memory (or anybody else's) does not read-out like a digital machine.

... "bulbous and bloated", or "extending corrections farther out" (isn't it necessary for distortion correction to have a pretty significant impact on the corners in order to be at all successful?).

The whole point of the Lightroom 3.41 compared with DxO Optics Pro 6.55 example was to show that LR 3.41's geometric correction was unable (despite my best efforts) have a "significant impact" upon the upper-left corner area of the (somewhat cropped) image-frame - whereas DxO Optics Pro 6.55's geometric correction was indeed able to do just that (without over-correcting the center area, as was the case when Lightroom 3.41 attempted the same).

Given that, I do not really understand quite why you pose your question (directly above). Of course, the answer would be "yes". The operational issue is, "when such an impact is made upon the edges/corners, what do the inner areas look like ?".  I think that DxO does use multiple reference-points, and in doing so is capable of implementing corrections that are more able to adjust outer areas without overdoing the corrections applied in the more central areas.

That is a factual matter. You argue that rectilinear distortion is simplistic in nature even in the case of multiple-element lens-systems. Another factual matter. I don't know for sure about that.

It would be interesting (though possible) that DxO Labs would create a geometric distortion correction system from characterizing lens-systems that is primarily related to human perception (and unrelated to their optical measurements). Anything is possible where it comes to "art" ?

What I do claim to "know" (and you in your own way claim to "know") is what seems to please our perceptual minds, and what we may also indeed perceive, but not concern our minds with. Those are not things that really can be litigated in "fact finding" endeavors. Thus, they are not things that can be declared as "important" or "unimportant" to the perceptual minds of others.

It seems that the best that we can do is to offer our own subjective perceptual preferences ?

Here is another LX3 wide-angle example for you. It involves crops that represent only part of the recorded image-frame, and subject matter that exists much closer to the camera lens. The two crops are not identical - so in viewing have a look at the general contour of the subject-matter.

LX3 in-camera distortion corrected JPG (cropped):

.

DxO Optics Pro corrected (cropped):

Do the same thing with these two Original images, and switch back and forth between them. A difference can be seen. Whether or not the aesthetics surrounding these visible differences constitute "meaningful" differences may be a matter of taste. The fact that one individual may prefer either one or the other correction method is valid - whether or not various metrics may or may not establish some kind of numerical "proof".

.

Then there exists an issue of corrections performed upon subject matter that exists far away from the center of the image-frame and nearer to the edges or corners. In the following case (a somehwat cropped DMC-FZ28 RW2 image), I was able to accomplish geometric corrections using DxO 6.55's manual controls (processing an 8-bit TIF) that Lightroom 3.41 was unable to accomplish in RAW processing mode (using the Panasonic image-file meta-data in conjunction with Lightroom 3.41's manual geometric distortion corrections).The differences seen are significant to my own eyes.

Lightroom 3.41:

Lightroom 3.41 RAW geometric distortion (auto + manual) corrections

Download the Original and look in the upper left corner of the image-frame in an image-viewer.

.

Now, download this DxO Optics Pro 6.55 manual geometric correction of an 8-bit TIF of the same image. It can be seen that DxO Optics Pro is capable of extending it's useful geometric corrections farther out into the image-frame than Lightroom (or Silkypix, or the OOC JPG, I find).

DxO Optics Pro 6.55 8-bit TIF manual geometric distortion corrections

I myself prefer the DxO Optics Pro geometric correction functional capability. Lightroom (your 4.x, anyway) does do some things (in my view) better than DxO Optics Pro - but not this. Of course, our perceptions are not immune from being shaped by what are our chosen preferred applications. And, subjective individual perceptions of any single performance element may also vary between viewers.

For more complicated forms of distortion, it is clear that more sophisticated methods are likely to yield noticeably better results. On the other hand, I wouldn't think it likely that the form of distortion generated by MFT lenses is as a rule very complex and haven't seen any sign of that with the MFT WAs I personally have/use. Complex forms of distortion are often the result of less than perfect attempts at optical correction and MFT lenses designed to be software-corrected for distortion are likely to avoid that particular problem.

Here is a geometrically uncorrected LX3 wide-angle RW2 processed using DxO Optics Pro 7.23:

Uncorrected

.

Here is the (in-camera corrected) Panasonic OOC JPG:

Panasonic LX3 corrected in-camera OCC JPG

.

Here is the best that I was able to do using RAW Therapee 4.0.9.184's manual geometric distortion corrections. It has a simliar contour as the Panasonic in-camera corrected OOC JPG - a contour that appears to have a single correction reference located at the center of the image-frame:

RAW Therapee 4.0.9.184 manually corrected

.

Download the Original versions of either of the above displayed corrected images and view them in an image-viewer, switching back and forth with the DxO corrected image displayed below. Note that because the LX3 in-camera OOC JPG is chopping-off a lot of the perimeter, the existing differences are easier to view using the (similar to the OOC JPG) RAW Therapee corrected image.

DxO Optics Pro 7.23 automatically corrected (normal 4:3 aspect-ratio)

The differences between the nature of the DxO correction and other methods can be readily seen, showing the "flatter" contour of the DxO (evidently multiple reference-point) correction.

.

Here is a somewhat wider-angle version using the same automatic DxO Optics Pro 7.23 geometric distortion corrections, taking advantage of it's ability to present a larger FOV (in cases where rectilinear barrel distortion exists in the recorded image). The resulting aspect-ratio is 1.392.

DxO Optics Pro 7.23 automatically corrected (wider 1.392 aspect-ratio)

DM ...

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