Resolution of M43 lenses

Started Mar 31, 2013 | Discussions
Anders W Forum Pro • Posts: 21,468
Re: Demonstration of Differences in DxO Geometric Corrections

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections
1

The DPR Gallery Originals of the images displayed below are full sized 16 Mpixel loss-less JPGs. Here is a synthetically created DMC-GH2 + LGV 14-140mm lens RW2 "checkerboard" test pattern:

DMC-GH2 + LGV 14-40mm Synthetic RW2 Test Pattern

.

Here is what Lightroom 3.6 (with Exposure -2.0 EV, maximum Contrast, no additional gamma correction) does to the RW2 test image when maximum manual barrel Distortion correction is applied. Download the Original image and display in an image-viewer at 20% magnification (which will collapse 5x5 pixel arrays into single display pixels). Note the single central pattern (visible at 20%).

Lightroom 3.6 - Maximum Barrel Distortion Correction - View Original at 20%

.

Here is what DxO Optics Pro 7.23 (with Exposure Compensation -2.0 EV, maximum global Contrast, no additional gamma correction) does to the RW2 test image when maximum manual barrel Distortion correction. Download the Original image and display in an image-viewer at 20% magnification (which will collapse 5x5 pixel arrays into single display pixels). Note the 4 peripheral patterns (visible at 20%).

DxO Optics Pro 7.23 - Maximum Barrel Distortion Correction - View Original at 20%

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

DM ...

Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections
1

Anders W wrote:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?" ...

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

Detail Man wrote:

The DPR Gallery Originals of the images displayed below are full sized 16 Mpixel loss-less JPGs. Here is a synthetically created DMC-GH2 + LGV 14-140mm lens RW2 "checkerboard" test pattern:

DMC-GH2 + LGV 14-40mm Synthetic RW2 Test Pattern

.

Here is what Lightroom 3.6 (with Exposure -2.0 EV, maximum Contrast, no additional gamma correction) does to the RW2 test image when maximum manual barrel Distortion correction is applied. Download the Original image and display in an image-viewer at 20% magnification (which will collapse 5x5 pixel arrays into single display pixels). Note the single central pattern (visible at 20%).

Lightroom 3.6 - Maximum Barrel Distortion Correction - View Original at 20%

.

Here is what DxO Optics Pro 7.23 (with Exposure Compensation -2.0 EV, maximum global Contrast, no additional gamma correction) does to the RW2 test image when maximum manual barrel Distortion correction. Download the Original image and display in an image-viewer at 20% magnification (which will collapse 5x5 pixel arrays into single display pixels). Note the 4 peripheral patterns (visible at 20%).

DxO Optics Pro 7.23 - Maximum Barrel Distortion Correction - View Original at 20%

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

Sure. DxO crops the image to a rectangular shape. If you ask LR kindly, I think it will do the same. Or if you ask DxO kindly, it might abstain from the cropping, which from a diagnostic point of view might be even better. If additionally, you make sure that the amount of correction applied by the two converters is exactly the same, it might be an interesting comparison.

 Anders W's gear list:Anders W's gear list
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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

Sure. DxO crops the image to a rectangular shape. If you ask kindly, I think LR will do the same. If additionally, you make sure that the amount of correction applied by the two is exactly the same, it might be an interesting comparison.

Well, the pixel-size is essentially the same (DxO has one more measly horizontal pixel). Are you suggesting that DxO Optics Pro up-samples their images by (heaven forbid) arbitrary amounts ?

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

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?" ...

Fine with me if you prefer to rephrase the question that way. Now what is your answer?

 Anders W's gear list:Anders W's gear list
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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?".

Fine with me if you prefer to rephrase the question that way. Now what is your answer?

There is only one truth, one answer for modern humankind. Adobe is God. Adobe uber alles ! Still waiting for your unified theory of DxO Optics Pro up-sampling their images by arbitrary amounts.

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

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

Sure. DxO crops the image to a rectangular shape. If you ask kindly, I think LR will do the same. If additionally, you make sure that the amount of correction applied by the two is exactly the same, it might be an interesting comparison.

Well, the pixel-size is essentially the same (DxO has one more measly horizontal pixel). Are you suggesting that DxO Optics Pro up-samples their images by (heaven forbid) arbitrary amounts ?

Yes, there's simply no end to it.

 Anders W's gear list:Anders W's gear list
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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:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?".

Fine with me if you prefer to rephrase the question that way. Now what is your answer?

There is only one truth, one answer for modern humankind. Adobe is God. Adobe uber alles !

So you are seeing the light at long last?

Still waiting for your unified theory of DxO Optics Pro up-sampling their images by arbitrary amounts.

I am afraid that's just a brute fact. No theory required.

 Anders W's gear list:Anders W's gear list
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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

Sure. DxO crops the image to a rectangular shape. If you ask kindly, I think LR will do the same. If additionally, you make sure that the amount of correction applied by the two is exactly the same, it might be an interesting comparison.

Well, the pixel-size is essentially the same (DxO has one more measly horizontal pixel). Are you suggesting that DxO Optics Pro up-samples their images by (heaven forbid) arbitrary amounts ?

Yes, there's simply no end to it.

Panini this, magister. Here in all it's glory is DxO's magical and mystically aligned Fisheye distortion correction at maximum setting. View the original at 20%, and you will see what William Blake saw.

DxO Optics Pro 7.23 - Manual Fisheye Distortion Correction - View Original at 20%

So you are seeing the light at long last?

Adobe's highly non-linear Exposure control and infamous hue-twisting is just so downright ... lame.

Still waiting for your unified theory of DxO Optics Pro up-sampling their images by arbitrary amounts.

I am afraid that's just a brute fact. No theory required.

I am so disappointed in you. Whatever happened to the principles of "intellectual honesty" ?

Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

Something rather different in nature is going on when DxO performs barrel distortion corrections ???

Sure. DxO crops the image to a rectangular shape. If you ask kindly, I think LR will do the same. If additionally, you make sure that the amount of correction applied by the two is exactly the same, it might be an interesting comparison.

Well, the pixel-size is essentially the same (DxO has one more measly horizontal pixel). Are you suggesting that DxO Optics Pro up-samples their images by (heaven forbid) arbitrary amounts ?

Yes, there's simply no end to it.

Ah, but the flip side of the coin would be that Adobe is down-sampling their images by arbitrary amounts. I shall await your full technical explanation and justification for such untoward practices !

Dr_Jon Veteran Member • Posts: 5,386
Re: Dropoff seems like a greater problem to me...
1

I should mention in passing that the 17-40 corners on full-frame are really bad IMHO (e.g. see the slrgear review, FF tab) , also I don't have an issue with banding in my 5DmkII, but then I don't do huge pulls on shadows 99.9% of the time. I find my Canon lenses (uncorrected or corrected in DXO) are noticeably better toward the edges than the 12-35 but have no interest in some great debate about it, as it's been done to death recently. I only mentioned Vignetting to explain what a previous poster was talking about, as Anders seemed to have missed it. I'm off to take some pictures...

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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Detail Man wrote:

Anders W wrote:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?" ...

Fine with me if you prefer to rephrase the question that way. Now what is your answer?

Ah, but having rephrased the question, I await your DxO processing to gather your evidence. Of course, your Adobe renderings are the picture of perfection, leaving no room for improvement.

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:

Detail Man wrote:

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.

OK. So let's approach it from the other end then. The link below shows an architectural shot with the 7-14 that we have discussed before although from a slightly different point of view:

http://www.dpreview.com/forums/post/50772988

As indicated, the first image is uncorrected, the second manually corrected in LR and the third autocorrected by LR based on instructions embedded in the RAW. Aside from the difference in how much of the uncorrected frame the two corrected versions manage to retain, what do you find unsatisfactory about either of them?

They look marvelous, Anders. But I thought that the issue under discussion was, "if they were to be corrected using DxO Optics Pro instead, would they perhaps look 'super-duper-marvelous' ?" ...

Fine with me if you prefer to rephrase the question that way. Now what is your answer?

Ah, but having rephrased the question, I await your DxO processing to gather your evidence. Of course, your Adobe renderings are the picture of perfection, leaving no room for improvement.

Quite. So why bother trying to prove the impossible.

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Detail Man
Detail Man Forum Pro • Posts: 16,799
Re: Demonstration of Differences in DxO Geometric Corrections

Anders W wrote:

Sure. DxO crops the image to a rectangular shape. If you ask LR kindly, I think it will do the same. Or if you ask DxO kindly, it might abstain from the cropping, which from a diagnostic point of view might be even better. If additionally, you make sure that the amount of correction applied by the two converters is exactly the same, it might be an interesting comparison.

OK, magister, I have now cropped the Adoobie image down to the girlie-man size of a mere 3499x2624 pixels (seemingly all that it could handle), and gratiously lowered the DxO Optiques Prose image size to a similar puny dimension. Once again, download the Original images and display them in an image-viewer at 20% size (collapsing 5x5 pixel arrays into single, centered pixels).

Lightroom 3.6:

Note the pattern that appears to imply a single centrally placed optical correction reference point.

.

DxO Optics Pro 7.23:

Note the four circular patterns that appear to imply four separate correction reference points.

I anxiously await your refutations showing that Adobe is the embodiment of crystalline perfection.

Note: The DPReview post-display system appears to be malfunctioning. This is my 2nd and final possible edit. If images do not display, click on the Gallery Page links to download the Originals.

DM ...

revio Senior Member • Posts: 1,755
Re: I disagree

Dr_Jon wrote:

I do agree with you, and added a like, but will say that if the trade-off for the distortion correction is some other attributes that are much better than you would expect but would be very hard to fix in software then it's perhaps not so bad a trade-off, e.g. better flare resistance (err, doesn't seem to do that) or better out-of-focus rendering (I like the 35-100, early days with the 12-35), or less vignetting (no) or less residual spherical aberration (probably not so important with m43 and f2.8) or ...

I have no idea which of these qualities it might have, it may well just be priced to match their production capability to demand. Simply pointing it out as another thing to consider.

(I have both the f2.8 zooms and they are okay if a little over-priced in my view, the latest Canon equivalents are a lot better, especially wide open, but a lot more money, size and weight. Horses for courses I guess.)

P.S. (edit) my GH3 doesn't do a great job correcting the 12-35 and leaves quite a lot of distortion in the JPEGs at the wide end, DXO does a much better job so perhaps I should see what gets thrown away to pay for that. (Actually I don't care, I prefer right-angle corners on rectangles, not triangles sticking out.)

Simple:

Lenses being large and very expensive, vs less expensive, and more compact; how can the choice be done other than preferring the latter, for use with cameras as small as the m4/3 cameras are?

How can this simple fact get so confusing, to so many people?

I, too, think Panasonic´s twin F:2,8 zooms are expensive.

But they are less expensive than their closest counterparts in CaNikonland....thus only a good thing that they, through use of software corrections in camera, can be made compact (as are the cameras) and at least a fair amount cheaper than the F:2,8 CaNikons...

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Aim & Frame

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texinwien Veteran Member • Posts: 3,326
Clarification & Correction

Anders W wrote:

texinwien wrote:

Anders W wrote:

texinwien wrote:

Anders W wrote:

texinwien wrote:

axlotl wrote:

The reviewers at Photozone appear not to have fully accepted that post capture lens corrections are now a normal part of the image making process.

Normal according to whom? Not all lenses require as much software correction as others. Some require very little. Some require much more.

So they RAW convert with RAW Therapee, demonstrate 5.8% barrel distortion at 12mm and decry that as "excessive".

It is pretty excessive for a $1300 lens.

But if, like the rest of us, you simply use the camera as designed and allow the distortion to be corrected automatically in camera then all you will see is a mild amount of residual distortion. In addition the Photozone reviewers say that the automatic distortion correction is "lossy" , however those of us who have actually used the lens for several thousand photos, often critically inspected for sharpness, are unaware of this supposed lossiness.

Whether you have noticed it or not, correction is, in fact, a lossy operation. There is nothing 'supposed' about that statement, and the Photozone reviewers are 100% correct.

They also criticise corner shading which is present but which I hardly ever notice in actual photos and if I do, it is easily removed in a RAW converter.

Relying again on software correction for a problem that should probably be optically corrected in a premium lens.

In other words they are complaining about lens attributes which are of no concern in the real world.

Not true. The attributes are of concern, which is why you must apply software correction in order to fix them. The point is, at what price should we expect a lens to be optically excellent? It costs less to build a lens with poor optics, then correct resulting problems in software.

As long as the manufacturers pass on some of the savings they realize from these cost-cutting measures, I think most are OK with the idea. If, however, a manufacturer builds a lens with poor optics and tries to sell it as a premium quality lens, there are plenty of discriminating buyers who won't appreciate the trick.

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?

I never said what you're asking me to defend. Software correction is practically free, however.

If you are not saying that it is done for the purpose of cutting costs, how then should we interpret what you say in the two paragraphs immediately above the question I raised?

There's not much to interpret, is there? It's a simple declaration. I'm not sure which words lead you to your interpretation. The statement, "it costs less to build a lens with poor optics, then correct resulting problems in software" doesn't require much interpretation, I don't believe, and your 'restatement' relies on something other than the words I wrote, it would seem.

I thought that what you said was meant to apply to the Panasonic 12-35/2.8, which, according to you, has "excessive [distortion] for a $1300 lens" and relies "on software correction for a problem that should probably be corrected optically in a premium lens". If what you said was not meant to apply to that lens, what would be its relevance in the present context?

It was meant to apply to that lens, but the restatement of my words in your original reply to me still does not follow.

Allow me to expound: I never, at any time or in any place claimed or implied that manufacturers design lenses to be software-corrected "only or primarily for the purpose of cutting costs". Those are your words, and not mine.

I said, "it costs less to build a lens with poor optics, then correct resulting problems in software." Your restatement does not follow from my words.

I could probably add an 'all things being equal' to the front of the statement to make it a little less arguable. I might also replace 'problems' with 'imperfections' then add 'than it does to build a lens with excellent optics in the first place' to the end.

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 have also not made that claim.

If you are not saying that the results are worse, how then should we interpret what you say in the two paragraphs immediately above the question I raised?

This is how you should 'interpret' them: all things being equal, it costs less to build a lens with poor optics, then correct resulting imperfections in software, than it does to build a lens with excellent optics in the first place.

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?

Nothing is wrong with it if the end results are as good. I never claimed otherwise. As a matter of fact, I specifically said that most are probably fine with the idea if the cost-savings are shared with the consumer.

So you are suggesting that it is a matter of cost-savings after all?

I'm suggesting that, all things being equal, it costs less to build a lens with poor optics, then correct resulting problems in software, than it does to build a lens with excellent optics in the first place.

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.

I don't have a problem with the strategy.

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.

Interesting theory- sounds plausible.

If you have any links to good reading on the subject, I'd be happy to have a look. Might save you some effort trying to retype what you've already written elsewhere.

There are lots of threads on the subject where this has been debated at quite some length. Here is one of them. See particularly the contributions by kenw.

http://www.dpreview.com/forums/post/39680143

Will brush up, thanks for the link.

tex

Thanks for supplying the informative link. It's worth a read for anyone who's interested in the subject.

Correction: After reading some of the posts at your link, as well as information elsewhere on the Internet, I've learned that optically-correcting barrel or pincushion distortion often (always?) causes a lens to suffer from mustache distortion. So it's not a question of whether we wish to correct all distortion optically, or not. It seems we'll have one sort of distortion or the other, if we rely on optical correction, only.

Manufacturers making lenses for OVF cameras tend to correct the generally more visible pincushion and barrel distortion in the optics, so the photographer can see in his OVF how the resulting photo will look. This, in turn, implies that these lenses are more likely to suffer from mustache distortion.

Pincushion and barrel distortion are easily corrected with software. Mustache distortion is much more difficult to correct with software. For this reason, manufacturers making lenses for EVF cameras tend to leave barrel and pincushion distortion uncorrected in the optics, relying instead on software correction, both in the camera and out. This implies that these lenses are less likely to suffer from mustache distortion, which, as noted above, is difficult (sometimes approaching impossible?) to correct via software.

So, I was wrong to imply that a premium m43 lens should have barrel or pincushion distortion corrected optically. Rather, by leaving such distortion uncorrected in the optics and relying, instead on software, manufacturers are able to make lenses that deliver images that, once processed, suffer from neither pincushion, barrel nor mustache distortion, something that may be either very difficult or even impossible to achieve with lenses manufactured for OVF cameras.

Interesting stuff.

Clarification: I also didn't wish to start a firestorm here. To be clear, I think the final result is the important one, no matter how it is reached. That is, the resolution and distortion tests should look at the processed images. That's all that counts.

I do think that manufacturers should share the savings with consumers where such savings are realized by using software rather than hardware correction. In other words, as a consumer, I would prefer that the manufacturers from whom I buy base their prices at least partly on their costs of manufacturing. If a manufacturer finds a way to build an equivalent widget for 1/10th of his previous costs, then offers the widget to me at twice the previous price, I'm likely to feel cheated and avoid the manufacturer's products in the future, when possible.

Lastly, I may be personally biased against the Panasonic 12-35mm and 35-100mm. I feel like these two lenses may be overpriced, but I'm not an expert on the matter of lens quality, construction costs and/or pricing. It could be due to a slight bias toward Olympus on my part coupled with a bias toward primes over zooms, at the moment.

tex

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exdeejjjaaaa
exdeejjjaaaa Veteran Member • Posts: 8,263
Re: I disagree
1

MAubrey wrote:

exdeejjjaaaa wrote:

Anders W wrote:

Dr_Jon wrote:

At the wide end of my 12-35 it needs a lot of correction and the Photozone results do show the centre sharpness is a long way above the edge at all apertures at 12mm, but whether that's software correction or the edges of the lens just being not-so-great in comparison to the centre I have no idea.

Exactly. While we know that the resolution of the 12-35 after distortion correction is worse than before, we can't know whether the end result is better or worse than it would have been for a lens designed so as not to require any software correction. Correcting one aberration is frequently at odds with correcting others and improving distortion characteristics by optical means may well come at the expense of lower resolution.

really ? take a peek @ olympus 12-35/2 or 35-100/2... optical correction adds weight, size and cost+price... but it always better than software correction just because you can always apply the same math on top of that... you don't have any single example of a properly optically corrected lenses (distortion and aberrations) that leads to reduced resolution... just FUD to justify underdesigned lenses to save on size/weight and cost to sell more.

Not true.

Every time you add a new element

no, no... don't cheat here - correction is not equal to always adding a new element - you can just use a proper material (more expensive that is)... / oh, and what about your double magenta filters ? I heard you did not notice any ill effects, did you ?  /

to correct one thing you risk "uncorrecting" another thing. In this case, the Olympus 35-100mm f/2 has massively worse flare compared the Panasonic 35-100mm f/2.8 http://www.lenstip.com/242.9-Lens_review-Olympus_Zuiko_Digital_35-100_mm_f_2.0_Ghosting_and_flares.html

http://www.lenstip.com/368.9-Lens_review-Panasonic_G_X_VARIO_35-100_mm_f_2.8_P.O.I.S._Ghosting_and_flares.html

Flare problems are particularly bad with these kinds of zooms, but the super high resolving Olympus 35-100mm f/2 is particularly horrible. And flare, incidentally, really hurts resolution.

flare hurts contrast (acuity), not resolution... and I will take more flare over crippled optics, because I do not shoot towards sun and w/o hood (that was a condition of experiment)... your mileage is different apparently.

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exdeejjjaaaa Veteran Member • Posts: 8,263
Re: I disagree

MAubrey wrote:

Dr_Jon wrote:

I'm sorry but I'm not signing up to m43 lenses magically being good because of optical corrections as it disagrees with what I see. There are a few very good m43 lenses (the 75 comes to mind, but I doubt much software is involved) and some good ones (20/1.7, 45/1.8, others) but I could name a whole bunch more Canon and Nikon lenses that are in the very good category and they don't seem to have much issue churning them out. Also I do think cost is a factor, as it means you can use lens elements with easier/cheaper to make shapes and ditch some of the ones needed to fix CA (although software CA repair does have a cost on image quality, it isn't magically free).

My Canon 70-200 has 23 elements in 19 groups with 1 fluorite and 5 UD elements and it optically wonderful. You can certainly see where they spent my money (just over twice the price of the 35-100).

My Panasonic equivalent (FoV/exposure-wise) has 18 elements in 13 groups with 3 UD-ish elements. Part of the lack of elements is presumably as they don't bother correcting the CA so much, so can dump the Fluorite and some of the UD. (Partly I suspect Canon are just flat-out better at designing their top-end lenses.) Optically it's more like the previous generation Canon though, some way behind. I'm still very happy with it and happy to pay the optical price of it not being super-great (f2.8 and the long end lag by more) for the size/weight saving. I think 20% less on the price would be fairer for the performance (the two Canon 70-200 f4s are also a lot better), but the world doesn't work that way and I get that. (Anyway I suspect the £800 odd I paid for the 14-140 back in the day was a worst deal price-wise.)

Your Canon with all those extra pieces of corrective glass gives the lens absolutely horrible flare properties.

http://www.lenstip.com/270.9-Lens_review-Canon_EF_70-200_mm_f_2.8L_IS_II_USM_Ghosting_and_flares.html

But your software corrected Panasonic is much, much better in that regard.

http://www.lenstip.com/368.9-Lens_review-Panasonic_G_X_VARIO_35-100_mm_f_2.8_P.O.I.S._Ghosting_and_flares.html

And in this case, the software corrected lens has higher resolution.

The Panasonic also has less (uncorrected) vignetting, incidentally...

you are comparing FF glass w/ m43/43 glass... try to  find m43 1.4 AF zoom then come swinging about vignetting.

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Re: Demonstration of Differences in DxO Geometric Corrections

Detail Man wrote:

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 ...

and ?

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