Lens Aberration - Importance and Removal?

Started Aug 14, 2012 | Discussions
WilliamDP
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Lens Aberration - Importance and Removal?
Aug 14, 2012

Hey,

I'm investigating the possibility of developing software for removing lens aberrations from digital images, and I would appreciate any feedback that photographers out there may have on a couple of points (I am not a photographer myself). By lens aberration I am referring to the likes of lens distortion, chromatic aberration, spherical aberration, vignetting, purple fringing...

As a very open question, what is the current need amongst photographers for lens aberration correction? For example, what is lacking in current software?

Which aberrations are most important? Which are not at all important?

What kind of photography cares most about aberration correction? (e.g. stock photography, architectural, wedding...) Which aberrations are important here, and why?

I am aware that Adobe enable users to create their own lens profiles for correcting certain lens aberrations (lens distortion, vignetting, lateral chromatic aberration) using the Lens Profile Creator. I'd like to get a feel for how important this ability to create your own profiles is to photographers? In other words, would you rather be given the freedom to calibrate your own lenses, or to just use supplied calibrations (possibly from unknown sources)?

Is standalone software an advantage or disadvantage relative to a plugin?

Some software on the market enables manual, as opposed to automatic, correction of certain lens aberrations. Typically this is enabled with an adjustable slider. How important is this distinction?

Any other comments on software correction of aberrations, or any comments that you feel are in any way related to the above, would be much appreciated. As I said I'm not a photographer, so I'm looking to get the perspective of active photographers.

Thanks!

Doug MacMillan
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 14, 2012

You might want to check the competition. Adobe offers this already. I use Lightroom 4 and it does a great job of correcting for wide angle distortion and chromatic aberration.

Are you aware you will have to develop a different correction for each lens? Adobe has an extensive database. The corrections it applies to my Canon 17-40 are completely different from the ones it applies to my Canon 85. It also reads the EXIF and automatically chooses the right lens profile.

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steephill
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In reply to WilliamDP, Aug 15, 2012

As well as Adobe you have DxO Optics Pro, Silkypix and a whole raft of other RAW converters including proprietary RAW converters from the various camera brands that can also do some corrections with own brand lenses. In camera correction is also possible reducing the need for a separate program.

I don't see much future for another third party solution here.

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Peter Berressem
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 15, 2012

WilliamDP wrote:

Some software on the market enables manual, as opposed to automatic, correction of certain lens aberrations. Typically this is enabled with an adjustable slider. How important is this distinction?

In an ideal world a lens wouldn't show any aberration at all and we wouldn't have to waste time fighting it. So, as others already mentioned, 'full automatic' is a great plus. Needs a large, updated lens library (see e.g. PTlens profiles).
http://epaperpress.com/ptlens/profileInt.html

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cheers, Peter
Germany

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hotdog321
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 15, 2012

All lenses suffer from lens aberration to a greater or lesser degree. I use Adobe CS6 with their standard lens profiles for my lenses, not user-created profiles.

My primary use for lens correction is for architecture, where lens correction is essential. A click or two will correct for things like barrel distortion with a wide angle lens and chromatic aberration.

I occasional use these corrections for fine art or even portraits, but it really is key in architecture where any distortion will jump out at you because of all the straight lines. I don't really see a market for yet another lens correction program; there are some good ones out there already.

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WilliamDP
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Re: Lens Aberration - Importance and Removal?
In reply to Peter Berressem, Aug 15, 2012

Doug, steephil, Peter, hotdog321, thanks for the replies.

I've checked into (most) of the existing software. Adobe offer correction of (lateral) CA, vignetting and lens distortion. However, as with PTLens, it relies on a lens profile existing for each particular lens. Many of the lens profiles accessible through PS and LR have been generated by Adobe users (not by Adobe), and then uploaded onto the Adobe server. The drawback here is that for uncommon and new lenses there may not be profiles available, and that the quality of the user generated profiles available for download is not guaranteed. Both drawbacks can be overcome by the user generating his/her own profile (to their desired level of accuracy). Have you calibrated any of your lenses yourself Doug? I found it an onerous process, but I am curious as to the appetite for such user lens calibration. I have the impression from talking to photographers that most photographers have only a handful of lenses, so having to calibrate each lens (

steephill, I am aware of a trend towards in camera correction of certain aberrations, but it is my understanding that all these in-camera corrections are applied to jpeg images only. RAW images are not corrected in camera (I could be wrong here...).

The gaps I see are at the top and bottom of the market (above and below Adobe). At the bottom end, Adobe and DxO are expensive. PTlens partly fills this gap, but it can only perform lens distortion automatically (AFAIK) - CA and vignetting correction are performed with sliders.

At the top end, Adobe's corrections aren't perfect (although possibly good enough?). DxO's are possibly better, but there is the reliance on DxO to provide the profile for every lens as it comes to market.

I would envisage standalone software that batch processes RAW images in order to automatically remove lens aberrations, but that also enables users to perform their own lens calibrations.

I am also interested in axial chromatic aberration correction and purple fringing correction. Adobe have recently announced a tool for purple fringing reduction, although it is not entirely automatic (as I understand it). As far as I am aware no other software can perform axial chromatic correction or purple fringing correction.

Any more thoughts?

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Doug MacMillan
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More Thoughts
In reply to WilliamDP, Aug 15, 2012

William,

It sounds like you've put a lot of thought in this project. Here's my viewpoint.

You see opportunity at the low and high end. At the low end, Lightroom 4 is ~$150. I don't think anyone who is not willing to spend that much will much care about lens correction, especially if it requires them to spend some technical time creating custom profiles.

You may have some success at the high end, but you would have to be able to clearly demonstrate the superiority of your software in correcting. I think the market would be fairly small, limited to architectural photographers and perhaps some well heeled gear heads.

I have not created a profile. Tell me what I would have to do to create one with the software you envision. Would it require careful setup and targets?

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Dr JLW
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Re: Lens Aberration - Importance and Removal?
In reply to hotdog321, Aug 15, 2012

I think Adobe CS5 and 6 are pretty good.

I use a camera whose lens is not in their profiles and I need it only when I shoot rasw which is not often but the lens correction filter works very well for me.

One thing I have noted is a shortcoming in Adobe is image stitchign. I frequently find that it can not put photos together when there is too much overlap. Also it often gets matching points wrong.

I think you might do better with an image stitcher that lets the user places the photos over each other and then the program stitches tehm together. Afterward some kind od interaction to find and fix stictching errors would be very handy.

Another feature would be a multi point warping transformation. The stictched images often make straightfeatures undulate. Adobe has a fix in its warping transforamtion but it is based on a 3 by 3 grid so it has to be used many times and usign in small subregions leads to tears that have to be patched.

For teh times I use it Adobe's lens correction filters work well I am not likely to buy more capability.

I am not a pro and I use a super zoom or middling image quality.

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WilliamDP
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Re: More Thoughts
In reply to Doug MacMillan, Aug 15, 2012

Doug, thanks for the feedback,

I have considered the project mostly from a technical viewpoint, so it's really good to get feedback from photographers.

I agree with you that at ~$150, LR is inexpensive. I don't have a feel for photographers' opinions on the relative 'value' of this figure, but I would point to the success of PTLens as an indicator that a certain segment of the market (possibly exclusively non-Adobe users) finds a less expensive option more to their likes. I guess a question that I should be asking is who the typical PTLens user would be?

I agree that the market at the high end would be small. However, demonstrating superiority would be easily done with simple objective image metrics (pixels of residual distortion or residual CA remaining after correction).

Creating a profile would likely consists of capturing images of a printed target ( 25 images for a zoom lens), with lens settings varied between each shot. The remainder of the profile generation would be performed by the software. The Adobe profile creation process seems overly complicated to me (in terms of camera placment, target framing, and number of images required).

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WilliamDP
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Re: Lens Aberration - Importance and Removal?
In reply to Dr JLW, Aug 15, 2012

Dr JLW,

If your lens is not in Adobe's profiles, what profile do you use to perform corrections for that lens? One created by yourself, or one created by another user and uploaded to the Adobe server?

In terms of stitching, I have performed a (very limited) amount of this myself. I haven't used Adobe software for this purpose, but rather Hugin or Autostitch. I've found these to perform excellently. Having said that, I've stitched images of natural scenes, so any undulations that exist are less likely to be apparent. Image stitching is not a trivial task, and I would expect that it's success (in terms of the undulations for example) is very much image dependent. Lens distortion can also significantly affect the quality of the stitch - I would expect better results to be achieved if lens distortion is removed prior to performing stitching.

Stitching is not an area that I had considered for development. However, I will examine this further......

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WilliamDP
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Re: More Thoughts
In reply to WilliamDP, Aug 16, 2012

Didn't mean to strikethrough that text in my last post.... please ignore strikethrough!

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nelsonal
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 16, 2012

This would probably be a good place to begin learning about what's corrected and what still needs work (the biggest issue seems to be a data one rather than a programming issue, lots of someones need to contribute many additional lens profiles to them).
http://lensfun.berlios.de/

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nelsonal
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Re: More Thoughts
In reply to WilliamDP, Aug 16, 2012

Unplanned strikethrough or other text effects get almost everyone once in a while. When you want to use a tilda use a backslash character first, like this: \~ then it will appear without striking all the later text.

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Dr JLW
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 16, 2012

I do the lens correction with the sliders under the custom tab. I do each one picture separately. They work very well fo rme, well enough that I can not imagine buying anything else for this.

I have not tried third party or special stiching programs.

For me Photoshop CS does all I need in lens correction but it falls short in image stitiching.

One other thing I have run into is correcting in-camera panaoramas. I have a Fujifilm superzoom with this capability. In good light it works very well but in low light starting at twilight, these panaoramas have stiching errors. Parts are shifted perpendicular to the pannnig direction.

If you are interested, I can send you some from my chamber of horrors. I might be intersted in a program that can fix these.

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gwlaw99
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 16, 2012

My suggestion is write a program that does this for iPhone jpegs as I have not seen one yet. There is already plenty of software that does this for a regular computer. DXO even has specific algorithms for each body and lens combination.

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WilliamDP
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Re: Lens Aberration - Importance and Removal?
In reply to nelsonal, Aug 17, 2012

Lensfun appears to have a database of lens profiles for corrections. And as you rightly point out the limitation here is a data limitation. This gets to the crux of the issue I think, which is whether it is better to supply the lens profile to the user (third party supplied), or to enable the user to generate his/her own lens profile (user generated).

The third party supplied case has the advantage that it is less (almost no) effort on the part of the user, but the disadvantage that he/she must rely on a third party to generate the profile for each of their lenses. This can lead to a delay for new lenses.

The user generated case has the advantage that the user is in complete control of what lens profiles he/she has (no reliance on third party), but the disadvantage that there is (some) more effort required on the user in terms of creating the profiles.

DxO and PTLens are firmly in the 'third party supplied' case, along with AfterShot Pro and Capture One. Adobe have compromised between the two cases, by allowing user generated profiles to be shared between users. The problem I see here is the lack of consistency of user generated profiles. For example a user may generate a profile for a zoom lens at only one focal length, thus it would not be suitable for the correction of images shot with that lens but at different focal lengths).

From my (limited) research it seems that most photographers have approx. 3 lenses (that get any sort of regular use). Hence the commitment of 1 hour per lens to generate lens profiles does not seem an undue burden on the user.

I guess it's a question of time commitment versus correction accuracy and availability.... I'd be interested in getting photographers' opinions on this.

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WilliamDP
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Re: Lens Aberration - Importance and Removal?
In reply to gwlaw99, Aug 17, 2012

gwlaw99, I considered the smartphone app route, but ultimately I did not think that smart phone users would notice most of the lens aberrations. Distortion would probably be noticeable, but given the relatively small screen size, chormatic aberration and the remaining aberrations wouldn't be signifcantly noticeable. Additionally, I have the impression that the majority of images captured with smartphones are 'social' (capturing the moment), in which case users would not typically care about lens aberrations. Of course I could be wrong about this...

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dsjtecserv
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Re: Lens Aberration - Importance and Removal?
In reply to WilliamDP, Aug 17, 2012

WilliamDP wrote:

Dr JLW,

If your lens is not in Adobe's profiles, what profile do you use to perform corrections for that lens? One created by yourself, or one created by another user and uploaded to the Adobe server?

In terms of stitching, I have performed a (very limited) amount of this myself. I haven't used Adobe software for this purpose, but rather Hugin or Autostitch. I've found these to perform excellently. Having said that, I've stitched images of natural scenes, so any undulations that exist are less likely to be apparent. Image stitching is not a trivial task, and I would expect that it's success (in terms of the undulations for example) is very much image dependent. Lens distortion can also significantly affect the quality of the stitch - I would expect better results to be achieved if lens distortion is removed prior to performing stitching.

Actually, correction for lens distortion is part of the stitching process, at least for well-developed software such as those you mention. Corrections for barrel and pincushion distortion are part of the equation that is used to warp each image to match the others, and assuming the capture was done well, the panorama should come together well even for lenses with severe distortion. There are limits however: lenses with complex (moustache) distortion aren't necessarily going to be handled as well. But I've never had a problem with that.

When I prep my raw pictures in ACR for a panorama, I apply the default lens correction for that lens, but then move the Distortion slider to zero, and let the stitching program (PTGui) handle the warping holistically.

Dave

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