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CornerFix for Windows available for download

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CornerFix for Windows Beta 0.9.0.2 is now available for download at:

 

SourceForge.net: CornerFix

 

You only need to download the executables - the source code is also posted, but you don't have to download that to use the program.

 

CornerFix for Windows is a small utility program designed to fix the “Cyan corners” problem, caused by color dependent vignetting

 

Note that this is BETA software - bugs are not only possible, but probable.

 

Key features are that:

 

1. Does not require that lenses be coded

2. Does not require the the Leica IR filter be used – any IR filter can be used

3. Adjusts DNG files directly – any DNG RAW developer can still be used, e.g., C1, Lightroom, etc

4. Free – distributed under the GPL.

 

Sean Reid's got a review of the program up on his site, and there are a few other threads on it here as well.

 

The current version is Windows only, but Graham Welland is hopefully going to do a Mac port. If he doesn't get scared off when he sees the source code.

 

Please read the QuickStart guide for installation instructions. If you don't follow all the steps, you WILL get messages like "This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem."

 

Enjoy

 

Sandy

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I will give it a whirl, I am in admiration of your generosity and programming skills, it is really appreciated.

 

Tom

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Agree with Bart & Thomas. Your great effort is very much appreciated here.

 

Best

Matthew

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After have read Sean's review of this neat program I can hardly wait for a Mac version... my 15/4.5 desperately needs it !

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Guest zebra

Yes, that's it! Great software idea, Sandy!

 

Peter

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Guest tummydoc

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Assuming one would first save the RAW file as a DNG, could one use this programme with an Epson RD1s? A friend has one and occasionally uses IR filters at indoor events. And, will there be any chance that it will later be modified to work with JPEG files as well? (Not admitting anything here, I swear

)

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Assuming one would first save the RAW file as a DNG, could one use this programme with an Epson RD1s? A friend has one and occasionally uses IR filters at indoor events. And, will there be any chance that it will later be modified to work with JPEG files as well? (Not admitting anything here, I swear )

 

Unfortunately, at this point, the answer is no and no.

 

While CornerFix could read an RD1 DNG, and even analyze the image, it could not write a "RD1 DNG", because it doesn't know how a RD1 encodes its raw data. And in order to be able to modify the DNG, CornerFix needs to re-encode the data it's worked on. While a DNG tells you how to decode the raw data, it doesn't tell you the encoding process, and knowing how to decode is not quite the same as knowing how to encode. CornerFix knows about M8 encoding not because of what's in the DNG, but because the M8 encoding is programmed into CornerFix itself.

 

As regards JPEGs - the mod is possible, but it would be a lot of work, and right now there are a whole bunch of things that are more urgent - such as batch processing. I suspect that upgrading CornerFix to handle more cameras in DNG format would be easier.

 

Sandy

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Beta 0.9.0.3 of CornerFix for Windows is now available. This is a bug fix release, it primarily sorts out a problem which could occasionally cause lens profiles to be inaccurate if profiles for multiple lenses were created in one session.

 

If you only generated one profile in any given session with CornerFix, this would not be an issue for you.

 

You can download here: SourceForge.net: CornerFix

 

Thanks to Carl Bretteville for the help on discovering this one.

 

Sandy

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Sandy,

 

Excellent update - this solves the problem I was experiencing.

 

The quality of the software with my uncoded Zeiss 21mm is impressive (using a very rough and ready profile).

 

Suggestion: Would it be possible when saving a converted picture by selecting File...Save image that the software automaticaly adds "conv" (or some other letter/number) before the file name so that the klutzier of us do not overwrite the original DNG file (which will happen sooner or later!)

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Sandy,

 

Excellent update - this solves the problem I was experiencing.

 

The quality of the software with my uncoded Zeiss 21mm is impressive (using a very rough and ready profile).

 

Suggestion: Would it be possible when saving a converted picture by selecting File...Save image that the software automaticaly adds "conv" (or some other letter/number) before the file name so that the klutzier of us do not overwrite the original DNG file (which will happen sooner or later!)

 

Yes, the one really big request from I think nearly everybody that's used the initial version is to improve the workflow, so I think that the next beta will be focussed on getting batch mode working, with some smart auto renaming. Hopefully that's going to be quite soon - as soon as its reasonably clear that the bugs in the current version are under control(!)

 

Sandy

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Yes, the one really big request from I think nearly everybody that's used the initial version is to improve the workflow, so I think that the next beta will be focussed on getting batch mode working, with some smart auto renaming. Hopefully that's going to be quite soon - as soon as its reasonably clear that the bugs in the current version are under control(!)

 

Sandy

 

Perfect...batching with auto-renaming is just what is needed. I'm currently away from home and office helping out a friend who is ill. But when I get back next week, I think John's CV 12 adapter may have arrived (John?) and I can get to work on some CV 12 profiles.

 

Cheers,

 

Sean

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These three figures were taken with the Summicron 35/2.0-asph, which is considered a marginal case. Still there is some red vignetting, and visible overall vignetting when the lens is used wide open. Each figure shows the traces of the red, blue and green intensities along a full frame diagonal from top left (0) to bottom right (300), averaged with its mirror image, top right to bottom left. The first figure compares the original R,G and B intensities as shot with the Leica UV/IR filter but lens detection OFF with the results of setting lens detection ON+UV/IR. Without correction, the red intensity drops at the corners to about 0.65 of its strength at the center of the frame, while the blue and green signals fall off to about 0.72 in the corners. The firmware correction raises the red intensity to about 0.75 at the corners of the frame but leaves the blue and green strengths essentially unchanged. So the red vignetting is corrected, perhaps over corrected, but overall vignetting is left unchanged.

 

The next figure, using the same color code for the lines, compares the three intensities before and after correction in CornerFix. I generated a profile from the .dng file shot at f/2.0 and used it with CornerFix to produce essentially a flat response across the field of view. There is some danger that this profile will overcorrect the corners on shots taken at smaller apertures, so in the third figure, I used a profile based on a test shot at f/2.8 with this lens. The result is constant red/green rations across the frame, and vignetting reduced to 0.85 at the corners, but not completely eliminated. The two profiles used (L104478.cfp at f/2.0) and L1004479.cfp at f/2.8) are available here and

here.

 

scott

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Well, with CornerFix, the real action takes place with DNG's, which we have to turn into JPGs to show here, so here are the four JPGs which I analyzed to make the curves above. First is f/2.0 -- OFF, then f/2.0 -- ON with UV/IR, then f/2.0 -- OFF corrected with the profile from the first shot, then f/2.0 -- OFF corrected with the weaker profile from shooting at f/2.8. Finally I'll add the jpg from shooting at f/2.8 -- OFF. I use a standard size of 900x600, so this may scroll on for a while...

 

scott

 

PS -- is vignetting a big problem with the 35? I don't think so, it's easily measured but not terribly visible. The numbers I plot are intensity (not RGB values, but with the gamma transformation removed by squaring the RGB numbers), to make the differences easier to analyze. I think a correction of the size of what I show using the 2.8 test shot would be a reasonable approach for all apertures. YMMV, especially if you shoot a lot in tungsten or mixed lighting.

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The extent to which Leica under corrects relative to what could be done is quite noticeable. Since I've been getting files from people post CornerFix getting released, one of the things that's interesting is the extent to which there seems to be differences between the optical centers of lenses. You can see that in the asymmetry of the curves that Scott posted. So one hypothesis is that variation in lens centering is actually why Leica under corrects - 100% centered correction on an off-center lens is potentially going to give opposite colors in opposite corners. If so, the possible implications are (and I'm speculating here):

 

a) It may be possible to enhance the accuracy of the CornerFix corrections by better taking lens centering into account - I'm busy analysing lens profiles at the moment to see what can be done.

 

Previously the theory has been that CornerFix's corrections will under perform the Leica firmware corrections on Leica coded lenses because the firmware can operate on the the original 14-bit sensor data vs. CornerFix operating on data that has been compressed and then uncompressed again. However, if the optical centering of lenses is a big issue, then CornerFix may have an advantage, even on Leica coded lenses, in that you can generate a profile specifically for your (off center!) lens

 

c) It may be worthwhile to introduce two new abilities into CornerFix - firstly, the ability to manually adjust for centering (a suggest from Carsten), and also it may be possible to add the capability to scale back on corrections, so not 100% correct, similarly to what Leica do. Perhaps that could be done separately in the luminance and color channels, so you could 100% correct for red vignetting, but not 100% for luminance vignetting.

 

d) Getting the WATE acceptably corrected in firmware might be an issue for Leica - The WATE is essentially a zoom lens, and zoom lenses are well known for being off center a lot of the time

 

Thanks to all those that have sent me reference images - keep them coming!

 

Sandy

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Dear folks, it is real great analysis here. And Sandy is suggestion is for sure most welcome. But pardon on my ignorance, what do you mean by off-centre lens? Is it a lens manufacturing defeats or something else.

 

First, we have the focus shift and now we have the off-centering on the world reowned 35mm lens, must be kidding....

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The extent to which Leica under corrects relative to what could be done is quite noticeable. Since I've been getting files from people post CornerFix getting released, one of the things that's interesting is the extent to which there seems to be differences between the optical centers of lenses. You can see that in the asymmetry of the curves that Scott posted.

 

...

 

Sandy

 

I don't believe that an asymmetry in the lens is required to explain the left-right asymmetry in the graphs that I plot. I shot a white wall that is very uniformly lit left to right, but less uniform from top to bottom. So I combined two traces across the diagonal from top left to bottom right and from top right to bottom left, but I didn't average the upper with the lower parts of the frame. I think the asymmetry is just a lighting difference.

 

scott

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c) It may be worthwhile to introduce two new abilities into CornerFix - firstly, the ability to manually adjust for centering (a suggest from Carsten), and also it may be possible to add the capability to scale back on corrections, so not 100% correct, similarly to what Leica do. Perhaps that could be done separately in the luminance and color channels, so you could 100% correct for red vignetting, but not 100% for luminance vignetting.

 

...

 

Thanks to all those that have sent me reference images - keep them coming!

 

Sandy

 

 

on c), I don't know if centering is so easy to detect in amateur lab work like I have tried. The illumination differences are hard to control, and I would prefer to only apply corrections which have been averaged over the four corners, as CornerFix presently does. But having two sliders, one for strength of the overall correction, and the second for strength of the red vignetting correction, where the test data choose the functional form, is a great idea.

 

And I'm happy to keep the images coming. No ACK required, as you might be inundated right now.

 

scott

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