Idiot's guide to CornerFix

[fotoism]

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Okay, don't laugh. I need an idiot's guide to CornerFix.

 

I installed the program hoping to correct the cyan corners in some CV15 pictures. The pdf that came with the program seems to aim towards those who has some background in post processing, which I had none. It mentioned lens profiles and there is only one included in the program for CV12. I used it but the cyan corners are still there. Maybe I used it incorrectly, maybe CV12 profile cannot be used for CV15 files.

 

Can someone tell me how you use this program, step by step? Where do you find the right lens profile ( in my case one for CV15 )? Or if there are some resources please point me to that.

 

Any help for this newbie is appreciated.

[carlmuck]

Okay, don't laugh. I need an idiot's guide to CornerFix.

 

I installed the program hoping to correct the cyan corners in some CV15 pictures. The pdf that came with the program seems to aim towards those who has some background in post processing, which I had none. It mentioned lens profiles and there is only one included in the program for CV12. I used it but the cyan corners are still there. Maybe I used it incorrectly, maybe CV12 profile cannot be used for CV15 files.

 

Can someone tell me how you use this program, step by step? Where do you find the right lens profile ( in my case one for CV15 )? Or if there are some resources please point me to that.

 

Any help for this newbie is appreciated.

 

Its actually pretty easy.

 

you can find profiles inside your camera:D

 

If you have a well lit solid color plane take a picture of it. (I've found that putting a piece of paper white un-lined paper over the lens and place the camera directly under a difuse source (flood light from the ceiling or overhead flourescent fixture) works ok. I've since purchased an "ExpoDisc" which works perfectly for this purpose.)

 

Now that you have an image of a white (or gray, or other solid colored surface) load it into your computer. Marvel at the vignetting of the lens and the color shift (cyan corners) of your filter.

 

Open Cornerfix and then "File->Open..." your image.

Once the image loads, select "Lens Profile->Create Profile"

After processing completes, select "Lens Profile->Save As ..." give the file a name (I usually name it after the lens, plus filter (i.e., Avenon 21mm/f2.8+BW486).

 

Now when you want to use it, open CornerFix and the "Lens Profile->Open..." then "File->Open..." your files.

 

c.

Edited March 17, 2009 by carlmuck

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[ho_co]

Phil--

Oops--while I was off hunting up my CornerFix instructions, Carl already sneaked in with the same advice!

 

 

As you discovered, the only profile shipped with CornerFix is the one for the 12 mm Heliar. For other lenses, you need to make your own.

 

Did you follow these instructions from p 4 of the CornerFix pdf?

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Edited March 17, 2009 by ho_co

[fotoism]

Thanks carlmuck and ho_co: I'll try what you have suggested and see what happens,

 

Do I need to create different profiles for different aperture and/or different ISO settings?

[carlmuck]

You can create as many profiles as you wish. I've done that (create different profiles based on aperture) but can't say it really makes any difference. The gross effects of angle of incidence on the filter dominate any variation based on aperture.

 

c.

[fotoism]

So I have followed the instructions and created a cv15 profile using f/8, iso160, lens detection and IR filter off. I used a piece of white foam over the lens with a spot light over it about 2 feet away, focus set at closest, exposure +2-1/3.

 

I then opened a file which was taken with lens detection and IR filter on. I always have a Leitz UV IR cut filter on this lens. The cyan corners ( or more like "sides" ) are obvious. I applied the newly created profile and voila! the cyan on two sides are gone but replaced with magenta!

 

I went into the image correction options and played with the luminance and chroma sliders. They were both set at 1.00. I fiddled with them and finally came to luminance 1.19 and chroma 0.49. Most of the cyan or magenta cast is now gone with the exception of the very corners, but I noticed the middle part of the picture is now slightly darker than the two sides. By adjusting the luminance I can darken the sides a bit to match the center but the corners begin to darken again.

 

Is the fact that the profile was created with lens detection and IR filter off and the picture was taken with both on that's causing the problem? Should profiles match exactly how the picture was taken exactly to obtain optimal results?

 

Please see below for the before and after files. I have not done any post processing other than CornerFix and resizing. Any comments welcome.

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[carlmuck]

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You say you created the profile with "IR filter off" do yo mean that the setting was OFF or that the filter was not installed?

 

Filter needs to be on, "Lens Detection" setting to "On" or "Off" but not "On + UV/IR".

 

Images to be corrected should not be processed in camera ("Lens Detection" NOT set to "On + UV/IR").

 

Using the "factory settings" works perfectly for me. Unless you've got a unique filter (some hot mirrors are stronger than others) i wouldn't monkey with the chroma and luminance. Also note that the chroma and luminance are intended to tweak you profile, not your images.

 

The image you posted above looks like it is only suffering from vignetting. Corner Fix can fix this as well, you just need to create a profile with different parameters (chroma to 0).

 

Though as I look at the processed file, it looks like it only needs to be white balanced. What raw processor are you using? The upper picture looks to be processed using the "Camera Standard" calibration, the bottom one "ACR 3.6." (Adobe's calibrations are "low" on green, and pull in more brightness as compared to the M8's "standard" profile.)

 

To see what magenta shift looks like, take your processed file and run it through again. The blue sky in the corners will take on a distinct pink cast.

 

c.

Edited March 17, 2009 by carlmuck

[sandymc]

Is the fact that the profile was created with lens detection and IR filter off and the picture was taken with both on that's causing the problem? Should profiles match exactly how the picture was taken exactly to obtain optimal results?

 

Yes. You have to have the same settings (and the same lens/filter) for the profile as for the image you are correcting.

 

Sandy

[fotoism]

When I first took the picture the IR filter was on the lens and I had lens detection and UV/IR turned on as well. But when I created the profile I left the filter on the lens but turn everything off in the menu. I don't know if that is causing some discrepancies.

 

The files I posted, both before and after, were DNG when processed in CF, but then saved as JPEG and resized for uploading in Paint Shop Pro without any further treatment. Maybe the compression used in PSP have caused problems, and I can try using CaptureOne.

 

Attached again is the same file but with luminance and chroma both set at default ( 1.00 ). Magenta is obvious at both sides with the middle part darker.

 

Looks like I have to start from scratch and redo the profiles using different parameters, then apply them to each picture according to how they were taken, in order to obtain best results.

 

Just to clarify: Since I always leave the IR filter on the lens, should I be creating profiles with lens detection to "OFF" in the menu regardless?

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[carlmuck]

As Sandy (the author of CornerFix!!) stated, your problem is correcting a corrected photo.

 

Set the "Lens Detection" to either "On" or "Off" but not "On + UV/IR" for all images you are going to adjust using CornerFix.

 

c.

[fotoism]

I recreated the profiles and then took pictures using the exact same settings for ISO speed and aperture. The only difference is that the lens detection and filter are OFF in the menu but I did use an IR filter on the lens.

 

I tried one set of profile and the matching picture and the initial correction in CF still showed magenta in place of cyan. Then I went in and adjusted the luminance to 0.80 and chroma to 0.50 - I prefer not to as suggested by carlmuck, but I don't know of another way to get around it. All the time I was dealing with the DNG files in CF and there was no prior manipulation of any kind on the files. After the adjustment it seem to yield better results than before: the cyan or magenta casts are gone and the uneven brightness is mostly corrected.

 

Below are the before and after pictures compressed in C1 into jepg and resized for uploading. At this point I am happy with what I got, given I started learning CF less than 48 hours ago, thanks to all those who helped, and sandymc for this program! I will continue to work on profiles in other setting and hope for the best.

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[ho_co]

You have to have the same settings (and the same lens/filter) for the profile as for the image you are correcting.

 

Phil--

Read Sandy's post!

 

Use the same settings for the profile as you use for the picture.

 

If you usually shoot with ID ON + UV/IR, then set the camera that way to create your profile.

 

 

If your profile was made with a different setup from the image you're correcting, it can't work right.

 

It's like calibrating a rifle for a target at 50 feet and assuming that will do for a target at 300 feet.

 

 

In practice, I find that ISO and aperture make no difference. A single profile for a given lens works for me.

 

I also question your method of making your profile file. Your method is probably fine, but I just use a white piece of paper. Some people use the sky. The important thing is that the object show no detail, because CornerFix will calculate that detail into its corrections. If you're using a piece of Styrofoam, focus the lens to infinity; if you're using the sky, focus the lens to its closest.

 

But really, I think the only thing you're messing up is that the profile and the image you're having to shoot have to match optically: Obviously you're using the UV/IR-Cut filter on the lens.

 

Now you can set the camera to

LENS ID OFF,

LENS ID ON, or

LENS ID ON + UV/IR.

 

(Despite Leica's instructions, I just leave the camera set to LENS ID ON + UV/IR because it seems to work in my case.)

 

But whichever of those three you choose, you must use the same one to create the profile file that you do to take pictures with the lens.

Edited March 18, 2009 by ho_co

[carlmuck]

Phil,

 

This is going to sound like a stupid question, but do you have an IR filter not just a UV filter?

 

Looking at your "unprocessed" image above, I don't see any cyan shift, I see vignetting. The photos below exhibit typical cyan drift. This is with a 21mm so I'd expect your 15mm to be even worse. I'm also using a B+W 486 filter which is somewhat stronger (more shift) than the Leica shipped filters. Note the tone of the concrete in the photo on the left.

 

c.

 

Edited March 18, 2009 by carlmuck

[fotoism]

ho_co:

 

I always have a Leitz UV/IR cut filter on the lens when I was creating profiles and taking pictures, so this is a constant. The variables are the menu settings: I tried both leaving the lens detection ON+UV/IR as well as OFF, with the filter still on the lens all the time.

 

When taking the picture for the profile I put the M8 on the desk with the lens pointing up, then I put a piece of printing paper over the lens and a desk lamp shining downwards toward the paper vertically, about 2 feet above. But then I notice with the light shining through the paper I can actually see patterns of paper fibers, that's when I switched over to a piece of styrofoam, which gives me a more even white image to work with without any visible patterns. I manually set the iso speed and aperture while making the profiles and when I took the pictures I took the same scene with matching iso speeds and apertures, that was 24 profiles and 24 matching pictures for each iso/aperture combination except iso 2500.

 

I used these 24 profiles to process their respective pictures and they all seem to make corrections in a similar way, changing the cyan cast into magenta cast, that's why I had to adjust the luminance and chroma.

 

I also tried creating a few profiles with lens and filter set to ON in the menu, took some more pictures and process them with these profiles, the results are the same.

 

I tried setting the wb to tungsten and auto for the profile pictures, does not make a difference on the processed pictures.

 

But as soon as I change the luminance and chroma from default to 0.80 and 0.50, things became better.

 

This almost makes me think if I should even use the UV/IR cut filter on this lens at all. I'll try again tomorrow without the UV/IR filter on the lens and see what happens.

[fotoism]

carlmuck:

 

I have the Leitz UV/IR cut filter on the lens all along.

 

The picture I uploaded are resized jpeg files so some of the details might have been lost in the process. Below are two 100% crop from a corner of the original files, before and after, and you will be able to see the color difference better.

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[carlmuck]

Maybe Sandy can help. Your situation is very odd...

 

c.

[ho_co]

Phil--

It sounds as if you're doing everything right, so long as the profile matches the camera setting in each case.

 

You and I both always use the UV/IR Cut filter. So I just set the camera to ON + UV/IR for shooting and (once months ago) for producing the profile.

 

I just choose the profile and run CornerFix. No further adjustments needed for the cyan edges.

 

At least the corrections you're having to make are consistent instead of all over the place. But from my experience they shouldn't be needed at all.

 

You've got me stumped as well, I'm sorry to say.

 

Sounds as if Carl and I are overlooking something very simple, since the results are the same no matter what corrections you use. I'm lost.

Edited March 18, 2009 by ho_co

[ho_co]

Another thought, Phil. You're getting cyan edges from the filter with the 15; that's expected.

 

But now when you apply CornerFix, it overcorrects. It should just remove the cyan and stop at neutral, but it keeps going and removes more cyan, leaving you with magenta.

 

IMO, that must mean a mis-matched profile. I can think of two ways that could happen:

 

 

FIRST:

Since the M8 behaves differently with each of the three LENS ID modes, you need to be sure that whichever mode you use when you shoot the picture, you use a lens profile made with that same mode.

 

In other words, if the camera is set to LENS ID ON + UV/IR when you shoot the picture you're going to correct, then the profile you're using must also have been shot with LENS ID ON + UV/IR.

 

 

SECOND:

The other thing that could be the culprit is the use of foam as your basis for even illumination.

 

Sandy's FAQ #8 says:

Can I use a diffusion filter rather than a grey card? Maybe. Some people have got good results. However, tests have shown that diffusion filters can introduce vignetting all of their own, which will distort your results.

 

If your foam profile is introducing its own vignetting, that might explain why CornerFix is overcorrecting:

 

The lens has a certain amount of vignetting on its own--that's what we're trying to correct.

 

Now if the arrangement you used for creating your profile also vignettes, that vignetting will also be added to the profile, and you'll get overcorrection.

 

I'd recommend you re-shoot your profile outside. It's almost impossible to get even lighting inside. A single bulb can't do it.

 

I laid a large white mailing envelope on the ground, focused to infinity, moved in to fill the frame, and shot. (The sun is a very even light source. )

 

Good luck! And keep us posted. I know we're close, because there's not much that can get messed up with CornerFix.

Edited March 18, 2009 by ho_co

[sandymc]

Taking a look at the thread above, the one thing that stands out to me as a potential problem is in your description for how you are generating the profiles - with a light shining on a piece of foam. If the light is close enough to the foam that there is light fall-off towards the edges of the foam, CornerFix will interpret that as vignetting, and generate a profile that doesn't actually match the lens.

 

Suggestion - generate a profile using sunlight - that's pretty much guaranteed to be uniform.

 

If you still have problems I'll take a look at your reference images and actual image - pm me to work out how to best get them to me.

 

Sandy

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[fotoism]

Sandy and ho_co:

 

Thanks for your analyses.

 

I suspected the desk lamp and the WB, too, but that piece of foam is very smooth and even without marks or patterns when I held it up against strong light, only 3" x3" and it completely covers the lens hood. The desk lamp has a frosted bulb which I thought might be okay for even lighting. But as you suggested a foot and a half away from the lens might not be far away enough for optimal even lighting and that could very well be one of the sources for error.

 

Today I have overcast here and I cannot generate new profiles with sunlight, instead I put a piece of nice and smooth stock white paper directly in front of the lens hood pointing the lens towards the sky avoiding all tree tops or buildings and took two pictures for generating profiles with the lens set at infinity and f/4.5. One picture was with the UV/IR filter off, the other with the UV/IR filter on the lens, and the menu was set to OFF and ON+UV/IR accordingly, both over-exposed at +2-1/3 stops.

 

The first profile I generated was without filter. I did not touch the luminance and chroma setting. I took a picture without the filter ( setting in menu OFF ), then processed it with this new profile. Everything looked fine. There was just a tad of cyan on the right but it was not that noticeable.

 

The second profile was with the filter, both on the lens and in the menu setting. A picture was also taken with the exact same setting and then processed with this with-filter profile. Luminance and chroma were left untouched at the default 1.00. The processed image showed magenta again, just like yesterday. Once again, when I went in to play with the luminance (0.80) and chroma (0.70) setting the picture came out better.

 

It seemed to be related to the filter. Without the filter the correction works fine but with the filter it over-corrects and require intervention. But then again there are so many people on the forums having success in your program then it must be something I was doing incorrectly.

 

I am using the CornerFix v.1.0.0.0., M8 with 2.004 firmware. the CV15 is the silver version, and the filter is Leitz UV/IR cut 13416.

 

When the sun comes out I am going to try again.