Magenta-limiting C1 profiles & PS technique

[Jamie Roberts]

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I recently made a comment in another thread about shooting without filters, and I know there are still people who do this, since I've had separate emails in the last few days about how to fix the IR magenta black issue for the M8 without filters.

 

Rather than reply separately to everyone, I thought I'd just respond here with a summary of some techniques.

 

These are only things to lessen magenta, not solve the problem. Unless you want the IR response of the unfiltered M8 (there are those that do, especially for BW), you should be using the filters for the M8.

 

On lenses 35mm and under, my net take-away is that those filters should be the Leica ones, not BW, for instance. They are subtly different, and the Leica ones work better with wides IMO.

 

Mitigating magenta in C1: use a profile

This is old news to most people here, but you can get rid of a lot of the magenta issue in C1, because C1 lets you apply an input profile to the camera.

 

You can't do this in PS ACR, Lightroom or Aperture. Or SilkyPix, for that matter. Just in C1

 

I worked up some profiles for use in C1 and they still work on the magenta problem. You can download them here:

 

http://private.james-roberts-photography.com/M8/m8_profiles.zip

 

There are two quite neutral profiles--a high saturation one and a low saturation one--and one where the contrast and saturation are pushed to extremes, a "chrome" profile.

 

None of them are "accurate" in an absolute sense. But with the right white balance, they often give pleasant results.

 

Installing them on Windows XP / Vista is as easy as unzipping them then right-clicking "install profile". On the mac it's a little more complicated; someone will chime in on how to do that (I don't have a mac yet).

 

Photoshop tricks:

There's no way to apply a profile to ACR or Lightroom (yet). You either get the ACR look or the built-in matrix of the M8 DNG file (Both of which are much better than they used to be with unfiltered M8 files, IMO).

 

Anyway, let's say you're bringing a DNG into ACR.

 

My method here is to get the white balance for the subject correct and mostly let the magenta fall in the neutrals where it will. This is important: fixing white balance outside of post is harder than getting rid of overly magenta blacks.

 

You can also tweak the saturation of the magentas and reds right in ACR or LR. Unfortunately, though, you can't make a selection in ACR. You need PS to do that, so I just go there.

 

Next, in Photoshop, if you can select the affected area very loosely with the marquee tool, then do it. Don't forget to feather your selection to make the selection very loose.

 

Then add a "selective colour" adjustment layer to your image. Only the selection will be affected; the rest will be masked.

 

Select "neutrals" then move the magenta slider towards green, which will essentially neutralize the cast. It won't take very much. If you like, you can also adjust the red slider and blue sliders as well, but only a little tiny bit.

 

If you then select "black" on the filter, you can even open up the darkness / lightness of the black / grey.

 

Because you are working in RGB, you may affect the way the overall object renders detail. If you're worried about this, you can change the mode of your adjustment layer from "normal" to "colour" and the luminance detail should be unaffected (in truth, I'm a big believer of doing stuff like this in LAB mode, but if you don't know how to do that, don't )

 

I hope this helps. Maybe someone with more LR experience can chime in here to help folks without filters.

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[robertwright]

thanks for posting this again, I just went full circle with the CV12mm, and I can see in many cases it is best to shoot unfiltered and do the rest in post.

 

It would be great if this LeicaWiki could get going to organize things like this, it is information that everyone will eventually ask.

[Paul_S]

Installing them on Windows XP / Vista is as easy as unzipping them then right-clicking "install profile". On the mac it's a little more complicated; someone will chime in on how to do that (I don't have a mac yet).

 

In Mac OS X copy the profiles to the <hard disk>/Library/ColorSync/Profiles folder.

[Baxter]

Thanks Jamie, I've found them very helpful

 

For Capture One V4 beta I recall having to do some renaming and copying to specific folders which was specified in another thread. Might it be best to place them here at the top of this thread with your other helpful instructions?

 

I'm finding that C1 with a combination of the Generic and your profiles is producing much better results than I am able to get from LR. Presume that this is because in Camera Calibration module, you are only able to specify a single correction to Hue and Saturation in each channel whereas an ICC profile is able to map many more adjustments to bring the actual response of the sensor in line with the expected values. Thus I cannot see why Adobe are persisting with this model, when using ICC profiles works so well for scanner input and printer output in Photoshop. Absence of soft-proofing in LR is detrimental to the product.

[orjanf]

Before I managed to get hold of IR filters I found all soft vegetation in this part of the world comes out various shades of red or yellow. Some palms are green if not quite right.

 

I tried profiles to no avail and then did my best to correct them in LR.

 

This is the best I could do using the HSL controls.

 

It is still very far from right and IR filters seem to be the only (fortunately easy) solution

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[Jamie Roberts]

Yes, foliage is hard. But there's plenty of ways to augment the green in those images. White balance is the key suspect here in both the original and worked shots.

 

How did you set it? The AWB on the M8 is lamentably, still broken.

 

A 5 second play with PS selective colour gives you this:

 

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though I have no way of knowing how "accurate" that is. It's certainly greener without getting rid of the "browns"--or blues--in the shot.

 

IOW, there's precious little magenta here to worry about, so I'm not sure why you posted this here. We weren't talking about foliage, but about synthetic blacks.

[Dan States]

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Jamie, your post tonight prompted me to load your profiles in C1 LE and go back to the images I shot before I got an IR filter. I know I'm pretty late in saying this, but the results are excellent!

 

In all the images I have put the profile through the magenta tint in black clothing is effectively removed, and the overall impact of the image is not changed in the least.

 

I will be using the profile for all my shots made with my 21mm Biogon, which is uncoded. I had been using cornerfix with good results, but I prefer this solution as it works perfectly with C1. Off with the filter!

 

Thanks for all you work!

 

Dan

[orjanf]

We weren't talking about foliage, but about synthetic blacks.

 

Sorry, I assumed the issues were related as the foliage comes out fine with the uv/ir filter on.

Thank you Jamie for the advice. The improvement is impressive. I enclose another jpg of the same area straight out of camera taken with uv/ir filter attached.

Different day but same lighting conditions to indicate roughly what the colurs should be like. WB set to daylight

In the worked file I had dropped it from 5700 to about 4800 in LR

These plants were in mostly in deep shade where the exposure is relatively long and, I guess, the IR component relatively high.

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[Jamie Roberts]

@ Dan--glad it works ok for you on those occasions where you need it! It's certainly a first step to recovering the colour in an unfiltered shot. Since my workflow usually also includes a trip through PS for printing, it's not the endgame for me. But I was always surprised at how workable the profile really was, especially in tungsten light.

 

@ Orjan--you're right, of course, and I apologise for coming across too strongly in my response. Foliage is the very hardest thing to work without a filter in my experience, because in a sense there's nothing but magenta where green should be...

 

And I see you're setting WB by hand, which in shots like those, is not a bad approach. Filters obviously give you the right colour balance there, but again it's surprising to me how much you can do in post.

 

For the record though, all my lenses have filters these days, and I only take them off when I think I'm going to get some undesirable artifacts from the extra plane of glass (it happens with very bright point sources sometimes, like candlelight).