Color Cast Removal part deux

MarkR

As threatened here, I have an image to work on in which the elimination of the color cast is crucial to the (ahem), artistic vision of the photographer, such as it is. :rolleyes.

Here's the setup:

Shooting raw with my K20d with 35mm f2.8 macro at the Memorial Art Gallery. No flash, no tripods or monopods allowed. Very variable lighting so I'm shooting high iso and AWB. Quite frankly, I'm struggling to keep up with my 5 year old Egyptologist, who desperately wants to see the mummy & sarcophagus of Pa-debahu-Aset:

So I'm walking/trotting down this corridor, and in all this antiseptic museum white, I see these bursts of green around me: the green of sleeve to the left, the green of a stained glass piece, and a painting on my right.

Here's the vision as I raised camera to eye: antiseptic white setting with small bursts of vivid colors, especially greens, on the left, center, and right of me.

When I say vision I'm not trying to be pretentious-- I know this snap isn't going to win any awards-- I just want to be clear what I'm attempting to convey with this picture.

Here's the original, coverted directly from raw. I do use a custom Adobe color profile, as the canned Adobe profile for my camera is quite bad. Anyway, it's underexposed and has a strong cast to it due to the (tungsten?) lights. It's underexposed probably due to the bright stained glass piece directly in front of me fooling my meter.

[URL="[url=http://hobbyist.smugmug.com/Photography/DGRIN/DGRIN/2951431_zDH69#1013419252_ksyN8-A-LB][img]http://hobbyist.smugmug.com/Photography/DGRIN/DGRIN/gallery-WB-noise/1013419252_ksyN8-L-3.jpg[/img][/url]"][/url]

Here's I white balanced the image as best I could, fixed exposure, and applied some fairly heavy noise reduction:



The next one is my best attempt at cast removal within raw: using the WB sliders and killing the mixed yellow lighting using the HSL sliders to drag down yellow saturation. Unfortunately, it starts affecting the artwork slightly:



Finally: here's the version that gets closest to my vision, and it'll take me a while to write up how I got to it, will add in when I have more time, but I think better can be done:



So I'd like to see how others approach this, given the parameters and the vision I've provided.

If I did this right, you should be able to click on the image to go to the gallery where the originals should be available for download. I'll have to see about finding a way to get the original raw file available as well.

pathfinder

Mark, this is an interesting situation, and a fairly common one I think today. I was not there so I need some information about the scene. I gather the lighting is a mixture of tungsten and fluorescent, giving the yellow green overall tone? Were the walls or the floor REALLY this white? If so, that makes things much easier, of course. You could have shot a grey

I do find fluorescent lighting a lot more today with the advent of Compact Fluorescent energy saving bulbs ( CFLs ) - they fit canisters, and even look like tungsten bulbs, but are green light, not warm yellow tungsten.

You could have shot a white surface to create a neutral jpg for a later custom white balance like with a WHiBal card, or used and Expo disc, but when just casually wandering along is not usually when we have color balance tools at our disposal. I do like this tool a lot - Shoot a frame of it in Av mode and it gives you a jpg for custom white balance, a frame to use in Adobe Camera Raw to use an eye dropper on for WB, and gives you an exact exposure right out of the blocks because it is a mid grey and your shutter speed in Av mode should put the spike in the histogram dead center. Use that exposure for shooting and you should be golden.

I looked at your jpg that you get by clicking on your image. I think you did a very good job, I found far more noise than your final image displayed when I tried to raise your exposure and correct your color balance.

MarkR

pathfinder wrote: »

Mark, this is an interesting situation, and a fairly common one I think today. I was not there so I need some information about the scene. I gather the lighting is a mixture of tungsten and fluorescent, giving the yellow green overall tone? Were the walls or the floor REALLY this white? If so, that makes things much easier, of course. You could have shot a grey

I do find fluorescent lighting a lot more today with the advent of Compact Fluorescent energy saving bulbs ( CFLs ) - they fit canisters, and even look like tungsten bulbs, but are green light, not warm yellow tungsten.

It was probably either tungsten or cfs that were very yellow-- as I said, I wasn't really paying as much attention as I should have. The mummy was calling to my child. :lol

But I remember everything being very white (walls, floor, ceiling.), which is why the greens stuck out at me.

And yes, I was not shooting smart when I shot this-- I'd like to think next time I would stop and at least use my ColorChecker passport (didn't own it at the time), but who knows. I did get at least one image I like out of that trip, so it wasn't a complete waste of time to bring the camera.

pathfinder

I play tourist a lot too, especially in museums.

Sometimes I can find a known neutral in the scene to balance off of, and sometimes you just have to wing it.

jjbong

pathfinder wrote: »

I looked at your jpg that you get by clicking on your image. I think you did a very good job, I found far more noise than your final image displayed when I tried to raise your exposure and correct your color balance.

Mark,

I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas?

BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot.

In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

jjbong

pathfinder wrote: »

I do like this tool a lot

Maybe this should be a new thread. How is this different from a WhiBal?

MarkR

jjbong wrote: »

Mark,

I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas?

BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot.

In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

I really need to make the raw available somehow. In LR3 I used pretty heavy color noise reduction (70%/50 detail) and moderately strong (~30%) luminance noise. I'm still trying to recreate what I did to get to the final shot-- I didn't document very well what I was doing, story of my life. I don't remember doing anything explicit to shadow areas, however.

MarkR

Raw is here: http://dl.dropbox.com/u/23168823/gallery-WB%20%26%20noise.PEF

pathfinder

jjbong wrote: »

Mark,

I started to play around with this image and was a bit confounded by the noise. Maybe it's because I didn't start with the RAW. Did you do anything explicit in your workflow to eliminate the noise in the dark areas?

BTW, a very nice communication of your vision and quite a good realization of it, granted not an award-winning shot.

In thinking about your vision, sterile means not only neutral but pretty bright. You did a pretty good job of getting both of these.

I had exactly the same issue, John, the noise just became very large, and hence I bailed. Since Mark has uploaded the RAW file we can give that a try now.

pathfinder

jjbong wrote: »

Maybe this should be a new thread. How is this different from a WhiBal?

A WhiBal card is a small card 5 x 7 or even 3 x 5 inches that is included in the image, at the time of shooting, and then used INSIDE Photoshop or ACR to click on with the White Balance tool, to obtain the correct color balance for the image. This can work pretty well.



The BalanceSmarter or the Lastolite color balance reflector, is an 18 % non specular grey disc - anywhere form 12 - 30 inches in diameter. You hold up the reflector in the ambient lighting, and with your camera in Av mode, shoot a full frame of the reflector. This will capture an even neutral grey image that on your camera's RGB histogram will appear as a single spike in the center of the span in each of the R,G,B channels. This frame can then be used to set a custom white balance within the camera to shoot custom white balanced jpgs. It also gives you the exposure, since you set the aperture, and the camera chose a shutter speed to give a single spike in the middle of the histogram. In other words, you use the same aperture and shutter speed ( EV ) that the camera used for shooting the grey card.

I wrote about color balance tools here - http://www.dgrin.com/showthread.php?t=90438


One of the nice things about the Lastolite reflector, or the BalanceSmarter disk is that they have a center cross of white lines for your camera to AF onto, and hence you do not have to remember to turn your AF off and then back on again as you do with white paper or an Expodisk, or a SpectraSnap ( which is another filter like the Expodisk )

All these tools do work, some are just faster and a bit easier. If you like the WhiBal card method, there is even a white bracelet of tungsten dioxide that I included in the discussion about color balance tools linked earlier.

jjbong

Here is my attempt. Noise was a problem throughout, as you might expect from a shot taken in these circumstances. Anyway, I didn't try to perfect the noise reduction, as that's not the point of this exercise, but I did try to make it not particularly distracting.

In Camera Raw (I'm using Photoshop CS3), I adjusted the exposure (higher) and black (to zero). I also set the white point using an arbitrary point on the white walls.

In PS, to eliminate noise, I used the Noiseware plug-in with defaults. I was left with a lot of yellow noise, so I went into LAB, and blurred the B channel, gaussian, at 15.8 px.

My interpretation of how to realize Mark's vision (sterile, burst of green color) was very light neutrals (e.g. white) except for the colors on the right of the image. So I had to kill the residual yellows in the darker parts of the hallway. I did this also in LAB, using a second layer, and Apply Image to the B channel, using the B channel of the background layer, inverted, 50%, Darken. That killed the casts nicely, giving this:



It has some of the characteristics of Mark's vision, but it's not bright enough or colorful enough.

I used the standard PPW color enhancement curve in the A and B channels, at a pretty high opacity (59%), and I used an L curve to brighten everything to make it more sterile. The final thing was to make the Exit sign less distracting by desaturating it with the Sponge tool. Through all of this, I ignored the blown-out areas in the background, as Mark did, I think correctly.

Sharpen and done.



I think it's somewhat better than Mark's attempt, so we'll see what Mark says. Maybe the green needs to be saturated more and lightened, which is not hard. Noise remains, but it may not be possible to get perfection here.

MarkR

I like the fact that you managed to keep the green reflections from the stained glass in front. The blue painting on the right I remembered as being more blue, but looking at the gallery's website, looked closer to John's: http://magart.rochester.edu/Obj731?sid=40024&x=659571

On first glance, yours seems somewhat reddish, but I have to think about this.

pathfinder

Marc, I finally went back with your RAW file to create this image..

I satred with the file in LR3, but had to take it out to CS4 where my NoiseWare plug in lives.

I took my white balance from the reflector around the tungsten bulb at the end of the hall ( I assumed it was Tungsten )

Once in Photoshop I used curves to reduce the blues in the upper tones, and the greens as well ( Maybe it was fluorescent after all - not sure )

I like what you and John have done to the hallways, but they are so white they look like a hospital, and the green transparency at the end of the hall looks all burned out. I decided that your original frame might be correct for that central area, so I brought a second unaltered copy of the image into Phtooshop, and airbrushed the green picture and green reflection at the end of the hall back into my editied image for this result.




The full size image is here - http://pathfinder.smugmug.com/Other/Large-files/1789718_YdTAs#1214933446_dAKNk-O-LB

The close end of the hallway in my image is much bluer, I suspect there was a window off to the left perhaps, and I did not correct that area of the image, and I left it dimmer as well. But I prefer the darker forground with the light and contrast at the end of the hallway where the transparency is displayed... It is one interpretation.

MarkR

Pathfinder, Interesting that both your and John's images have a distinct magenta -- and in your case, even purple--tint. Definitely like how you brought back the stained glass and the reflection.

Just out of curiousity, what DNG profile did you use in raw under the color calibration tool? As I mentioned before I use a custom dual-illuminant one because the Adobe Standard that shipped with LR3 was very off from my camera, specifically a magenta tinge. (The "Camera Standard" profile is much closer to my custom profile than the Adobe one is.)

MarkR

Here's another picture of that same hallway during another visit for reference. I feel like an archivist, finding pictures I didn't even know I had.
Looking at the raw, the only thing I did was custom white balance (2500/+8), raised the exposure +.70, and raised the brightness in the highlights.

pathfinder

Marc, The file I received for some reason was a PEF, but my LR called it a jpg, not RAW file, and thus the profile was embedded, and I was offered no choice about the camera profile.??

My goal with this image was to correct the far end of the hallway, which I felt was lit by the artificial lights, which I assumed were tungsten. When I measure the end of the hall I think the walls are pretty neutral. Both your and Johns's images are much brighter in the forground than mine. Mine is actually blue in the upper left corner still, one of the reasons I suspected an outside window up there.

I went through a phase where I tested different profiles ( Canon has at least 6 or 8 different ones )for an image, but for EOS images, now I just use Adobe. It seems to work pretty well for my Canon cameras.

I wasn't certain if the stained glass and reflection would match your remembrance, but am happy it meets with your approval. I kind of thought is was the center of you image originally, and I hoped it had been exposed correctly at the time. Seems like that was an accurate guess.

Your new image of that hallway is probably lit by tungsten without contamination by sky light. I see the stained glass is similar to my rendering too.

MarkR

Hmm.. not sure if you were only getting the embedded preview jpg? Not sure why it would not let you modify the PEF custom calibration-- K20D has been supported since LR1.4!

I will check the dropbox file again and see if I can see what went wrong.

Edit: looks right, at 17.1 MB. I can try converting to DNG and posting to see if that helps.

pathfinder

The file was a PEF file, but it displays with an embedded profile???

MarkR

Definitely should not be an embedded profile! I believe that is only for pre-rendered images (jpegs and such.) If I pull it from my dropbox and open it in CS5 I get the usual range of profiles (4.4, Adobe, Camera, Custom). I have converted it to a dng and uploading it.

DNG http://dl.dropbox.com/u/23168823/gallery.dng

jjbong

MarkR wrote: »

On first glance, yours seems somewhat reddish, but I have to think about this.

I did a pretty aggressive color enhancement using an AB curve in LAB to enhance the saturation of the greens on the right, and this would have also enhanced the magentas. The fix is to change the curve in this step to be steep in the negative A region and less steep in the positive A region. Alternatively, use a blend-if to reduce the enhancement in magenta areas.

If you like the overall effect, I can re-do with this change. Otherwise, otherwise.

MarkR

Ok, coming back to this image, I thought I'd take a look at some ways to remove color casts in general, and how they affect this image in particular.

First, of course, is a strict raw-based workflow, which I prefer. Unfortunately I was never quite able to get there in LR3/ACR. I suspect that if I was using a tool like Bibble or Aperture, which have more tools available for local correction, things might have gone smoother. Waiting for Lightroom 4 ...

In the meantime, it certainly doesn't hurt to do the heavy lifting (white balance) in raw, and then move into Photoshop, which has a dizzying array of tools for dealing with this kind of issue.

My new favorite tool (because I recently found out about it and it's surprisingly effective,) is the "neutralize" option in the Match Color adjustment. I like it because 1) it often works very well, 2) doesn't seem to adjust contrast the way one of the Auto tools does, 3) and it is incredibly easy to use. When I ran it on this image it moved a little to far into blue/purple territory. Luckily it comes with a very nice fade slider-- sliding it to about 50% gave me this:



Not bad for less than 10 seconds worth of work!

Another method that is often effective is the curves tool-- but in RGB mode I quickly became frustrated. .

Moving into L*a*b* mode gave me a little more flexibility-- by flattening the middle of the a* and b* curves I was able to kill the cast completely-- at the expense of the more saturated colors. I was able to mask the paintings and more saturated items back in, and the end result is fairly satisfactory, I think:



My last try was with a commercial plugin: Colorwasher from thepluginsite.com. Ideally, this is a run and go plugin, but with this kind of image does require a little bit of fussing over the sliders. I ended up fiddling with just four: the three main color cast sliders (cast, shadows, and highlights), and the fix saturation button. The end result is pretty decent, and slightly faster than the L*a*b* method, but not by much. It does also keep a slightly yellow cast at the end of the hallway which I haven't made up my mind about.



(Note, I did not attempt to match brightness/exposure across all three images.)

Trying to bring some closure to this:

1. Get it right in camera, so you don't have to fool around in Photoshop. Words to live by.

2. It is critically important to understand and be able to communicate what the desired outcome of your "fooling around in Photoshop." If you don't know where you're going, you can't tell when you're there. Furthermore, "obvious" corrections aren't always the desired ones.

3. I hope we can get more dgrinners to participate in these kinds of threads! Lots of smart people with smart ideas around here.

jjbong

MarkR wrote: »

Moving into L*a*b* mode gave me a little more flexibility-- by flattening the middle of the a* and b* curves I was able to kill the cast completely-- at the expense of the more saturated colors. I was able to mask the paintings and more saturated items back in, and the end result is fairly satisfactory, I think:

I also found LAB very useful in the exercise. When you mention masks, I'm not sure whether you mean constructing a mask of the object or masking based on color (A and B channels). Either works, and I think generally masking by color looks less "photoshopped". But however you did it, your result looks natural. The other mask-like option here is blend-if. This image is pretty ripe for that, as the colors you want to enhance are generally not those you want to get rid of (casts)

1. Get it right in camera, so you don't have to fool around in Photoshop. Words to live by.

Right on. Over time, I've noted the mistakes I've made taking the shot that I had to correct in post. In this case, I'm not sure how you could do it (other than improve the exposure). The color is caused by factors you can't correct in the shot, lighting mainly.

2. It is critically important to understand and be able to communicate what the desired outcome of your "fooling around in Photoshop." If you don't know where you're going, you can't tell when you're there. Furthermore, "obvious" corrections aren't always the desired ones.

I thought you did a commendable job of stating what you saw and what you wanted to bring out. This also applies in composition. Clearly, you can't specify it 100%, the yellow in the hallway background being a good example of this. Do you want them or not?

3. I hope we can get more dgrinners to participate in these kinds of threads! Lots of smart people with smart ideas around here.

Right on.

MarkR

jjbong wrote: »

I also found LAB very useful in the exercise. When you mention masks, I'm not sure whether you mean constructing a mask of the object or masking based on color (A and B channels). Either works, and I think generally masking by color looks less "photoshopped". But however you did it, your result looks natural. The other mask-like option here is blend-if. This image is pretty ripe for that, as the colors you want to enhance are generally not those you want to get rid of (casts)

Actually, I just created layer mask and used a soft black brush to paint back in the areas where I wanted to increase the color.

Right on. Over time, I've noted the mistakes I've made taking the shot that I had to correct in post. In this case, I'm not sure how you could do it (other than improve the exposure). The color is caused by factors you can't correct in the shot, lighting mainly.

I think if I had slowed down I could have controlled exposure better. I also now own a Colorchecker passport. Remembering to use it is another matter ... :lol

I thought you did a commendable job of stating what you saw and what you wanted to bring out. This also applies in composition. Clearly, you can't specify it 100%, the yellow in the hallway background being a good example of this. Do you want them or not?

Right on.

beebibi

So I'd like to see how others approach this, given the parameters and the vision I've provided.


Hi, Mark... you did well - definitely not easy! I used your JPEG image. I found out that this task was not a straightforward color-cast job. Trial and error - If I hadn't taken descriptive notes in the layers I would have been totally lost....:D

Thanks for letting me have a go - I just post the end result for now and if necessary I will go back and piece it all together...

(Please bear in mind that English is not my native language - I am American but came originally from Germany so if something reads funny pls tell me...:D)

beebibi

[ Oh, dear... I just realized that this is a thread from March 2011 - well, never mind, I did enjoy this and will follow the tutorials - need to get to know more about LAB and "Blend If" and, of course there will be always something to learn

MarkR

Beebibi,

Don't worry about the age of the post-- especially in Grad School. Consider instead the techniques that are discussed. Are they still timely and relevant? Do you have a better way of doing them?

It would be great if you could show your work.

beebibi

MarkR wrote: »

Beebibi,

Don't worry about the age of the post-- especially in Grad School. Consider instead the techniques that are discussed. Are they still timely and relevant? Do you have a better way of doing them?

It would be great if you could show your work.

Well, I did post my interpretation of your idea - look above and yes, the techniques are still relevant, of course....there are so many ways to get to great results, aren't there?

MarkR

beebibi wrote: »

Well, I did post my interpretation of your idea - look above and yes, the techniques are still relevant, of course....there are so many ways to get to great results, aren't there?

There are a million ways to achieve a given result in Photoshop. However, this is grad school which deals, among other things, with techniques and ideas.

beebibi

MarkR wrote: »

There are a million ways to achieve a given result in Photoshop. However, this is grad school which deals, among other things, with techniques and ideas.

I am not quite sure that I understand ... I worked thru from your original JPEG image (untouched I thought) to the pic I posted in my previous message and hoped to get feedback on whether I got close to your ideas of what you wanted to achieve with this shot. If you thought it was worth it and of any interest to anybody to get further info on my technique - how I got from 'here' to 'there' , then I would be happy to go thru the steps I took...

Here is the image I submitted before:

beebibi

MarkR wrote: »

Ok, coming back to this image, I thought I'd take a look at some ways to remove color casts in general, and how they affect this image in particular.

First, of course, is a strict raw-based workflow, which I prefer. Unfortunately I was never quite able to get there in LR3/ACR. I suspect that if I was using a tool like Bibble or Aperture, which have more tools available for local correction, things might have gone smoother. Waiting for Lightroom 4 ...

In the meantime, it certainly doesn't hurt to do the heavy lifting (white balance) in raw, and then move into Photoshop, which has a dizzying array of tools for dealing with this kind of issue.

My new favorite tool (because I recently found out about it and it's surprisingly effective,) is the "neutralize" option in the Match Color adjustment. I like it because 1) it often works very well, 2) doesn't seem to adjust contrast the way one of the Auto tools does, 3) and it is incredibly easy to use. When I ran it on this image it moved a little to far into blue/purple territory. Luckily it comes with a very nice fade slider-- sliding it to about 50% gave me this:



Not bad for less than 10 seconds worth of work!

Another method that is often effective is the curves tool-- but in RGB mode I quickly became frustrated. .

Moving into L*a*b* mode gave me a little more flexibility-- by flattening the middle of the a* and b* curves I was able to kill the cast completely-- at the expense of the more saturated colors. I was able to mask the paintings and more saturated items back in, and the end result is fairly satisfactory, I think:



My last try was with a commercial plugin: Colorwasher from thepluginsite.com. Ideally, this is a run and go plugin, but with this kind of image does require a little bit of fussing over the sliders. I ended up fiddling with just four: the three main color cast sliders (cast, shadows, and highlights), and the fix saturation button. The end result is pretty decent, and slightly faster than the L*a*b* method, but not by much. It does also keep a slightly yellow cast at the end of the hallway which I haven't made up my mind about.



(Note, I did not attempt to match brightness/exposure across all three images.)

Trying to bring some closure to this:

1. Get it right in camera, so you don't have to fool around in Photoshop. Words to live by.

2. It is critically important to understand and be able to communicate what the desired outcome of your "fooling around in Photoshop." If you don't know where you're going, you can't tell when you're there. Furthermore, "obvious" corrections aren't always the desired ones.

3. I hope we can get more dgrinners to participate in these kinds of threads! Lots of smart people with smart ideas around here.

Mark, I am glad I did find this forum - very informative. I like your LAB mode try the best. Just recently I got into it a bit more and think it's extremely helpful.

Thanks for spelling it out and trying different approaches !

MarkR

beebibi wrote: »

I am not quite sure that I understand ... I worked thru from your original JPEG image (untouched I thought) to the pic I posted in my previous message and hoped to get feedback on whether I got close to your ideas of what you wanted to achieve with this shot. If you thought it was worth it and of any interest to anybody to get further info on my technique - how I got from 'here' to 'there' , then I would be happy to go thru the steps I took...

Here is the image I submitted before:

I think you did great. How did you achieve your final image. Show your work!