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Input/Output/Workflow Scanning, printing, color management, and discussing best practices for control and repeatability

Colour correcting skin by volume

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  #1  
Old 08-09-2007, 07:42 PM
mikoe mikoe is offline
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Colour correcting skin by volume

I have been frustrated by the flat, pinkish (or greyish), sallow look of skin from various digital cameras. Only recently, I tried the conversion to CMYK then entering values (Y30,M24,C8) which seems to work fairly well most of the time for caucasian skin. Only problem is this workflow is very time intensive. I can't figure out how to do an action for it as right after converting to cmyk and opening up curves, you have to use command shift + eyedropper tool. Since the point you click on will vary every time, how can you do an action for it? Is there a better, simpler way?

Essentially my question is, how do you guys colour correct for skin in large batches (hundreds of photos at a time)? Is there a plug-in for photoshop that's fairly consistent with flesh tones? I know how to do it using the above method, and I'm very happy with the results, but it's a 10 to 15 step process, and it's just not realistic going forward. This is the missing link for my wife, who's a photographer. She can't comfortably switch completely to digital because of this skin tone dilemma.

It's so close right now. Actually got everything calibrated to the point where I can take photos I've corrected to the lab, and they return prints that are pretty close to what's on my screen (holy grail?). Now if I could just get this skin tone thing nailed!

EDIT:
I added an example of an image that has a poor exposure and needs work, just for illustrative purposes. This is the in the ballpark of skin quality I'm referring to. Even the corrected version is probably too yellow, but you get my point.

http://i116.photobucket.com/albums/o...ginalimage.jpg

http://i116.photobucket.com/albums/o...35/ccimage.jpg

Last edited by mikoe; 08-09-2007 at 08:14 PM.
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  #2  
Old 08-09-2007, 07:50 PM
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mistermonday mistermonday is offline
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Re: Colour correcting skin by volume

Mikoe, it is hard to tell what you mean by pinkish greyish sallow skin, without seeing a sample or two. However, if you are getting this consistently, then there could be something wrong with your camera or its settings. I use several digital cameras and consistently get excellent skin tones. The other possibility is that your workflow, either on import (color management) or post processing is modifying the image's color. It might be a good idea to post a sample or two here for comment.
Regards, Murray
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Old 08-10-2007, 12:15 AM
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mistermonday mistermonday is offline
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Re: Colour correcting skin by volume

The orig image looks "flat" or washed out. This is usually what you get when either the Contrast and / or the Saturation setting in your digital camera is set on the low side, or your camera may be set that way by default. If you look at the histogram, both the composite and the individual R,G,B, channels you can see that all of the data is bunched up in a narrow peak in the center, with exception of small amounts on the right side representing the blown out dress. Typically you can fix these images with a curve adj layer to boost the contrast. Often a Z shaped curve but in this case a S shaped one. A small movement will make a big difference as you can see by the one I used below. A small increase in Saturation is often helpful or required.
If you do not want to have to retouch many images, then I recommend you go into the settings menu of the camera and bump up the default contrast setting to the next level. If images taken of bright colorful scenes like lanscapes etc also look washed out you may want to boost the saturation setting in the camera as well.
Regards, Murray
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File Type: jpg Mikoe Screenshot.jpg (76.1 KB, 23 views)
File Type: jpg Mikoe Rev MM.jpg (56.1 KB, 52 views)
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Old 08-10-2007, 05:09 AM
duwayne duwayne is offline
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Re: Colour correcting skin by volume

I looked at the properties and they indicated the image was taken with a Nikon D70. I agree with mistermonday that it appears to be a problem with the camera settings. I have a D80 but think that D70 has about the same adjustment. On the Shooting Menu select Optimize Image then Normal (which is still a little soft on the D70) or Vivid. The other option is to use Custom.

For existing picture, my "first cut" (in RGB mode) is to dup background then Image => Adjustments => Levels and press Auto. In the Levels window under Options, I check the Snap Neutral Midtones and Enhance per Channel Contrast. The results have a little more Cyan than I like.

Next, dup background again and change mode to CMYK (don't flatten) and repeat the above steps (Same setting in the Levels Option window). The results on CMYK Levels Auto are a little too red so I blend (with the opacity slider) 50% RGB Levels Auto with 50% CMYK Auto. See attached blended results below.

This can all be recorded as Action. I've never tried it but think that Actions can be run in batch mode.

BTW - Here's a web page that desctibes your problem and two other solutions.
http://www.smugmug.com/help/skin-tone
Attached Images
File Type: jpg originalimage-a.jpg (66.0 KB, 25 views)
File Type: jpg originalimage-levels auto.jpg (69.7 KB, 39 views)
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Old 08-10-2007, 06:06 AM
hkhailey hkhailey is offline
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Re: Colour correcting skin by volume

This site has a neat product for helping with the color balance of any digital photo using Black and White Points. You could incorporate it in a script but you would have to run it in interactive mode.

http://www.digigrey.com/en_index.html

It's basically a card that you use to take one picture where you are shooting, then having that photo open to use as the reference for B&W points. I tried the concept by making my own version and printing it on white card stock and it works great.

The advantage of the Digi-grey is that it is molded in the correct shade of grey in a thick material that will not fold or fade, The black is flat and the white is a brilliant white. So, that is one item I plan to purchase in the very near future.

As far as totally automating a batch process for volume, I think quality is sacrificed for speed.
Therein lies the need to control the white balance (and other settings) as effectively as possible. "Auto" may or may not be the best setting and the flash (the problem in your original photo) is not always the best thing to use indoors like with film cameras (bet your wife doesn't believe me. Wives love the flash). You can change ISO speeds with a flick of the finger (or auto-magically) so that if you have decent light to see with, you can usually get a decent picture.

Attached is a shot that has only been resized to fit this post, nothing else at all (yet). It was taken with no flash in a church.

I recently did a wedding using mostly ambient light, also.

Take care,
Keith Hailey
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File Type: jpg 0706240001b.jpg (57.6 KB, 21 views)
File Type: jpg 0707140130.jpg (77.0 KB, 29 views)
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Old 08-10-2007, 07:22 AM
hkhailey hkhailey is offline
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Re: Colour correcting skin by volume

On using Black and white points, I use Paint Shop Pro 9, but other photo editors have the same thing that works about the same way.

It just seems easier to me with a lot less steps than CMYK, and more accurate than using the Auto Color Balance, especially using the Digigrey I mentioned in the previous post.

PSP defaults to the "Last Used" settings. So, you can Process the first shot with the digigrey in it, using the script recorder. Then run the batch with the script.

But, if you use the Digigrey and you change lighting, you need to reshoot another sample Pic. So, Instead of having one big batch, you could end up having to run several batches, one for each lighting situation (each sample) which is still much easier than doing each picture individually.

C'ya, Keith
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File Type: jpg B&W Points.jpg (98.5 KB, 50 views)
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  #7  
Old 08-10-2007, 07:32 AM
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Ziaphra Ziaphra is offline
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Re: Colour correcting skin by volume

There is some excellent info on skin here:

http://www.smugmug.com/help/skin-tone
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  #8  
Old 08-10-2007, 08:53 AM
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mistermonday mistermonday is offline
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Re: Colour correcting skin by volume

Mikoe, the inputs from the other members are useful techiques for corrective actions. However, the idea of having to twiddle and tweak every image is not one of efficiency and convenience. They should only be the exception. There should be no need to have to shoot with a white balance card.
The solution is to get it right 90% of the time in the camera.
I have a Nikon D70S, a D100, & a D200. Nikon has been very conservative in its default settings for a number of reasons, the most significant being that it is easier to correct an underexposed image than one in which the highlights are blown away. For the D100, I need to bias the exposure by +0.7 ev or else the images are slightly underexposed and flat. For the D200, it is +0.3 ev. I have not profiled the D70 but would expect it to be closer to the D100 (same technology). Nikon also sets the default contrast, Sharpening, and Saturation to a lower level. These are not faults, just a conscious decision to err on the conservative side because settings which are too high will create damage to an image which is difficult to correct. Don't be afraid to boost these settings from the custom menus. You should find a noticeable improvement and you won't need to rely on Photoshop to get good results on every photo you take.
Regards, Murray
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  #9  
Old 08-10-2007, 09:04 AM
Ant Ant is offline
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Re: Colour correcting skin by volume

You think that the guys at the lab don't color correct for printing those contacts/prints? With digital, you have to do it yourself - you are the lab. Welcome to digital photography. If you are converting to cmyk and not printing to a cmyk device, ie. converting to cmyk, making your adjustments and then re-converting to rgb to print you are doing it wrong and losing color information. Set your eyedropper to 3x3 average or 5x5, not point sample and read the numbers in cmyk, your image does not have to be converted to cmyk to correct by the numbers. Every image will be different, shot under different conditions and of different people/subjects. To my knowledge, there isn't an action or program that you can run to do this automatically with sufficient results.
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Old 08-11-2007, 04:57 AM
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Alison Alison is offline
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Re: Colour correcting skin by volume

Hi Mikoe,

I used a levels adjustment layer, and edited the red, green and blue channels. If all the images are taken in the same light, you can simply grab the levels adjustment and drag it to another image.

I would suggest looking at which white balance mode you are using.

Auto TTL white-balance with 1,005 segment RGB sensor, Incandescent, Fluorescent, Sunlight, Flash, Cloudy,Shade, Preset Custom.
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