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Welcome aboard!! I would recommend as a starting point getting some good books on the subject. Two books I would suggest is Katrin Eismann's Photoshop Restoration & Retouching and Michael Kieran's Photoshop Color Correction. They're the real pros at explaining color correction which can be very simple or extremely difficult. Both books come with a CD of images that you'll find very helpful in working thru the color correction problems.

Cheers
Dave

Agree with Dave ..

Katrin's book is almost a "mandatory" buy for anyone doing photo restoration.

In the meantime, a couple of articles to get you going...

http://www.adobeevangelists.com/pdfs/photoshop/tipsandtricks/CorrectByNumbers.pdf

http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf

If you're working in CMYK, Dan Margulis has written a great book specifically on color corrention, although he does go into an amazing amount of detail, so prepare to have your mind blown away! The 2nd link is a copy of one of the chapters out of his book.

Hope you get on ok.

Victoria

Hello and welcome to RP!

The easiest way to color correct an image is by using the curves neutral picker: Go to image/adjustment/curves. Click the neutral color picker between black and white color picker in the lower right of the window. Locate a real neutral spot in the image, gray, dark white or something and click. This automatically adjusts the colors.

Another way is to use color balance or the curves tool with the three channels, but that's a little too pro I guess?

http://www.adobeevangelists.com/pdfs/photoshop/tipsandtricks/CorrectByNumbers.pdf

Might help as well!

Patrick

Dawghair
Welcome to RetouchPro

What program are you using?
Are you working in RGB or CMYK?
If all your pictures are similar then post one here and someone will help.

The second link that V.bampton posted (above) is probably the best tutorial on the WWW.

I have a couple of related questions.

Is there anything that you can’t do using curves in RGB alone?
Is there any advantage to converting to LAB etc?

I understand I can adjust brightness/contrast/colour etc.
But What about something like copying the red channel to the blue channel?
Is that possible using only curves? Or am I doing that already in a different way?


Ken

Hi dawghair,

Welcome to RP! :pleased:

This is something I really can't help you with .... :o: .... but I know you'll get a lot of help by Members who are really very good at it ...

I'm merging your two Threads since they are about the same topic ... :classic:

Dawghair
I have a couple of related questions.

Is there anything that you can’t do using curves in RGB alone?
Is there any advantage to converting to LAB etc?

I understand I can adjust brightness/contrast/colour etc.
But What about something like copying the red channel to the blue channel?
Is that possible using only curves? Or am I doing that already in a different way?


Ken

Hi Ken

There are LOADS of things you can't do in RGB curves alone. In a real world situation though, processing loads of pictures, sticking with RGB will do you nicely. LAB is great in that you can affect the luminosity values without affecting the colour at at all, but unless you're working on a nightmare picture, it's rarely needed.

Copying the red channel to the blue channel... you mean literally replace the blue channel with red? I can't think of a way of doing that with curves. A direct replacement - how about you turn off the other channels, so you can only see red - ctrl+A to select all, ctrl+C to copy, turn the red channel off, and the blue channel back on, and ctrl+V to paste - and bingo, you now have a replaced channel. That changes the colours though, obviously - is that what you had in mind? What are you planning on accomplishing?

If you can post a couple of examples Ken, we might be a bit more help!

Victoria

Patrick

“Locate a real neutral spot in the image”

You make it sound easy. I’m still learning and maybe this gets easy with practice. One way I have found to ‘Find’ a neutral is to set the foreground colour to mid grey then
Select > color range > sampled colors
By lowering the fuzziness the mid greys can be found. (if there is one)

Victoria.
Thank you for your response. I suppose my question should have been
Is there anything you can’t do with curves that is in the image > adjustments section

I was thinking of very damaged pictures. The way you mentioned of replacing a channel is the way I do it now (or use the channel mixer). I was thinking that because the channel mixer is in the image > adjustments section there must be a way to do this with curves.
I think I’m beginning to answer my own question. Replacing a channel is an attempt to improve the luminosity of that colour.

Ken

I suppose my question should have been
Is there anything you can’t do with curves that is in the image > adjustments section

Curves are powerful, but the other tools are there for a reason - they can't all do exactly the same job. There is some crossover between tools - there's more than one way to accomplish almost everything - but just using curves won't cover every scenario.

Off the top of my head, I can't think of a way of increasing the saturation a great deal just using RGB curves, whereas with Hue/Saturation that would be easy. Selective colour is another tool that is almost impossible to replicate using curves alone. Does that make sense?

I was thinking of very damaged pictures. The way you mentioned of replacing a channel is the way I do it now (or use the channel mixer). I was thinking that because the channel mixer is in the image > adjustments section there must be a way to do this with curves.
I think I’m beginning to answer my own question. Replacing a channel is an attempt to improve the luminosity of that colour.

Sounds like you've got the idea Ken. It is one of those situations that there are loads of different ways of working, and the way you choose will depend entirely on the specific picture.

Victoria.
Thank you for your reply.

One reason for my questions is that I downloaded Curvemeister demo from
http://www.curvemeister.com/
It watermarks the results but it is fully functional and I liked the idea of being able to pin skin tones, hair etc all in one tool.

But I suppose a tool like this would be more useful to a learner, and someone more advanced would not really need these extra curves features. Like you have just explained it still cannot do everything.


Ken

Hi Ken,

sorry for being so unprecise. What I meant by saying "find a neutral spot", I'd post an example:

Imagine you have a photo with a sever blue cast, anything on the picture is blue. Then just locate a spot on your picture that you know right from your mind that it's supposed to be gray, white or something in between, without any color. This is a neutral!

Does that lighten things up?

Patrick.
Thank you for your reply. I think I’m beginning to understand.

I am at the moment trying to work through this workflow
http://www.luminous-landscape.com/tutorials/workflow1.shtml

It seems pretty good and I think Dawghair may be interested in reading it.

I just wondered what you all think of a workflow like this. Is there anything missing?

Sorry if this is off topic a bit

Ken

I had a quick view of this workflow, but I guess it's worth looking a little bit closer ;)

Two things popped into my eye:

- The author says it's needed (somewhere in the middle) to convert to LAB. I see no use in converting an image and losing valuable information occuring when converting 8-bit RGB to LAB (oh my god what a sentence)

- I also discourage using the Levels to "stretch" a histogram. If an image really has no white or black spots anywhere, why should I create them and ruin the midtones?

*goingonreading*

- The author says it's needed (somewhere in the middle) to convert to LAB. I see no use in converting an image and losing valuable information occuring when converting 8-bit RGB to LAB (oh my god what a sentence)

I'd always understood, Patrick, that converting to and from LAB was lossless. Not quite sure where I read that, and I haven't got time to look right now as I'm meant to be getting ready for work! Any thoughts though?

Victoria

I'd always understood, Patrick, that converting to and from LAB was lossless. Not quite sure where I read that, and I haven't got time to look right now as I'm meant to be getting ready for work! Any thoughts though?

Victoria

Well, following up from my own thought, I went hunting for where I'd read it. Seems there's quite a debate going on! Anyone who's crazy enough to want to get bogged down in the debate, you'll find it here http://www.ledet.com/margulis/ACT_postings/ColorCorrection/ACT-LAB-damage.htm Dan Margulis, Chris Murphy, Andrew Rodney, and some of the other colour correction bigwigs have been debating the point.

End result seemed to be that any conversion, whether it be to LAB or anything else, does result in some data loss, but the conversion to and from LAB is pretty close to lossless, and therefore not a problem in a real world environment unless you plan on converting the file back and forth a few hundred times.

ok, i got lost a long time ago on this thread.... what is LAB? i know rgb, cmyk and hsl, but what is LAB?

Craig

ok, i got lost a long time ago on this thread.... what is LAB? i know rgb, cmyk and hsl, but what is LAB?

Craig

Sorry Craig! LAB is another colour mode, like RGB, CMYK etc, but it's device-independant. You'll find it in the Image > Mode menu along with the others. In short, the L channel is lightness or luminosity, with A & B holding the colour information. It's great for being able to make changes without affecting the colour at all - it's often used for sharpening, where you don't want to introduce any coloured halos, so you just sharpen the L channel. You can get a nice black and white by changing to LAB and throwing away the A & B channels too. There's a quick intro here http://www.creativepro.com/story/feature/12869.html

v.bampton,

thank you. i use paint shop pro 7.xx and i simply dont have this mode. i figured it was another mode like you said, but just wanted to clear this up a bit to be sure. and yes, i could see where just sharpening the 'L' would have advantages. one of these days i'll upgrade :)

Craig

Hm, may I add my two cents about sharpening in LAB?

I used to do that as well, but there's a way to avoid the problems when sharpening in LAB:

- Stay in RGB or CMYK, as you prefer and sharpen as usually.
- Immediately after applying the sharpening filter, go to Edit/Fade. Leave the slider as is but change the blending mode to Luminosity.

Same effect, but without the conversion to LAB ;)

Patrick

It's with some trepidation that I weigh in here again. Here's an interesting thread you should check out http://www.retouchpro.com/forums/showthread.php?t=10296&page=1&pp=15&highlight=sharpening

One of my posts is a close up of a blue Heron. The second image was sharpening in LAB then converted back to RGB. The third image was sharpened in RGB, faded and changed to Luminosity. To my eyes there is a very noticeable increase in black content in the feathers in the third image. To be fair, I often try them both and get very similar results. But when there have been differences, it has "always" been in favour of the LAB adjustment. Just my 2 cents "again!". To me it's worth working in LAB for sharpening but it will always be a debatable point.

Dave

One of the first things you should do is purchase a color corection plugin. For example one called Color mechanic Pro. All you need to do is look at the original image. Decide which object in the image is most definately supposed to be white. then in two more steps the entire image is color corrected.
Take a look at th my example. The left image is a digital camera set for the wrong lighting type. The right image is after a white balance. Whie balancing is the process of telling your camera "this is supposed to be white" your camera then takes that knowledge and displays all other color data properly.

Welcome aboard!! I would recommend as a starting point getting some good books on the subject. Two books I would suggest is Katrin Eismann's Photoshop Restoration & Retouching and Michael Kieran's Photoshop Color Correction. They're the real pros at explaining color correction which can be very simple or extremely difficult. Both books come with a CD of images that you'll find very helpful in working thru the color correction problems.

Cheers
Dave

I read a lot of great reviews on this Katrina's book. but one reviewer complained: "Further, there is too much restoration and not enough retouching here, and the very important Liquify Filter recieves only scant coverage."

The Lquify filter important? I've never ever used it. HAs anyone else? And what would put it at the level of "important"?
Pete Janak

I can think of a few instances where I'd use the liquify filter, but not too many involved with restoration, and in retouch, only really with "Beauty" jobs, with any regularity.

Depends on whether you do a lot of beauty work as to whether this is a "major" tool for you or not.

But if you're wondering whether to purchase Katrin's book or not, my advice is buy, it's worth every penny.

Well I’ve ordered Katrin Eismann's Photoshop Restoration & Retouching Book. and I’ve worked my way through that tutorial/workflow. It’s certainly complete if not a little overboard and controversial (LAB). But I’ve found the bits that I will find useful. The one thing that workflow does not cover is colour correction so I re-read Victoria’s Link.
http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf

I’ve read this before but it’s now beginning to make some sense. All the Pro’s seem to work in CMYK. And when talking about skintones they talk about Ratios. I can understand why they prefer to talk about ratios rather than actual numbers But I don’t understand why CMYK is the chosen mode. Why does no-one seem to work in RGB. Surely those ratios would still work in RGB and I would get the same results?

I did find one reference to RGB skintones and it was talking about ratios of
Red 150
Blue 100
Green 90

Will I get the same results?
As you can probably tell. I’m trying to avoid this RGB>CMYK conversion. I’m not sure why.


Is Michael Kieran's Photoshop Color Correction that Duv Suggested the best book to buy?


Ken

As you can probably tell. I’m trying to avoid this RGB>CMYK conversion. I’m not sure why.

You're quite right in avoiding an unnecessary conversion to CMYK, because every time you convert, you lose colour data.

Most pros correct in CMYK because that's exactly what they'll use to print - CMYK presses. Photographers tend to use RGB because inkjet printers prefer RGB data, and wet process digital labs use RGB. Unfortunately there's not much been written specifically for photographers though!

The theory is the same - find a neutral white point, black point, and midtone. Look at the RGB numbers, and any time the numbers are approximately the same, (ie. r128, g128, b128) you've got a neutral (it's actually easier to remember than CMYK!). And better still, if you get those points neutral, your skin tones should be spot on too! You can always set the eyedropper to show RGB and CMYK numbers in the info pallette if you want to double check against CMYK numbers.

It mostly comes with trial and error, and a bit of experience, but if you follow those guidelines, you should be in the right ball park. Work on adjustment layers (levels or curves are your best bet), and then if you make a mistake you can easily change it.

I tend to use 1 levels layer to adjust the picture to neutral (white, mid, and black), and then put another layer on top to add a little red and yellow back into the midtones/highlights as I prefer a warmer look.

Victoria

Ken, I would suggest the following. General color correction is perhaps easiest in RGB. Matching numbers for shadows, highlights and midtones (blacks, whites and greys) is pretty easy to comprehend and get acceptable results.

Most prepress work for fashion, glamour etc is done in CMYK and I guess it is why more info is written for skin tone correction in CMYK. This also gives you an additional ink to work with.

Flipping back and forth between RGB and CMYK can cause some degradation. How much and can you notice it should be considered.

There is a way to have the best of both worlds without degradation. It's called "Correcting in CMYK without converting the original file to CMYK". Here's how:

Select Image > Duplicate, then Image > Mode > CMYK.
Make your skin tone adjustments
Select All > Edit > Copy
Activate the original RGB file and select Edit > Paste.
Change the pasted layer's mode to Color.

The end result is a color corrected file in RGB that was done in CMYK without the degradation. Just one of many tidbits in Eismann's book.

Michael Kieran's book does not deal with skin tone correction per se but is a definitive guide to Color quality of digital images in RGB, CMYK, LAB and HSB.
It may be better suited to the intermediate to skilled but if you have any understanding at all about color correction, you should still find lots of nuggets of good information.

Dave

Thanks for your replies.

I am quite happy setting Black and White points But I disagree that this always puts the skin right. I cannot judge colours by eye and must check numbers. I can make Colour casts disappear just by staring at them.

I have just tried Duv’s suggestions.

I followed the steps and my skin tone looked great. I left the magenta as it originally was (40) and corrected the cyan from 0 to 13 and yellow from 20 to 50.
Superb I thought, so I pasted the corrected layer back into my RGB picture and set the mode to colour.
I guess setting the mode to colour is to keep the quality of the original RGB image.

I have checked the numbers and my highlights and shadows have now slipped a bit.
Should I now add a layer mask to keep the original highlights and shadows (IE just use the skin tones from CMYK) OR should I do another levels adjustment.
Or maybe I should have done the colour correction Before I adjusted the levels but I don’t think that is the correct order.


Thanks Duv. It looks like I ordered the right book.

Ken

Ken, you're now into tweaking which is a good thing in that you are trying to "fine tune" your image. Reworking your shadow numbers a bit shouldn't have too much effect on the skin tone. By the way, did you get some color shifts or did the numbers stay equal but went up or down. ie. did it go 25 25 25 to 25 30 19 or did it go to 31 31 31? Also be careful if you haven't sharpened your image yet because that can also cause color shifts. Your suggestion for a mask sounds good, just be very careful with what you have acheived. I've screwed up a ton of photos trying to tweak them to the nth degree.

Dave

Duv. Thank you

My numbers for the Highlights and shadows did not change that much but now I don’t know which are right.

Shadows have gone from 8,10,10 to 4,13,0
Highlights have gone from 252,249,253 to 247,250,255
Skin has gone from 239,174,172 to 227,184,150

But this does make the eyes and teeth a touch Blue (in theory). Also the hair has changed a touch
Now I don’t know which is correct. Would you recommend to I make a skin mask or should I flatten the image and do another levels correction for the highlights and shadows?

I was just thinking could a similar method be used for RGB>LAB for sharpening.

Ken

Shadows have gone from 8,10,10 to 4,13,0
Highlights have gone from 252,249,253 to 247,250,255
Skin has gone from 239,174,172 to 227,184,150

But this does make the eyes and teeth a touch Blue (in theory). Also the hair has changed a touch
Now I don’t know which is correct. Would you recommend to I make a skin mask or should I flatten the image and do another levels correction for the highlights and shadows?

I was just thinking could a similar method be used for RGB>LAB for sharpening.
Ken

Ken, I'm flying a bit blind here not knowing your image but maybe think about the following:
With skin tone there is usually a bit of latitude for an acceptable range. Are you still happy with the skin color? If so, don't make more work for yourself than necessary. Mask it and adjust around it.

Your original Highlite and Shadow numbers "might" be a little on the extreme side. What do you get when you rebalance to about 35 shadows and 240 highlights. Your adjusted highlite blues is blown out at 255 so I'm sure you are seeing too much blue in the teeth. So make sure you only mask the skin and not the eyes and teeth when you make your adjustments.

Sharpening in LAB is a good way to go..not the only way..but a good one. No loss in quality so you don't have to blend LAB back into RGB.

Duv

I’ve adjusted the highlight and shadow and the skin still looks great so I’ll leave it there.
I can’t wait for my book to come if there are tips like that in it.
I’ll stay with this method as I think it’s the easiest.

There are a couple of people in this thread who do not agree about LAB being Lossless. And from what I have read I think they may be right. That is why I mentioned it.

I’ve just become a senior member. People will think I know what I’m talking about now. :question:


Thanks again Duv.

Ken

I've never,ever, seen any loss in converting back and forth from LAB to RGB or CMYK. But here's a method that accomplishes the same thing and is quicker:

Sharpen your RGB image with Unsharp Mask. (For that matter it's the same for LAB or CMYK)
Go Edit > Fade Unsharp Mask
Change mode from Normal to Luminosity.

Dave

ps: congrats on becoming a senior..must make me a gereatric.

Conversion to CMYK is a good thing if you are going to press.

I do a lot of four color process printing (books, brochures, caltalog sheets etc.). You need talk with printer and determine what their preferred color space is. Obtain their icc profile, if you can, and add it to your Color Settings working space.

In the printing process, there are many colors that just don't print as you see on the computer screen. They are considered "out of gammut" for the process colors CMYK to reproduce. Converting your finished piece to CMYK (using their icc profile as the CMYK color space) will assure better results.

I always save my work in Photoshop in RGB photoshop and the last steps in preparing a graphic for magazine quality print is to save a version as a CMYK TIFF (in the appropriate icc profile) and then tweaking any final curves adjustments for contrast.

BTW... In PS, under the View Menu, you can view "Gamut Warning". This will show you (in your selected mask color) the areas of the project that will color shift when printed in CMYK. You have some control over these areas by adjusting hue and saturation before converting to CMYK TIFF. If you do a lot of prepress work, this view is also good in the color picker because it limits the color palette to colors that will print correctly in CMYK.

If you need to add text or customer logos that require PMS colors (which usually get converted to CMYK when sent to RIP, you should have a Panton "Spot to Process" color swatch book which will show you the way those Pantones are going to print in CMYK. (No problem if the customer is going to pay for additional spot colors for their logo colors, but most don't want to add the expense of additional colors and press runs).

Swampy, this is excellent info, especially for the original poster.

Cheers
Dave