RGB colour Retouching???

[EV0BEE Junior Member Find all posts View Profile Close EV0BEE]

Hi all,

I'm new here, in fact this is my first post. I have a question and i need to investigate the way people are color retouching in RGB.

As it stands the company i work for retouch CMYK images of products to a cmyk breakdown specified by a color book and an actual garment.

Now we will be moving to an RGB workflow and therefore all correction will be done in RGB. Now the way I understand it is that retouching in RGB you work in a lighting controlled room with a color calibrated monitor and correct it by eye in a color controlled environment. If you are required to correct to specific values you correct to LAB values. Thats how I understand it!

Is there anyone else doing anything different as a professional retoucher color correcting in RGB?

Thanks in advance

Scott

[andrewrodney Senior Member Find all posts View Profile Close andrewrodney]

Re: RGB colour Retouching???

CMYK is a highly device dependent color space meaning for all the thousands of devices out there that produce a CMYK output, each color space is different and unique.

RGB is also device dependent but there are far fewer such spaces you need to worry about when editing your images. There is a class called RGB working spaces and there are only a few you need to worry about. For example sRGB, Adobe RGB and ProPhoto RGB are three such very common spaces. The big differences is in their color gamuts. The neat thing about all RGB working spaces is that when R=G=B, you always have a neutral! Find out what the boss is using for your RGB working space and you're set. CMYK or RGB, you need a well calibrated and profiled display or what you see is science fiction. Stick with the RGB space, you can if you wish use Lab color picker for numeric feedback but stay in that RGB space, do not convert to Lab (zero reason to do so, time consuming and without high bit data, potentially very destructive).

IF you are as unfamiliar with Lab values as RGB, little reason to attempt to learn both, just work with the RGB info. Zero is a black hole, 255 is the whitest white and now you know where to find or create a neutral value anywhere in the tone curve.

The beauty of an RGB workflow is you (someone) can convert to any number of CMYK output color spaces based on the print conditions. You can't do that with CMYK (well with device links you can but a lot of the toothpaste can't be put back into the tube).

Moving to an RGB workflow makes far more sense and is a far more modern way to be working, far more flexible. Good luck.

This may help:

http://www.adobe.com/digitalimag/pdf...p_colspace.pdf

[Shoku Senior Member Find all posts View Profile Close Shoku]

Re: RGB colour Retouching???

There are advantages to working in LAB, RGB , and CMYK. There is real benefit to understanding all ten channels, and using them as editing spaces when necessary. Somethings can be accomplish easier in LAB, somethings in RGB and others in CMYK. You may not need LAB often, but when you do, you'll be glad you have it.

I recommend two books:
Professional Photoshop and Photoshop LAB Color, both by Dan Margulis.

[andrewrodney Senior Member Find all posts View Profile Close andrewrodney]

Re: RGB colour Retouching???

I recommend two books:
Professional Photoshop and Photoshop LAB Color, both by Dan Margulis.

Just try to ignore the piss poor reproduction and image quality, a sign! Both good books for those handed lemons who have to make lemonade. Best if possible to not start the process with lemons!

[andrewrodney Senior Member Find all posts View Profile Close andrewrodney]

Re: RGB colour Retouching???

Further, here's how you can work in RGB, totally avoid CMYK until you know and are able to convert to the output color space if you have to, where Lab is darn useful but without having to convert from RGB to Lab: a video on correcting skin tones without having to resort to CMYK:

Low Rez (YouTube)
http://www.youtube.com/watch?v=dWaFDKrNrwc

High Rez
http://digitaldog.net/files/SkinToneVideo.mov

[EV0BEE Junior Member Find all posts View Profile Close EV0BEE]

Re: RGB colour Retouching???

Thanks guys,

Reading Professional Photoshop ATM. I keep trying to stress the need for calibrated monitors but they're expensive and we work for Mr Scrooge. To color correct an image from a sample the idea now is to get a CMYK split from a product via a color book, input the cmyk values and see how that equates in RGB. Personally i think this will be inaccurate. Thank you for your input in advance.

Scott

[skoobey Senior Member Find all posts View Profile Close skoobey]

Re: RGB colour Retouching???

You can always set the eyedropper to read CMYK or LAB values, and you can rely on HSB information as well.

Biggest CMYK advantage is having an extra channel to play with, but except for that and the fact things going the opposite ways in adjustment layers, I know no difference between CMYK and RGB.

There is no reason for anyone to work in lab. Even colorizing and some of the "special" effects can be achieved in RGB. If someone can post an example of something that can't be done in RGB on CMYK but can in LAB?

[andrewrodney Senior Member Find all posts View Profile Close andrewrodney]

Re: RGB colour Retouching???

I keep trying to stress the need for calibrated monitors but they're expensive and we work for Mr Scrooge.

So the effect of this on the final output has no cost to Mr. Scrooge? What about ONE highly calibrated and profiled display used for final tweaking, would he buy that? Does he understand that RGB and CMYK (or Lab) values are not like cheese, they don't age or change over time unless someone alters the values. So the numbers you see today and in a year should preview the same way. The cost of a really good colorimeter is under $300.

To color correct an image from a sample the idea now is to get a CMYK split from a product via a color book, input the cmyk values and see how that equates in RGB. Personally i think this will be inaccurate. Thank you for your input in advance.

What CMYK flavor based on what output are you referring to? CMYK is highly device dependant, every CMYK device can produce a different set of values to produce the same color appearance. There isn't one CMYK (or RGB although there is one Lab). There are thousands if not more.