RetouchPRO

Go Back   RetouchPRO > Technique > Photo Retouching
Register Blogs FAQ Site Nav Search Today's Posts Mark Forums Read


Photo Retouching "Improving" photos, post-production, correction, etc.

lower cyan without increasing magenta?

Reply
 
Thread Tools
  #21  
Old 03-08-2017, 12:19 AM
marameo's Avatar
marameo marameo is offline
Senior Member
 
Join Date: Oct 2014
Location: The Eternal City
Posts: 139
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Sabrina81 View Post
As I tried to point out earlier, the CMYK method for adjusting skin tones does not comvert the image to CMYK. It just uses CMYK values to get a rough idea which colors to adjust.
It makes sense. Whereas lab is absolute, one will use the larger cmyk working profile such as coated swop as a reference and "proof setup" to control skin values and check the ink density while staying in working RGB.

My question is how to bring the image within the 300 total ink range while staying in RGB. Is the selective color method to be used at this stage (bring CMY down and up the K in the shadows) or does it only work in CMYK?

Thanks
Reply With Quote top
  #22  
Old 03-08-2017, 01:30 AM
klev klev is offline
Senior Member
 
Join Date: Jun 2010
Posts: 1,053
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by marameo View Post
My question is how to bring the image within the 300 total ink range while staying in RGB. Is the selective color method to be used at this stage (bring CMY down and up the K in the shadows) or does it only work in CMYK?

Thanks
There are a couple important points. First 300 isn't universal. As I mentioned, you will typically have a submission spec. There's no absolutely general rule, because the specifications themselves relate to particular devices. Usually if people are working with cmyk, they are preparing for a particular target. If there are multiple targets, yet they need to deal with setting vector graphics and other annoying things, they will start with (for lack of a better term) the highest quality output, then make further adjustments as necessary.

You can't adjust like you're working with cmyk from an rgb space. It doesn't generate a black channel until you make a conversion, and there aren't any perfect tools for doing this. In general, if your submission specs say cmyk, you send a proof indicating your intent.

The point of this that you can't directly adjust based on cmyk from some other space, but the RGB tools (and even the LAB tools) are sufficient for most things. CMYK spaces tend to have a much narrower gamut outside of maroon and dark brown tones, so it sometimes feels easier to control. You can still work without it. If you're importing layers from CMYK back to RGB, you're likely to end up with an overly complicated workflow.

I wish I knew a good book to suggest on cmyk and printing processes. There are a lot of details, and I won't claim to be an expert.
Reply With Quote top
  #23  
Old 03-08-2017, 04:53 AM
Tony W's Avatar
Tony W Tony W is online now
Senior Member
Patron
 
Join Date: Mar 2010
Posts: 1,362
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Shoku View Post
True. And it is also true that every color space has it's limitations. That's why we use CMYK, RGB, and LAB. We use what works, and that can vary from image to image.
Don't take what I have said and am about to say as a criticism of your companies methods.

Obviously you are happy with what you are doing and getting good results, so really end of story- I guess .

TBH for me RGB and Lab both fine as their limitations seem to be less than CMYK. As an instance and by necessity a generalisation typically Adobe RGB and above (gamut size wise) are much wider gamuts for photo editing purposes.

As a general rule of thumb in digital it is usually suggested that if you require to end up with 'X' amount of data then ideally you should start with twice the data.

Choosing an 'early binding' workflow by converting to your flavour of CMYK immediately is not wrong but does carry with it a potentially heavy disadvantage in as much as your files are limited to only the one device.

Say you need to convert this CMYK image at a later date e.g. web or an inkjet printer (many can exceed Adobe RGB gamut let alone CMYK) it is not a massive stretch to imagine that you now have a CMYK file where the gamut has been severely clipped and no way to restore the lost data.

Therefore I am of the opinion that the so called 'late binding' workflow, working in RGB and finally converting to your CMYK flavour of choice will present the best results offering flexibility.

As an example of a 'late binding' workflow, I am currently collaborating on a book about a Japanese soldier in WW2 with an historian and author.

I hasten to add that my collaboration only extends to photographic duties. As such it involves restoration of images mostly greyscale but some colour along with the photography for the book jacket. So far 60 images have been restored.

At this time the printer or method of printing not finalised, but the author is rather keen to have a pretty large image of a shot of Shanghai printed for his wall alongside others. Working with RGB in this case is a necessity as the destination CMYK not known but even if it was known the images are going to be used for different purposes and the safety of the wider RGB gamuts may prove useful.

Quote:
Originally Posted by anderson234 View Post
I could learn a lot from your discussion. I appreciate it.
But at this point, I care most about the numbers/pattern that Lee Varis's CMYK method showed us, which directly helpes me quickly adjust skin tone to normal. Maybe RGB or LAB is better, but I need that pattern, too. I'll try to find it within RGB and LAB.
I now appreciate you may be only talking CMY numbers while staying in RGB.

If this is the case it does not really matter what number system you use as long as it makes sense to you and you really need to go by 'the numbers". You may also note that in at least one article he suggests using HS layer which may be easier to deal with correction of this type over Selective Colour. I am making another assumption that this is the article in question
www.varis.com/PDFs/RGBSkinTone.pdf

Quote:
Originally Posted by Sabrina81 View Post
The Lee Varis CMYK method for adjusting skin tones does not involve converting an RGB image to CMYK. The image remains in RGB. A sample point is set to read out CMYK values, which are used as a rough reference guide to determine which colors to adjust.
Now I understand that may be the case it really does not matter what number system you use, even the Dewey decimal system would work if implemented in the Adobe systems (Just a lame joke in case anyone thinks I am serious)

As the thread has strayed somewhat from the OP's intent for those who may be interested a pdf article from Jeff Schewe - Preparing images for delivery

https://www.adobe.com/digitalimag/pd..._reproprep.pdf
Reply With Quote top
  #24  
Old 03-08-2017, 07:58 AM
Shoku Shoku is offline
Senior Member
Patron
 
Join Date: Apr 2010
Posts: 256
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Tony W View Post
Working with RGB in this case is a necessity as the destination CMYK not known but even if it was known the images are going to be used for different purposes and the safety of the wider RGB gamuts may prove useful.
I understand. Having more data to work with is always a good thing.

What I mean is this: Each color space has advantages for retouching.

LAB allows you to separate color from Luminosity (I know you can also do this with adjustment layers in RGB and CMYK). LAB allows you to increase saturation in a more natural way, unlike the sledge hammers of Selective Color or Hue Saturation.

RGB has more definition in each channel, which is great for many things, especially images that are overly dark and where detail may not be possible to regain if in CMYK. It is also best where a quick move to neutrality is needed via denaturation.

CMYK has a black channel, which has many advantages with regard to detail, shape, and the ability to use GCR to preserve neutrality when printing. It is also the most intuitive because the colors are defined by density percentage.

All the above color spaces offer more options than I mentioned, and together they give the retoucher 10 channels to manipulate toward the final product. Now, you may not need to use all 10 (in fact most of the time three or four are all that are needed), but it's nice to know all 10 are available if needed.

Regarding a wider RGB gamut: This is fine if you never intend to print via offset CMYK. However if the final output includes CMYK, then finalizing toward that color space allows you to retain visual appearance in both CMYK and RGB. It is always frustrating for clients who send us wide gamut files that cannot be reproduced in CMYK without loosing saturation and detail. A good marketing campaign will allow for CMYK limitations so their brand is identical across multiple media.

Regarding that book you mentioned: For best reproduction of your greyscale images I recommend using a GCR CMYK color profile to get the best contrast while retaining neutrality.
Reply With Quote top
  #25  
Old 03-08-2017, 11:03 AM
marameo's Avatar
marameo marameo is offline
Senior Member
 
Join Date: Oct 2014
Location: The Eternal City
Posts: 139
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Shoku View Post
[...] A good marketing campaign will allow for CMYK limitations so their brand is identical across multiple media.
This is it!

Quote:
Originally Posted by Tony W View Post
[...] As the thread has strayed somewhat from the OP's intent for those who may be interested a pdf article from Jeff Schewe - Preparing images for delivery

https://www.adobe.com/digitalimag/pd..._reproprep.pdf
Quoting from the pdf article: "I just never show my clients the original RGB file [...] So, my clients really never see anything they can't get in print "
Reply With Quote top
  #26  
Old 03-08-2017, 11:53 AM
Tony W's Avatar
Tony W Tony W is online now
Senior Member
Patron
 
Join Date: Mar 2010
Posts: 1,362
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by marameo View Post
...Quoting from the pdf article: "I just never show my clients the original RGB file [...] So, my clients really never see anything they can't get in print "
And ?

This is correct, as there is no such thing as universal CMYK. I do not know how many different CMYK flavours exist but there are many - as many as there are CMYK devices!

Being a device dependent colour space means that the CMYK data will print differently from one device to another and is why it is so important to have the correct profile for conversion from RGB to CMYK

It follows therefore that it is good practice to provide a proof of what the client will receive even though it may be an imitation on different media. The same will be true should the client wish to use that data for other media web, hi quality inkjet printing etc.

You could of course take the view that all must match. In doing so you will need to crush potential image IQ by using the lowest common denominator this being CMYK. Leaving IQ behind on the table is something that many will not tolerate and clients also need to understand the differences between systems and quality gains and losses.

This does not take away from the fact that you should start with the best data and that data ideally twice what is needed.

Last edited by Tony W; 03-08-2017 at 12:10 PM.
Reply With Quote top
  #27  
Old 03-08-2017, 12:45 PM
andrewrodney's Avatar
andrewrodney andrewrodney is offline
Senior Member
 
Join Date: May 2010
Location: Santa Fe
Posts: 1,072
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Sabrina81 View Post
None are "correct." You and I have been around this track before, so let's just agree to disagree. I find the CMYK method useful. But it isn't a method to find "correct" skin tone values. So let's not thrash that straw man yet again.
It's not a method for anything beside describing the scale of a pile of numbers for some specific output device!
Reply With Quote top
  #28  
Old 03-08-2017, 12:52 PM
Shoku Shoku is offline
Senior Member
Patron
 
Join Date: Apr 2010
Posts: 256
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Tony W View Post
You could of course take the view that all must match. In doing so you will need to crush potential image IQ by using the lowest common denominator this being CMYK. Leaving IQ behind on the table is something that many will not tolerate and clients also need to understand the differences between systems and quality gains and losses.
Everything you said is true.

On average, 90% of our clients insist that the final products match. This demands not only precise adjustments for different papers and presses, but also enough communication so they understand the potential differences that cannot be avoided.

Example: a branded color that must match from Website, to an un-coated cover stock that will be laminated on one side only, to 100# glossy text stock with a matte coating. This can be frustrating for us as well as the client, but we do our best and our clients keep coming back.

As far as quality - once the adjustments are done the CMYK should visually match the final RGB as close as possible. The best way to ensure this happens is to finalize the CMYK and then convert to RGB. I have never had a client complain about losing the IQ - as long as the visual result is what they want, with no visible quality issues.
Reply With Quote top
  #29  
Old 03-08-2017, 04:35 PM
Sabrina81 Sabrina81 is online now
Member
 
Join Date: Jan 2017
Posts: 38
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by andrewrodney View Post
It's not a method for anything beside describing the scale of a pile of numbers for some specific output device!
As I said before (and won't bother saying again), I find the CMYK method useful for adjusting skin tones. You obviously don't, and that's fine with me.
Reply With Quote top
  #30  
Old 03-08-2017, 10:04 PM
Shoku Shoku is offline
Senior Member
Patron
 
Join Date: Apr 2010
Posts: 256
Re: lower cyan without increasing magenta?

Quote:
Originally Posted by Sabrina81 View Post
. . . I find the CMYK method useful for adjusting skin tones.
Me too. As I mentioned before the numbers are intuitive and easier to understand, and the results are quick and easy.
Reply With Quote top
Reply

  RetouchPRO > Technique > Photo Retouching


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Blues appearing magenta quadwing Input/Output/Workflow 9 10-20-2016 10:50 PM
Want to remove the blue cyan band in this photo jaiswalnilesh Photo Restoration 1 08-14-2012 09:28 AM
Magenta cast when printing cahn Hidden Power Support 7 01-01-2007 10:28 AM
Increasing image depth - Looking for ideas duwayne Photo Retouching 3 06-28-2006 07:51 AM
Screen, Multiply Explained... dpnew Hidden Power Support 3 12-28-2003 11:46 AM


All times are GMT -6. The time now is 02:57 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
SEO by vBSEO ©2011, Crawlability, Inc.
Copyright © 2016 Doug Nelson. All Rights Reserved