Letterbox Mike
New Member
Yeah Bob, I'm not sure what you're doing but I just tried what you're talking about with about 20 vastly different files, all CMYK, and observed absolutely no color change whatsoever in any of them.
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rgb...cmyk....so cornfused!...ugg
- Thread starter Big House Signs
- Start date
bob
It's better to have two hands than one glove.
Merely because you couldn't detect any color difference does not mean that the files were identical.
By the numbers...
1. Open a CMYK jpg in your favorite program. Mine's Corel.
2. Export the image to another file, call it 'File1.jpg', in CMYK.
3. Import 'File1.jpg'.
4. Export the image to yet another file, call it 'File2.jpg', in CMYK.
5. Do Start->Run... enter 'command' in the text box
6. In the command window do a CD to the directory that contains File1.jpg and File2.jpg.
7. Do 'FC File1.jpg File2.jpg'
8. The differences, if any, between the two files will list in the command window.
Whether there might be visually detectable or even comparative differences depends on just what is in the files. End case colors like red, blue, green, yellow, etc are well defined and probably don't encounter much in the way of shifting. On the other hand, delicate mid-range colors such as a taupe or most any other pastel tone for that matter often can see a dramatic shift.
sjm
New Member
Bob, as was already mentioned saving a jpeg out multiple times degrades the quality because the compression used is a lossy one. This in turn effects the file structure and using FC to compare to the original will show differences.
However further to that and to be sure there are not other factors confusing the issues, how would you suggest I set my Colour Management Policies in my favorite program?
1) Off
2) Preserve Embedded Profiles
3) Convert to Working CMYK
eye4clr
New Member
Let's do another test....using a file format that doesn't destroy the image and change the numbers in an effort to compress the file size. Something more appropriate like TIFF.
Here's the straight forward test that actually reflects something we might do in a normal day.
1. opened a CMYK file using the embedded profile
2. dropped 4 photoshop color references with the eyedrropper. I think you'll recognize the colors i dropped on by the numbers.
3. i did a save as and closed the image
4. opened the "re-saved" image using the embedded profile
5. WHOA! look at those numbers. Holy crap, they're the same. Amazing. Maybe, just maybe, it is the TIFF that makes the difference.
Here's the straight forward test that actually reflects something we might do in a normal day.
1. opened a CMYK file using the embedded profile
2. dropped 4 photoshop color references with the eyedrropper. I think you'll recognize the colors i dropped on by the numbers.
3. i did a save as and closed the image
4. opened the "re-saved" image using the embedded profile
5. WHOA! look at those numbers. Holy crap, they're the same. Amazing. Maybe, just maybe, it is the TIFF that makes the difference.
sjm
New Member
Easy fellow, what you speak is true. I deliberately refrained from replying in the RGB profiling thread regarding GCR and UCR because I was trying to make a point. We can discuss this further here if you like.
Anyways to keep things short just yesterday a client submitted an Illustrator and PDF file for me to output so they can match that colour to a paint.
In the Illustrator file the colour was 80% black, while in the HiRes PDF they supplied from Illustrator it was C=30 M=40 Y=30 K=55. From memory that's what I recall though from just 80% Black in Illustrator to a CMYK mix suggests something went wrong.
How would you proceed?
Anyways to keep things short just yesterday a client submitted an Illustrator and PDF file for me to output so they can match that colour to a paint.
In the Illustrator file the colour was 80% black, while in the HiRes PDF they supplied from Illustrator it was C=30 M=40 Y=30 K=55. From memory that's what I recall though from just 80% Black in Illustrator to a CMYK mix suggests something went wrong.
How would you proceed?
Time and time again bob has proven he doesn't understand color spaces.
Bob, you're confusing translation with conversion. When a CMYK file is read in an RGB device the color information is translated for display. The color data is never converted unless you specifically change color spaces.
Even jpeg compression doesn't mess with color space conversion, what it does is mess up actual pixel data through compression that creates artifacts with new color values. This is NOT the same thing as a color shift.
Let's pretend we have one big block cyan taking up the entire canvas.
File Information:
Color Space: CMYK Swap 2
Color Value : 100 C 0 M 0 Y 0 K
When you open up the file in PS, PS will read the 100C and translate the information to RGB values, send them to the monitor and the monitor will display accordingly.
The file has not changed color space. The values of the pixels have not changed CMYK mixture.
When you hit save again Photoshop does nothing with the RGB values provided for monitor displays.
It looks at the data file and saves:
Color Space: CMYK Swap 2
Color Value : 100 C 0 M 0 Y 0 K
No conversion has occurred to the file data.
Bob, you're confusing translation with conversion. When a CMYK file is read in an RGB device the color information is translated for display. The color data is never converted unless you specifically change color spaces.
Even jpeg compression doesn't mess with color space conversion, what it does is mess up actual pixel data through compression that creates artifacts with new color values. This is NOT the same thing as a color shift.
Let's pretend we have one big block cyan taking up the entire canvas.
File Information:
Color Space: CMYK Swap 2
Color Value : 100 C 0 M 0 Y 0 K
When you open up the file in PS, PS will read the 100C and translate the information to RGB values, send them to the monitor and the monitor will display accordingly.
The file has not changed color space. The values of the pixels have not changed CMYK mixture.
When you hit save again Photoshop does nothing with the RGB values provided for monitor displays.
It looks at the data file and saves:
Color Space: CMYK Swap 2
Color Value : 100 C 0 M 0 Y 0 K
No conversion has occurred to the file data.
iSign
New Member
got all that Paula? :ROFLMAO:
me neither... but I save as RGB 99% of the time & I've read threads such as this for 5 years & 99% of others send RGB files as well... that's all I need to know.
I print large CMYK color charts (showing hundreds of swatchs, with CMYK values printed right there) on my most common media, but I output those charts as RGB files as well... then I know what cmyk values to set up in illustrator or photoshop, to get matching colors on my chart... by saving final .tiff file as RGB. I also use .tiff files 99% of the time, even for all my vector artwork.
By coming up with my own standard workflow, and remaining consistent with that, & using my Pantone-to-CMYK fan-deck, or those CMYK charts I mentioned.. I have 5 years of consistent results, happy customers.. and I never took any Greek classes or made a single profile of my own... works for me
me neither... but I save as RGB 99% of the time & I've read threads such as this for 5 years & 99% of others send RGB files as well... that's all I need to know. I print large CMYK color charts (showing hundreds of swatchs, with CMYK values printed right there) on my most common media, but I output those charts as RGB files as well... then I know what cmyk values to set up in illustrator or photoshop, to get matching colors on my chart... by saving final .tiff file as RGB. I also use .tiff files 99% of the time, even for all my vector artwork.
By coming up with my own standard workflow, and remaining consistent with that, & using my Pantone-to-CMYK fan-deck, or those CMYK charts I mentioned.. I have 5 years of consistent results, happy customers.. and I never took any Greek classes or made a single profile of my own... works for me
sjm
New Member
What? PhotoShop has a Colour Management Policy of Convert to Working CMYK ... please explain what that means.
sjm
New Member
So you claim to have developed your own work flow. Please do tell which Pantone-to-CMYK fan deck you possess? Is it the U or C? Maybe your clients are just happy with pleasing colour?
I don't let any of my programs do auto conversion of color spaces, I set them to respect embedded profiles, if none available then it asks.
Working CMYK is the "default" color space that the CS suit assumes you want to use. I believe default CMYK is US Swap 2.
If you open a CMYK file that's embedded with anything else, and your color settings say to automatically convert, then yes when you open a non Swap 2 file it will be mapped and converted between color spaces.
Big House Signs
New Member
got all that Paula? :ROFLMAO:
I print large CMYK color charts (showing hundreds of swatchs, with CMYK values printed right there) on my most common media, but I output those charts as RGB files as well... then I know what cmyk values to set up in illustrator or photoshop, to get matching colors on my chart... by saving final .tiff file as RGB. I also use .tiff files 99% of the time, even for all my vector artwork.
By coming up with my own standard workflow, and remaining consistent with that, & using my Pantone-to-CMYK fan-deck, or those CMYK charts I mentioned.. I have 5 years of consistent results, happy customers.. and I never took any Greek classes or made a single profile of my own... works for me
I have been so crazy bz...it is just now that I have been able to read these posts. Wow! and so many opinions! And alot of it is way over my head.I have been staying in RGB and everything seems ok. The dam flexi 8.6 not so much. Tomorrow I am sure I will be on the phone with tech support....and my new designer starts. We have so much work I hope I can get this chick up to speed quickly.Thanks so much for everyone's suggestions. You guys are great!
Paula
eye4clr
New Member
agreed.
eye4clr
New Member
Thanks so much for everyone's suggestions. You guys are great!
Paula
Regardless of the techno bull the process you describe should work fine. Yes, there are ways to improve on it further. But for a safe, simple, repeatable process that avoids all the PDF and EPS file problems, you're likely safe 99% of the time.
luggnut
New Member
that's not true... it is if you choose a RGB red that is way out of gamut and have it set to render perceptual... because it will map it back to almost orange.
but if in photoshop or any design program if i pick my red and watch the cmyk values in the picker window i can choose a red that will print great. i'm still in RGB but in photoshop's color picker window you can see LAB, RGB, CMYK, and HSB values... then i set my rendering intent in the RIP to relative colormetric
sjm
New Member
What do you when there is no embedded profile?
sjm
New Member
I don't do drama, though challenge people like you who make false claims. As you said you have developed a workflow for Pantone-to-CMYK. Pantone themselves understand all CMYK spaces are different. Yet you magically have a workflow as you claim works. Please share that with us.
Best I remind you of the disclaimer Pantone has writen on their Solid to Process fan books or as you say fan deck.