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png and jpgs with different RGB make-up

Community Beginner ,
Feb 22, 2023 Feb 22, 2023

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After designing a logo for a client in putting together various format, I am finding that the rgb make-up of the png and jpg formats differ. Should this be the case?

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correct answers 1 Correct answer

Community Expert , Feb 22, 2023 Feb 22, 2023

What Kevin is getting at, is that numbers are dependent on the color space used. The same visual color will yield different numbers in sRGB, Adobe RGB, ProPhoto etc."RGB" is not a color space, just a generic color mode.

 

If there is an embedded color profile in the file, that defines the colors. Numbers withut a specified color space are undefined.

 

All that said, one single digit up or down sounds much more like the result of jpeg compression. The jpeg algorithm compresses the color component

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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What color profiles are attached to the two files?

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Community Beginner ,
Feb 22, 2023 Feb 22, 2023

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they are both rgb, but differ slightly.

png 26, 88, 167

jpg 27, 88, 168

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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Sorry @jean DeBenedictis  I meant the specific color profile - is one Adobe RGB and another sRGB?

You can check by going into each file and choosing Edit>Convert to Profile - what does the Source say on each?

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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What Kevin is getting at, is that numbers are dependent on the color space used. The same visual color will yield different numbers in sRGB, Adobe RGB, ProPhoto etc."RGB" is not a color space, just a generic color mode.

 

If there is an embedded color profile in the file, that defines the colors. Numbers withut a specified color space are undefined.

 

All that said, one single digit up or down sounds much more like the result of jpeg compression. The jpeg algorithm compresses the color component much more aggressively than the luminance component, and this variation in numbers is a side effect of the compression. If you need absolutely accurate numbers, don't use jpeg.

 

Jpeg compression is destructive, non-reversible and cumulative.

 

EDIT cross post

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Community Beginner ,
Feb 22, 2023 Feb 22, 2023

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Right…profile. They are both Adobe RGB.

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Community Beginner ,
Feb 22, 2023 Feb 22, 2023

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Maybe I'm over analyzing. I'm putting together logo guidelines so trying to give accurate numbers.

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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Then extending what D Fosse said, to increase the chance the guidelines will be implemented properly, the guidelines should say that the stated RGB values should match when in Adobe RGB color space only, and when using a format with lossless compression (PNG, TIFF, PSD…).

 

The point is that if the RGB values are supposed to be 26, 88, 167 in Adobe RGB, they are probably different in sRGB, definitely different in CMYK (might need another set of values for print but again, be sure to specify which CMYK), and might not match if lossy compression is applied as JPEG does.

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Community Beginner ,
Feb 22, 2023 Feb 22, 2023

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Right, got it. Thanks all.

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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Lots of good advice in this thread.

Since this is a logo, I presume that it contains text and/or graphics, in which case PNG is a much better choice than jpg.

The jpg format is designed for continuous tone photographs and does not render text and solid colors well, and uses lossy compression. PNG renders text and colors really well, and uses lossless compression. It also does a good job with photographic images, but with a much larger file size than jpg.

 

For print, consider giving your client a tiff file, it will print much better than a jpg.

Although PNG wil produce a high quality image, it is designed for screen viewing, and not used much for printing.

 

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Community Expert ,
Feb 22, 2023 Feb 22, 2023

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Maybe I'm over analyzing. I'm putting together logo guidelines so trying to give accurate numbers.


By @jean DeBenedictis

The numbers are only "accurate" if the scale of the color space is defined. Were you told to be working in Adobe RGB (1998) and provided specific RGB numbers? 

Think of it this way: someone tells you to build a wall that is 3 feet high. But you work in meters, not feet. There's a big difference between 3 feet and 3 meters even though both share the same number (three). 

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

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