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I need to convert a bunch of tiff (CMYK) images to png (RGB) to process them through a certain program, and then convert them back to tiff (CMYK) again.

As far as I know, both formats are lossless. So can I simply convert them using Photoshop with default parameters and not have any losses in quality? Or are there some details that I should know before doing so?

  • Why both conversions? Covert to RGB.. save as new file. You'll still have the original tiff files. – Scott Jul 27 '17 at 10:47
  • They are not entirely lossless, first of rounding will occour second the roundtrip to rgb can and will permanently destroy color info in certain color ranges, as well as the entire K channel – joojaa Jul 27 '17 at 10:52
  • @Metis, the program doesn't support tiff – Mr. Doe Jul 27 '17 at 11:38
  • I don't think I was clear... so your intention is to take an image, run it through this program, then use the results? And the final image must be CMYK for print? What's this "program" do exactly? A better option may be to find a way of working with the CMYK file. – Scott Jul 27 '17 at 11:47
  • @Metis, yes, it has to be CMYK for printing. My images have various backgrounds. The program just removes the background from an image (it does this automatically, so there's no need for me to do anything but upload an image). BTW, the program is burner.bonanza.com. I use the free version, it doesn't support tiff, but supports jpg (which is lossy) and png (which will require converting to RGB). I tried some other web and desktop applications, but they usually don't do this automatically and require some guidance from me in order to remove the background. – Mr. Doe Jul 27 '17 at 12:13
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Simple answer: No.

Longer answer: You will not loose image data as such (They wont start to display compression artefacts etc), However in converting between CMYK and RGB then back, you will basically completely screw up the colours. As CMYK and RGB are not compatible colour spaces.

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    You will also loose precision of color in 2 rounding operations. – joojaa Jul 27 '17 at 10:50
  • @joojaa, so if I understood you guys correctly, I will only have losses in the colors (CMYK->RGB->CMYK), not in the "quality" of the images (TIFF->PNG), right? By the way, my images were not initially CMYK, they were previously converted from RGB – Mr. Doe Jul 27 '17 at 11:45
  • In THEORY, ish. But I've seen theory and reality SOOO far off in the past... image processing is very prone. for example loosing/changing certain colours may alter contrast, which in turn could degrade "Quality" – Digital Lightcraft Jul 27 '17 at 11:56
  • @Mr.Doe obviouslycolor is part of quality. But with some definition of quality. – joojaa Jul 27 '17 at 12:15
  • If you have saturated colors - particularly reds and blues, you'll lose them in the conversion from RGB to CMYK. There are very few colors that you'll lose in a CMYK->RGB conversion, mostly saturated yellows, that aren't common in most imagery especially since most CMYK images came from RGB images. You might lose some data the CMYK->RGB conversion but it will be hard to notice. – Jeremy S. Jul 31 '17 at 15:46

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