Hi,
1: PNG
I can see no reason whatsoever to choose PNG for printing images. I think it’s a bad idea.
Wikipedia agrees
"The PNG working group designed the format for transferring images on the Internet, not for professional-quality print graphics"
see: Portable Network Graphics
TIFF or flattened (no layers) PSD would be better, if you are confident on size JPEG is OK too, but not my favoured file type since it compresses data and can damage appearance if subsequently croped or resized (and, if saved as JPEG again, inevitably, recompressed).
PDF is OK for print, but its more for documents with text and graphics than simple image files.
2: CMYK? why? and what CMYK?
For general inkjet and some laser prints (printers without RIP software) RGB is the better colour format.
For offset press, digital press, some laser printers, Inkjet with RIP etc, CMYK image type is needed, BUT you should never simply use image / mode CMYK to achieve this without consdieration, since that defaults the important RGB to CMYK conversion to whatever CMYK ICC profile has been chosen in color settings.
CMYK (just like RGB) needs the right ICC profile to properly describe the colour and relate it to visual appearance. Think of it as a language, your RGB data can be translated to CMYK but first we need to know more about the "language" the printing device understands.
A CMYK ICC profile contains the "language" information needed to give correct colour balance for a specific printing condition, (machine, ink, paper).
In the profile, each required original colour has an ink recipe calculated to provide accurate colour and tone (within device capability) on a specific device type with specific ink and paper.
If a printing service just asks for "CMYK" you need to know "what CMYK" i.e what CMYK ICC profile to use (in the conversion from RGB to CMYK) - if they can't tell you its best to use another printing service.
To hit the colour dartboard you have to know where to aim the dart.
Guessing on ICC profiles for CMYK conversions or simply using whatever ICC profile happens to be set in color settings (in many cases that may be the default of SWOP) is the road to disappointment with printed image colour rendition, unless, by some coincidence, that’s just what your printer wants..
I hope this helps
if so, please "like" my reply and if you're OK now, please mark it as "correct", so that others who have similar issues can see the solution
thanks
neil barstow, colourmanagement.net
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