8 Bit or 16 bit , sRGB or Pro Photo

Started Sep 11, 2019 | Discussions thread
technoid Senior Member • Posts: 2,276
Re: The difference is ...

gscotten wrote:

I printed out the test file from Lightroom to my Pro-100 first using the 8 bit driver and then the 16 bit XPS driver. Then, because I don't know how Lightroom's print engine works, I printed it again with Qimage using the XPS driver. Aside from the slightly better sharpening/scaling from Qimage, the three prints are virtually identical.

The iPhone photo below shows a difference in ambient light across the three prints as indicated by the whites of the backgrounds, but in the same light they look the same.

I have never seen a difference between the 8 bit and 16 bit outputs from the same file.

Nor have I. On  exactly one occasion I've seen a difference between 8 or 16 bit printed tiff files and JPEG but that's because jpeg doesn't actually render a full 8 bits of resolution. It compresses and throws out information that exists in an 8 bit tiff file. Even so I've only see one file where the difference was visible using highest quality jpegs. Lower quality jpegs frequently suffer banding but lets not go there.

Ken's obviously visible differences are clearly due to the differing color spaces chosen, not the bit depth nor the driver. There may be some banding in images caused by different bit depths, but that is not apparent in his images.

Yep. Exactly so.

The synthetic ball test contains colors that are significantly out of gamut on every printer I know of.

Bill's balls in ProPhoto have many colors that can not only never be printed by any theoretical printer, they also have lots of colors that are "imaginary colors" and are mathematical constructs that don't exist in the human color gamut. They are most useful in evaluating how smoothly a profile's perceptual intent maps these out of gamut "colors" to something pleasing.

The balls were originally designed by Bill Atkinson to be printed from device space, not ProPhoto, in order to visually examine how smoothly RGB printers mapped their gamut boundaries. The source for this was an email from Bill that Andrew Rodney helpfully shared on this forum some years back.

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