I recently got a question from a client:
I am looking into having some high-quality scans made from my transparencies, and there are some choices involved, mainly 8 bit vs.16 bit. The vendor’s web site said an 8 bit scan would look just as good to the human eye as the 16 bit scan, at much less cost. Don’t know much about this kind of thing, do you think the 16 bit scan is necessary at almost twice the price?
The choice of 8- vs. 16-bit has everything to do with maintaining quality when editing/manipulating the file.
Itâ€™s true that – in the end – 8-bit and 16-bit will not look any different, on screen or on a print, BUT (and itâ€™s a big BUT)…. When adjustments are made to any file, such as color or contrast changes, and even sharpening, 16-bit allows much greater headroom before the image starts to degrade from the changes. This is due to the fact that a mathematical description of color in 16-bit contains much more data than an 8-bit description.
An example of problems would be visible bands in a smooth gradient, such as a blue sky. Adjustments to a smooth blue sky in 8-bit will start to break down the image and reveal banding much more than if working in 16-bit.
So I always recommend capturing the maximum amount of data possible from the beginning, and staying in 16-bit as long as possible through the editing process.
The only exception to this is for images that go straight from scan to print with no editing at all, but obviously this is most often not the case. (One example would be someone shooting digital JPG and outputting directly to a printer, which is somewhat common for wedding and portrait photographers.)
So if you feel that some of your images wonâ€™t need much tweaking in Photoshop, or have images you donâ€™t care that much about quality, it MIGHT be ok to stay with 8-bit for those images.
But my philosophy involves starting with the most data and maintaining it as long as possible through the image production pipeline.
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