What happens to 16 bit vs 8 bit when enlarged

[michael]

I am trying to determine what a vendor who does large format posters for my company needs for the best quality. I can supply them with a 16 bit file or 8 bit. If the image is used for a poster and is enlarged over 500% by specialized rip or software. Would it be significantly better in quaility if the image I supplied them with was a 16 bit as opposed to a 8 bit. I have arguments from my coworkers some for and some against. I have some experience in large format billboard industry and tend to lean towards the 16 bit choice. Especially taking in to consideration the types of enlargements that files needed.

[jetcode]

why not ask the vendor - no one is going to turn down 16 bit files

[Greg Lockrey]

All 16 bit vs 8 bit will give you is smoother color transitions which for the most part you can not see. Very few people in the world can. If you have "banding" issues in areas of a solid color, then by all means go with 16 bit. Bare in mind, going from an original file that's 8 bit to 16 won't help at all. If the original file is 16 then you can test the 8 bit file first before converting it.

[JohnnyV]

I'd recommend staying in 16 bit as long as possible... especially when resampling but that depends on the rip also.

Sending the file to the printer is different story:

http://www.harrington.com/bitinfo.html

[Ken Lee]

What matters most, as JohnnyV has pointed out, is that your image capture and editing be done in 16-bit. Try to avoid destructive edits - use layers where possible, instead.

This will let you retain the best quality image, and avoid "banding", as demonstrated by the image below.

When you're done editing your image, you can save the image as 8-bit, and send it to the printer if you like. Conversion down to 8-bit, should be the last step. Keep the 16-bit original, and toss the 8-bit version if you like.

http://www.kenleegallery.com/images/tech/steps.jpg

[Greg Miller]

Be sure to flatten your file before converting from 16 bits to 8 bits or else you will lose much of the benefit of having worked in 16 bit up to that point.