Question about 16-bits vs. 8 bits channel mode in PS

I read somewhere that you will get better quality prints if processs the photo in 16-bit mode. The only problem is, the developers near my house say they can't process 16-bit photos. They need to convert it to 8-bit mode first.

Is there a big difference in quality between the two? Do I have to find some kind of specialist to develop my 16-bit photos.

If your original file is 8-bit, converting to 16-bit won't accomplish anything. You can't add color information that isn't there.

However, an image created as a 16 bit file, edited, then down-sampled to 8-bit will usually have smoother color transitions than a native 8-bit file.

Ultimately, 16-bit will yield better results, but the files are much larger.

There are shops that can print 16-bit. I don't think it requires a specialist, just a fully equipped shop.

And I when I finally got them on the CD and took them to the place, the guy said he was going to have to convert them back to 8-bit before he could develop them.

It turns out, he couldn't even process CMYK mode photos so I ended up having to put the photos in RGB 8-bit mode. So much for all the extra bells and whistles on PS CS2.

If you process the photos in 16 bit mode, you'll get a lot less banding - or conversely you'll be able to do a lot more pushing - in 16 bit mode since it has about a magnitude more colors available to put between color A and color B. Instead of a1a1a1a4a4a4a4a8a8a8a8a12a12a12a12a16b it'll go a1a2a3a3a4a5a6a7a8a9a10a11a12a13a14a15a16

then you can down sample that, and have a much smoother image

and do your processing in 48 bit space instead of 24 bit space, you keep more of the subtleties in the original data. As a final step, convert it to 24 bits for printing.

This page ( http://www.normankoren.com/digital_tonality.html ) goes into some detail, much of it quite technical, about this, but the "bottom line" of the argument is found near very end of the page with a pair of histograms - one (when the calculations were done in 24 bit space) showing the loss of several levels of data and the other (48 bit) showing a continuous range of tones. In short, by doing your processing in 48 bit space you get better results even after the final conversion to 24 bits for printing purposes or conversion to jpeg.

However, if you are beginning with 24 bit data, the author of Picture Windows Pro (which has been offering 48 bit processing for several years) says that there is little to gain by processing the data in 48-bit space, other than making the calculations take a bit longer. ( http://www.dl-c.com/discus/messages/2/321.html )

(edit typo)