Photoshop, 8 bit/ 16 bit pr. channel

[Tore]

Are to submit images to an imagebureau.
They want images scanned in highest possible bit depth.
For me this mean scanning in 16 bit/channel.

So far so good.
When I want to do adjustments to the scanned image I cannot add a new adjustment layer. I have to convert to 8 bit/channel to be able to work with layers...

When I convert to 8bit/channel, will I loose any of the scanned information?
Will I have to convert back again to 16 bit/channel.... or will photoshop only produce interpolated information when I do this?
Is there any reason to convert back again to 16 bits/channel?

I see that going from 16Bits/channel to 8bit/channel reduces filesize by 50% less and doubles the other way....

Apreciate any comments from experienced users....

Tore

 

[zefir]

Tore: PhS allows some operations to be done in 16-bit accuracy for
TrueColor scans.
Apply these first after scanning and convert then to 8-bit-per-channel (bpc).
The present state of the art doesn´t allow a consequent 16bpc handling.
The computation for 8-bpc is anyway done with intermediate higher accuracy.
A sequence of 8bpc applications will decrease the quality by and by.
I am sure, that the majority of users is not able to perceive this.
Offset printing allows anyway only 60..100 levels per channel.
JPEG compression is possible for 8bpc only.
---Gernot

 

[askIllustrator]

The standard resolution for printing is 304.8 ppi at 100%. If you scan your image at least 300 ppi in 8bit your images will print just fine. If the image is going to be blown up before printing you need to compensate for that in the scan. So if its printing at 200% the original size you need to scan it at 600 ppi etc.