8 bits/channel compared to 16/bits per channel

[kentucky]

after upgrading to cs2. i noticed my pics default on rgb - 8 bits per channel. For printwork, when i convert to cmyk should I click on 16 bits/channel or does it matter.
thanks.

 

[jimoblak]

You should only use 16 bits if your output device or workflow supports it.

If an image is loaded as 8-bit, switching to 16-bit does not improve it and just adds file size.

 

[DarkLogan]

So if you start a new document just leave it at 8 or change that to 16 ???

 

[jimoblak]

If you know that your output is capable of 16-bit then you can start new documents or edit existing 16-bit images in 16-bit.

The reason that Photoshop defaults to 8-bit is because the majority of output is 8-bit.

 

[blueark]

If an image is loaded as 8-bit, switching to 16-bit does not improve it and just adds file size.

True, but sometimes if you have to make drastic global adjustments to an image, converting to 16-bit mode first reduces the quantization errors that can cause noise and gaps in your histogram. In general, it doesn't give a noticable advantage, but sometimes it's worth keeping in mind for troublesome images.

 

[kiddpete]

Actually, I think the input device should be the control. If the input device supports more than 8 bits, and the image warrants additional precision, I retain it. If you don't, you are throwing away color information. Both my camera and my scanner support more than 8 bits.

I don't see a lot of reason to convert an 8 bit image to 16 bit.