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View Full Version : 8 bit/16 bit and raw


emogirl
01-22-2007, 11:55 AM
I was editing some raw images today and i wasnt able to convert them to jpegs when i was done, only gave the option of psd or tiff. ..... took me a while to figure out i had to convert from 16 bit to 8 bit.... but i never had to do that yesterday or last week!!! did i change something without knowing it?? what should i normally be editting in?? i dont know what the difference is between 8 & 16 bit. help! thanks

damar
01-22-2007, 05:32 PM
Here's a good place to start:
http://www.earthboundlight.com/phototips/8bit-versus-16bit-difference.html

You may have used some filter in your processing that required the image be automatically converted to 8 bit and that's why your save options were different. Especially if you did a B&W conversion.
In your program, open your Help Topics in the upper tool bar. There's a search feature where you can type in "8 bit" etc. It'll bring up a list of related info.
If you use the "Save For Web" feature, you can still save as a JPG in 8 bit mode, as many times as you want and at whatever size you choose for each save and it won't affect the current edit.

More good info:
http://epaperpress.com/psphoto/index.html

Oldthumbs
01-22-2007, 06:17 PM
16 bit has a greater color depth (more color values) than 8 bit, which gives you room to retain more color levels during editing. Like damar said, check out the help menu in PS and/or search on the web. The tools you can use in PS to work on 16 bit images are not as plentiful as those available for 8 bit images, so you will need to convert a 16 bit image to an 8 bit image to take advantage of them.

There is some argument as to whether one can REALLY tell the difference between 8 bit and 16 bit in the final product. Personally, I wouldn't really worry about having to use 16 bit editing.

As to why you were working in 16 bit without knowing it, when you open a RAW file in PS using the PS RAW plug-in, you have a choice to open in either 8 bit or 16 bit mode. In the bottom left corner of the window there is a drop-down box where you can choose which bit depth to use. It was probably set to 16 bit when you opened the RAW file.

Ray

Windy
01-22-2007, 06:19 PM
Kim on the first page of processing you have a box down the bottom that says Depth there you can select 8 bit or 16bit.

Here is a write up on colour depth
http://en.wikipedia.org/wiki/Color_depth
and here
http://www.cambridgeincolour.com/tutorials/bit-depth.htm