RE: Adobe RGB 1998 VS ProPhoto RGB

With a topic title like this, your thread is going to attract an awful lot of views in anticipation of the kind of answers you've been getting. 

As station_two pointed out that Color Space is large.

When converting images from a large Color Space to a smaller one (for example when preparing an image to be CMYK printed commercially) the results can suffer especially when working in 8bit.

This naturally falls under what station_two summed up with

it can give you all kinds of grief if you don't know exactly what you are doing

but I thought it might be worth pointing out right away.

Edit: Had missed Jeff’s post that also referred to the bit depth. 

You need to learn some basics about color management and color spaces (and bit depth) before any answer you get will make sense to you. Do you understand color space (working spaces in Photoshop)? Do you understand the differences between sRGB, Adobe RGB and ProPhoto RGB? Do you understand the differences between 8-bit and 16-bit bit depth? Those would be topics you would want to read up on. Google is your friend.

As it stands, any answers won't mean much unless you have some basics under your belt.

ProPhoto RGB is just about the widest color space.  It's used by photographers.

As some noted authors and celebrities like to put it, "ProPhoto RGB is the only color space real men use".

However, because it is soooooo wide, it can give you all kinds of grief if you don't know exactly what you are doing.  It contains many, many, MANY more colors than you can see on any monitor, it even encompasses what can only be termed "theoretical colors" because they're outside the visible color range in the physical world.

Don't even think of going there unless and until you have fully digested the classical treaties on the subjects of Color Theory and Color Management.

Here are some illustrations that might help you understand what I mean.