On Friday 28 September 2007 17:28:36 jim feldman wrote:
> Greg wrote:
> > I appreciate all the info and discussion on this.  It's a lot more than
> > I expected...and that's a good thing.
> >
> > I guess what I really want to know is, am I going to see any noticeable
> > loss if image quality from my 12-bit images?
> From prints? no.  On your monitor?  maybe. You will notice it when you
> try and correct for under or over exposure or gamma, and you'll notice
> it more in the underexposed areas where sensor noise will be more
> visible.  Much of this would be done in the UFRAW converter which DOES
> use all the bits, so you can argue it's less of an impact.
> > Also asked but not answered, are imaged displayed in their original
> > bit-depth or as 8-bit?
> Once the image is pulled into GIMP, it's 8/24 bit for processing and
> display.
> Here's a reasonably quick experiment.
> Gather a few images that represent your typical shooting
> Download UFRAW and the GIMP (maybe not so quick depending on your
> download speeds).  Pull your 12/36bit image into UFRAW and make whatever
> exposure/balance tweaks needed and then have it hand it off to GIMP.
> Have both images up at the same time.  What do your eyes tell you?

The problem is this is not the way to test the difference between differing 
bit depth. Monitors have their own limitations is display and gamut which 
result in an inability to portray differences between  8 bit and 16 bit 
images.. Professionals need to supply images which are for presentation on 
many grades of alternative media. IF a professional were to say "well I 
cannot see the difference on my monitor" his statement would be interpreted 
as a dec;aration of an inability to understand the basics. 

 There is no way that 8bit images can complete with 16 bit images -- the 
vision of the screen is a very impure and lossy projection of any image and 
the greater the bit depth  the greater the loss of image quality and gamut. 
So basically this approach tells you nothing but the fact a screen display 
has very limited capabilities.
> I've posted this before, and in case you missed it, you really need to
> do a bit of digital "darkroom" 101.  Go to www.normankoren.com and read
> through his site. Really.
> I'm not trying to be pedantic or condescending, but when you finish
> going through his tutorial, you'll be asking questions that will get you
> more targeted answers.  You might drop him a little paypal gelt when
> you're done because people charge $500 for one day seminars to present
> similar material.
> jim
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