Re: 16 bit editing...

[Michael Greer <mgreer316@yahoo.com>]

Mark,

Thanks for posting. That's the first time I've witnessed anybody posting
anything for examination when this topic comes up. I appreciate it.

Now, in examining the images and their histograms, what I see is a lack of
contrast in the 8 bit edited image relative to the 16 bit edited in the lower
end. If the exact same curve adjustment operations were performed, I don't
understand how this difference came about. Anyway, when I adjust the 8 bit
image's curve lower end to closely match the 16 bit image curve's lower end,
then the results are almost identicle.  

I've posted the 8 and 16 bit edited images that you posted untouced. I've also
posted the adjusted (or corrected as I call it) 8 bit image. Alos, I've posted
the 8 and 16 bit histograms along with the 8 bit corrected histogram. If you
notice, the orginal 8 bit image has a relatively narrow range in the low end.
Narrow ranges will ALWAYS lead to dull/flat looking images. The 16 bit and 8
bit corrected ranges are pretty much the same and thus, the results are pretty
much the same.

Navigate to http://greeraa.com/albums/bit_depth/ to see.

--- mrkeene@attbi.com wrote:
> Mike,
> 
> Here is a real world comparison for you.
> 
> http://www.pbase.com/mark_kn/16bit_vs_8bit_editing
> 
> The image was taken with a Canon D60 in RAW mode and converted to a 16 bit
> TIF.
> A duplicate was made and converted to 8 bit.
> An equal amount of levels were applied to both images.
> The files were then resized to 640x480 for speed of loading and saved as JPG
> quality 10.
> No other manipulation was performed.
> 
> Download the images (they are ~80k each). Look at the original. Notice how
> far
> down in the shadows the lower portion of the image is. Now observe the
> Johnson
> grass in the lower right foreground on the 16 bit edited file compared with
> the
> 8 bit edited file. Draw you own conclusions.
> 
> Regards,
> 
> Mark K.
> 
> 
> On Tue, 21 May 2002 04:23:57 -0700 (PDT), you wrote:
> 
> >
> >Dave,
> >
> >Many times I preserve my images in 16 bits throughout my editing sessions
> >because the theory of using 16 bits in editing sessions makes sense to my
> >rational mind. But I gotta tell you, I have yet to actually see these
> >differences in real pictures. MANY are very passionate about editing in 16
> >bits. They give you the reasoning. They present charts and graphs. They give
> >you test cases (like color bands), instruct you to perform various editing
> >functions, then tell you to evaluate the histogram to see the differences.
> But
> >in all my years of doing this, I have yet to have 1 person present 2 real
> >pictures, one edited in 8 bits, the other in 16 bits, that actually reveals
> the
> >difference. It's not just me either. Dan Margulis, author of Professional
> >Photoshop apparently has a standing bet. From what I've heard, he's
> challenged
> >anybody to produce an image that reveals the difference in the image, not in
> >charts or graphs. From my understanding, nobody has done it yet.
> >
> >I stand ready to be convinced because the reasons to edit in 16 bits do make
> >sense to me. So much so that I do edit in 16 bits many times for "just in
> case"
> >reasons. But until I acutally see an example of the difference, I'll never
> be
> >fully convinced that it matters.
> >
> >> 
> >> 
> >> Bob,
> >> 
> >> Just wanted to ask a few questions regarding 16-bit editing.  Are you
> >> working in B&W or color (maybe both)?  I've read that the main benefit of
> >> 16-bit editing is in the preservation of shadow detail, but it sounds like
> >> you apply it to most if not all of your images.  The dumb question to ask
> >> would be "Do you really see a big difference?" but obviously you do or you
> >> wouldn't make the effort.  So instead I'll just ask if you could maybe
> make
> >> a few comments describing images in which you've compared 16-bit and 8-bit
> >> editing (perhaps from your original testing?)
> >> 
> >> I haven't tried it yet with my color work in that I tend to work with
> large
> >> files (300 meg scans that can get very big, very fast), and I'm afraid
> that
> >> going to 16-bit might clog my Mac a bit.  Your comments will be
> >> appreciated...
> >> 
> >> Dave Schrader
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >
> >
> >=====
> >Visit my digital photography web site along with a lot of other interesting
> stuff at http://www.mikegreer.com. Also, Greer and Associates
> (http://www.greeraa.com) offers studio photography, digital imaging services,
> web site design/construction, and training. 
> >
> >Mike Greer
> >
> >__________________________________________________
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=====
Visit my digital photography web site along with a lot of other interesting stuff at http://www.mikegreer.com. Also, Greer and Associates (http://www.greeraa.com) offers studio photography, digital imaging services, web site design/construction, and training. 

Mike Greer

__________________________________________________
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