Re: filmscanners: ColorSteps?

[Arthur Entlich <artistic@ampsc.com>]

Richard,

I ran into a problem with Photoshop 4.01 on the PC where it posterized 
badly when I did levels adjustments in 16 bit.  The problem did not 
occur if I worked in 8 bit.  It usually happened in midtones going quite 
dark blue-black.

I never printed these so, I have no idea what they would have looked 
like. However, I was told by some it was probably a graphic/video card
driver problem.  I had upgraded to the newest version, so I contacted 
Diamond, my videocard manufacturer.  They admitted there were some 
incompatibilities with the card I had and Photoshop, and suggested I 
update the card on a trade in basis.

On a last attempt, I upgraded to Photoshop 5.0, and magically the 
problem went away, so it was either a PS and Diamond problem, or a PS 
only problem, but it's gone now, and I did not replace my videocard or 
have I upgraded the driver since.

I recognize your situation is on a Mac, and I don't know if any of this 
relates, but obviously PS Version 4 for Windows was buggy.

Art

Richard Starr wrote:

> --- You wrote:
> You will be able to chack whether it is the file, or a problem with the 
> display/graphics system, by viewing the histogram. Contouring shows up as 
> missing bit values, leaving the histogram looking like a mangy dog's comb.
> 
> What file type is this, and what processing has been done (and by what) en 
> route to the screen? And what scanner/software?
> --- end of quote ---
> Thanks for the answers to this.  I am still finding my way with my 
>semi-disabled
> Nikon 3510AF.  Full resolution scans take 15 minutes and correcting the color
> misregistration takes 10 more.  Until I can afford a modern scanner, I'm still
> in the dark ages.  The film in one case is either Kodak 1000 negative film or 
>an
> 800 negative film from maybe Agfa.   Definitley available light material shot 
>in
> my little Olympus XA4 (a jewel.)  I would have done some curves or gamma
> adjustments in Photoshop.  Maybe a curves adjustment in the Nikon software for
> one of the pictures.
> 
> The odd thing is that the posterization seems to show in the display and not 
>in
> the print.  This suggests a bug somewhere in the software or hardware.  It's
> Photoshop 4.0.1 on a SuperMac with an ATI video board and a Sony monitor.  
>It's
> all good stuff.
> 
> Still, this  Photoshop version  is a little buggy, I think.  I used to use 
>this
> version on a 68000 Mac and it worked better with regard to previews anyway.  
>On
> the PPC Mac (it installs as a ppc version)    checking and unchecking preview
> boxes may or may not affect the display depending on the thing being 
>adjusted. 
> When the display is previewed, the adjustment affects the whole screen,  so 
>the
> background becomes magenta or darker or whatever.   It's hard to make subtle
> judgements that way even if the image fills most of the screen.  I don't think
> the 68k Mac version did these things.  Maybe later versions don't. 
> 
> (Holding the mouse down on the drag strip of the control window in many
> functions does cause the display to go back to the unpreviewed version in some
> of the control windows but not all.  This seems to me to be sloppy 
>programming,
> probably corrected in later versions. )
> 
> So given these little probs with Photoshop, maybe there is something that 
>causes
> slightly unreliable display.
> 
> Rich