Re: Nikon D200 (for alt)

Well, then, the chip makers need to be more careful and/or more
sophisticated. If there is that electronic bleed in all chips, such as
CPU's, the governors that turn a bit on and off take care of it (seldom
does the amount of electricity passing through a gate correspond
precisely to on/off). Based on what I saw of CMOS photos a few years
ago, that didn't seem to have the fringing, I assumed the problem was
with CCD's. This could, of course, be a fawlty [sic] assumption. I
probably know just enough to be dangerous.

So, I guess digital will remain a 35mm/snapshot replacement for me for
the foreseeable future.

Thanks,
Pam

Tom Ferguson wrote:

> ...
>
> "Bleed" is what I "think" Pam was worried about. Unfortunately,
> separating the three color channels won't fix the problem. When you
> photograph a junction of very bright and very dark (backlit branches)
> in digital you often get a "fringe" distortion in a green/cyan/purple
> color. What usually causes this is that pixel set #1 (RGBG) gets the
> backlit sky (very strong light) and pixels set #2 gets the edge of the
> branch (very weak light). Some of the electrical charge generated by
> pixel set #1 "bleeds/leaks" into the adjacent pixel set #2. This
> causes the fringing.
>
> In general, larger sensors have less of this problem. The little
> pocket sized digital cameras use a chip about 1/8 inch, bad bleeding.
> The DSLRs use a chip about 1 inch, much less bleeding, the really $$$
> medium format chips (closer to 2 inches) are even better. I haven't
> seen any great difference in the current DSLRs, even between the APS
> and full sized versions :-(
>
> Some folks claim this purple fringe is a lens issue. To a small extent
> I agree. Wide angel lenses with small exit pupils and any truly poor
> lenses with astigmatism (or is it chroma??) will, on a digital, often
> give a similar looking error. In my experience, the sensor bleed issue
> is the far bigger problem.
>
> ...
Received on Mon Feb 6 16:47:18 2006