From: John Sheehy on 10 Oct 2009 10:45
Paul Furman <paul-@-edgehill.net> wrote in
> OK, this makes sense, the posterizing issue is not really visible in
> any sort of normal exposure.
It shouldn't be visible in any kind of exposure. My comments about the
limit of the value of RAW bit depth or the number of RAW levels is based
on torturous tests!
> What about Floyd's comment below that the
> noise level remains the same but exposing to the right increases the
> signal so that overwhelms the noise?
The read noise (including any dark current) stays the same, in an
absolute sense. In a relative sense, it changes. For shot noise, it
changes in both an absolute sense *and* a relative sense.
> That seems to tie the two
> together in a comprehensible way. The LL link just makes a lot of
> sense, it can't be complete BS.
Well, the reasons given for the benefit are not correct. You could take
one shot with normal exposure, and one with +1 EC, now using the top RAW
stop, and the benefit would still be there if you quantized the top stop
to 300 levels, instead of ~8000. According to my calculations and
emulations, no current DSLR needs more than 300 levels for the top stop
(some older models with few, large pixels may need about 325).
From: Paul Furman on 10 Oct 2009 15:29
> Paul Furman wrote:
>> An interesting related issue I don't understand is how the exposure slider
>> works in Lightroom or ACR. I don't know how to duplicate that effect in
>> photoshop with curves, levels, etc. Those all do like you describe, moving
>> the middle parts of the histogram but there isn't an easy way I can see to
>> shift the whole exposure. Hmm, the middle slider on levels comes close but
>> still doesn't match the effect.
> Image | Adjustments | Exposure... ?
Hmph, CS1 doesn't have that.
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From: Porte Rouge on 10 Oct 2009 16:07
On Oct 10, 1:57 am, fl...(a)apaflo.com (Floyd L. Davidson) wrote:
> And how you can say "nothign to do with the increments
> by which the camera's controls change the exposure" and
> then describe camera controls changing the
> exposure... is amusing.
I think he meant the increments on the controls are arbitrary(1/3,
1/2, or 1 stop for each click on the dials.
From: Floyd L. Davidson on 10 Oct 2009 16:15
Porte Rouge <porterougeman(a)gmail.com> wrote:
>On Oct 10, 1:57�am, fl...(a)apaflo.com (Floyd L. Davidson) wrote:
>> And how you can say "nothign to do with the increments
>> by which the camera's controls change the exposure" and
>> then describe camera controls changing the
>> exposure... is amusing.
>I think he meant the increments on the controls are arbitrary(1/3,
>1/2, or 1 stop for each click on the dials.
But that does happen to be *exactly* where the term "stop" came
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: Porte Rouge on 10 Oct 2009 17:37
> >I think he meant the increments on the controls are arbitrary(1/3,
> >1/2, or 1 stop for each click on the dials.
> But that does happen to be *exactly* where the term "stop" came
I'll let you and Alan figure out where "stop" came from.
The amount of change in exposure per click on the dials on my DSLR is
arbitrary, I choose how much I want.