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Archived from groups: rec.photo.digital.slr-systems (More info?)
On Tue, 14 Jun 2005 22:55:56 GMT, the cup of JPS@no.komm overfloweth with
the following:
> In message <ja8ta19mhkdjbus4m9e4gmaga5k7dqcrtq@4ax.com>,
> G Winstanley <stan@orange.net> wrote:
>
> >On Sun, 12 Jun 2005 21:52:16 GMT, the cup of JPS@no.komm overfloweth with
> >the following:
> >
> >> [snip]
> >
> >> ...The difference
> >> is, the lower the ISO setting on the camera is, the less RAW, digitized
> >> numbers there are to represent the subject, therefore posterizing it
> >> more.
> >
> >How does this work exactly? Why shoudl a lower ISO reduce the digitization
> >range of the camera?
>
> Did you catch the context from which that was snipped. The context was,
> given a fixed *absolute* exposure (same f-stop and shutter speed; same
> lighting on subject), the higher ISO will digitize the data better (if
> it's gain-based ISO).
>
> >I don't see that the dynamic range is changed at all,
>
> I wasn't talking about DR, per se, but about digitization data. If a
> certain absolute exposure gives RAW data just short of clipping (4095)
> at ISO 1600, then the highest RAW numbers will be just below 256 at ISO
> 100. Dark areas that average 160 at ISO 1600 will average 10 at ISO
> 100, becoming highly posterized.
>
This makes a little more sense now. In fact after reading the rest of the
replies posted in this sub-thread I've got a better idea what you're trying
to say in general, although I think Ben seemed to get closest to a
real-world précis with his "...if that means going to a higher ISO, don't be
shy" comment.
Stan
On Tue, 14 Jun 2005 22:55:56 GMT, the cup of JPS@no.komm overfloweth with
the following:
> In message <ja8ta19mhkdjbus4m9e4gmaga5k7dqcrtq@4ax.com>,
> G Winstanley <stan@orange.net> wrote:
>
> >On Sun, 12 Jun 2005 21:52:16 GMT, the cup of JPS@no.komm overfloweth with
> >the following:
> >
> >> [snip]
> >
> >> ...The difference
> >> is, the lower the ISO setting on the camera is, the less RAW, digitized
> >> numbers there are to represent the subject, therefore posterizing it
> >> more.
> >
> >How does this work exactly? Why shoudl a lower ISO reduce the digitization
> >range of the camera?
>
> Did you catch the context from which that was snipped. The context was,
> given a fixed *absolute* exposure (same f-stop and shutter speed; same
> lighting on subject), the higher ISO will digitize the data better (if
> it's gain-based ISO).
>
> >I don't see that the dynamic range is changed at all,
>
> I wasn't talking about DR, per se, but about digitization data. If a
> certain absolute exposure gives RAW data just short of clipping (4095)
> at ISO 1600, then the highest RAW numbers will be just below 256 at ISO
> 100. Dark areas that average 160 at ISO 1600 will average 10 at ISO
> 100, becoming highly posterized.
>
This makes a little more sense now. In fact after reading the rest of the
replies posted in this sub-thread I've got a better idea what you're trying
to say in general, although I think Ben seemed to get closest to a
real-world précis with his "...if that means going to a higher ISO, don't be
shy" comment.
Stan