From: David J Taylor on
"Mike Russell" <groupsRE(a)MOVEcurvemeister.com> wrote in message
news:1szocmugrm49z$.dlg(a)mike.curvemeister.com...
>> Paul Furman wrote:
> [re Image | Adjustments | Exposure... ]
>>> Hmph, CS1 doesn't have that.
>
> Here's something similar that will work on most versions of PS
> http://www.anntorrence.com/blog/2008/02/multiply-and-screen-to-adjust.html
>
> --
> Mike Russell - http://www.curvemeister.com

Seems like a grossly overcomplicated way of adjusting gamma. Can't that
expensive program do that directly? My much cheaper program can.

David

From: Wilba on
Floyd L. Davidson wrote:
> Wilba wrote:

[How to measure exposure headroom between an ETTR JPEG and the raw.]

>> Set an exposure that looks correct according to ETTR. Shoot.
>> Overexpose by one increment (e.g. 1/3 step). Shoot. Continue
>> up to say 3 steps over. Open the raw files in your everyday raw
>> developer. Find the most over-exposed one from which a image
>> without clipping can be recovered. The over-exposure in
>> that one is your headroom under those conditions. How's that?
>
> Wrong.

OK, a taunt rather than an explanation. I'm clear on what you're here to
achieve.

For anyone else who's interested ...

DPreview's tests of the 450D show around 1 to 1.5 steps between the JPEG and
raw curves on the highlight side
(http://www.dpreview.com/reviews/canoneos450d/page21.asp - "RAW headroom"
section). Combine that with the typical -1/3 to -2/3 exposure compensation
required to get a good ETTR histogram with that camera, and you have
something in the region of two steps headroom, similar to my experience.
They said they got "perfectly usable results" even with -3 or -4
compensation in PP, but I can't vouch for that.

Here's a similar conclusion for a 5D arrived at by a much more rigourous and
involved method -
http://www.libraw.org/articles/Canon-5Dmk2-headroom.html.

A similar method with a Foveon sensor yeilds only 1/2 a step -
http://www.imaging-resource.com/PRODS/SD9/SD9A12.HTM.


From: DRS on
"Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message
news:87d44vn1t3.fld(a)apaflo.com
> sigh... <sigh(a)noaddress.com> wrote:

[...]

> Obviously there *is* a huge volume of information
> available in a histogram; and very little of it has
> anything at all to do with setting exposure. E.g., the
> *contrast* information does *not* help set exposure.

Nobody ever said it did. That straw man with you are obsessed has been
exploded several times. The only thing setting contrast to minimum does (in
this context) is expand the histogram so that it more accurately depicts the
dynamic range in the Raw image so that the photographer can make a more
informed decision about what if anything to *subsequently* do to the
exposure. Everybody can see it except you and that is the only claim that
has been made for it (except by you).



From: Floyd L. Davidson on
"DRS" <drs(a)removethis.ihug.com.au> wrote:
>"Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message
>news:87d44vn1t3.fld(a)apaflo.com
>> sigh... <sigh(a)noaddress.com> wrote:
>
>[...]
>
>> Obviously there *is* a huge volume of information
>> available in a histogram; and very little of it has
>> anything at all to do with setting exposure. E.g., the
>> *contrast* information does *not* help set exposure.
>
>Nobody ever said it did.

Well, not more than 100 or so times in this thread.

>That straw man with you are obsessed has been
>exploded several times.

*What* *has* *been* *exposed* *is* *that* *you* *can't* *cut* *the* *mustard*.

All those claims of knowning everything about
histograms, and when asked to give an analysis of two
examples you could not produce.

>The only thing setting contrast to minimum does (in
>this context) is expand the histogram so that it more accurately depicts the
>dynamic range in the Raw image so that the photographer can make a more
>informed decision about what if anything to *subsequently* do to the
>exposure.

You say "Nobody ever said it did", and then once again
claim it does. What nobody has ever claimed is that
*anything* thing works until *subsequently* to an
exposure! Your remarks are illogical weasel words.

>Everybody can see it except you and that is the only claim that
>has been made for it (except by you).

Everybody realizes that the process is to make an
exposure and then subsequently make exposure adjustments
based on what the histogram shows before making another
exposure.

The problem is that setting the camera for low contrast
isn't very useful, and might even make some (high key
image) histograms more difficult to read.

The *valid* way to make a histogram more useful is to
make it more accurate. That can be done by changing the
White Balance adustment of the camera. (A fact you
would recognize if you actually understood what
histograms are.)

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: Wilba on
DRS wrote:
> Floyd L. Davidson wrote:
>>
>> Obviously there *is* a huge volume of information
>> available in a histogram; and very little of it has
>> anything at all to do with setting exposure. E.g., the
>> *contrast* information does *not* help set exposure.
>
> Nobody ever said it did. That straw man with you are obsessed has been
> exploded several times. The only thing setting contrast to minimum does
> (in this context) is expand the histogram so that it more accurately
> depicts the dynamic range in the Raw image so that the photographer can
> make a more informed decision about what if anything to *subsequently* do
> to the exposure. Everybody can see it except you and that is the only
> claim that has been made for it (except by you).

Floyd is arguing with the demons in his head (and losing).

Is there anything else left to discuss amongst the rest of us?