On Thu, May 23, 2013 at 12:50 AM, Bruce Walker <bruce.wal...@gmail.com> wrote:
>>>> The "underexposure" is exactly the problem: in most cases although
>>>> the JPEG (or the embedded JPEG in the RAW that we see the histogram
>>>> for) is overexposed, the actual RAW data is under exposed, to the
>>>> point that almost 25% of the histogram contains nothing.
>>>
>>> Since this strange effect only occurs after you tweak the camera
>>> settings to achieve this elusive UniWB thing, I'd respectfully suggest
>>> reseting your JPEG settings back to normal.
>>
>> On the contrary, this effect I've noted is **before** making any
>> "special" settings, i.e. straight "normal" settings.
>
> Ciprian, can you describe a scene or circumstances in which you have
> observed this very odd behavior? Maybe an example image? I'm
> non-plussed because in all of my shooting I've _never_ experienced
> that. And I can safely say that I've shot in just about every known
> lighting condition. [Known to me. :-)]
At the link below you'll find the following:
* the `.dng` which is the raw image; (this is the only option for
K-30 for RAW;)
* the `.jpeg` from the camera; (I was shooting RAW+;)
* the `.thumb.jpg` which is the extracted JPEG from the `.dng` via `dcraw`;
* the `.ppm` obtained from `dcraw` without WB;
* the `.txt` obtained from `rawshack`;
http://data.volution.ro/ciprian/e3a8d2a8f1098b9053f28369c7a42a36/
The picture was taken in a bright morning, at a distance of about
30cm, without touching any of the image parameters except of shooting
in RAW, and manual mode. (This is the "best" out of other shots.)
Although I must make a small correction to my initial statement: I
was under the wrong impression that the RAW was **completely**
underexposed, which seems it was not the case. However in half of the
"higher" levels (from 1024 to 4095) there lies less 10% of the pixels,
meanwhile the midlevels (256 to 1024) contain almost 50% of the
pixels. (I've taken the red channel as the scene is dominated by red.)
However my main statement that the JPEG is blown out, meanwhile
the RAW is somewhat underexposed still holds, as by looking at the
JPEG histogram you have the impression of an overblown red channel,
meanwhile the raw histogram says otherwise.
> Now elsewhere you have explained that you want to doctor or calibrate
> your histogram in aid of calculating exposures for doing ETTR. You
> might want to consider that ETTR is considered by many to be no longer
> relevant and even harmful. I don't follow the notion anymore myself.
>
> Have you read this?
>
> http://theonlinephotographer.typepad.com/the_online_photographer/2011/10/expose-to-the-right-is-a-bunch-of-bull.html
Interesting. I've not read it. I'll have to go through it.
Thanks for the pointer! (I'm still learning, thus if there are
also other pointers on the subject please send me a link.)
> Even doing nothing but RAW shooting I know that once you clip your
> highlights, they are gone. Pure white. No recovery possible. Complete
> loss of "value".
Yup, I've learned this the hard way, as one night while doing some
long exposures to a lightened fountain (and trying to practice ETTR)
I've blown the water columns, and all my photos (except two) were
completely useless (and even those two were so-so)...
> Possibly still okay for showing to your parents. :-)
Yup, they loved those overblown photos. Parents: they can't be
objective with their children... :D
Ciprian.
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