20D or 5D

"Jeremy Nixon" wrote in message
...
wrote:

The assumption was that the ISO 50 setting would result in saturation at
50%
reflectance (i.e. ISO 100 is the lowest setting that actually works, and
ISO 50 is a 1 stop pull).

That assumption is totally wrong.

In what way is it wrong? I can't see any way in which a "pulled" ISO 50
isn't just a more confusing way to dial in +1 EC.

When you dial in +1 compensation, your camera changes either shutter speed
or aperture, which may not be a good idea.

What you COULD do is under expose by one stop, and then pull it back up in
RAW conversion--which is essentially the same as pushing film.
I've done this with amazingly good results.

In message taNPe.9804$Us5.4073@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

"Jeremy Nixon" wrote in message
...
wrote:

The assumption was that the ISO 50 setting would result in saturation at
50%
reflectance (i.e. ISO 100 is the lowest setting that actually works, and
ISO 50 is a 1 stop pull).

That assumption is totally wrong.

In what way is it wrong? I can't see any way in which a "pulled" ISO 50
isn't just a more confusing way to dial in +1 EC.

When you dial in +1 compensation, your camera changes either shutter speed
or aperture, which may not be a good idea.

Or, it may be exactly part of the shooting at ISO 50 experience.

What you COULD do is under expose by one stop, and then pull it back up in
RAW conversion--which is essentially the same as pushing film.
I've done this with amazingly good results.

Nowhere near as good as pulling by a stop, though. Pulling always
results in less quantization or posterization, and less noise; pushing
gives more of all.

--


John P Sheehy

wrote in message
...
In message taNPe.9804$Us5.4073@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

"Jeremy Nixon" wrote in message
...
wrote:

The assumption was that the ISO 50 setting would result in saturation
at
50%
reflectance (i.e. ISO 100 is the lowest setting that actually works,
and
ISO 50 is a 1 stop pull).

That assumption is totally wrong.

In what way is it wrong? I can't see any way in which a "pulled" ISO 50
isn't just a more confusing way to dial in +1 EC.

When you dial in +1 compensation, your camera changes either shutter speed
or aperture, which may not be a good idea.

Or, it may be exactly part of the shooting at ISO 50 experience.

What you COULD do is under expose by one stop, and then pull it back up in
RAW conversion--which is essentially the same as pushing film.
I've done this with amazingly good results.

Nowhere near as good as pulling by a stop, though. Pulling always
results in less quantization or posterization, and less noise; pushing
gives more of all.

But pulling by a stop assumes that you can still get a usable shutter speed.
If you're shooting anything with movement, that could be restrictive,
couldn't it?

In message HnOPe.9812$Us5.6049@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

But pulling by a stop assumes that you can still get a usable shutter speed.
If you're shooting anything with movement, that could be restrictive,
couldn't it?

Of course it could. You shoot at ISO 50 in ISO 50 conditions. Who
suggested otherwise?
--


John P Sheehy

wrote in message
...
In message HnOPe.9812$Us5.6049@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

But pulling by a stop assumes that you can still get a usable shutter
speed.
If you're shooting anything with movement, that could be restrictive,
couldn't it?

Of course it could. You shoot at ISO 50 in ISO 50 conditions. Who
suggested otherwise?

Sure.
I guess in my brain it goes back to my original question...of whether the
sensor itself is more sensitive, or if they are just going through the
process described.
If it's truly more sensitive, you could push that true 50 IS0 and retain the
same quality as pushed 100 on other sensors (or there abouts...).

Don't mind me... My brain is fried today.

In message 9bPPe.9819$Us5.6712@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

wrote in message
.. .
In message HnOPe.9812$Us5.6049@fed1read02,
"Mark²" mjmorgan(lowest even number wrote:

But pulling by a stop assumes that you can still get a usable shutter
speed.
If you're shooting anything with movement, that could be restrictive,
couldn't it?

Of course it could. You shoot at ISO 50 in ISO 50 conditions. Who
suggested otherwise?

Sure.
I guess in my brain it goes back to my original question...of whether the
sensor itself is more sensitive, or if they are just going through the
process described.

Is "sensitive" the word used to describe low native ISO? That sounds
kind of counter-intuitive to me. Sensitive should mean quality
recording at high ISOs, IMO.

Anyway, we're not talking about a 1-stop ND filter; we're talking about
actually shooting at ISO 50, with reduced headroom. That's not really a
lot to ask for, from many DSLRs, as they already have quite a bit of
headroom to begin with.

I just placed my Gretag-Macbeth Color Checker card against the wall,
after incident metering for ISO 32. I then shot the color checker with
my Canon 10D in manual mode with those settings (1s at f/1.4) with the
camera set to ISO 100. The brightest square (the white one) registered
no higher than 3787 anywhere in the RAW data. Clipping in the 10D set
to ISO 100 occurs anywhere from 3997 to 4006, depending upon the
vertical line of pixels a pixel is in (strange but true). I had no
problems using Adobe Camera RAW getting an image that looked like the
card.

The guy in the other posts who was demanding "100% reflectance" really
had no idea how undemanding his demand was!

The reason why digital images clip if you're not careful is not that
there is little headroom, per se; it's because the metering has no idea
where "middle grey" is in the image, and will unknowingly pull the image
to ISOs that are too low to salvage the image. JPEG is more
unsalvageable than RAW.

If it's truly more sensitive, you could push that true 50 IS0 and retain the
same quality as pushed 100 on other sensors (or there abouts...).

???

I have no idea what context you're working in here.

--


John P Sheehy

Mark² mjmorgan(lowest even number wrote:

I guess in my brain it goes back to my original question...of whether the
sensor itself is more sensitive, or if they are just going through the
process described.
If it's truly more sensitive, you could push that true 50 IS0 and retain the
same quality as pushed 100 on other sensors (or there abouts...).

ISO 50 would be less "sensitive", not more. But it would mean that they
were able to pull usable data from the signal a full stop lower than
before (more like lower signal to noise ratio than higher sensitivity),
which would be a good thing -- but if that were the case, they wouldn't
hide ISO 50 behind a custom function, they would advertise it.

--
Jeremy |

In message ,
Jeremy Nixon wrote:

Mark² mjmorgan(lowest even number wrote:

I guess in my brain it goes back to my original question...of whether the
sensor itself is more sensitive, or if they are just going through the
process described.
If it's truly more sensitive, you could push that true 50 IS0 and retain the
same quality as pushed 100 on other sensors (or there abouts...).

ISO 50 would be less "sensitive", not more. But it would mean that they
were able to pull usable data from the signal a full stop lower than
before (more like lower signal to noise ratio than higher sensitivity),
which would be a good thing -- but if that were the case, they wouldn't
hide ISO 50 behind a custom function, they would advertise it.

Well, you have to know what you're doing to take proper advantage of it.
The amount of headroom available at ISO 100 is actually plenty, to the
person who meters for 100 with an incident meter or grey card, or uses a
"sunny-f/16" approach in bright daylight. Exposures vary much more
wildly with automatic exposure, due to the weighted approach used for
exposure, and the firmware-pulled ISO 50 is more likely to lead to blown
highlights.
--


John P Sheehy

"Jeremy Nixon" wrote in message
...
Mark² mjmorgan(lowest even number wrote:

I guess in my brain it goes back to my original question...of whether the
sensor itself is more sensitive, or if they are just going through the
process described.
If it's truly more sensitive, you could push that true 50 IS0 and retain
the
same quality as pushed 100 on other sensors (or there abouts...).

ISO 50 would be less "sensitive", not more. But it would mean that they
were able to pull usable data from the signal a full stop lower than
before (more like lower signal to noise ratio than higher sensitivity),
which would be a good thing -- but if that were the case, they wouldn't
hide ISO 50 behind a custom function, they would advertise it.

Sorry guys..

I had several related thoughts in my head at the same time which I didn't
connect at all well in my writing. I was...and am...to describe my thought
well... Perhaps I'll return when I'm coherent.


I've been working on a still-image video creation for the last 5 days,
almost without stopping.
My brain is mush, and the various "breaks" I've taken to scan the NG haven't
left me in a good mind-set for accurate thought communication...

Ignore my last several posts until I can explain what the heck I was
referring to.
Believe it or not...it related to something that made sense...
I just didn't...well...make sense.

In article , wrote:
In message coh.net,
(Philip Homburg) wrote:
Maybe a 'fog mode' is a good option for a consumer camera, but normally,
you compensate for errors in exposure meter using the exposure compensation
setting. There is no point in adding artificially low ISO settings just for
cases where the camera tends to underexpose.

You've got it all wrong. The cameras are leaving plenty of headroom by
default; you lose "extra" headroom by pulling ISO 100 to 50; not working
reflectance. In fact, if you shoot in RAW, pulling one stop has about
the same headroom as an unpulled JPEG with a normal contrast setting, on
most cameras.

So, you are saying that Canon cameras can be overexposed by one stop at the
lowest ISO setting?

This seems to contradict the measurements of Roger N. Clark
(in http://clarkvision.com/imagedetail/dynamicrange2/)
who saturates the sensor of a 1D mk II at +0.3 stop.


--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency