20D or 5D

(Philip Homburg) wrote:

In article , wrote:
In message ,
David Littlewood wrote:

Even more extreme.

It's not really all that uncommon a situation where you can do that. I
have taken many pictures with the EC set to +2 with no blown highlights
resulting.

Of course, you have the issue of how to get this
right in the heat of the moment. I guess this is where prior experiment
and experience comes in....

It's simply a matter of estimating contrast. If you see a reflection,
for example, in glass backed by something white, shooting at 0 EC is a
huge mistake. If you can't compromise DOF or shutter speed by "exposing
to the right" at ISO 200, then go to ISO 800 and +2; you will have a
cleaner RAW capture than if you did ISO 200 and 0 EC. Same concept
applies in fog, or in a field right after sunset or under heavy clouds
when no sky is in the image, etc.

Your are talking about measurement errors. If you take a picture in fog,
afer sunset, etc. that includes a white piece of paper you still need a
camera that is capable of capturing 100% reflectance. If is only when you are
taking pictures of dull gray objects that you can leave out one or more stops
of head room.

I can't see the point of a setting that cannot record 100% reflectance.


No white paper has *ever* been manufactured that has 100% reflectance.

The nearest you will get to 100% reflectance is a ...

.... well, I'll just leave it to you to figure that out.

;-)

In message coh.net,
(Philip Homburg) wrote:

In article , wrote:

It's simply a matter of estimating contrast. If you see a reflection,
for example, in glass backed by something white, shooting at 0 EC is a
huge mistake. If you can't compromise DOF or shutter speed by "exposing
to the right" at ISO 200, then go to ISO 800 and +2; you will have a
cleaner RAW capture than if you did ISO 200 and 0 EC. Same concept
applies in fog, or in a field right after sunset or under heavy clouds
when no sky is in the image, etc.

Your are talking about measurement errors. If you take a picture in fog,
afer sunset, etc. that includes a white piece of paper you still need a
camera that is capable of capturing 100% reflectance.

In the heavy fog, if 100% reflectance is 100% luminance, then 18%
reflectance is going to be around 60-70% luminance, and pitch black
might be 55% luminance. The histograms are very narrow in a dense fog,
with any distance between the camera and subject, no matter what the
reflectance range. I was writing in the context of automatic exposure,
which will, by default record and render a scene in dense fog as a spike
in the middle of a histogram. What I am saying is to get that spike all
the way to the right, even if it means using a higer ISO to preserve
f-stop and shutter speed.

After sunset, light is very even on the ground (if there are no
artificial lights), and a 100% reflectance object in an average
intensity scene can usually be compensated by +1 stop without clipping
RAW data. If the brightest details are not much brighter than the scene
average, then you can go more than a stop. A deer against the bushes,
for instance, could easily handle +1.66 EC or even more in diffuse
light.

If is only when you are
taking pictures of dull gray objects that you can leave out one or more stops
of head room.

The absolute level is irrelevant; the relative levels within the scene
are all that matter as far as recording the data is concerned. White,
black, grey, all the same thing in terms of optimal recording. Of
course, it is often difficult to expose a shades-of-black subject close
to RAW saturation, even at the highest useful ISO.

I can't see the point of a setting that cannot record 100% reflectance.

Me either, but what does that really mean? You have to record the
brightest thing that you don't want to clip below RAW saturation.
--


John P Sheehy

Note the usual Pixby/Douglas MacDonald approach - as soon as he is
called on for his usual mistakes and misinfornation, he immediately
starts slinging the insults and killfiling.

If you can't debate, insult and change the subject. That's Douglas'
motto.

"Leonard" wrote in message
...
Skip M wrote:


I was wondering about that 1/200 flash synch. Defeatured to distance it
from the 1 series?


Just like the EOS-3.

- Len

And the EOS5, too, if I remember right. Now that you mention it...

--
Skip Middleton
http://www.shadowcatcherimagery.com

"Stacey" wrote in message
...
Skip M wrote:



It stands to reason that even a mediocre center would deteriorate to
poor,
or even unusable, edges.

Why? If this is from camera shake etc as people have tried to blame it on,
does camera shake somehow effect the edges/corners more than the center?

--

Stacey

Because the edges are already less sharp than the center. So poor focus, or
camera shake, or whatever, would diminish the usability by the same amount.

--
Skip Middleton
http://www.shadowcatcherimagery.com

In article , wrote:
In message coh.net,
(Philip Homburg) wrote:
Your are talking about measurement errors. If you take a picture in fog,
afer sunset, etc. that includes a white piece of paper you still need a
camera that is capable of capturing 100% reflectance.

In the heavy fog, if 100% reflectance is 100% luminance, then 18%
reflectance is going to be around 60-70% luminance, and pitch black
might be 55% luminance. The histograms are very narrow in a dense fog,
with any distance between the camera and subject, no matter what the
reflectance range. I was writing in the context of automatic exposure,
which will, by default record and render a scene in dense fog as a spike
in the middle of a histogram. What I am saying is to get that spike all
the way to the right, even if it means using a higer ISO to preserve
f-stop and shutter speed.

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.

If is only when you are
taking pictures of dull gray objects that you can leave out one or more stops
of head room.

The absolute level is irrelevant; the relative levels within the scene
are all that matter as far as recording the data is concerned. White,
black, grey, all the same thing in terms of optimal recording. Of
course, it is often difficult to expose a shades-of-black subject close
to RAW saturation, even at the highest useful ISO.

It isn't when you are talking about ISO settings. Reflected light should be
measured using an 18% gray card. Of course you can maximize to use of the
sensor by measuring the high lights using a spot meter, and setting exposure
for those. But that only works if the sensor can record 100% reflectance.

I can't see the point of a setting that cannot record 100% reflectance.

Me either, but what does that really mean? You have to record the
brightest thing that you don't want to clip below RAW saturation.

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).

Such a setting is useful only if the highlights are at least one stop below
'white'.


--
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

In article , Gisle Hannemyr says...

What's wrong with a built-in flash ?

Position too close to lens (results in red-eye), no bounce, too
limited range in most situations. I'd say the built-in flash like you
find on the Canon 20D or Nikon D70s is inadequate, even for casual
work. Whether I bring a DSLR or a P&S, I always pack at least one
external flash unit.

Obviously an external flash is better, but you might not always carry it
with you.
--

Alfred Molon
------------------------------
Olympus 4040, 5050, 5060, 7070, 8080, E300 forum at
http://groups.yahoo.com/group/MyOlympus/
Olympus E300 resource - http://myolympus.org/E300/

In message coh.net,
(Philip Homburg) wrote:

In article , wrote:

In the heavy fog, if 100% reflectance is 100% luminance, then 18%
reflectance is going to be around 60-70% luminance, and pitch black
might be 55% luminance. The histograms are very narrow in a dense fog,
with any distance between the camera and subject, no matter what the
reflectance range. I was writing in the context of automatic exposure,
which will, by default record and render a scene in dense fog as a spike
in the middle of a histogram. What I am saying is to get that spike all
the way to the right, even if it means using a higer ISO to preserve
f-stop and shutter speed.

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.

If is only when you are
taking pictures of dull gray objects that you can leave out one or more stops
of head room.

The absolute level is irrelevant; the relative levels within the scene
are all that matter as far as recording the data is concerned. White,
black, grey, all the same thing in terms of optimal recording. Of
course, it is often difficult to expose a shades-of-black subject close
to RAW saturation, even at the highest useful ISO.

It isn't when you are talking about ISO settings. Reflected light should be
measured using an 18% gray card. Of course you can maximize to use of the
sensor by measuring the high lights using a spot meter, and setting exposure
for those. But that only works if the sensor can record 100% reflectance.

What does that mean? It sounds like a logical tick to me, not an actual
issue. First of all, pulling by a stop in RAW *DOES* generally allow
for 100% reflectance to be recorded. You seem to have difficulty with
this concept. Secondly, all that matters in recording is what is in the
scene. You get the best quality recording by using the highest ISO that
gives the shutter speed you need, the f-stop you need, and just barely
comes close to clipping desired highlights.

I can't see the point of a setting that cannot record 100% reflectance.

Me either, but what does that really mean? You have to record the
brightest thing that you don't want to clip below RAW saturation.

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.

Such a setting is useful only if the highlights are at least one stop below
'white'.

Not at all.
--


John P Sheehy

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.

--
Jeremy |

In message ,
Jeremy Nixon wrote:

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?

It is wrong in assuming that by pulling one stop, you can not record
100% reflectance, as metered with a grey card with an external meter or
an incident reading.

Most DSLRs will record up to at least 200% reflectance in the green
channel, 320% reflectance in the blue channel, and 400% reflectance in
the red channel, without pulling. Pulling by a stop halves those
figures.

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

It depends on your intentions. If you're shooting a slide, or a JPEG in
which you have no control over the conversion, then EC can be used to
register the tonal ranges in a way as to reflect the scene as viewed by
a human. If you use +1 EC to get a lower exposure index, then you
really *ARE* shooting at that lower ISO; you're simply over-riding the
logistics of the camera settings.
--


John P Sheehy