Canon 50D Auto ISO Question

Anyone know if the Canon 50D has programmable auto ISO like the Nikon
system?

For example, you can program the lowest shutter speed you want to use and it
will automatically increase the ISO if it needs a slower shutter speed than
that for correct exposure? For example, if you are shooting at ISO 100 in
AV and pre set the lowest shutter speed to 1/30, if it needs 1/15 it will
automatically bump it up to ISO 200 and use 1/30 instead?

Also, can you set the maximum ISO it will automatically choose? For
example, if you don't want it to automatically go above ISO 800, you can set
it to stop at this ISO?

wrote in message
news
Anyone know if the Canon 50D has programmable auto ISO like the Nikon
system?

It would appear to have some type of auto-sio function which is no
where as customizable as Nikons.


For example, you can program the lowest shutter speed you want to use and
it
will automatically increase the ISO if it needs a slower shutter speed
than
that for correct exposure? For example, if you are shooting at ISO 100 in
AV and pre set the lowest shutter speed to 1/30, if it needs 1/15 it will
automatically bump it up to ISO 200 and use 1/30 instead?

Doesn't appear so. It would appear you have to use Tv mode to set a
shutter speed. In manual mode it appears setting this results in fixed
iso400.

Also, can you set the maximum ISO it will automatically choose? For
example, if you don't want it to automatically go above ISO 800, you can
set
it to stop at this ISO?

Doesn't appear to be the case. DL a copy of the manual and look at p64
yourself.




Cheers. Just looked at the manual, but doesn't seem to give much info on
how it works. Unfortunately, I don't know anyone with a 50D that I can play
with either.

If you can't tell it what minimum shutter speed you want, I wonder what
parameters it uses? For example, does it just use a base shutter speed
setting of say 1/60? Does it change depending on what focal length is being
used, and if so, does it takes IS into consideration?

"Paul" wrote in message ...
Anyone know if the Canon 50D has programmable auto ISO like the Nikon
system?

For example, you can program the lowest shutter speed you want to use and
it will automatically increase the ISO if it needs a slower shutter speed
than that for correct exposure? For example, if you are shooting at ISO
100 in AV and pre set the lowest shutter speed to 1/30, if it needs 1/15
it will automatically bump it up to ISO 200 and use 1/30 instead?

Also, can you set the maximum ISO it will automatically choose? For
example, if you don't want it to automatically go above ISO 800, you can
set it to stop at this ISO?

It is an obvious extension of shutter priority. You select the speed and it
automatically selects the aperture, and once the lens is wide open starts
increasing the ISO until you need flash.

You could also auto adjust - the camera will pick a suitable aperture and
speed, but once the speed it too slow for hand held it starts adjusting the
ISO, unless it detects a tripod.

wrote in message
...
On Thu, 9 Oct 2008 14:35:29 +0100, in rec.photo.digital.slr-systems

Cheers. Just looked at the manual, but doesn't seem to give much info on
how it works. Unfortunately, I don't know anyone with a 50D that I can
play
with either.

If you can't tell it what minimum shutter speed you want, I wonder what
parameters it uses? For example, does it just use a base shutter speed
setting of say 1/60? Does it change depending on what focal length is
being
used, and if so, does it takes IS into consideration?


Can't help you here, I shoot Nikon's, was just interested enough to
look given I have a few friends and know their 20Ds don't have any
kind of auto-iso function. I use it a fair bit, though really wish
Nikon would allow faster minimum shutter speeds to be set than the
1/250s in my D200/D300.


No probs. I think I have found the answer. Looking at a review of the 5D
II, it says the following:

"Auto ISO in all modes except manual:
The Mark II now features an automatic ISO option where the camera selects
the sensitivity (in the range ISO 100 - 3200). In Auto, Program and Aperture
Priority the camera attempts to maintain a minimum shutter speed of 1/focal
length (hence with a 24 mm lens it will try to maintain 1/25 sec or faster).
In manual mode Auto ISO is fixed at ISO 400."

I would assume that the 50D is the same (apart from ISO 1600 Max). Although
there is no mention if
this changes if you are using a lens with IS.

Not a problem if ISO 1600 on a 50D is totally noise free. As it isn't, I
would prefer it to give you the option to manually over-ride it. It sounds
like at 300mm it will select
1/320, when I know I can get away with 1/30 on a lens with IS if the
subjects are relatively still and so could use a much lower ISO.

The Nikon system seems to allow you to tell the camera what you want, but
doesn't take focal length into concideration. The Canon system takes focal
length into concideration, but AFAIK doesn't allow you to over-ride the
camera.

Why not have a true ISO priority mode?

You choose the shutter speed and you choose the aperature, and the ISO is
adjusted automaticlaly.

Is any DSLR manufacturer doing this?

In article , just bob
wrote:

Why not have a true ISO priority mode?

You choose the shutter speed and you choose the aperature, and the ISO is
adjusted automaticlaly.

Is any DSLR manufacturer doing this?

just use auto iso in manual mode.

just bob wrote:

Why not have a true ISO priority mode?

You choose the shutter speed and you choose the aperature, and the ISO
is adjusted automaticlaly.

No, true ISO priority would be you chose the ISO, and the shutter speed
and aperture are adjusted automatically - like P mode on most cameras.

Is any DSLR manufacturer doing this?

What you describe (you set shutter speed & aperture, ISO adjusted
automatically) sounds very like the TAv mode on the Pentax K20D.

Pentax also seem to have a few other clever settings, such as program
line adjust and their "Green" mode, which look like they could do all
the OP was asking for and more.
--
Alex Monro
Exeter, UK
Running on Linux (Kubuntu 7.1)

In rec.photo.digital Paul wrote:

| I would assume that the 50D is the same (apart from ISO 1600 Max). Although
| there is no mention if
| this changes if you are using a lens with IS.
|
| Not a problem if ISO 1600 on a 50D is totally noise free. As it isn't, I
| would prefer it to give you the option to manually over-ride it. It sounds
| like at 300mm it will select
| 1/320, when I know I can get away with 1/30 on a lens with IS if the
| subjects are relatively still and so could use a much lower ISO.

I have a 450D. It allows me to choose an ISO in M, Av, and Tv modes. I have
a choice of 100, 200, 400, 800, 1600, and "AUTO".

I'm guessing at what actually happens with an ISO setting. I believe it uses
this setting to determine how to interpret the raw pixels values captured by
the sensor to convert the image into a JPEG file. This would emulating using
different film speeds (which are intrepreters of incident light levels).

If my guess is correct, then the RAW files should be the same under the same
exposure setting, regardless of the ISO setting.

Presumably the "AUTO" setting for ISO would choose an ISO interpretation that
produces a better light balance for the given exposure conditions.


| The Nikon system seems to allow you to tell the camera what you want, but
| doesn't take focal length into concideration. The Canon system takes focal
| length into concideration, but AFAIK doesn't allow you to over-ride the
| camera.

I have manual settings on my 450D that let me control the exposure, and so far
it has let me do whatever I want, even if it is dumb (like bracketing across
20 stops).

A higher ISO is going to take a weaker exposure and crank it up numerically
to have values that in a JPEG file will display at visible pixel values. If
the exposure really is weak, there will be more noise. That's just a fact
of science. You can post process the files (either RAW or JPEG, but you get
all the original info with RA) to crank up the effective ISO even beyond the
maximum 1600 setting, but you will get even more noise that way. You could
reduce noise by chilling the sensor. Special cameras for astrophotography do
that. Some have simply heat sinks. Others have active cooling systems. A
radical one might even have liquid nitrogen cooling (I've heard of it being
done).

--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
| Usenet from these places, find another Usenet provider ASAP. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

wrote:

You can post process the files (either RAW or JPEG, but you get
all the original info with RA) to crank up the effective ISO even beyond the
maximum 1600 setting, but you will get even more noise that way.

True.

I have quite a number of shots on 20x30cm which were nominally
ISO 1.600 (more like ISO 2.000 on the 20D), pushed 2 or 3 stops
in RAW --- i.e. ISO 8.000 and 16.000. The noise is visible if
you look for noise, but not bothersome; getting reasonable
colours is much harder.

You could reduce noise by chilling the sensor.

Only if dark current noise is the problem.

Special cameras for astrophotography do that.

They also often do multi-minute exposures.

Some have simply heat sinks. Others have active cooling systems. A
radical one might even have liquid nitrogen cooling (I've heard of it being
done).

Liquid helium is also commonly used.

-Wolfgang

"Paul" wrote in :

Anyone know if the Canon 50D has programmable auto ISO like the Nikon
system?

No. It has an "auto" value for ISO, but it is programmed by morons, who
don't seem to understand anything about how Canon DSLRs work in regards
to ISO and noise, or about the needs of users.

For example, you can program the lowest shutter speed you want to use
and it will automatically increase the ISO if it needs a slower
shutter speed than that for correct exposure? For example, if you are
shooting at ISO 100 in AV and pre set the lowest shutter speed to
1/30, if it needs 1/15 it will automatically bump it up to ISO 200 and
use 1/30 instead?

No. 50D auto-ISO gravitates to ISO 400

Also, can you set the maximum ISO it will automatically choose? For
example, if you don't want it to automatically go above ISO 800, you
can set it to stop at this ISO?

No, but it doesn't go above 400 unless it really, really needs to. Even
if you have it set to Tv-priority, it will hold the ISO down to 400 when
it should be at 1600, which makes absolutely no sense, as ISO 400 will
give a noisier image than 1600 when 1600 is the right ISO for the maximum
aperture, the set shutter speed, and the lighting.

In manual exposure mode, "auto-ISO" is fixed at ISO 400! Manual exposure
(TAv) mode is the one where I would use a properly-working auto-ISO the
most.

An intelligent auto ISO should have *NO* hesitation to raise the ISO as
necessary, at least in manual exposure mode ("TAv") and in Tv mode.
There is no intelligence, whatsoever, in Canon's system. Whoever is
making the decisions on auto-ISO for Canon is an incompetent moron.

I really don't understand why so many people are interested in limiting
the high end of ISO. My problem with Canon "auto-ISO" is that it doesn't
go high enough.

Do you like blurred images? Under-exposed images?