Glitch with Canon 300D?

wrote in message
...
In message ,
"Woollyzone" wrote:

No I didn't, but I didn't think there was any light coming in from
behind.
Its possible there was however, so I'll try again and take your advice
and
see if it makes any difference. Thanks for incredibly quick response!

Quite a bit of light can come in through the viewfinder. Outside in
bright daylight, I have seen f-stop and shutter speed figures on the top
LCD of my cameras that showed a considerable amount of light, only to
realize that the lens cap was on. For example, in Av mode at f/8, the
shutter speed might read 1/4. Cover up the viewfinder with my finger,
and it goes to 30s.

Wow, I'm going to check that out. I should be putting the cover on for my
long night exposures.

Greg

In message ,
"G.T." wrote:

Wow, I'm going to check that out. I should be putting the cover on for my
long night exposures.

Of course, there actually has to be a light source behind the camera to
have a problem!

OK, now I just did an experiment and realized something. I just shone
(is that a word?) my 2M candlepower flashlight into the viewfinder of my
20D, in AV mode, with lens cap on, and snapped a picture. The camera
metered for full exposure, but the resulting image was extremely dark,
so I guess it affects metering much more than it does the actual
exposure. That makes sense, when you consider the fact that the mirror
goes up against the prism area during the exposure.
--


John P Sheehy

wrote in message
...
In message ,
"G.T." wrote:

Wow, I'm going to check that out. I should be putting the cover on for
my
long night exposures.

Of course, there actually has to be a light source behind the camera to
have a problem!


Yeah, after Santa Anas blow the smog out I've been taking night shots of
downtown LA 12 miles to the south of me. From my back patio I have my
neighbors patios lights to contend with

Greg

BJ in Texas wrote:



Did you cover the viewfinder/eye peice? That is often the
source of stray light.


It would never reach the sensor with the mirror up.
--

Stacey

wrote:

If you take an image immediately afterward with the same ISO and
exposure time, with the lens cap on and the viewfinder cover, you have
the necessary data to subtract it.

I know the 20D has dark frame substraction (toggleable via custom
functions), doesn't the 300D?

-Wolfgang

Wolfgang Weisselberg wrote:

wrote:

If you take an image immediately afterward with the same ISO and
exposure time, with the lens cap on and the viewfinder cover, you have
the necessary data to subtract it.

I know the 20D has dark frame substraction (toggleable via custom
functions), doesn't the 300D?

The 10D doesn't have it, so it's unlikely the 300D does either (but
only an owner can definitely say).

The 20D/etc implementation of dark frame subtraction leaves a lot to be
desired though. As far as I can tell, it collects one (1) dark and
subtracts that. While this will removes any biases, it does add noise.
Better would be for the camera to gather 10 or more darks, average
them, and then subtract that from images. A convenient UI for this
would be something like the "manual white balance" stuff: pick and
choose from a set of already captured darks. For most uses, though,
this is probably not an issue:

http://www.lrgb.com/20dadark.html

a page that even includes a 300D dark frame, amplifiers aglow.

wrote:
In message ,
"Woollyzone" wrote:

No I didn't, but I didn't think there was any light coming in from behind.
Its possible there was however, so I'll try again and take your advice and
see if it makes any difference. Thanks for incredibly quick response!

Quite a bit of light can come in through the viewfinder. Outside in
bright daylight, I have seen f-stop and shutter speed figures on the top
LCD of my cameras that showed a considerable amount of light, only to
realize that the lens cap was on. For example, in Av mode at f/8, the
shutter speed might read 1/4. Cover up the viewfinder with my finger,
and it goes to 30s.

Great. But since when did this become an issue that can affect only a _portion_
of the picture? Light does indeed enter through the viewfinder, which can screw
up the _metering_ (thus affecting the entire picture), but it doesn't normally
reach the sensor (or the film). The OP states that only a portion of the image
was affected, which means that it has nothing to do with the viewfinder.

--
Best regards,
Andrey Tarasevich

"Wolfgang Weisselberg" wrote in message
...
wrote:

If you take an image immediately afterward with the same ISO and
exposure time, with the lens cap on and the viewfinder cover, you have
the necessary data to subtract it.

I know the 20D has dark frame substraction (toggleable via custom
functions), doesn't the 300D?

The 300D, no, the 350D, yes, but only for longer exposures, bulb only I
believe, or ISO1600.

Greg

In message ,
Wolfgang Weisselberg wrote:

wrote:

If you take an image immediately afterward with the same ISO and
exposure time, with the lens cap on and the viewfinder cover, you have
the necessary data to subtract it.

I know the 20D has dark frame substraction (toggleable via custom
functions), doesn't the 300D?

I never heard of it having that feature.

I wish it were available on the 20D on shorter exposures as well; some
of the pattern noise other than hot pixels, in short exposures, are
similar frame to frame. Vertical banding is repeatable; horizontal
banding is unique per frame. Of course, it would be nice if the black
frame had a filter run on it to remove the pixel-frequency noise.
Anything that isn't a line, a glob, or a streak should be filtered away.
Two black frames could verify what is repeatable and what isn't even
further. I wouldn't mind losing some burst speed for an optional higher
quality mode.
--


John P Sheehy

G.T. wrote:

wrote in message
.. .
In message ,
"Woollyzone" wrote:

No I didn't, but I didn't think there was any light coming in from
behind.
Its possible there was however, so I'll try again and take your advice
and
see if it makes any difference. Thanks for incredibly quick response!

Quite a bit of light can come in through the viewfinder. Outside in
bright daylight, I have seen f-stop and shutter speed figures on the top
LCD of my cameras that showed a considerable amount of light, only to
realize that the lens cap was on. For example, in Av mode at f/8, the
shutter speed might read 1/4. Cover up the viewfinder with my finger,
and it goes to 30s.

Wow, I'm going to check that out. I should be putting the cover on for my
long night exposures.

My 300D came with a viewfinder cover. It is a rubber bit
with some groves on the side meant to be threaded onto
the carry strap. Works just fine.

---- Paul J. Gans