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Do I have a bad CMOS sensor on my Xsi?

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LabHappy said:
It's not hard to tell which way is north in that photo Brian. The
stacking really brings out the trails!

As a further experiment, I took the shot below to see if any amp glow
showed up. Once again, the full moon is not your friend if you are
trying to image stars, but for my purposes it served.

ISO 100, f22, 33 minute exposure with temps in the 60s and minimal
use of the LCD. LENR set to Auto and High ISO NR set to On.

No evidence of any amp glow whatsoever. A moonless night would make
the star trails pop much better and my back yard doesn't make the
most interesting backdrop.

I'll have to further experiment with a range of ISO settings. These
photos are time consuming because if the exposure is half an hour,
the camera takes an equal length of time processing the image but at
least you can watch TV while it's all going on.



--
Click to expand...
--Im amazed stars show up at f22. I guess theres a lot of lattitude in doing this.

If you try the stacking method you can turn off the LENR. You dont want to be recording dark frames between shots. Heres 1 more shot using burst mode & 30 sec times. No need for expensive interval timers you just need a simple locking release. I went a little too hot with the flashlight. I'll Have to try some full moon shots to illuminate the foreground.



Brian Schneider

 
And you actually replied to my post...
http://forums.dpreview.com/forums/read.asp?forum=1031&message=28608598

I'm guessing that the light leaks through the space between the main mirror and the front of the mirror chamber or between the sub-mirror and the edges of the semi-transparent area of the main mirror. Here is a picture, jpg from the camera, not edited in any other way than resize:



Anyway, what the original poster is experiencing is "amp glow". I have made some tests regarding the effect of extensive use of live view on image noise, and, indeed, the noise goes higher, but it's not noticeable in normal shots.
 
Brian D. Schneider said:
--Im amazed stars show up at f22. I guess theres a lot of lattitude
in doing this.
If you try the stacking method you can turn off the LENR. You dont
want to be recording dark frames between shots. Heres 1 more shot
using burst mode & 30 sec times. No need for expensive interval
timers you just need a simple locking release. I went a little too
hot with the flashlight. I'll Have to try some full moon shots to
illuminate the foreground.
Click to expand...
--

I was afraid of washing things out with the full moon out, that's why I tried f22. The star trails are kind of anemic however. I'll have to try again in a week or so when the moon is less of an issue. The flashlight is a neat idea. How long did you illuminate the church? Was it for just one of the stacked exposures?

I agree, stacking makes a lot of sense, but right now I'm testing the limits of where I get the amp glow. If LENR is set to auto, I wonder at what threshold it kicks in time-wise?
 
LabHappy said:
Brian D. Schneider said:
--Im amazed stars show up at f22. I guess theres a lot of lattitude
in doing this.
If you try the stacking method you can turn off the LENR. You dont
want to be recording dark frames between shots. Heres 1 more shot
using burst mode & 30 sec times. No need for expensive interval
timers you just need a simple locking release. I went a little too
hot with the flashlight. I'll Have to try some full moon shots to
illuminate the foreground.
Click to expand...
--
I was afraid of washing things out with the full moon out, that's why
I tried f22. The star trails are kind of anemic however. I'll have
to try again in a week or so when the moon is less of an issue. The
flashlight is a neat idea. How long did you illuminate the church?
Was it for just one of the stacked exposures?

I agree, stacking makes a lot of sense, but right now I'm testing the
limits of where I get the amp glow. If LENR is set to auto, I wonder
at what threshold it kicks in time-wise?
Click to expand...
--Flashlight was abt 30 sec just on the last exposure.

I read (but havnt tried it yet) that for star trails with full moon you are limeted to abt 8 min before the foreground gets too bright. If its clear tomorrow night I might give it a try. Not tonight tho its almost time for Prison Break, cant miss that!!
Brian Schneider

 
After shooting what amounts to hours of 1-5 minute exposures with LENR on auto and high ISO NR on, but the LCD dark, I've concluded that heat from the LCD is responsible for the phenomenon I was seeing. I haven't seen it since using EOS utilities remote shooting and my laptop to do many, many sequential long exposures (I can watch TV while the program controls the camera).

Also, I've taken very long exposures (up to an hour or more) with the LCD dark and I don't see the amp glow. So I've concluded that I DON'T have a problem.

Below is an image using two exposures stacked in Photoshop, one 45 minutes and the other 65 minutes, ISO 200, f11, 18 mm, tweaked to get rid of the ugly red sky glow/light pollution from Reno and to get a pleasing color. I didn't have a church steeple so I used a fir tree.

Thanks again for all the helpful responses.

Ed.

 
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