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Old 28-07-2009, 08:45 AM
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hotspur (Chris)
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amp glow issue

HI

just wondering if any canon 450D users have "amp glow" in their long exposuers.

I just used mine for the first time last night.and noticed it in top left hand corner after one and half minute exposuers.Does the "in camera"

noise reduction remove this?i forgot to activate it,i really didnt have much time,and wanted to see if the camera worked,i will try and post pic

in DSO,of M7 it 2minutes 9 seconds

also,does the live image,have ten times mag tool,as in 40D?

regards Chris
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Old 28-07-2009, 10:58 AM
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Astrobserver99 (Rob)
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Hi Chris,

I don't know about amp glow in the 450D, probably someone else can help there. Whether it's amp glow or something else, the builtin noise reduction (dark frame subtraction) will definitely remove it. If you can, you're better off taking a few dark frames and processing these later on your PC.

Cheers,
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Old 28-07-2009, 11:34 AM
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Omaroo (Chris Malikoff)
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Being the consumer model, the 450D I'd assume will show amp glow - some worse than others. For 2 minutes, yours is pretty prevalent. I have a 350D and a Nikon D40 and neither generate appreciable amp glow until they've run 8-10 minutes. It isn't to be confused with thermally-induced CCD readout noise (which ICNR will remove most of) either - it's different. The higher end 40/50D 1D, etc, bodies turn the readout amplifiers (at the edge of the sensor) off during exposure, and only initialise them on read-out at the end of the exposure, so they don't suffer from it. You pays your money, you get better results, like with anything I guess. Whether the exposure your doing is a light or dark, I think that the amps are kept on regardless - so ICNR won't remove it. Can someone correct me here?

The best way to get rid of it is take a few dark frames with the same exposure details as your lights and get your stacking program to process them out in one hit.

Last edited by Omaroo; 28-07-2009 at 05:23 PM.
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Old 28-07-2009, 01:28 PM
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hotspur (Chris)
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re amp glow

Ok,thanks to the two people that replied,i will do a few more tests re

INCR,otherwise just crop the image,or shorter ones stacked,i dont do

a huge amount of astro pics,I did have the choice of 450D or 40D,there

is little price difference in body only,i chose the 450D for a few reasons,

not price related,i got tired of CF card,in the 300D,and its smaller which

suited my "in field" applications.

Is there any body on this forum that has a 450D canon???,surly their must be someone with one,

hope to get some feed back

regards Chris
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Old 28-07-2009, 03:17 PM
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Chris ICNR is the way to go, I never image with out it and never take seprate darks, and expose up to 7-9 minutes with out any AMP glow at all.
My image runs are doubles of coarse, but that suits me fine.

But then others here do it differently.

Leon
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Old 28-07-2009, 03:57 PM
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Omaroo (Chris Malikoff)
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Quote:
Originally Posted by leon View Post
Chris ICNR is the way to go, I never image with out it and never take seprate darks, and expose up to 7-9 minutes with out any AMP glow at all.
My image runs are doubles of coarse, but that suits me fine.

But then others here do it differently.

Leon
I think that the 5D also turns off the amplifiers during the exposure cycle Leon, as opposed to the 450D which does not - which is why you don't get amp glow and Chris would even with ICNR set on. Doing ICNR on the5D would leave your images pretty clean I'd imagine!
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Old 28-07-2009, 03:58 PM
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I got caught out on this recently. My camera battery run out before I took my darks (and I only have one battery - new one is on order!). By the time the battery was recharged, the camera had cooled down too much, and the darks did not match the images any more

I think I'll try ICNR next time. I guess it would give a better correlation between the light and the dark.
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Old 28-07-2009, 04:06 PM
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You might find an "off amp" (during exposures) mod for the 450D on the net. I did this mod on my 300D, but it was pretty tricky, youd need tech skills for that.

It might be worth trying flats of the same exposure time, but you would have to dark subract them and use a very dim light scource
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Old 28-07-2009, 04:43 PM
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Quote:
Originally Posted by hotspur View Post
Is there any body on this forum that has a 450D canon???,surly their must be someone with one,
Hi Chris,

I have a Canon 450D that I use for Astrophotography. 5 minute to 10 minute subs show no sign of amp glow. The 450D and newer models of cameras turn off amp glow during long exposures so you will definitely not have a problem with the newer models of these cameras.

Live view is a great feature especially for focusing with the 450D.

Hope this helps.
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Old 28-07-2009, 04:47 PM
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Same here, I had no amp glow on my 450D.
Here's a 10minute dark that's been stretched to buggery.
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Old 28-07-2009, 05:25 PM
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Omaroo (Chris Malikoff)
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Ah ha! OK - so the 400D was the last of them that don't turn off the amplifiers?

In that case - why is Chris getting amp glow on his 450?

Chris - this is amp glow - is this what you're getting? Are you sure you're not talking about read noise instead?
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Old 28-07-2009, 05:27 PM
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Try imaging with a DC power supply over a battery. And bask in the glory.
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Old 28-07-2009, 05:29 PM
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I used to get plenty of amp glow from my old 350D.. anything over say, 2 minutes and I'd get a rather large glow in one corner of my images..

I found darks would remove it. however the darks had to be taken at a similar temperature to the lights...

From my knowledge of how ICNR works, it should remove amp glow if its present. Being that it is noise generated by heat of the amp during the exposures, it should show up in an ICNR "dark"

Give ICNR a go, failing that, darks is the way to go...
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Old 28-07-2009, 07:12 PM
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re amp glow

THANK YOU, Chris,Humayun,Leon,Matty and everyone with your help

It has really helped me alot,Yes Chris thats what i had in that pic you showed.

Matty,and Leon put me right,i just went outside and took a 2 minute 10 second pic,with dark frame following for in camera reduction,MMM smooth as!

yes Leon,i like your way of doing astro pics,that suits me too!

But Humayan had a great fix it,i have a Jay car D.C power supply unit,its got digital display for amprage,voltage and fine adjust,it cost $400,

i got it for my antique train set,so can use it on my camera too!

thanks again to everyone who took the time to help.

Cheers Chris
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Old 28-07-2009, 07:29 PM
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Chris, now that you mentioned that about my camera, I remember that I actually new that, but had forgotten and spoke before I thought again.

Leon
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