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Ags

The noise produced by a Canon 1100D at various ISO settings and temperatures

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Interesting :) I wonder how the improvements introduced with Digic 4 affect those figures. At least we know that the dynamic range has been increased 4 times - a big help with the large dynamic range of most DSOs. With newer processors we cannot assume figures for earlier processors will apply. Canon are very likely to have introduced extra image processing to improve their cameras for terrestrial use. We aren't told how this affects very long exposures and very low light levels or whether extra processing is applied to the RAW image or just to the more commonly used JPEG.

For AP there seems little difference between models in the Digic 4 range - the higher priced models just adding features for normal terrestrial photography. eg. fold out screens are irrevelent, higher pixel count only makes for smaller image sensing areas and hence reduced sensitivity. All this means that the 1100D works out best value for money for AP and this must be our reference for the current situation in Canon cameras for AP.

I have been trying to find out what the new Digic 5 processor adds if anything and AFAICT there seems to be no improvement for AP.

Edited by Gina

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higher pixel count only makes for smaller image sensing areas and hence reduced sensitivity

it's not quite that. The smaller pixel can hold a smaller number of electrons and consequently can never be as low-noise as a larger pixel. On the other hand, you can average a few small pixels to simulate a larger pixel but guess what, you pay the price of many read errors instead of one!

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it's not quite that. The smaller pixel can hold a smaller number of electrons and consequently can never be as low-noise as a larger pixel. On the other hand, you can average a few small pixels to simulate a larger pixel but guess what, you pay the price of many read errors instead of one!

Yes, so the result is much the same - worse off with the smaller pixels. Edited by Gina

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Camera seems fine and everything seem to be working as expected. I'm currently waiting for the temperature to stabilise ready for a darks test run. I going for +10C tonight. I'm covering the warmer values while this mild weather remains - they may not be attainable once we start getting frosts again.

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Now settled down nicely at +10C EXIF T and I'm running a darks test run :)

Back on schedule again :)

Edited by Gina
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I used to be plagued by banding, it was apparent in my 450D at ISO 400, 800 & 1600, the higher the Exif temp the worse the banding was.

I've used my 'Honis-style' cooler box for almost 3 years now and I'd almost forgotten about banding.

At Exif temps below 12C I never notice it any more and colour is also more vibrant.

I've never profiled my camera but tried moving from my usual ISO 800 to 1600 the other night after reading this thread. The results were pretty awful, and I think I'll stay with 800 in future, well with this camera anyway. Saying that, I completely agree that if you want to get the best out of your camera then you really do need to profile it.

Cheers,

Ian

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Although fairly clear ATM, more cloud is forecast so I've set up for another darks test run tonight - this time at 8C. I've added in some 12m subs at all ISOs now making the run last all night.

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Loking at some preliminary results suggests that cooling really pays off at longer subs, so adding in longer subs will test this out.

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Loking at some preliminary results suggests that cooling really pays off at longer subs, so adding in longer subs will test this out.

Yes, that was what I found with my much abbreviated testing a while back. I've added 3 samples of 12m of each ISO onto the end of the run starting tonight. I may be able to change it to 4 samples another night if I can get started earlier.

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Last night's +8C run seems fine and I now have a +15C test darks run set up and running. A slight excursion up to 16C for 4 samples but I think it's settled down now at 15C. I've got the full 4 samples of 12m for each ISO now and the run is due to finish about 7am which I think will be dark enough not to show any light leakage. The noise level should be pretty high at 15C and 12m too.

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Current state of play :- Now have data for EXIF T values of -10C, -4C, 0C, 6C, 8C, 10C, 12C and 15C

Here's a table showing data already captured :-

post-13131-0-14369800-1353418517_thumb.p

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It's very mild tonight and I've been trying to do an 18C run but so far with no cooling other than convection the EXIF T is running at 17C. Ambient temperature is 11.5C. If I want to get any warmer data I shall have to either arrange warming or wrap up the cooler in insulation to stop it working. Actually, that gives me an idea - I could do higher temperature runs during the daytime if I have the cooling off and wrap the whole camera box and cooler in black polyether foam (or an old dark blue anorak :D).

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Got it running at 18C now and has been for an hour so we'll see what happens overnight just relying on the ambient temperature staying reasonably constant as we have no set-point control running.

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I wonder if tin foil might be more light proof?

On the other hand I don't know if we need to go higher than 17C - my tests suggest a closed 1100D (i.e. with lens and lens cap on) stabilizes as Ambient+11C - a DSLR connected to a scope will cool better.

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I wonder if tin foil might be more light proof?

Yes, I should think it is.
On the other hand I don't know if we need to go higher than 17C - my tests suggest a closed 1100D (i.e. with lens and lens cap on) stabilizes as Ambient+11C - a DSLR connected to a scope will cool better.
I think I'll just stop at whatever tonight's run gives as far a high temperatures goes. It might be a bit up and down but the EXIF T is in the filename. I'll concentrate on the lower temperatures after tonight. 5 more nights will complete the set. Plus some 12m subs some of the other temperatures lack. Those should take under 2 hours each - 7 data sets, one for each ISO (84m) plus temperature change for the next lot.

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It was, as I expected, a variable temperature overnight with the ambient temperature dropping in the early hours. The EXIF T varied between 16C and 19C.

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Progress table :-

post-13131-0-29462200-1353498355_thumb.p

Edited by Gina

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I don't suppose you have the raw file available from the -10C 8m you did do you Gina? .. I wouldn't mind seeing what the noise is like.

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I don't suppose you have the raw file available from the -10C 8m you did do you Gina? .. I wouldn't mind seeing what the noise is like.

Yes, I do. Which ISO would you like. I have 4 samples/subs at each ISO from 100 to 6400. I'll upload a sample to Dropbox and post the public link.

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Here's a selection that are already in Dropbox - ISOs 400, 1600 and 6400 of 8m at -10C. They are in the public area so anyone cane download them :)

400 :- https://dl.dropbox.c..._480s__-10C.CR2

1600 :- https://dl.dropbox.c..._480s__-10C.CR2

6400 :- https://dl.dropbox.c..._480s__-10C.CR2

Edited by Gina

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Yes, I do. Which ISO would you like. I have 4 samples/subs at each ISO from 100 to 6400. I'll upload a sample to Dropbox and post the public link.

Around 400 ISO if possible Gina ?

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:)

I've downloaded the 400ISO to try, but my graphics program only loads files as 8-bit at the moment, will have to update to work with 16-bit cause the noise level in your image is flat now, too low for my program to show lol

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:)

I've downloaded the 400ISO to try, but my graphics program only loads files as 8-bit at the moment, will have to update to work with 16-bit cause the noise level in your image is flat now, too low for my program to show lol

Try the 1600 or even 6400 - they might be noisy enough :) I think allowing for 16 bits would be a good idea though :) Edited by Gina

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Gina: could you upload 1 each of all of your 120s subs @ iso 1600?

I have done some testing myself and found that below +10 the noise is very low and below +5 there is mostly random noise. My tests were done at 120s @ iso 1600 with a 450D and 600D.

Some of the test images with the 600D at 120s @ iso 1600 were pretty much the same as bias frames...maybe there is no point in going extremely cold or to use dark frames at all since the noise is random?

I can post some pics when i have done some sorting of all test images.

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