All,
I have a new cannon 50d, I seem to be having a problem with red noise even with auto noise reduction on.
Anything above a 2 minute exposure is so noisy its useless.
Its connected to live view computer only and the battery is removed and the ac power fitted.
If anyone has any tricks or methods for reducing noise Im all ears.
Thanks in advance
iso 800 (but tried higher and lower same result) ambient temp 18 to 20c which is high I know but you still should be able to get a 5 to 10 min shot at least with a min of noise .....shouldnt you?
If I use the battery the noise is way way worse due to the battery heating up, so I now have ac adapter, this helps a lot but still fairly hideous amounts of noise.
At 2500 bux Im somewhat peeved
I noticed while searching for DSLR cameras that they limit to 30S exposures possibly due to this reason. A lot of DSLR users mod their camera to take onger exposures. Maybe this is needed could need some cooling.
Best leave that up tto the rest of the AP forum members.
no they have a bulb setting that allows you to take as long a shot as you wish, from what I can see there are folks with unmodded bog standard dslrs taking good shots of half an hour , sure there will be noise that can be eradicated or reduced with darks etc but their results are good.
I did a few 30sec shots on m42 , they were great the fov compared to my ccd's is amasing but I need more data for dimmer objects and you can only get away with telling your mates "this is a close up of the horse head neb without the horsehead" so many times
Bear in mind, that the more exposures you take (once stacked) it will assist in removing noise.
Mind posting a 5-minute light and dark frame here so we can see just how bad it is?
Stack 40-odd images at 5-minutes a pop and you'll have a virtually noise free image. Bearing in mind that dark frames should be taken immediately after the light frames. I take, at a bear minimum, one hour worth of darks.
Thanks that sounds like good advice, I was just taking the one or two and they were so noisey I wasnt bothered about doing anything with them, also will shooting in RAW help?
I can shoot a 5min dark tonight no problems
they may be a bit big to post tho most are coming out at 5 plus meg.
which is another thing I need to get my head around.
Maybe I should read all my books before bothering you nice folks.
I only just became good at ccd shots and now I feel like Im starting from the bottom again ( I think Im getting too old for this sh!t)
One or two images are always going to yield a lot of noise.
It's when you shoot lots of images (and, don't listen to people who say you only need a handful of exposures; take as many as you possibly can) and stack them using a median combine algorithm of some description, that the detail starts to emerge and the noise lessens.
You don't have to post the full frame images. Feel free to reduce them to something like 800x533 and save them so that they're less than 200 KB for this forum.
Definately shoot in raw. And follow Octanes advice.
Also bear in mind that DSLRs are not meant to take loooonnnng exposures.
The 'Bulb' setting is really a hold-over from the days of Ektachrome 64 and before, where the studio would be darkened and the image exposed with flash units.
Also the number of pixels has IMHO, passed the point of diminishing returns. Images on the 50D are noticably more noisy than those on the 40D (check out the comparisons on dpreview.com). Even with the truly amazing DIGIC processing, it still can't account for all situations.
Stick with shorter exposures and try to shoot at around 400-640 ISO. That should help some.
Happy snapping!
Peter
Good advice, yes shoot raw and if you are new to this I would enable long exposure noise reduction, makes the processing easier till you learn the ropes. Keep away from very high iso`s and shot as many as you can manage and stack these.
Done 2 darks with the 20D and the 40D both 5 min long at 22 degrees iso 800. Shall post a 100% crop of each this arvo. At a quick visual look both look very similar but have heard the 50D is a bit noiser compared to the 40D. That`s why I got the 40D over the 50D.
Here is the 100% crops of my test yesterday. Canon 20D top and the Canon 40D underneath. Both done as raw and cropped and converted in PS to jpg. Unaltered in any other way.
Tell you the 20D has heaps less thermal noise.
I always had the impression that the 40D was slightly better?
Might have to keep the 20D yet!
with what your saying gary theres a difference in the cameras by quite a fair amount, i read somewhere for instance the 350d and the 40d that the 350d's iso 800 was the 40d's iso 400.
Ide hardly belive that canon would go so far backwards when it came to noise and amplification of their sensors, irrispective of this problem temperature is 90% the cause of such noise, if you turn a dedicated astro ccd on and don't use tec, it will most likely look similar to the noise profiles you hvae shown.
My M42 shot that recently gained 1st place in astronomy WA's Astrofest had NO reduction shots aka no flats, no bias, no darks no nothings. yet its silky smooth without any noise ninja, noise works help.
what was the good news for that. Temperature blimy it was close to zero degrees. From this night on darks only reduce so much noise, but as bert has pointed out, it leaves holes in your fine faint data basically killing the image. so if you want limited/no noise you need to cool her down!
