Long exposure noise

steve.82

steve.82

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Well, lacking any kind of remote shutter at the moment, I thought I'd get out there and have a play stacking 10x30sec exposures on top of each other, resulting in this...

Untitled-1-2.jpg


Other settings - F/9 ISO100 70mm NR-on

I know the subject is dull, just trying to nail the technique down at the moment.

Are these things that go away on a true long exposure (the vertical bands particularly)?
 
eewww. You shouldn't really get noise at 100ISO, even with a 30sec exposure. And I'm not convinced I'm looking at noise anyway. I'd suspect its a stacking issue.

1st thing I'd suggest is to turn off the in camera NR - then try a couple of 30sec exposures and see what they look like without stacking. I think your stacking s/w is screwing your pics.
 
I agree... that looks like some photoshop/stacking problem fo sho.

how does a single capture look compared to the stacked version?
 
Nope it's not the stacking, a single exposure looks pretty similar with the levels stretched out.

Will try without NR thanks
 
ok here's a single one, but levels stretched a fair amount. I really think it's just the light levels are too low to drown out the background noise of the sensor.
IMG_6535.jpg
 
steve.82 said:
ok here's a single one, but levels stretched a fair amount. I really think it's just the light levels are too low to drown out the background noise of the sensor.
Click to expand...

how stretched out?

do we have an original unmolestered photo that we can see?

else you have a sensor from nikon d60 at iso400 by the looks of that image...
 
Oh and for the stacking, levels weren't played with, but each additional exposure was added to the one beneath
 
steve.82 said:
Here you go, all raw adjustments set to 0 (apart from wb)
Click to expand...

riiiiiiight... yeah, here's the problem, you've got what, I believe, is possibly the most under exposed image in the history of photography.

As the original image ISO100 is so dark, you've then had to 'push' the exposure up in the software, which as a result is effectively 'pushing' the ISO up.

I'm crap at explaining things but here goes... (I can do a very detailed version if what I write is just confusing) the problem is with a dark image that most of the data is contained contained within a a very small portion of the effect image data space - in other words I can bet that the file size of that image is tiddly, and because the file size is tiddly there isn't much information available to the software when you want to 'push' the exposure. This consequently means that the graduations of colour in the dark area is very low and thus went you want to push the exposure to compensate you get very very significant 'noise'

This is why it's always better to over expose than under expose when compensating

The trick is usually done when you want to 'boost' beyond the ISO limit on the camera, so for an xxxD series the limit is 1600ISO. if you underexpose the image by a stop, and then increase the exposure back to the correct level in Lightroom/photoshop etc then you've essentially pushed the ISO to 3200.

So basically the camera is fine, you just need to increase the shutter duration for longer and/or open the aperture up in future.
 
Ooooh most underexposed image in the history of photography... I'll take that title! :cool:

Thing is the levels weren't bumped up at all in the 1st image, but 10 equally underexposed images added to each other.

Quite happy to sit there for 10mins+ with my finger on a remote button, just hope the noise stays at the level it is in a 30sec exposure.... or does it build and build and build? Hmmm, best way to answer would be to try, but lacking remote capability at the moment. Unless I took my laptop outside.... perhaps tomorrow :thumbs:

edit: PS - had a nose through your gallery section, impressed with the nightclub photography!
 
steve.82 said:
Ooooh most underexposed image in the history of photography... I'll take that title! :cool:

Thing is the levels weren't bumped up at all in the 1st image, but 10 equally underexposed images added to each other.

Quite happy to sit there for 10mins+ with my finger on a remote button, just hope the noise stays at the level it is in a 30sec exposure.... or does it build and build and build? Hmmm, best way to answer would be to try, but lacking remote capability at the moment. Unless I took my laptop outside.... perhaps tomorrow :thumbs:

edit: PS - had a nose through your gallery section, impressed with the nightclub photography!
Click to expand...

Thanks dude! Nice of you to say :D (need to update it actually, seem to be doing just a lot of rubbishy macros at the moment :| )

Honestly don't sweat it, I did a 20 minute exposure on my 10D before and I think a 40 minute on the 40D (both at ISO100) and the noise is nothing to be concerned about, particularly when you resize for the interwebs as the averaging across the noise comes into play and reduces to insignificantish levels :thumbs:

you might find the odd pixel might get hot (1 on the 10D but none on the 40d or the 1d) but it's nothing major. On the flipside if it's out long enough and it's cool the noise will be reduced anyway as the noise occurs partly due to the heat of each pixel, so cooler climates often produce low noise levels... at the expense of your batteries, they take a beating in low temps.

so the 1st image you posted was a 10 stack of unmolestered images, but then the final image was then adjusted, yar?
Either way it wouldn't make much difference as the software still has a tiny weeny amount of data to play with.

with the stacking you want to still be exposing so you're atleast pulling some light to a decent amount and then stack those all together.

ads :D
 
adsayer said:
so the 1st image you posted was a 10 stack of unmolestered images, but then the final image was then adjusted, yar?
Either way it wouldn't make much difference as the software still has a tiny weeny amount of data to play with.
Click to expand...

Post 1 - created from 10x unmolested images, totally as shot, no levels, just resized

Post 5 - single exposure 'stretched'

Post 7 - one of the 10 unmolested exposures

Hmmm, looks like I need a remote! Laptop won't make it do bulbs...

Yeh those club pics were ace, you kinda see and remember those colours but I don't think I've ever seen them captured like that
 
Its not a noise issue. You're trying to get data out of underexposed pics when the data isn't there. Adding lots of under exposed pics onto the stack just gives you mush - as you've seen.
 
Yep, that i get. But what I'm hoping is that noise doesn't keep adding up through a long exposure too, and stays at the level it is in post no7.

Remote ordered and on the way :)
 
Ooooh looks handy!

I think I saw something a few days back, may have been on this forum. Deep sky stacker was it? I think it did a similar thing, but from what I could tell, tries to follow the rotation in the stack so you end up with one bucketload of stars.
 
steve.82 said:
Yep, that i get. But what I'm hoping is that noise doesn't keep adding up through a long exposure too, and stays at the level it is in post no7.

Remote ordered and on the way :)
Click to expand...

I use a 450D which I think has a sensor about on par with yours. This is a 5 and a bit minute night exposure, iso 100, f4, 10mm. It should give you an idea of the kind of quality to expect.
buxton2d.jpg

It's had a bit of a curves tweak, and I'm not sure but I may have cloned out a few hot pixels here and there

Noise does increase with exposure length, but to nowhere near the degree you've got on yours.
 
I don't get it... Why did you not just use the camera bulb option with a 2 sec timer to avoid shutter press shake if you didn't have a remote???
You don't have to hold the shutter button down, one press is fine :D
 
neo2810 said:
I don't get it... Why did you not just use the camera bulb option with a 2 sec timer to avoid shutter press shake if you didn't have a remote???
You don't have to hold the shutter button down, one press is fine :D
Click to expand...

Perhaps on the 40d, but I've just tried that on my 450 with no joy. The timer stops counting down the second you're off the sutter button. Shame as that would be a really useful feature to have.
 
The Matt said:
Perhaps on the 40d, but I've just tried that on my 450 with no joy. The timer stops counting down the second you're off the sutter button. Shame as that would be a really useful feature to have.
Click to expand...

You're right, how bizarre. I'm sure the 400D has a click on/off for bulb? That would be a strange step backwards... :thinking:
 
I am pretty sure my old 350D's had it as well. Cant think of any reason why they wouldnt have added this to the 450D.

Stew
 
Maybe they want you to buy their overpriced wireless remote. Up yours Canon, I got a cheaply made 3rd party cable release instead.
 
neo2810 said:
You're right, how bizarre. I'm sure the 400D has a click on/off for bulb? That would be a strange step backwards... :thinking:
Click to expand...

Unless it's tucked away in a menu somewhere mine is a hold for bulb :( Looking forward to trying it though!
 
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