A serious noise issue... software to the rescue?

[KenC]

Another trick that will make this sort of noise in dark areas unnoticeable under any normal viewing conditions is based on the fact the noise is either much brighter than the dark area or much more highly colored. Decrease color saturation in the dark areas (excluding the lighter patches) and also use levels or curves just to knock down the highlights (again excluding the patches). This takes almost no time and works very well if the end product is not a large print or projection.

 

[Dao]

If you want to take a photo like this I suggest rather than go for a 2 hour exposure, go for 120 1minute exposures. Then using free image stacking software combine the shots. .

Sounds like a lot of work I'm more of a lazy photographer haha.
I'm sure this problem would have been a lot less severe if I had used the long exposure noise reduction feature in the first place.

If you use long exposure noise reduction, will it take twice amount of time to take one shot? i.e. 2 hours shot will take 4 hours.

 

[unpopular]

No. It takes longer to write the file, not take the shot. As for stacked exposures, it really depends on how you do it. If you stacked two 2h exposures, then yes, it would take twice as long. However, it is also unlikely that only two exposures would significantly reduce noise.

What Garbz was saying is that you can take 120, 1-minute exposures and combine them together to get the same effect, without having noise problems.

As for being a lot of work, that's what intervalometers are for.

 

[ceejtank]

This might be a really stupid question...

but to me it looks like there is way too much light to leave it open for 2 hours.... how is this image not completely white?

 

[unpopular]

^^ I am thinking this started at dusk, so the sun was completely set within 15-30 minutes. Small aperture or ND may have also been used.

 

[fokker]

This might be a really stupid question...

but to me it looks like there is way too much light to leave it open for 2 hours.... how is this image not completely white?

It was actually completely dark when I took the photo... like completely dark. The sun had set hours ago, the yellow light on the horizon must be from the distantly setting sun. This was shot at 400 ISO and f/5, to give you an idea of how little light there was. The faint orange glow on the trees in the bottom left is from our campfire, about 150m away.

 

[fokker]

If you use long exposure noise reduction, will it take twice amount of time to take one shot? i.e. 2 hours shot will take 4 hours.

Yeah that's correct - the camera takes a second shot immediately after the first, at the same ISO and shutter speed but with the shutter closed, and the resulting noise is then subtracted from the first photo in the camera.

 

[ceejtank]

This might be a really stupid question...

but to me it looks like there is way too much light to leave it open for 2 hours.... how is this image not completely white?

It was actually completely dark when I took the photo... like completely dark. The sun had set hours ago, the yellow light on the horizon must be from the distantly setting sun. This was shot at 400 ISO and f/5, to give you an idea of how little light there was. The faint orange glow on the trees in the bottom left is from our campfire, about 150m away.

Hm... I now have an overwhelming desire to try this.,,,

thanks for the input. FWIW I like your shot. Noise be damned. ahha

 

[unpopular]

If you use long exposure noise reduction, will it take twice amount of time to take one shot? i.e. 2 hours shot will take 4 hours.

Yeah that's correct - the camera takes a second shot immediately after the first, at the same ISO and shutter speed but with the shutter closed, and the resulting noise is then subtracted from the first photo in the camera.

Huh. That isn't how mine works. You cover the camera lens once, and it records a dark frame which it uses on all future long exposures.

 

[unpopular]

This might be a really stupid question...

but to me it looks like there is way too much light to leave it open for 2 hours.... how is this image not completely white?

It was actually completely dark when I took the photo... like completely dark. The sun had set hours ago, the yellow light on the horizon must be from the distantly setting sun. This was shot at 400 ISO and f/5, to give you an idea of how little light there was. The faint orange glow on the trees in the bottom left is from our campfire, about 150m away.

In this case, the multiple short exposures would not work.

 

[Garbz]

Huh. That isn't how mine works. You cover the camera lens once, and it records a dark frame which it uses on all future long exposures.

This is what I would refer to as a Bad Idea(tm). Noise levels, especially hot pixels are highly temperature dependant. This is why it's important to take the darkframe immediately after the main frame. One of the crazies on the astro forum I regular actually takes a dark frame every 10 images for exactly this reason. I do mine at the end of a shooting session but this has bitten me before and resulted in a few hot pixels, which naturally turned to long streaks once star rotation was compensated for.

Sounds like a lot of work I'm more of a lazy photographer haha.
I'm sure this problem would have been a lot less severe if I had used the long exposure noise reduction feature in the first place.

Actually no. Notice how your image is quite bright? Long exposure noise reduction works on subtraction and the principle hope that your image will actually be rather dark since it's taken at night. Instead of bright red green and blue dots you will have ended up with black dots. It looked just as bad the one time I've done it.

Which of the stacking software available do you recommend?

I am currently using Deep Sky Stacker, but I will admit I've not used this particular software for any terrestrial photo. It does however have the option to disable star registration which is what you need when you're doing startrails. I get the feeling the software I used on previous startrails was called "Image Stacker" but goodluck with such a generic name on Google. That software at the time had a neat feature which allowed you to stack images by picking the max value for each pixel and incorporating it into the final. This had the real benefit of cutting straight through light pollution allowing you to do a several hour startrail right in the middle of a bright city if you wanted to. Naturally you'd only see a few stars though.

 

[Psytrox]

You could try to use photo ninja or noiseware from imaginomic. Imaginomic has a free edition (called community edition). Photo ninja I think is free to try. I've never actually tried these programs, so I don't know how well they work. But they could be worth a try.

 

[Overread]

If you use long exposure noise reduction, will it take twice amount of time to take one shot? i.e. 2 hours shot will take 4 hours.

Yeah that's correct - the camera takes a second shot immediately after the first, at the same ISO and shutter speed but with the shutter closed, and the resulting noise is then subtracted from the first photo in the camera.

Huh. That isn't how mine works. You cover the camera lens once, and it records a dark frame which it uses on all future long exposures.

That sounds like a dust removal mode not a noise removal mode. I seem to recall something about them, though from memory you'd take a photo of a pure white scene/paper and then it would subtract the dark spots (ie dust on your sensor) from all subsequent photos.

 

[unpopular]

Yeah. That's how dust removal would work. Obviously you have to shoot through the dust. But my camera doesn't have that feature.

This is for hot/stuck pixels. The camera instructs you to place a lens cap on, and make a long exposure. It then applies that information to long exposure noise reduction. It then takes about 20-sec to write the file, but you only need to take the long exposure once, unless new hot pixels show up.

If you can predict where the noise is going to be, then you don't need to take a new exposure every time. Why do other cameras take two exposures?

 

[Garbz]

Why do other cameras take two exposures?

Thermal effects on noise performance. It better have done it at least once for every shutter speed and ISO setting otherwise it's pointless to do.