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

[fokker]

I went camping this weekend in an amazing location (base of the three sisters mountains near Fernie, BC). The stars were out in force so I decided to sacrifice sleep for some long exposure photos. I had time for 2 exposures at 2 hours each, unfortunately I screwed up one of them (spent a long time setting up everything but forgot to change the mode dial to bulb mode for the final shot, came back 2 hours later to find I had taken a nice black frame at 30 seconds ) and got one decent shot. Unfortunately I had decided not to use the long exposure noise reduction function because it would have meant I only go to take one photo in the time I had. Now it seems that a 2-hour exposure on a 5D2 at 400 ISO, even in cold weather, is a disaster as far noise is concerned. Here is the photo I ended up with and a 100% crop:

Lighroom 4 can't do anything for this noise, and I don't really have a couple of spare hours to go through and try and fix this with the clone tool. Is there some software that will work against noise of this type?

 

[Overread]

I've a feeling those dots are just way too clear and firm for noise software to really tackle the worst of them. You might have luck if you were to blur the area somewhat, then run the noise software again and then maybe overlay the blurry noisefree over the regular and blend them a little with layermasks - with maybe another run of noise removal after that? (I have - no idea if that works at all its just a wild mad idea).

 

[Tony S]

If you really want to clean it up now, just use a small clone tool and handle each spot individually. It will take a while but the results can be good.

 

[fokker]

Tony - I'm hoping that I won't have to take that very time-consuming route as i'm not the most patient person at repetitive tasks like this. I figure it will work okay though so it is my last resort.
Overread - I think you're probably right about the specks being too big for noise removal software, but you never know what's out there, figured it could be worth a shot.

 

[KmH]

Rather than the clone tool, I would use the Spot Healing Brush tool and in the Tool Options bar turn on Content-Aware.
Tip: the [ key makes the spot smaller, and the ] key makes the spot larger, though you can 'paint' a small area too instead of making the spot bigger.

Get the big bright noise, and don't sweat the small and dim stuff to much.

 

[fokker]

Wow... you did the whole picture. How long did that take you? Thanks for the tip I will look into this now.

 

[KmH]

Well I posted the crop at 2:52 and some minutes later decided to do the full image and posted it at 3:14. So, at the longest I spent 22 minutes, but it was likely closer to 15 minutes.

Only the dark parts show the noise, so the brighter sky and brighter parts of the left side of the photo don't need very much work.

 

[fokker]

Here is my final version of the photo:

I opened the image in photoshop and started using the spot healing tool, which was working well but I decided on a whim to try the 'remove dust and scratches option', and it actually did a brilliant job of removing the noise specks with no appreciable loss in quality or sharpness overall.

 

[Overread]

Nice!

I've not seen that option before (might be one of those - missing in elements 6 features).

 

[Ulriksen]

Nice, I really like the outcome! Gorgeous startrails!

 

[KmH]

Nice!

I've not seen that option before (might be one of those - missing in elements 6 features).

PsE 6 has the Spot Healing Brush and Proximity Match option, but not the Content-Aware option.

 

[Garbz]

Those a hot pixels, a function of sensor noise and the technology simply not keeping up with your exposure. There's a reason cameras designed to expose for 2 hours at a time are mounted to massive peltier units and the sensors kept at -30deg.

There is a way though. Hot pixels reset between frames and are a function of temperature and more importantly exposure duration. 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. The result will have next to no noise and very few if any hot pixels. This is the way us astronomy people take 20+ hour exposures over multiple days of really faint objects without light pollution problems.

 

[fokker]

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.

 

[Buckster]

There is a way though. Hot pixels reset between frames and are a function of temperature and more importantly exposure duration. 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. The result will have next to no noise and very few if any hot pixels. This is the way us astronomy people take 20+ hour exposures over multiple days of really faint objects without light pollution problems.

Which of the stacking software available do you recommend?

 

[unpopular]

EnfuseGUI

http://imagefuser.sourceforge.net (mac os only)

Both use the same backend.

The process will actually reduce noise and possibly somewhat increase bit depth if you output a 16-bit image. If on every step you alternate 1m and 2m exposures, or even cycle through 1m, 2m and 3m you'll also get better shadow detail to work with.