Reducing noise in digital photos
topic relations: technology
A while back, I stumbled across this article on Luminous Landscape about how to increase your signal to noise ratio when taking digital photos. It's an interesting concept and is quite true. For a proper explanation, check out their article. But in a nutshell, you simply expose your scene such that the histogram is bumped up as far right as possible, without blowing any highlights.
I decided to do a quick test of it for myself and found the results to be quite impressive for my particularly noisy compact point-and-shoot camera.
Here are two 100% crops of the same scene, shot at two different exposure settings:
The photo on the left was taken on program auto exposure, while the image on the right was taken on full manual exposure.
With the manual exposure, I opened up the aperture and decreased the shutter speed until the histogram was bumped up to the right-most edge as the Luminous Landscape article suggests. I then imported the photo into The Gimp and adjusted the brightness and contrast levels to produce the image above-right. The levels themselves could probably use a bit of fine tuning, but for only a few minutes of tweaking, the results are considerably better. The resulting image on the right in itself is not completely noise free, but compared to the image on the left, it looks as if they were almost taken by two completely different cameras.
I do realize that they say you should be working RAW mode, and alas, my camera does not sport a RAW mode. But it still seems to work in principal. Not as ideal, but I can visibly see less noise.
With respect to how often I am going to apply this principal, I'm not sure. Because while this method produces very clean pictures, it also requires post-processing to make the images usable afterwards. Moreover, the slower shutter speeds required to do this might make it difficult to use this without a tripod. The photo on the left was shot with a shutter speed of 1/8", while the one on the right was shot with a speed of 1.6". I don't think I can hold my hand that still.
Nevertheless though, if you have the time and chance to, it's definitely a good idea to "expose right."
http://www.luminous-landscape.com/tutorials/expose-right.shtml
3 comments
As for pods, have you ever considered investing in a monopod? They're basically single legged tripods (in case you didn't gather that from the name) that allow you some more support while still offering you flexibility in movement, as they really shrink down very well. I think they're great ideas for photographers who don't have time to set up a tripod for every shot.
Also, just a note, I've actually got ahold of a 35mm SLR, so I'll be working with film for a little while :)
I have a tiny tripod, which I bring with me mostly everywhere. Haven't thought about a monopod. Have you found that they help considerably for taking shots with slower shutter speeds?
That's pretty cool that you got a hold of an SLR camera as well! Working with film could get a bit expensive after a while though... but sure lots more fun!
@jpike: if you're using film, keep a lookout for black's boxing week specials - they've been known to clear out 200 iso film for $3.99 (or cheaper) with processing included.
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