A look at noise in low light for low, mid, and high ISO

I learned an interesting lesson. When confronted with low light (light meter didn't even register for 24fps and ISO320--which is what the digital video was shooting and this wasn't any old high def either. Check out Red when you get the chance!)

Anywho, I found myself with a problem... shooting with light below my lens' capabilities (Nikon 50mm f/1.8).

What to do, indeed. I really wanted to shoot like I do with any other
setup, iso 100 (little to no noise), but I pretty much could count on a black
image. No good at 200 or 400 either.

Yep that was pretty much what I expected and shooting at 1/40sec I
could almost guarantee a slightly fuzzy shot becuase of hand shake. I do pretty well with
slow shutters, but as the rule of thumb goes (focal length <= shutter
speed--no less) I was shooting with a 50mm prime. That
means I should be shooting with no less that a 1/50sec shutter speed.
But wait! That fast and I shoot a bunch of black photos!

So here is the photo shot at ISO 200. I can still make out the cast, but it's way too dark!
Fine I'll boost the iso... let's say ... 500. Well this is a little better but still too dark.
What becomes very interesting to me is when I boost it to iso 1600. Hey, this is looking good!!! And this is really amazing. The boost in sensitivity has really boosted the signal to noise. (Of course it would, just like when you boost the gain on a micro phone--more line noise, but louder sound. As long as you have sound, you won't here the noise.) And besides, it's better to get the shot than not, right? Now the fun real begins, because when I get home and loaded them into lightroom, I discovered something truly amazing. Remeber that "signal to noise" thing above? Well, it means a whole lot at any ISO. lower light, will allow noise to creep in at any ISO--just less of it with the lower sensitivity. Why, well it has to do with the light coming in versus the noise inherent in the sensor and electronics (I'm a digital man, but its pretty much the same thing for and film. You know... grain!)

Ok, enough blabbering... Let's take a closer look; first pre post.

Here are the crops of these images (left to right ISO 200, 500, and 1600)

Hmmm ... yeah ok, I can see the ISO 1600 pretty good, but looks pretty noise. Can I do any better?

Let me make one post fix and boost the exposure on the ISO200 and 500 by +2 and the 1600 by +1.

This should equalize the levels a little better. What do we get? (Same order as before, 200,500,1600)

Is it me or does the lack of noise NOT make up for loss of range and detail (because of hand shake ). I can clean up some of the noise in the 500, even the 1600, but I cannot add any low key info back into the photo for the ISO 200--that's a BIG problem. If you need further proof, I'll take these to the next step and reduce noise.

One last note about all this. Shoot RAW. Period. The options available to you in post for a photo in RAW vs JPG are worth every extra megabyte!