In recent years the latest DSLRs have come with the ability to shoot at incredibly high ISOs. The tradeoff of course when you shoot at these high ISOs is you get a lot of noise in the image too. But you get the shot, so it’s the choice between having a noisy image and having nothing. One of the things I’ve found interesting to test is how clean can you get high ISO shots. The new Canon 5D Mark III will shoot at ISO 102,400, so how clean can you get an image taken at ISO 102,400? Looks like pretty clean!
When processing my images I’ve always been interested in how clean I can get the image without losing detail. I’ve tried all sorts of noise reduction software and they each have their pluses and minuses. The very best way to reduce noise of course is to shoot at a low ISO. But I’ve been interested in seeing how well I can reduce the noise in a high ISO image.
Over the years I’ve come up with various ways to process my images to reduce the noise in very high ISO shots. When I got my new Canon 5D Mark III I had to test out ISO 102,400. Straight out of the camera it’s pretty noisy. But apply some noise reduction, reduce the image size, and it’s not horrible. For getting a shot you wouldn’t have otherwise or having a picture for the web, it’s not that bad.
One way to reduce the noise in an image is to take an over exposed image, reduce the exposure in processing, and then combine that image with the properly exposed one. The combined image will greatly reduce the noise in the shadows. You can also combine/average multiple images together to increase the signal to noise ratio in order to reduce the noise. Those techniques will be what I’m showing here.
So let’s see some samples! Here’s a crop from an image taken at ISO 102,400 that was just converted to jpeg in Canon’s DPP. It’s all default settings, no extra adjustments:
The shadows have a lot of noise. If you’re just looking for a snapshot, it can be used. But anything else and the details are really gone. I want you to notice two things to see the difference. The sign in the background on the left isn’t even readable. On the right side of the image is a building, and there’s nothing on it right? It’s just black. Here’s the same crop after doing a combination of exposures:
Pretty big improvement huh? Notice the sign on the left, now you can actually make out the words. The building on the right, there are three signs we couldn’t even see before. Now we can see and read all the signs except for the times under the “OPEN”. But we aren’t done yet! This time, notice the solid colors of the carousel – the green, red, and yellow. Let’s do a combination of exposures and averaging:
Now check the solid colors between the last two. They’ve gotten cleaner, less grit in them. We still can’t quite make out the times that the carousel is open though.
I’ve been working on a new method of combining the exposures and it’s so far looking very promising. I already know that the new method brings out details in the very dark shadows well. I’m still working on some kinks, because the solid colors aren’t as clean, but I know what I need to do to get them as clean as the last. But here you can see the results of the new method, look at the open sign that we couldn’t read the times before:
Now we can clearly read the times that the carousel is open! But as you can see the solid colors aren’t as clean as before. Here’s a comparison of those sections side by side. The left is the original image, the center is with exposure combination and averaging, and the right is the new method I’m still working on.
And keep in mind, I’ve done NO noise reduction on the jpeg images, the raw converter’s noise reduction is set at it’s default setting for ISO 102,400 images. That’s the only noise reduction that’s been done. I’ve also done NO sharpening to these images.
The new method does bring out more details in the shadows, just need to work on it some more to make it better. While you can really clean up high iso shots doing this, it’s got limited uses. Moving subjects wouldn’t work very well, since you are combining images. There can also be a lot of processing involved to do this. I’ve tried this on low ISO shots and while it does work, the benefits aren’t that great since the shots are already low in noise.
But it is interesting to see what you can do with an image shot at ISO 102,400!
Canon 5D Mark III
Canon EF 70-200mm f/2.8L IS II USM Telephoto Zoom Lens
Slik 700DX Tripod
Bogen 3030 3-way pan/tilt head