ISO & Noise Level

[Daniel Browning]

Could someone please tell me why ISO of 3200, 4000, 5000, 6400 is even an available option on the 7D?

Because everyone has different shooting conditions, processing software, display resolution, and taste.


For shooting conditions, the color temperature of the light has a significant affect. In "bad" light, the could be a very big imbalance between the color channels. For example, red and green might be OK, but blue could be two stops darker. That means evenyou might have the camera set to ISO 3200, the blue channel is *effectively* ISO 12,800. So unless you get rid of that blue channel noise somehow (such as by converting to black and white without using much blue), the result will be as noisy as if you had set it to 12,800 in "good" light.


Processing software makes a big difference as well. For example, Lightroom 2 made a terrible mess of noisy images -- all blotchy and clumpy. LR3 is much better. The style of the post processing makes a huge difference too. High contrast, low-saturation, low-dynamic range image development shows noise a lot less than low-contrast high dynamic range images.


Display resolution is another vital factor. Every time you divide resolution by four you can increase ISO 1 stop and still have the "same" noise level. For example, if you felt that ISO 1600 was the highest you could go and still print a full-resolution 18 MP 18x12 beauty, then you would find that printing a 4.5MP 9x6" would give you the same noise visibility at ISO 3200. And 1 MP 3x4.5" print would again be the same at ISO 6400. And a 200x200 facebook image would look fine at ISO 12,800.


Taste is the big and obvious factor. Some people dislike noise more than others. (Personally, I actually *add* noise to my images.)

[ddt0725]

Thank you, Daniel! That is exactly how I needed explained to me!! I figured there had to be some reasoning behind it or it wouldn

[Sheiky]

I for one dislike ISO and I guess what I found out is probably what Daniel is saying. I don't like to get higher than ISO1600 on my 5D. But mainly because I view my images big and like to have the full benefit of all the megapixels. However lately at a wedding I also shot ISO1600 and for some reason, the shots with extra light from a flash look well....pretty amazing for ISO1600 shots.


I have seen this before and I don't know what's up, but the lightsource definitely plays a big role in ISO-noise as far as I''m concerned.


The noise application that I have is called noise-ninja. A lot of people and companies use it, but it does make your images softer. At least I think my poster prints look better without it. For some reason with printing you also get rid of some of the noise.


Don't ask me how though [A] Probably the smooth transitions between the different colors of ink or somethink.


But honestly, I also don't get why they put ISO12800 and even 25600 on my 5D other than marketing purposes. ISO6400 is actually very nice with video. But the same story here again, noise depends a lot on lighting conditions.


Jan