New answers tagged noise
No. The same amount of light goes to the part of the sensor you are using with a DX lens on your FX body, so ISO is not impacted. When you use the DX lens you use less of the sensor, keeping the ISO / Shutter Speed / Aperture relationship unchanged.
Well, sort of. If you use only part of the sensor — as you do in DX crop mode — you are inherently gathering less light. (The light per area is the same — so your exposure settings are the same — but you have less area.) That means that if you print at the same size as you would an image from an FX lens, your print inherently has less light per area — or, to ...
ISO is all to do with your camera the ISO proformance will be the same nomater what lens is on your camera. I will say that quality of light has a big impact on noise. ISO 1600 in a dark room will be more noiser (I think that's a word) that 1600 outside in the sun.
I agree with @mattdm 's link to "What is noise..." as fairly comprehensive, but not complete today. It would be conventional to say that the glass and metal of a lens does not add noise to the image. A simple definition of noise might be the random disturbance of an image. In other words, if you took the same picture again and again, what might change ...
I would have said "no" a week ago, however I have change my opinion. Yes, a cheap lens can cause noise, at least in video. I was shooting with a RED in the mountains, and my good mid range lens was destroyed. I used the 18-55mm as back up. I was switching between the kit 18-55mm to my 70-200mm f/4 L-series. Same ISO, same settings and there is a huge noise ...
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