1D mkii iso noise

I have 2 1D mkii's the other day I used both bodies set at the same settings for everything one had a 300mm and one a 70-200 2.8.

When looking at the shots the noise on one was a lot more than the other both were set at iso800.

Both cameras were serviced in June by Canon.

Any idea what would have caused this.

The only way to test if it's a result of a camera malfunction is to test them both in as near identical conditions as possible.

I've taken shots at iso 1600 on my 400d/xti which have very little noise (exposed to the right, lots of light) and some which look bad even at iso 400 (under exposed, shooting into darkness).

ICee wrote in post #7001092
Any idea what would have caused this.

Underexposure and/or more shadow area in one image vs another.

cdifoto wrote in post #7001149
Underexposure and/or more shadow area in one image vs another.

Agreed. Underexposure/shadow will make the noise monster rear its ugly head

cdifoto wrote in post #7001149
Underexposure and/or more shadow area in one image vs another.

It could have been shadow as it was a very dull day and I was shooting red kites in flight at a feeding station, they were coming down from a height so I was shooting into the light, then shooting with a field behind them.

Could the magnification for the lens have made any difference as it was the on with the 300mm lens on that showed the most noise?

No, because the sensor is the last part in the equation. The light comes through the lens and hits the sensor. For the lens to magnify the noise it would somehow have to travel from the sensor through the lens and out the other side.

It's exposure that affects noise, not the lens.

Thanks. I think I need to keep an eye on my histogram a bit more. At least I know it's me and not the camera.

the lenses could have made the 2 bodies meter differently, so the darker images would have more noise. Also one body could have had some EC dialed in which would make a huge difference.

From what I've noticed, wider lenses see more background and if on eval metering will get better exposures at times... Not all the time, but the FL will definitely change what the meter sees and how it meters.