Light sensitivity of different size sensors?

[normadel]

I was fooling around last night and decided to test how very low room light works.

Took same picture of my barely-illuminated family room...almost could not see at all....with my Rebel T1i, 50D, 60D and recently-acquired 6D. ISO set on Auto, Program exposure mode. To my surprise, the three crops produced good pictures of a warmly- lit room, but the 6D image was very very dark..

The crop-sensor images were set comparably at ISO 1600-3200  at 2.5-4 second exposure. The 6D was at ISO 12800 for 1/6th second exposure.

Why the huge variation between the full-frame  6D and the crops, in selected ISO and overall exposure?

[normadel]

I guess I am trying to do a demonstration that shows the higher light sensitivity of the 6D. 

Setting both cameras to the same manual settings...aperture, speed, ISO...produces equal images, in subdued light. Taking a picture in almost-total darkness seems to give the edge to the 60D.

What test will illustrate the superior sensitivity of the 6D's sensor?

[jrhoffman75]

Possibly here:

Photographic Dynamic Range versus ISO Setting (photonstophotos.net)

[kvbarkley]

The various lenses might have different "T" values, too.

[normadel]

Hmmm....I'll try testing with the same lens on both camera.

[ebiggs1]

Your test is meaningless. You have you many variables. I would also go with M mode and set each camera exactly the same. All shooting the exact same subject. Otherwise you learn nothing.