I was listening to the RC (previously [and belovedly] know as the Red Centre) last night, and they went into greater detail about testing a digital sensor for it's native ISO. That got me wondering. So using the described method, I tested a Rebel T2i that a friend had and the results were indeed surprising.
To test your sensor, cap the lens (or better, use the body cap) and fire off an all black shot at your lowest ISO. Repeat sequentially for all ISO's up through the range.
Next, look at your file sizes? See how the higher your ISO the larger the file size? Weird huh? "But it's all black?!"
Finally, I threw the pictures into Aperture and massaged the Histogram till I had each image spread across the whole field. Take a look:
(Because of the method I used to spread the color information across the histogram, what you loose is the progressive "fogging" of the images. They slowly get lighter as you go up the ISO)
Canon Rebel T2i ISO 100: Original JPG File size: 1.3 MB
Canon Rebel T2i ISO 200: Original JPG File size: 1.2 MB
Canon Rebel T2i ISO 400: Original JPG File size: 1.5 MB
Canon Rebel T2i ISO 800: Original JPG File size: 1.8 MB
Canon Rebel T2i ISO 1600: Original JPG File size: 2.3 MB
Canon Rebel T2i ISO 3200: Original JPG File size: 3.2 MB
Canon Rebel T2i ISO 6400: Original JPG File size: 4.1 MB
Original Images:
http://www.datafilehost.com/download-278799ff.html
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