Quick Question

[KC Jr 54]

Well, digital cameras don't actually change hardware to change ISO speed, they just adjust the exposure and processing

Doubling ISO speed = Increase exposure by 1 stop... I was shooting .7-1 stop underexposed, so I essentially doubled the ISO to 3200.

You could set your camera to ISO 400, underexpose 2 stops, and it would become ISO 1600, but the in-camera processing would still be for 400, so it'd probably turn out with a bit more noise


Is that comment be true !?

[gjl711]

I do not believe so. I am looking for the white paper I read it in, but I believe what happens is that by upping the ISO, additional stages of amplification are used. I'll post the white paper when I find it.

[gjl711]

Found it here (http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary/). Bit of a tough read but what happens is that the gain of the amplifier is changed. Maybe what the originally poster was trying to say is that you can get similar results in certain circumstances by changing the aperture, but it is definitely not the same thing.

[E-K]

I think they may have been trying to convey the idea that changing the ISO on a digital camera does not make the CCD/CMOS sensor more sensitive per se, it just generally ups the gain like the volume control on a guitar amplifier.

Generally you are better increasing the ISO/gain/amplification then underexposing but somewhere between ISO 800 and ISO 1600 you will likely find that the hardware gain produces a result no better than underexposing and using post processing (assuming you shot RAW of course).

e-k