Does Sigma deceive us with the ISO rating?

Started Apr 14, 2012 | Discussions thread
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Halldor Eiriksson Senior Member • Posts: 1,974
Re: Does Sigma deceive us with the ISO rating?

Chunsum J Choi wrote:

you should explain sunny 16 as well.

On a clear and sunny day, aperture is f16 and speed is 1/ISO. If ISO is set at 100, it's 1/100th of a second.

If you want to use f11 instead, you raise the speed to 1/200s.
f8 gives the speed of 1/400s

If it's not sunny, but bright, you lower the aperture one stop.

If it's overcast, not raining, you lower the aperture one stop again and so on.

It's easy to get really good at this, it takes practice.

If this rule gives constantly wrong exposure, I would draw the conclusion that the ISO rating is not correct.

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