Explain ISO

LarryMartin830 · Mar 10, 2009

Well ever since i got my D40 i have always kep the ISO on 200 but can some one plz explain to me whats the difference's in higher iso and whens the best time to use each

Steph · Mar 10, 2009

This thread and this one may be a good start. Get back to us if what is written there does not make sense to you.

Mike_E · Mar 10, 2009

Also go here http://en.wikipedia.org/wiki/Film_speed while remembering that digital cameras were modeled on film cameras to gain immediate acceptance by photographers who would have blown digi off if they would have had to have relearned their craft. I bring that last bit up to tell you why you're reading a page on film to find out what ISO is all about.

Garbz · Mar 10, 2009

As Mike said it's based on the ISO film ratings. As far as the digital camera the ISO settings modify the sensor characteristics, signal amplifiers, and analogue to digital converter inside the camera in a way to ensure that the sensitivity of the final image is the same as it would be if recorded on film.

EOS_JD · Mar 10, 2009

ISO is VERY important in setting your exposure - especially in low light. Read the links carefully and when setting exposure give careful thought to all three variables in your exposure calculation.