2007-10-25 01:21:58 · 4 answers · asked by alfie h 1 in Arts & Humanities ➔ Visual Arts ➔ Photography
ISO is a standard for measuring film speed but it is now extended to apply to digital cameras too.
As you double the ISO you double the speed and vice versa. So if you double the ISO you can half the exposure time or reduce the aperture one stop.
The rule is:
Faster ISO for low light conditions or fast moving objects
Lower ISO for less grain and noise.
2007-10-25 01:25:13 · answer #1 · answered by Anonymous · 1⤊ 0⤋
ISO is a measurement of the sensitivity to light of a light sensitive surface whether film or digital sensor. The higher the ISO number the more sensitive the surface.
Look at this hypothetical example, using a constant f-stop, to see what happens to our shutter speed as we change our ISO:
ISO 50
f8 @ 1/60 sec.
ISO 100
f8 @ 1/125 sec.
ISO 200
f8 @ 1/250 sec.
ISO 400
f8 @ 1/500 sec.
ISO 800
f8 @ 1/1000 sec.
And if we keep our shutter speed as the constant:
ISO 50
1/60 sec. @ f4
ISO 100
1/60 sec. @ f5.6
ISO 200
1/60 sec. @ f8
ISO 400
1/60 sec. @ f11
ISO 800
1/60 sec. @ f16
That is how ISO affects exposure. If our examples could be duplicated in the real world, all the exposures in both examples would be identical.
2007-10-25 09:20:45 · answer #2 · answered by EDWIN 7 · 1⤊ 0⤋
Just as an expansion on what Peter said - increasing the ISO also decreases the image quality. Where at ISO 100 you may have a nice clean image, if you put it up to ISO 800, the image will be full of 'grain' or noise.
2007-10-25 08:46:28 · answer #3 · answered by Piano Man 4 · 1⤊ 0⤋
OSI is like the film speed on a 35MM SLR it allows the exposure time to be faster (1600) or slower (100)
2007-10-25 16:03:51 · answer #4 · answered by Mike 4 · 0⤊ 0⤋