Help with ISO

Started May 15, 2013 | Discussions thread
jrtrent Veteran Member • Posts: 4,683
Re: Help with ISO

TheVyper06 wrote:

I'm sure this has been ask before but I can't find a thread on it, so can someone help explain to me what ISO does?

I haven't really experimented with it much and from what I have researched I still don't understand it well. So if anyone has some insight I would appreciate it.

Sjgcit has covered what ISO is very well, and given links to some great articles (the one by Fred Parker has been particularly helpful for several of my friends over the years).

What remains is for you to see what effect different ISO settings have on your camera's output quality.  A short Nikon article puts it this way, "Raising ISO sensitivity amplifies the electronic signal, which also amplifies any noise in the signal; as a result, the higher the ISO sensitivity, the more obvious the effects of noise on your photographs."  Sometimes the effect of noise isn't necessarily just more grain, but also a smudging of detail as noise reduction features try to mask the appearance of the noise itself.  Imaging Resource didn't have a full review of the A65, but DPReview said that its image quality was the same as for the A77, and Imaging Resource had this to say about that camera's noise characteristics at different ISO settings:

"The Sony A77's images are quite clean and detailed at ISO 50 through 200, and even ISO 400 looks quite good. Some noise "grain" is noticeable at ISO 800, as well as a small amount of smudging in lower contrast areas, but the camera did a good job of holding on to fine detail here. There's some stronger smudging of fine detail at ISO 1,600, but detail remains good. At ISO 3,200, fine detail suffers from higher luminance noise and more aggressive noise reduction, though some detail remains. Chroma noise starts to become more noticeable at ISO 3,200 as well, but it's not too bad. As you might expect, fine detail disintegrates at ISO 6,400 and especially at 12,800 and 16,000, where chroma noise also becomes much more noticeable and images have a strong stippled effect."

The best thing is for you to experiment with your camera and see where you find its image quality deteriorating past the point that you want to live with.  That might differ with your intended output needs.  That is, if you normally make small prints for a photo album, you might find that even a fairly high ISO setting works just great.  For larger prints, or even viewing pictures on computer monitors or televisions, a higher ISO might result in a drop in quality that would annoy you.  As an example, for my Sigma SD14, I found that ISO settings of 100 or 200 looked great for color, and I was willing to go as high as 400 if I knew I'd be converting to black and white.  Sometimes, capturing a picture under dim conditions is important enough to you that you'll put up with higher noise levels just to be able to get any picture at all (most of the time, I'm happier if I just put the camera away until lighting conditions improve).

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