 BetterPhoto Member |
setting your ISO When I set my ISO to 100 and look at pic details it is at 100 not any lower.But when I set it at AUTO it can be lower then 100 isn't lower better.But we are told to set the ISO at 100.explain ? Olympus c740uz
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robert G. Fately |
Robert, ISO is a measure of the sensitivity to light - the higher the number, the more sensitive. This is similar to film speeds, which used to be measured in ASA and is now called ISO as well (ASA = "American Standads Association" and ISO = "International Standards Organization"). As with everything in life, there is compromise to be made. With film, higher ISO leads to more grain. WIth digital imaging chips, higher ISO settings lead to noise, which is due to different reasons but looks much like grain in dark shots. Thus, the general rule of thumb is to use the lowest ISO (film or setting) you can get away with (and still get the shutter speed and aperture you want). Of course, with digital cameras, you can change that ISO setting from shot to shot. Now, according to dpreview this camera allows for that auto setting as well as your manually setting a few ISO ratings. Unlike film, of course, the chip inside is not changed when you change this setting - you're just telling the camera to amplify the signal more with higher settings. A chip has a certain base level of sensitivity - my guess is that the chip in your camera has a base level a bit lower than 100 but for the sake of ease the lowest setting you can manually make is 100.
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Craig Paulsen |
100-200 are great iso's and the highest I would use is 400(not for blow-ups).Anything needed over that and I would use fill flash.
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Jon Close |
In general, the lowest ISO setting will give the least amount of noise/grain. ISO 100 is the lowest ISO setting that one can set manually on the C-740. That the AUTO ISO setting may sometimes set a lower ISO can be viewed as either a limitation or a feature. ;-) It may not be truely operating at an ISO lower than 100, but emulating it with its internal software.
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William K. Shank |
Like my camera, I bet when you have your camera set on Auto it is also deciding on what to set your ISO at. If you go to take a photo in low light it is going to change the ISO to 400 for an example. Look at your manual you should find aomething in there about what all Auto mode sets.
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