 Anja Lenner |
ISO and digital Can someone explain the ISO sensitivity on a digital camera?? How come it is there when there is no film in the camera?? And does it work in the same way as with film camera??
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x |
Anja, are you new to digital, or new to photography in general?
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Jon Close |
It is a measure of the light sensitivity of the recording medium, whether film or digital. It is the same standard for both. The higher the ISO number, the greater the sensitivity to light. For example, you can shoot shorter shutter speeds and/or smaller lens apertures in lower light with ISO 400 than with ISO 100. There are trade-offs in using higher ISO settings. The higher ISO films tend to be "grainier" than low ISO films. In digital there is more "cross-talk" and noise between the individual pixel sensors at higher ISO settings.
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Michael H. Cothran |
ISO, which stands for "International Standards Organization," was established in the latter part of the 20th century to set and monitor international standards, including such things as film speed. It uses the same system previously put in place by the ASA (American Standards Association). This is why ISO and ASA settings are the same! Cameras may be set manually or with bar coded film. The setting adjusts your in-camera meter to read appropriately for the speed film you have. The setting does not change unless you manually change it, or insert a coded film of another ISO. This system of light sensitivity measurement has also been adapted for use in digital cameras as well, most likely since the transition from film to digital would be more understandable by photographers. Michael H. Cothran www.mhcphoto.net
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Anja Lenner |
I am pretty new to digital. I know what ISO stands for, and what it does when it comes to film. Just not too sure how it affects the digital medium. So if I would use ISO800 on my digital camera, what negative effects would this have?? Someone was mentioning noise above, is that the only one? And then sometimes this might be what you are after...
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Kerry L. Walker |
Changing the ISO in digital would give you about the same effects - good and bad - as you would get by changing to a higher or lower ISO film.
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Anja Lenner |
OK. I just find it a bit hard to understand, since there is no film... And what about the noise?
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Kerry L. Walker |
ISO is just a measure of the sensitivity of the capture medium to light. Makes no difference whether it is film or digital. What is your question about the noise.
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Anja Lenner |
Jon said (above) that there will be more noise with a higher ISO setting...
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x |
Noise sucks. Grain is cool. Thats about the long and short of it. I was known, in small circles, to shoot often using 3200 film. Talk about a grainy 8x10. But, when it comes to noise, I absolutely hate it. I am comfortable shooting at ISO 800 with my digital cameras. At 1600, it gets dicey. Above 1600, only when absolutely necessary. I will sacrifice quality, just to get the shot, when need be. Jerry
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Kerry L. Walker |
Noise is the digital equivalent of grain in film. I Don't mean to sound condescending but it has nothing to do with sound. I have no idea why they picked that term.
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Anja Lenner |
the name "noise" (I think) got something to do with that the image distortion is added by the image recording circuitry.
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x |
Kerry, the difference is that noise really looks bad to me. Of course, kids growing up with digital will probably think noise looks cool, just like I like grain. I'll probably learn to appreciate it once I get more comfortable with it. But, I don't think it's the same thing. It is the digital equivilant, but I think it's a whole different thing. And, I do think noise is an appropriate term. I had it explained to me once in great detail and completely understood it, but I can't repeat it.
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Steven Chaitoff |
Anja, you're right. Noise often appears because the recording circuitry generates random weak electrical signals that get mixed in with the strong signals that the light coming through the lens generates. When you increase the ISO on your digital camera, all that does is amplify the elecrical signals – both the good, strong ones you want and the weak noise ones as well - which is why the higher the ISO, the more noise there is. Technically speaking, digital noise and film grain are two totally different phenominons that aren't related at all. But since they look sort of the same, and also tend to increase as sensitivity increases, you can use the same "ISO" scale to talk about them both. As for why the numbers are the same, as Michael said that is probably just a convenience measure for the photographer so when you hear ISO 50 or ISO 3200, you can know what kind of noise/grain to expect regardless of whether you're shooting digitally or with film. Of course, things are changing especially with the high end DSLRs; because of some clever engineering you can end up with nearly noiseless shots even at traditionally grainy numbers.
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Anja Lenner |
Thanks Steven, that explains it pretty well... So now it is just to go out and do some tests I guess, to see how a specific camera works!! I must just say that this is a fantastic site!!
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Kerry L. Walker |
Gee guys, you went way over my head with the noise explanation. All I know is that less is better (except in the case of my hair).
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Wayne L |
It seems that most camera makers want to go up with ISO 800-1600-3200-6400 and yet none seem to go down (without tricking the camera) Why doesn't someone go to 50 or 25 as a standard ISO to get a better or cleaner pic? Is this not possible, yet? If 100 is the sharpest the camera can produce than it wouldn't matter. Wayne
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
You're partly dealing with a carry over from why iso100 was so popular in film than any iso lower than that. And you're partly dealing with whether it's practical to make a sensor go from 50 to 1600 and above, both from a picture quality standpoint, cost, and if most of the buyers would actually ever use it. Most of the buying public for film, if they wanted small grain, where happy with iso100. But those same people also needed, whether real or imagined, some form of security with a manageable shutter speed. So an iso of 100 looked more appealing than an iso of 50. Small grain and a higher speed. Plus, iso100 films got so good, was there any noticeable difference? Most situations, even if your purpose for which settings you set your camera or lights to, if it depends on iso, then iso100 is low enough. If you're looking for shallow depth, how many times have found yourself where iso 100 was too high for that? Even the brightest part of the day. But the ability for high iso, low light, that's just something more people find themselves wanting or needing. Next topic, what's with the rash of 3+ year old questions popping up?
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Marianne Fortin |
Here's a good explanation: http://www.cambridgeincolour.com/tutorials/noise.htm
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