ISO settings

Discussion in 'Photography Beginners' Forum' started by fragged3d, Mar 1, 2007.

  1. fragged3d

    fragged3d TPF Noob!

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    I have searched the forum and other forums, I have searched yahoo and google, but I have found nothing that clearly explains this to me.

    I would like to know about ISO settings, what they do and how high you need them? Is the ISO adjustable in increments or are there presets? I have read so far that if you have a moving object you need a higher ISO, what is high and what is low? Is the ISO something you mess with everytime you take a picture?


    Thanks,
    <R>
     
  2. fmw

    fmw No longer a newbie, moving up!

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    If you want the best image quality you will lock your ISO as low as it will go and then use a tripod if a shutter speed is required that you can't hand hold. If image quality is not the issue, then use whatever is the lowest ISO that will allow you to hand hold at the required shutter speed. The higher the ISO, the more noise is introduced into the image and the worse the quality of the image.
     
  3. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    ISO (International Standards Organization) in photography, goes back to film. In many places, it used to be called ASA (American Standards Association). It's the number given to the sensitivity of the film or sensor. The higher the number, the more sensitive to light.

    With a digital camera, a higher ISO setting means that the electrical signal from the camera's sensor is amplified. This means that you can get an exposure with less light (smaller aperture or faster shutter speed). The three things that control exposure are aperture, shutter speed and ISO. So if you increase the ISO, you can get a faster shutter speed...which is why we bump up the ISO for action shots.

    The actual numbers are the same as film has been for years. 100 is low but some do go lower. 400 is middle of the road (on a DLSR, it's high for a digi-cam)...800 is higher, 1600 is higher yet and some go to 3200.

    The problem with a higher sensitivity...is that there are compromises. In film, a higher ISO film had larger grain which became visible...giving us 'grainy photos'. With digital, there is no 'grain'...but the amplification of the signal causes some interference which causes digital 'noise'...so we get 'noisy images'.

    So the usual advice is to keep the ISO as low as possible. Unless of course, you need to turn it up to get a faster shutter speed (or a smaller aperture).
     
  4. fragged3d

    fragged3d TPF Noob!

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    Thanks guys, this is helping!

    At what ISO is the normal for a DSLR to start the noise? I am concerned that the noise starts in my camera for anything above 400 according to reviews.


    <R>
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Each camera is different and there are many things that affect how much noise shows up. If you look close enough...you can find noise at the lowest setting from any camera. It's up to each of us to determine how much noise we can tolerate. It's also up to us to decide when we need to sacrifice and accept some noise in order to get a sharper image (shooting sports, for example).

    A lot of reviews will have ratings for the different ISO levels. It might say that at 100 it's excellent, at 400 it's good, at 800 it's noisy but acceptable and at 1600 is unusable...etc.
     
  6. WDodd

    WDodd TPF Noob!

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    Wouldn't it depend on what you are shooting as well? Such as people, and of course sporting events require a higher ISO, but what about flowers?
     
  7. fragged3d

    fragged3d TPF Noob!

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    What other settings contribute to noise and aid in which ISO level you need to shoot? This may be something I need to set on my camera and experiment with to correctly understand. The pics I have seen come from my camera are horrible at 800 and 1600, but at 400 they are sweet!

    I will be shooting a lot of stunt riders(motorcycle), would I need a high ISO?

    <R>
     
  8. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Well not really, if you don't want noise, the rule still stands that you should keep it as low as possible. If you need to have a faster shutter speed and you can't or don't want to open the aperture any further...then the last option is to increase the ISO. This holds true for any situation...it's just that some situations require a faster shutter speed.

    You will want to get accurate exposure...because noise is 'brought out' in an image when you try to change the tonal values. Dark areas (underexposed) look especially bad when you try to lighten them.

    The trick is to know what shutter speeds you need. First is the rule of thumb for hand held shots. The shutter speed should be as fast as the focal length of the lens, or faster. So if you have a 50mm lens, then the shutter speed should be at least 1/50 (1/60). If you have a 300mm lens, the shutter speed should be at least 1/300 etc. So if your shooting hand held and the shutter speed that the camera/meter is giving you is too low...then you need to open the aperture and/or increase the ISO.

    For moving subjects there is not set rule as to what shutter speed you need. There are too many variables....you just have to experiment and learn from experience. Faster is better for freezing the action...but how much noise are you willing to deal with...to get that faster shutter speed?
     
  9. stumpfoot

    stumpfoot TPF Noob!

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    So if I were shooting with a film camera (which I am) Doing landscape (or any non action or non moving subject) I would use a lower film speed Such as 200-400? Now this question is assuming during the day, What about at sunrise/sunset?
     
  10. JamesD

    JamesD Between darkrooms

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    For landscape, the general advice is to use as slow a film as you can, so you can achieve greatest detail in the image. My starting points would probably be Ilford Pan F Plus (ISO 50) for B&W; Kodak Portra 160 VC (or NC, both ISO 160) for color negative; and something like Kodachrome (ISO 64) for slides. They're all slow films, and slow films tend to yield very little grain and excellent resolution. If you're printing at a 1-hour lab, however, then just about any ISO 100 (or thereabouts) will be more or less the same.

    On the other hand, if I were shooting action, I might go with an ISO 400 during the day, and ISO 800, or even one of the ISO 1600 or 3200 black and white films, when light levels are low. Kodak's T-Max P3200 film is good stuff, and I've heard good things about Ilford's high-speed films, too.

    For reference, the difference between ISO 50 and ISO 3200 is 6 stops. That would take your shutter speed from 1/60th of a second (ISO 50) to 1/4000th of a second (ISO 3200). That can help put "stop motion" in perspective.

    For sunrise and sunset, it depends. If you can keep your exposure under a few seconds, then the same principles apply. If the exposure is more than a few seconds, it may fall into the reciprocity failure zone of the film, at which point you will want to either increase aperture (limiting depth of field) or use a faster film (increase grain and decrease resolution). At sunrise and sunset, however, light is low, and shadows will be deep, while highlights may still be high. In that case, increased grain may not be an issue. It depends on your application.

    Ultimately, if you have to use a higher ISO film, but resolution is too important to allow much grain, use medium or large format (which uses larger film, diminishing the appearance of grain). If, like me, you can't afford medium or large format, then you're out of luck and will just have to make do.

    So, to summarize... Basically, use as low an ISO as you can. If you're shooting in low light, or action, increase film speed as necessary, but don't overdo it unless you want more grain.
     
  11. stumpfoot

    stumpfoot TPF Noob!

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    Thanks James, I think you covered it very nicely! I always used around 400 to 800 irregardless So I am looking forward to trying the lower speeds.
     
  12. Garbz

    Garbz No longer a newbie, moving up!

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    On the other side the noise is perfectly exceptable for normal viewing. The problem most people get into in digital photography is they take an image and the first thing they do is zoom in when looking at it.

    If you think about what this image would look like printed on 6x4 then an image at ISOs even higher than 800 still look great. If you wanted to get closer then a longer lens is in order.

    Ok that said this all falls down if you actually want to enlarge photos. If you are outside on a sunny day you often need not shoot above ISO100, and if you want the sharpest picture possible you should probably be using a tripod regardless.
     

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