Juggling Aperture, ISO, and Shutter Speed?

Discussion in 'Photography Beginners' Forum' started by Box801, Aug 8, 2010.

  1. Box801

    Box801 TPF Noob!

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    I understand all of these terms individually, but how do they all come together? Such as when I increase the aperture a full stop, by what amount should I adjust the ISO and shutter speed?

    I'm wanting to know what the universal rules are.

    I hope you guys know what I'm talking about...:lol:
     
  2. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    [ame="http://www.amazon.com/Understanding-Exposure-Photographs-Digital-Updated/dp/0817463003"]Amazon.com: Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera (Updated Edition)…[/ame]

    No Noob should be without it. :D
     
  3. Sapper44

    Sapper44 TPF Noob!

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  4. MrBarney

    MrBarney TPF Noob!

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    Definitely read up, but the short answer to your question is that you can measure each of them in stops. You seem to know what a stop of aperture looks like (f/1.4, f/2, f/2.8, f/4 etc.). A "stop" of shutter is double or half of the current value (depending on which way you are going) and the same for ISO. You can trade a stop (or several, or fractions of a stop) for another and the exposure will remain the same.

    Your camera meter should confirm this if you try it.
     
  5. KmH

    KmH Helping photographers learn to fish Supporting Member

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    Changing the aperture also changes the total depth-of-field (DOF).

    To maintain the same exposure, leave ISO alone and decrease the shutter speed a full stop.
    "Increase the aperture", means to make the lens opening larger. That lets in more light so the shutter needs to be open for a shorter period of time to avoid overexposure. Changing the shutter speed also effects how it stops motion, if any. Shortening how long the shutter is open makes it easier to stop motion.

    To maintain the same exposure, leave shutter speed alone and decrease ISO a full stop. "Increase the aperture", means to make the lens opening larger. That lets in more light so the image sensor needs to be less sensitive to light to avoid overexposure.

    In short, to maintain the same exposure when you change one of the exposure triad, you need only change one of the other 2 in the opposite manner. You just need to be aware how DOF, motion rendering, and image noise (from ISO and overall exposure) will also change.
     
  6. Olympus E300

    Olympus E300 TPF Noob!

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    Well said KmH...:thumbup:
     
  7. white

    white TPF Noob!

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    In photography, think of a stop as a unit of measure. If you increase your shutter speed by one stop, then you need to open up your aperture by one stop to compensate. Most people adjust shutter and aperture to get their desired effect, iso is rarely changed. But the same principle applies: increase the iso from 200 to 400 is one stop, and you'll need to either change shutter or aperture to compensate.
     
  8. NateWagner

    NateWagner TPF Noob!

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    honestly though... I think ISO would be useful to be changed more frequently... In other words as camera makers move along, auto ISO could become a very handy feature (some already have it, and there can always be improvements made...)
     
  9. pgriz

    pgriz Been spending a lot of time on here!

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    The lowest ISO (in digital cameras) usually gives the least amount of noise and processing artifacts, so use the lowest ISO the scene allows you. In other words, go to the lowest ISO, and change only if you can't get a decent picture because it's too dark.

    Shutter speed tends to be less important than aperture for most shooting situations (exceptions: action, or using a telephoto lens), so you would usually set the aperture based on the amount of depth-of-field you need for your picture. You then let the camera set the shutter speed (this is the A-priority mode).

    For subjects that move fast, or lenses that magnify movement (ie, telephotos), you need a fast shutter speed to "freeze" the action. Under those circumstances, figure out what is the slowest shutter speed you need to get the result you want, set it using T-priority mode, and let the camera handle the aperture.

    Now let's say you've got the ISO set to 100, and you've decided that F/8 gives you the desired depth-of-field, and using the A-mode the camera gives you a suggested shutter speed of 1/8 sec. Let's also assume you are using a focal length of 50mm on an APC camera (giving you an effective focal length of 80mm equivalent on full-frame), and you're hand-holding. Probably the slowest speed you can get away with without blurring is 1/60 sec or 1/90 sec. That is about 3 1/2 stops of exposure (1/8 to 1/16 to 1/30 to 1/60 plus another half stop to 1/90) which means you need to boost the ISO by the same amount to get the exposure you want. That would be: 100 to 200 to 400 to 800. So in this scenario, you have increased your ISO because otherwise you could not get the exposure you would need to get (f/8 at 1/60 sec with a 50mm lens on an APC camera).

    Now let's say you're really not happy with the amount of digital noise you're getting at ISO 800. Then your options are to use a tripod, or to spend mucho bucks on a VR or IS lens or similar system that reduces the apparent vibrations by as much as 4 stops (according to the marketing propaganda). Then you might get away shooting 1/8 sec., and have an acceptable image. Realistically, however, your shot will still be blurry-looking as it's hard to focus when the scene is dark.
     
  10. Boomn4x4

    Boomn4x4 TPF Noob!

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    Long answer short:

    Its a 1 to 1 relationship. If you increase something 1 stop, you need to decrease something else 1 stop

    A "stop" is doubling or halfing the light that reaches the sensor (or needs to reach the sense in the case of ISO).

    If you have 10 units of light hitting the sensor and its property exposed, and you drop the shutter speed 1 stop, half the light will reach the senosor meaning only 5 units of light are hitting the sensor. So you need to either move your aperture 1 stop letting in double the light (doubling 5 back to 10) or moving your ISO one stop so that it only requires half the light.
     
  11. Morpheuss

    Morpheuss TPF Noob!

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    what I personally did was played with the shutter speed on my camera with the iso set at 100 since that seems to be pretty good from reading the forums and found out the slowest i can go hand held since I don't have a tripod yet and also to know how slow i can go when a tripod might not be able to be used and the apeture the more dof you want the higher the apeture but if the subject isn't to far away you can shoot wide open to get more light to the sensor.

    Higher ISO makes your sensor more senative to light but if you go to high you get grainy photos the slower the shutter speed the longer your shutter stays open oviously but to slow without using a tripod all you get is blurred photos and the higher apeture like 2.8 you have a more shallow dof because your apeture is wider than say 7.0 which is really small. I found it the easiest and the most fun to shoot in different lighting situations when you can control it and just play with them and see how they work together.
     

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