IS and "stops"

Discussion in 'Photography Beginners' Forum' started by MDesigner, Jun 26, 2008.

  1. MDesigner

    MDesigner TPF Noob!

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    Question: when the manual for my IS lens says that when IS is enabled, it approximately gains you 4 stops.. does that mean if I'm at f/5.6, turning on IS will approximate a shutter speed that would've been chosen for f/1.4?
     
  2. reg

    reg TPF Noob!

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    No - it lets you handhold LONGER, it doesn't make shutter speeds SHORTER. I think I have a little chart somewhere...

    Edit: Well, NO, I don't. But I do have this:

     
  3. MDesigner

    MDesigner TPF Noob!

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    Right.. I know it doesn't make the actual shutter speeds faster. What I mean is, when they say IS gains me 4 stops.. if I'm at f/5.6, does it shoot as if I were at f/1.4? And of course I don't mean DOF or any of that..
     
  4. reg

    reg TPF Noob!

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    No, it doesn't. It shoots as if you were at f/5.6, 1/8 second exposure, but had taken a Valium beforehand.

    ALL it does, is make shots that would have been shaky and blurry before, crisp and clean.

    But I don't need it to make me a taco, so I guess it does its job well.
     
  5. fredpb

    fredpb TPF Noob!

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    IS or VR does not change camera settings or "operation".

    If you are shooting a low light subject, the lens corrects a certain amount of movng or vibration. That is the action of IS.

    This elimination of some movement, like camera shake or unsteady hands at 1/10 second....without IS you would shake enough to lose sharpness or you may blur the picture. With IS the camera corrects the shake for a sharper picture.

    The number of stops you get is iffy. The more you shake, the less "stops" you get. IS has it's limits.

    You could say you would get the results of 1/250 for a picture when the camera speed is really 1/30th.
     
  6. MDesigner

    MDesigner TPF Noob!

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    Hehe.. I think I'm failing to communicate clearly. And yeah..English is my first language :)

    I fully understand IS doesn't change any of the operations such as shutter speed, aperture, etc. I know exactly how it works. The manual says it can gain you around 4 stops. I understand that's not REALLY adjusting your aperture.. it's a "simulated" gain of 4 stops. My question was.. what do they mean exactly by "4 stops"? If I'm shooting at ISO800 1/4" @ f/5.6, and I THEORETICALLY have a 4-stop gain.. then what exactly in my stats above (ISO800 1/4" @ f/5.6) has changed?? If someone tells you you just got +4 stops... what does that mean?
     
  7. elemental

    elemental TPF Noob!

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    If I understand correctly, it means that it simulates the stability you would have with a four stop faster shutter speed, so your picture is as "stable" and sharp as a shot at 1/60. Think shutter speed, not aperture. Four stops seems like a pretty big gain, but then again the whole "rating by stops" thing is pretty gimmicky anyway.
     
  8. MDesigner

    MDesigner TPF Noob!

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    There we go. That's the part I don't understand..actually, two big questions have been buzzing around in my head lately:

    1) Why do people use the term "stop" to refer to either shutter speed, aperture, or exposure compensation? If someone says "bump it up by 2 stops," how the heck do I know what they're talking about?
    2) What unit of measurement is a "stop"? If someone gives me a shutter speed like 1/200, and says "add 3 stops"... what is that exactly?

    With apertures, I think I know the order of stops, for the most part.. f/1, 1.4, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc. So f/11 + 4 stops = f/2.8. But what about shutter speeds?
     
  9. ANDS!

    ANDS! No longer a newbie, moving up!

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    It's probably not even referring to aperture, but shutter speed. Stops are genernally reserved for aperture value, but they can also refer to shutter-speed values. Or they could be referring to both.
     
  10. MDesigner

    MDesigner TPF Noob!

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    Here's a good example of what's confusing me:

    From another thread..

    What is "1 stop of light"?? -1EV? A 1-stop reduction in aperture? (going from f/5.6 to f/4)? I just don't get it..
     
  11. rob40wilson03

    rob40wilson03 TPF Noob!

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    I took the original post to mean: "what is the numerical value of a stop?" for example, is one stop equal to one sequential change in aperture value?

    im afraid i dont have a great answer for it though
     
  12. kundalini

    kundalini Been spending a lot of time on here!

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    It's a very confusing subject, so don't feel bad. Pick up the book Understanding Exposure and it will help a lot.
     

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