ISO, Shutter Speed, & Amount of Light

Discussion in 'Photography Beginners' Forum' started by VAFalconFan, Jan 26, 2012.

  1. VAFalconFan

    VAFalconFan TPF Noob!

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    Hi guys. I recently bought a Canon T3, my first DSLR. First of all, I love it, and have gotten some great pictures already, although more by chance then skill, as I was just using some of the main shooting modes. Right now I am trying to photograph some coins in detail. I don't have a macro lens which I know would help, I just have the 18-55 mm lens included with the camera. Anyways, I have a question about a few of the various settings. I have looked at several websites discussing the functions of ISO, Shutter Speed, and proper lighting, but I couldn't find or overlooked my question of how they relate in a specific situation. I currently have a very basic copy stand setup, and am using the self-timer function, so there is no vibration of the camera. My question is : are amount of light and shutter speed interchangeable when there is no vibration of the camera? For example, I am shooting at ISO 100, and to have the coin properly exposed, the shutter speed has to be at 1/5. If I had better lighting, from what I understand, if I shot at the same ISO 100 and 1/5 shutter speed, it would be overexposed, correct? So to then have it properly exposed, I would have to increase the shutter speed to maybe 1/10 or 1/20. Would the quality of the picture be the same in both situations? Would there be any point in having stronger lighting in that situation? I hope my question made sense, and thank you in advance to anyone who reads this, I appreciate any information you can provide.


     
  2. o hey tyler

    o hey tyler Been spending a lot of time on here!

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    I suggest you also read into aperture and how that effects exposure.

    Yes, if you increased the amount of light from a properly exposed photograph at ISO 100 1/5s... Assuming the aperture is also a constant, your shutter speed would need to be increased to properly expose the photo.

    If you had stronger light, you could also shoot at a narrower aperture and get a larger DoF if your subject is large.
     
  3. adversus

    adversus TPF Supporters Supporting Member

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    Correct. What you are referring to is the Exposure Triangle. Rather than type out a tutorial, I direct you here:
    http://www.cambridgeincolour.com/tutorials/camera-exposure.htm

    If your ISO and aperture doesn't change, and your light increases, your shutter speed will have to increase to maintain correct exposure. Like-wise, if your ISO and aperture stays the same, and your light DECREASES, you need a slower shutter speed to achieve exposure.
     
  4. KenC

    KenC Been spending a lot of time on here!

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    One thing to keep in mind is that you never have "no vibration" especially if you don't lock up the mirror, which shakes the camera slightly when it moves away from the shutter. There is a range of shutter speeds where this small amount of vibration can be significant, perhaps about 1/30 down to about 1 second. When shutter speed is faster than that, it is fast enough to freeze the motion created by the vibration, if slower, the time the vibration occurs becomes insignificant compared to the total time the shutter is open. So, if you are starting out at about 1/5 there may be some benefit to more light (or slightly higher ISO) so you can use a faster shutter speed and not have to lock the mirror (assuming you can lock it on a T3 - I don't know.
     
  5. KmH

    KmH In memoriam Supporting Member

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    Use the carriage return keyboard function (Enter) to make your posts more readable.

    For links to lighting info and the other basics:

    http://www.thephotoforum.com/forum/...allery/267492-info-those-new-photography.html
     
  6. VAFalconFan

    VAFalconFan TPF Noob!

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    Alright guys, thanks for the responses.

    KmH, thanks for the advice on spacing in my posts, I'll try to remember that for the future.

    As for the aperture value, I already have it at the maximum value (5.6), so that's the reason I wasn't considering that in my question. Also, my subject is very small, about the size of a penny. Actually, exactly the size of a penny, lol.

    KenC, interesting, I didn't know about that. With that information I guess I will revise my question a bit.

    One of the links that were provided had a nice table that I think will help illustrate my question : Camera Exposure: Aperture, ISO & Shutter Speed

    I'll try and post the table, but I don't know if it will show up correctly. It shows the relation of aperture, relative light, and shutter speed for equal exposure.

    f/221X16 seconds
    f/162X8 seconds
    f/114X4 seconds
    f/8.08X2 seconds
    f/5.616X1 second
    f/4.032X1/2 second
    f/2.864X1/4 second
    f/2.0128X1/8 second
    f/1.4256X1/15 second



    Under all of these different settings, I understand that the "exposure" will be the same, but will the picture quality be the same, i.e. detail? If that is the case, is there any point to having a stronger light if you could just shoot with a faster shutter speed? With KenC's information - around 1/30 sec. being the point when the vibration of the mirror is frozen - assuming an aperture of f/5.6 (maximum of my camera) - also assuming that the picture is properly exposed at ISO 100 and shutter speed of 1/30 - would the picture quality be better if I had 2x the relative lighting and increased the shutter speed to 1/60? Or would it be exactly the same? Or if I had 8x the relative light, and increased the shutter speed to 1/240?

    If I'm over-thinking this, please let me know.
     
  7. o hey tyler

    o hey tyler Been spending a lot of time on here!

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    The picture would be better quality if you stopped down the lens to the "sweet spot." Probably between f/8 and f/11. It doesn't sound like you understand that aperture has more to do with sharpness and detail than shutter speed (however it plays a roll too).

    In my opinion, you are getting far ahead of yourself. 1/30s is VERY SLOW for any kind of shooting other than still life on a tripod, or night shooting. If you have a subject that is even slightly moving, or a focal length longer than 18mm on a crop frame camera, you are going to get camera shake and motion blur.

    Shutter speed doesn't effect the overall "sharpness" of an image, that's more of a lens property. Not using the proper shutter speed for the focal length you are using will cause blur.

    You always want to have your shutter speed at LEAST 1/focal length. So if you're shooting at 50mm on a full frame DSLR, you'd want your shutter speed to be at least 1/50s. If you're shooting on a crop frame, you'd probably want at least 1/60, perhaps 1/80s.
     
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  8. Derrel

    Derrel Mr. Rain Cloud

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    Here's a bit of friendly advice for you, and for virtually any newcomer with a kit 18-55 lens: SHOOT AT ISO 400. I repeat, shoot at ISO 400.

    If you wanna get to that "sweet spot" of f/8 to f/11 that o hey tyler mentioned, the easiest way to make that happen, along with f/8 to f/11 being paired with a shutter speed high enough to ENSURE sharp images--is to elevate the ISO level up, and away from ISO 100.

    ISO 100 is fine, if there is plenty of light. But it is actually a dangerous ISO level for beginners, for shots in sub-par light, for moving subjects, when shooting on-the-go, etc.,etc..

    Elevating the ISO to 400 moves the overall settings into the realm of "safe" under a much wider ranges of situations. The lower noise of ISO 100 is a mythical benefit to most beginners, and in many,many "kit lens" situations. ISO 100 leads to smooth, low-noise, blurry images under many,many situations. Trust me--forget all about ISO 100 with your new Canon. You do not need to be at ISO 100 to get good pictures.
     
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  9. WhiskeyTango

    WhiskeyTango No longer a newbie, moving up!

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    Each of the three components of exposure (Aperture, shutter speed, and ISO) have secondary effects. Aperture strongly effects depth of field (DoF), shutter speed effects motion blur, and ISO effects grain or noise.

    While you can have numerous technically correct exposures (i.e. double your shutter speed and halve your aperture), there is usually a creative, or artistic, reason to choose one over the other. If you want a shallow DoF to isolate a subject from its background you would want wide apertures, which would push you to shorter exposures, or lower ISO's. If you are trying to freeze motion, you would want high shutter speeds, which would push you to open up your aperture or increase your ISO.

    Usually, your creative reasoning will tell you which of the technically correct exposure combinations to choose from.
     
  10. VAFalconFan

    VAFalconFan TPF Noob!

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    My subject is 100% still. It is a coin laying on a table.

    Also, the coin is on a blank background, so don't I want the narrowest depth of field possible?

    In my original post, I mentioned that I had a very specific situation that I was talking about.
     
  11. WhiskeyTango

    WhiskeyTango No longer a newbie, moving up!

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    Not necessarily... You have a plain, i.e. non-distracting, background to begin with. There's no reason to shorten DoF to separate the coin from it. What you want is a tack sharp image, and that won't happen wide open. You'll want to be a couple of stops above that.

    The good news is that if you're tripod mounted, you don't care about the longer exposure time needed, and if you're starting at ISO 100, you have LOTS of room to move there too before noise becomes a problem.
     
  12. analog.universe

    analog.universe TPF Noob!

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    Right, you would want a deeper field in this situation. Something important to remember is that at any given aperture, you get a shallower depth of field as your subject moves closer to the lens. So for something small like a penny, where you're way up close, I'd choose something like f/11 to start, and see where that got me.

    Being on a tripod gives you much more flexibility. The caveat is that mirror slap will still have an effect unless you're on a fairly intense tripod. So you want to lock up your mirror (a nice easy way to do this is just use one of the silent shooting modes in live view, your manual will tell you how to enable them).

    You can make this whole thing a lot easier by just lighting the subject better. If you haven't got an off camera flash, you can just use a regular lamp (the brighter the better). Most of the time when people do this type of photography (close up's of stuff that doesn't move), they use multiple strobes and pour a tremendous amount of light onto the scene.
     

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