Adjusting Exposure...Shutter Speed vs Aperture

Discussion in 'Photography Beginners' Forum' started by Shades of Blue, Dec 17, 2015.

  1. Shades of Blue

    Shades of Blue No longer a newbie, moving up!

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    I'm beginning to use Manual mode on my Nikon D5000. In my high school days, I was a big Auto guy, and recently I've been using either A or S priority modes. I understand metering, and I am ok with compensating either shutter speed or aperture to get exposure.

    What I'm struggling to understand is when you would choose to use either shutter or aperture, and how you decide on adjust one over the other. To me, it has to do with adjusting the shutter for moving objects vs adjusting the aperture for depth of field....but it can't be that simple can it?


     
    Last edited: Dec 17, 2015
  2. KenC

    KenC Been spending a lot of time on here!

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    some things are

    Shutter speed is also important in minimizing camera movement.
     
  3. john.margetts

    john.margetts No longer a newbie, moving up!

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    Yes, it can! Why do you want it to be complicated? Many people make photography very complicated because they have a psychological need to be doing complicated things but if you are interested in producing excellent pictures photography is quite simple.


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  4. Shades of Blue

    Shades of Blue No longer a newbie, moving up!

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    Oh trust me...the last thing I want is for this to be even more complicated haha. I guess I was just asking if there were any other artistic reasons one might choose one over the other.
     
  5. john.margetts

    john.margetts No longer a newbie, moving up!

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    Artistic reasons: aperture controls depth of field and sharpness (f/5.6 to F/11 for Max sharpness, F/2 or /22 for softness)
    Shutter controls motion freezing - long shutter speeds give motion blur, short shutter speeds give frozen motion. With no tripod, shutter speed needs to be at least twice the focal length of the lens (with a crop sensor).

    That really is about it.

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  6. TCampbell

    TCampbell Been spending a lot of time on here!

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    Most of the time I'm not shooting something speed-sensitive and so I use aperture priority.

    When you approach the shot... consider either (a) is there anything in this shot that needs a fast shutter speed to freeze movement, or (b) would benefit from having a particularly slow shutter speed to create deliberate blur and imply motion?

    If the answer to those questions above is 'yes', then I shoot in shutter speed priority mode (Nikon S for Shutter speed / Canon Tv for Time value mode).

    If you spend most of your time shooting 'action' photography (sports, action wildlife, etc.) then the answer to those questions might be 'yes'.

    If the answer to those questions is 'no' (and this is true of most shots), then I use aperture priority mode (Nikon A for Aperture control / Canon Av for Aperture value). This is because in these situations, Aperture allows more creative control. If you need a broad depth of field, you get that by stopping down. If you need either a lot of light or a shallow depth of field you get that by opening up.

    If you spend most of your time shooting non-moving objects (which is probably true for most non-sports photographers) then most of the time you would be better off shooting in Aperture priority mode.

    These guidelines moderately over-simplify things because sometimes limits of the camera constrains your choice so you can't just shoot the exposure you want because you want it... the lighting has to make that exposure possible. If you count all the full stops of shutter speed on a typical DSLR camera, you can go from 30 seconds to perhaps 1/8000 and that's 14 full stops of exposure adjustment just on the shutter speed dial alone -- meanwhile the f-stops doesn't have quite that much adjustment. Assuming you have an f/2.8 zoom lens ... and it can go from f/2.8 to f/22 then that's 7 stops -- half as much room for adjustment as the shutter speed dial.

    This means means that even if I am shooting sports and I want to freeze action using, say, a 1/1000th sec shutter speed while shooting an indoor basketball game and you have a zoom lens with an f/3.5-5.6 focal ratio ... and at your focal length f/5.6 is the widest possible aperture. This would result in an underexposure because the camera would want to use an f-stop lower than is possible for the attached lens. You can crank the ISO but you probably won't like the noise in the images.

    So more than likely you'll "prefer" to control the shutter speed, but you may instead set the ISO to the higher ISO you would be willing to use given the noise and then still shoot in aperture priority (setting the aperture to wide-open for your lens) and then let the camera use whatever shutter speed it can.
     
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  7. Shades of Blue

    Shades of Blue No longer a newbie, moving up!

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    Extremely helpful post! Thank you!

    Ok, so let's say I shoot in aperture priority mode, can you also use metering? Or is metering done automatically in A or S mode because you are allowing the camera more control? Sorry, I'm on a trip right now and can't just grab my camera until the weekend. I thought I read metering only works with manual mode.

    My situation is that my outdoor portraits have members here commenting they are underexposed. I do generally use aperture priority, and I like to go as low as my 55-200mm lens will allow to induce background blur, which is f/4. I have been fooling around with metering in manual mode, but I can't understand why I'm struggling to get decent exposure in other modes.

    Could it be because my automatic focus setting is set to the auto mode? I bet that's it! Maybe I should switch that to Spot mode.


    PS: This site has already increased my curiosity 10 fold in just being a member for 2 days. I've been taking photos for years and getting nothing more than "those look great" from family and friends. I come here and immediately I'm given constructive criticism and I've seen how learning more about my camera could do wonders for my work. I've never had to worry so much about it because my pictures look good enough for the average person, but the potential is much greater with real feedback.
     
    Last edited: Dec 17, 2015
  8. Ysarex

    Ysarex Been spending a lot of time on here!

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    The meter is functioning in all modes. Using the meter in a way that directly sets either shutter speed or f/stop is not allowing the camera more control. If you use the camera in full manual and rely on the camera meter then all you're doing is slowing down the same process.

    With the camera in Aperture Priority, Shutter Priority or Program mode you can bias the exposure plus or minus with the EC (exposure compensation) control.

    Not an auto focus problem. Your meter has different modes of operation (matrix/evaluative, average, spot, etc.) and it's necessary for you to understand how those work and use them effectively.

    Another consideration concerning the f/stop selection that hasn't been mentioned is overall lens performance (IQ). The lens IQ will vary over the the f/stop range -- this is more than just DOF. At either end of the f/stop range either lens aberrations or diffraction will become factors that degrade overall IQ.

    Joe
     
  9. TCampbell

    TCampbell Been spending a lot of time on here!

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    To expand slightly on Joe's reply... the meter "always" activates and takes reading... it's what it does with those readings that changes depending on the mode.

    In "manual" mode, the meter set anything based on the meter reading (because that's up to you). It lights up an arrow in your viewfinder indicating if it thinks your current settings would result in a "correct" exposure vs. an over-exposed or under-exposed image... but it is merely offering you advice and not actually taking control of your exposure (since you are in manual mode, it's up to you to change the exposure settings based on the advice it is offering.)

    Also, the meter in the camera is probably showing you the metering with a range of 3 stops both above and below the correct exposure. This means if you want to deliberately overexpose or underexpose a shot, you can.

    In Program, Aperture priority, or Shutter priority mode, the camera doesn't just offer advice, it adjusts settings for you.

    When I shoot concert events, the stage usually has a black background and the lighting on the performer might be fairly bright in contrast to the background. If the camera is allowed to meter the "whole" scene (evaluate everything) then it's going for a middle-gray exposure... that means it will try to average the lighting and bring up the blackness to a muddy gray and this will result in blowing out the relatively small areas that are actually brightly lit. So to compensate I might either (a) spot meter on the performer's face (in the same way photographers tell you to "focus on the eyes", I might suggest you "spot meter on the face") because that's where I want the exposure to be accurate and frankly I want the black background to be a rich black and not a muddy gray. But an alternate way to shoot might be to use an automatic mode such as shutter priority (aka "Tv"), aperture priority (aka "Av") or even Program mode... but then use "Exposure Compensation" on the camera to tell it to deliberately under-expose the shot.

    The camera's light meter has two issues...
    #1 it uses "reflected" light to measure the scene instead of "incident" light.
    #2 it might be evaluating the entire area (or most of it) visible through the viewfinder... instead of the subject in the scene that you actually care about.

    The camera believes that every exposure should average out to a middle-gray tonality and there's a problem with how the meter works. The camera can't tell how much light is landing on a subject... it can only detect how much light is reflecting off that subject and making it's way back to the camera. So you can easily imagine how if we have the identical light source in a room, but in one shot we paint most things in the room with flat-black paint the room will seem very dark. If we paint most things in the room with white paint the room will seem very bright -- even though we technically didn't change the lighting. Some surfaces reflect more light than others. If you use a hand-held "incident" light meter, you can place the meter right in front of your intended subject (metering facing the light... not the subject) and it will tell you how much light is "landing" on the meter. That's the true amount of light. If you set the exposure based on that "incident" metering then you'll get a much more accurate exposure because black things will actually look "black" and not gray. "white" things will actually look "white" (and not gray). And middle-gray tonality things will actually end up with a middle-gray tonality.

    If you let the camera meter the "whole scene" you get the following issues:

    (1) If your scene is dominated by blacks that are actually supposed to be black, then the meter will think the shot is underexposed and try to boost the exposure -- resulting in something that is really overexposed.
    (2) If the scene is dominated by whites (think "winter snow scene") then the camera will think the shot is overexposed and try to reduce the exposure to bring those whites back down to gray -- resulting in something that is underexposed.

    You can usually change the metering mode so that the camera doesn't meter the "whole" scene... but only a portion of it (or at least biases the meter reading toward a smaller part of the scene). Cameras might have modes such as "partial metering" or "center weighted" metering or "spot" metering.

    Being aware of how the metering system works and being able to anticipate what it's likely to do will help you be a bit more clever as to when you can trust letting your camera evaluate the whole scene (Nikon "matrix" metering) vs. metering for a specific target and locking the exposure on that reading (learn to use exposure lock). It will also help you be a bit more clever as to when you should probably deliberately over-expose or under-expose relative to the camera's recommended exposure setting.
     
  10. Re3iRtH

    Re3iRtH TPF Noob!

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    Thanks Tim, very informative. I have started out mostly using the manual mode, only because the first serious photographer I have met after purchasing a DSLR, uses manual pretty much all of the time. We are usually shooting landscapes, some water, and a lot of sunrise/sunset photos. My question is, is there a problem with mostly learning on manual mode as a beginner?

     
  11. john.margetts

    john.margetts No longer a newbie, moving up!

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    There is only any point in using manual mode if you are using a separate light meter. If you are using the camera's meter to determine exposure in manual mode you are merely making an easy job unnecessarily complex - you will end up with the same exposure as you would if you used either aperture priority or shutter priority settings.

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    Last edited: Dec 18, 2015
  12. AKUK

    AKUK No longer a newbie, moving up!

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    Just to add to all the above, another reason to choose shutter or aperture when controlling exposure is when mixing ambient and flash light sources. Generally a flash fires faster than the shutter (up to the sync speed) and so is unaffected by the shutter speed. The shutter controls the ambient light only. The aperture will control both ambient and flash power (as does ISO). If you use manual flashes/monolights, then this is particularly important to note. If using a TTL flash, then the camera takes care of the flash power.
     

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