Choosing Aperture

Discussion in 'Digital Photography' started by salvatore, Mar 4, 2008.

  1. salvatore macrumors member

    Aug 26, 2007
    After several months of research, I picked up a Nikon D80 and two lenses (18-135mm and 55-200mm VR Nikkor) recently.

    Ive done a considerable amount of reading[1], and am curious about how others are deciding upon aperture values when doing basic 'walking around' shooting. By this I mean generally tripod-less and wanting to capture whatever is going on around you at the time. For example, I went walking through Boston last weekend taking photos and quickly found myself paying more attention to which aperture I should use for shots than what was going on around me.

    I have a clear understanding of aperture and its relationship to shutter speed, light, and ISO. What I found slightly overwhelming were the myriad aperture values to choose from and when to chose *just* the right one. Using aperture priority, I played around with several shots before moving to shutter priority and letting the camera pick the aperture value once I was metered properly.

    My question is: is there a rule of thumb for 'basic shots' Ive overlooked, or do I need to get in the habit of metering with my eyes first to reduce camera-adjustment time when shots present themselves?[2]

    I dont want to replicate a P&S, rather Id like to gain a more rapid understanding of what to choose and when.

    [1] Including Peterson's 'Understanding Exposure'.
    [2] Obviously this response is 'it depends'; its the various experiences of the board Im in search of, though.

    Images are here:

    starting with _DSC0002.

    She's an old server, so be gentle.
  2. harcosparky macrumors 68020

    Jan 14, 2008
    Selecting an aperture is something you have to decide on for various shooting circumstances. Aperture determines DOF ( depth of field ).

    Decades ago, before the advent of auto-focus and digital manual lenses had a 'chart' on the near the mount. It would show you the DOF for a given aperture.

    I am not a good teacher, though I understand DOF and aperture affects, here is an online tutorial explaining it in detail.

    Go to that site and snoop around, I am sure there is some interesting reading there.

    I snagged two pics from that site to give you an example of the effect aperture has on depth-of-field.

    First one is a f/22, second one is at f/2.8

    Attached Files:

  3. phiberglass macrumors 6502a


    Oct 3, 2007
    That's a great example ^^

    I usually shoot in Aperture Priority mode, or TV to adjust shutter speed for action shots and panning shots, and sometimes manual, but I'm not a full manual guy yet :(
  4. salvatore thread starter macrumors member

    Aug 26, 2007
    Thanks for the link; I'll definitely do some reading.

    I understand the effect aperture has on DOF for images such as the posted example; its the larger scale scapes I seem to have a mental block for. As phiberglass said, Im not a manual person either...yet.
  5. taylorwilsdon macrumors 68000


    Nov 16, 2006
    New York City
    Basically, the background blur, or bokeh, is stronger depending on how close you are to the maximum aperture of the lens. Its a beautiful effect in some circumstances, but if you want as much detail as possible captured, you will need to stop down the aperture (I like f/8 on a f/2.8 fixed or f/5.6 on a f/1.8 fixed lens for high detail shots).

    This depends on available light, of course. You can't shoot f/8 if you are handholding a shot at night.

    Play with the settings of your camera and take lots of test shots. Only then will you learn what the sweet spot for your lens and camera are.

    edit - I have a d80 too and my favorite lens is the 50mm f/1.8. Its a great lens to learn on because it has a fixed aperture and generally excellent image quality. Consider picking one up used for around $90, if you have the means. Your current lenses have variable apertures which will make it more difficult to have a gold standard stop-down, and you will need to adjust as you zoom.

    When I shoot with my 18-200mm VR lens, I shoot one or two light stops down because the VR allows a crisp image with a longer shutter.
  6. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    Of course you are always constrained. You have to expose correctly to you have only a few combinations that work. You are asking how to choose which of them.

    I think what you need to do before you even frame the shot is decide how you want the final image to look like. Does the subject need to be isolated? Is it moving and you want to freeze or show-off the motion? How close should you be? Do you want to render the scene as darker or lighter? If the dynamic range is wide which part will you expose for?

    Once you have made the above decisions the selection of which Aperture/f-stop/ISO to use is determined for you.

    The other side of this coin is that if you think you have all of the f-stop and shtter speed combinations to choose from you have not thought enough about the result you want.

    In the real world it is never so easy because you will make decisions that are in conflict with each other. For example you might want a lot of depth of field but that might force you to chose between a to-slow shutter speed (and blur) or using a high ISO (and noise in the image) So you have to compromise all three.
  7. sonor macrumors 6502

    Jan 15, 2008
    London, UK
    If you were in a desperate hurry and didn't want to think too hard you could turn on Auto ISO (max 1600) on your D80, set it to Aperture Priority and chose f/8. This would be a fairly safe setting for a lot of different situations - but when you studied your photos you'd realise that many of them would have been much better if you'd chosen a more suitable aperture. There isn't a correct aperture for a particular scene - there are many variables and it depends on what you're seeing and how you want to represent it.

    Having said that I know some photographers who seem to shoot nearly everything at f/4. This generally gives them sufficiently limited depth of field to make the main subject stand out, but without the focus being too tight - and most pro lenses will be very sharp at f/4. This obviously wouldn't work for everything - certainly not macro or landscape photography.

    One way to learn is to go out and shoot similar scenes many times with different aperture settings and see what the results are.
  8. OreoCookie macrumors 68030

    Apr 14, 2001
    Sendai, Japan
    Or use Auto ISO + P. I use that when I hand over my baby to friends.
  9. salvatore thread starter macrumors member

    Aug 26, 2007
    All good replies; thanks everyone.

    I understand there's not a silver bullet, and my choice depends upon what image Im trying to capture along with what effect Im trying to have. It looks as though I need to do a better job of understanding my intention, and thus shot, ahead of time. Along with more experimentation, Im sure this sort of confusion will quickly fall by the wayside.
  10. bam bam macrumors newbie

    Sep 27, 2007
    Chicago area
    In one of Scott Kelby's books he mentions keeping the camera in P (Program) mode if you are just walking around taking pictures. That seems to work best for me too. A lot of pix are in the f/5 to f/8 range.

    I'm a relative newbie (~1 yr) with DSLR and photography - I have a D80, too. I'm just looking to get some nice shots of the kids and scenery, not trying to win the Pulitzer prize here.

    A lot of times I'll shoot in A then switch to P just to see what the camera's meter would have picked as aperture and shutter speed for the same type of shot. It's a nice check and you can learn as you go.

    I'll also do the P + Auto ISO (max 800 for me).
  11. nutmac macrumors 68040

    Mar 30, 2004
    Shutter Priority
    My default mode. Since my hands aren't super steady, I refer to this general shutter speed rule: focal length (compensated for crop factor) = 1 / shutter speed. For instance, my camera (EOS 400D) has 1.6x crop factor. When shooting with 50mm lens, I choose the shutter speed of 1/80 second, although I frequently get away with half a stop slower. If the aperture value becomes too low, I compensate with higher ISO speed and/or flash. When shooting a still subject with image stabilized lens, I set the shutter speed accordingly (generally no more than 2 stops, even with 4-stop image stabilizer). On occasion, I intentionally use slow shutter speed (usually with camera mounted on tripod) to get long exposure or blur effect.

    Aperture Priority
    Some folks use Aperture Priority as the default, but I use this mode only when I want to control the depth-of-field (DOF) or stuck with a lens with limited "optimal image quality" range (e.g., some lenses deliver excellent result only at certain aperture settings). Since DOF varies depending on the focal length and distance from the subject, I sometimes refer to DOF calculator.

    For my wife or strangers. "Hi, can you take a picture for us?" mode.

    For taking pictures under very limited light.
  12. salvatore thread starter macrumors member

    Aug 26, 2007
    What's the difference between P and Auto in this circumstance?
  13. Edge100 macrumors 68000

    May 14, 2002
    Where am I???
    I use Aperture Priority (Av) mode for almost everything. To me, controlling aperture size is (usually) of paramount importance, since it controls DOF.

    If I really need to control shutter speed (if I'm shooting sports, or trying to achieve a particular effect, such as time-lapse of a waterfall, for instance), then I'll switch to shutter priority (Tv). The problem with Tv mode vs. Av is that in Av mode, the camera will keep lowering shutter speed if you need more light; it's up to you to keep the camera steady. In Tv mode, by contrast, the camera can only open the aperture so far, so for a given shutter speed, you're limited as to how much light can be let in.

    Here's a nice link with some recommended aperture values based on lighting conditions, based on the old "Sunny 16" rule.

    As was pointed out above, you dont want to shoot at shutter speeds greater than 1/focal length, unless you have (a) a tripod, (b) image stabilization, or (c) very steady hands.
  14. HooHar macrumors member

    Nov 18, 2007
    Nottingham, UK
    In a nutshell...

    I clicked on this thread cos I thought it was about choosing Apple Aperture above Adobe Lightroom.... interesting though nonetheless...

    I would suggest that whenever making images - 9 times out of 10 - we either want to err to one extreme or the other of the aperture scale. We want to blur the background to simplify the image and draw attention to the subject, or we want to keep as much as possible in focus from "front to back". There are rare 1 time out of 10 occasions when these intentions are less important but mostly it's a choice one way or the other.

    We therefore need to decide on a wide or a small aperture respectively. We also want to always avoid camera-shake.

    If we choose a wide aperture to blur the background then camera shake is least likely as we have chosen a combination to let the most light into the lens for any given exposure. Hence enabling the use of a fast shutter-speed.

    If we choose a small aperture to achieve the maximum depth-of-field, then camera-shake risk is greatest for the opposite reasons.

    In most situations there are a variety of possible combinations. As a landscaper - I ALWAYS use a tripod and this suits landscape situations where I want a large depth-of-field (and has other benefits which keep me using it even when I don't). So for Landscape - always use a tripod - it means you NEVER HAVE TO CONCERN YOURSELF WITH WORRIES ABOUT CAMERA SHAKE regardless which aperture you choose (same for architectural).

    The other genres of photography just luckily happen to be the ones where a large depth-of-field is not so important - eg: Sports, Wildlife, Portraiture.
    In these genres, it's not only more suited to use handheld, but you're more likely to be happy with max aperture and a blurred background to draw attention to your subject.

    For instances like this where camera shake is a more of a concern (because you are hand-holding) although protected against (because you're using a wide aperture generally), we have to consider minimum shutter-speed according to the rules stated above [1/(effective focal length)]. Then, again depending on our ideal needs for depth-of-field, we have a choice of how to play this scenario. If we want to err towards deep depth-of-field with more in focus from front-to-back then we generally want the camera to use the slowest possible shutter-speed - we should therefore use shutter-priority to ensure that this minimum shutter-speed is used on all of the shots (to ensure that the smallest aperture which will still avoid camera shake is always automatically chosen). If we want to err towards shallow depth-of-field (ie wide-apertures) then we want the camera to always allow the widest-aperture for any given scene. Well - if you choose aperture priority and select the widest aperture that your lens is capable of, you'll get the fastest shutter-speed for every light-level you're shooting in (bingo!). But what if it's not fast enough to avoid camera shake. Then you have two choices - either go back to using a tripod, or select a higher ISO (making your camera more sensitive) and accept some fall-off in image quality (due to increased noise - only really a problem for most SLRs above 400 - quite variable).

    That's it in a nutshell!

    What about street photography I here you say. Bloody hell - OK - well this is more tricky - your ideals will change more for each image in this scenario. Some images you'll want to shoot with a more landscape leaning (deep DOF) and others will be shots requiring wider apertures. Decide which style you're leaning towards on any particular shoot and then decide on either setting Shutter-Priority with minimum shutter-speed for lens used, or using Aperture-Priority and selecting the max-aperture for the lens - you then have to experiment a while before deciding on your ISO for the shoot.

    Hope that helps.... :confused:

    How do you guys approach the dilemma?


    I think we should get all this sorted in our heads first - before we start thinking about diffraction effects - just to pre-empt the next reply !
  15. nutmac macrumors 68040

    Mar 30, 2004
    Although implementation can vary (I use Canon), auto is generally full automatic -- ISO speed, flash, shutter speed, aperture, and exposure. And some auto mode limits the type of file format (on Canon, automatic is locked to JPEG).

    Program mode is similar to manual mode on compact P&S cameras -- it takes over both the shutter speed and aperture, while letting you tweak few things such as ISO speed, flash, and exposure.

    Those are really valid points and excellent reasons to picking Av over Tv. That said, when you are shooting against limited light, especially with f/4 max aperture lens or worse, you will be hunting for extra shutter speed more often than DOF.

    Both aperture and shutter speed priority modes are grouped as "creative modes" and for good reasons. They open up many creative opportunities for budding photographers.

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