Over the past few years, I’ve had several people ask me how to set bracketing exposures on camera bodies for multiple exposures.  When I say multiple exposures here, I am talking in excess of 3 shots.  The reason for this is because by default, most Canon cameras (at least all the ones I’ve put my hands on) only have a single over and underexposure allotment on each side of the initial exposure settings.

Let’s take a look at the numbers…say we meter a scene and it says that according to the center point, we should be at f8, with an ISO of 100 and a shutter speed of 250.  So, if we want to expose this multiple times over and under that initial group of settings, since Canon only allows 1 over and 1 under, we will need to make additional adjustments if we want more than the 3 exposure set.

Here’s the entire f-stop range (well, not all of it, but enough for our purposes):

fstop

So, in order to get the full range of exposure, our aperture would need to manually be set to f2.8, f8.0, and then f22 and then let the camera capture the over/under.

For ease of manipulation I always start at the lowest end and work my way up, so in this scenario, I’d start with f2.8, press the shutter 3x, then move up to f8, repeat the shutter press 3x, then finally to f22 and press the shutter 3x.  That would give me a nine stop range of the same image at different exposure settings.  It goes without saying here that in such scenarios, you would want to:

  • Be shooting on a tripod
  • Be using a remote release (or timer)
  • Be using mirror lockup
  • All other settings remain constant
  • and that lighting conditions aren’t changing appreciably
  • You are set to manual focus
  • Your lens is set to its hyperfocal distance

Things that are problematic with bracketing in aperture priority are:

  1. Your depth of field is changing considerably as you move from f2.0 to f32.o so much of what is out of focus at f2 will be considerably sharper at f32 even though you are set at your hyperfocal distance.
  2. Lighting conditions will change.  Unless you are in a studio environment and flash is the only light source, ambient light is constantly changing,and this will have an impact on your exposure values.  Granted if you move quickly and methodically, this can be minimized, but due to the ever-changing values of light, this is something to consider!
  3. Weather conditions will change.  The scene that was perfectly still 30 seconds ago while you did the first bracket may not have perfect stillness for the second bracket set.  Changes in wind speed, direction, and intensity can blur things like flowers, branches, grass, and even some objects that you otherwise would consider fixed.  (Ever see a lamp post in a strong gusty wind?  Or a street traffic signal?)

Any other mechanics, pros and cons or points of discussion I missed here?  Feel free to chime in with your thoughts on bracketing exposures based on apertures.  Don’t forget to tune in tomorrow too for the backeting exposures on shutter speed, along with its pros and cons.  Happy shooting and don’t forget the Twitter v bloging poll from yesterday!  If you’ve already voted, tell a friend!

12 thoughts on “Setting bracketing exposures – aperture priority

  1. If you want to hear a reader’s feedback 🙂 , I rate this post for four from five. Decent info, but I just have to go to that damn google to find the missed bits. Thank you, anyway!
    p.s. Year One is already on the Internet and you can watch it for free.

  2. Unless you have constantly shifting scenes, I don’t see what the problem with only 3 pictures per bracket is.

    There are plenty of custom functions for you to be able to quickly access the menu to increase the stop gap of the bracket.

    If you don;t want to use auto bracketing, it is probably slightly easier to just shift the exposure, it just takes a spin of the wheel on a Canon. This would let you take exposures over the entire range…

    1. Hi Kris,

      Thanks for stopping in. As for the 3 picture bracket, you’re right – most people could manage with only a 3-stop range, which is what happens in the bracketing, as it will over and under-expose the median by one stop on each side. I also agree that it’s a fairly easy spin of the dial to do this manually. As a counterpoint, let me just clarify that I have gone out shooting on many occasions and seen scenes where the dynamic range of the scene was much larger than a 3-stop range would accommodate. In such instances, a 3-shot sequence would not be nearly enough fo a dynamic range to accurately express the scene. Finally, on the subject of spinning the dial, while it is fairly easy if you are adept with your gear – it helps when first getting your feet wet to know that the auto-bracketing setting is there to help you out so all you have to do is press the shutter 3x.

      Again, thanks for stopping in and taking the time to comment – it’s the varied perspectives and approaches to photography that make me learn so much more about photography, and in turn, share that knowledge with the larger community! 🙂

  3. If you are shooting bracket exposures for HDR merging then you really want to stick to a constant aperture and adjust the shutter speed to give you the exposure differences. There are quite a few reasons for this, the most important being exactly what you mentioned… the depth of field changes. This will cause the HDR merge to create excessive artifacts and make your post-merge clean up a nightmare.

    I think it is important to understand how to change the exposure using manual mode and adjusting the shutter speed especially if you are shooting Canon. I hate the fact that the majority of Canon’s only shoot 3 bracketed images in bracket mode. I cannot say for sure but it seems like a software limit rather than a hardware limit. Being able to shoot 3, 5, 7, or 9 would be such a huge improvement to this feature especially since HDR photography is getting really popular these days. Even the 1D is limited to 3 shots… ARGH!

    I will second your advice on using a tripod, manual focus, and release shutter button. Critical items for shooting bracketed images for all the obvious reasons!

  4. As with anything, there is always another way to achieve a similar result – informative post Jason

  5. I agree with Scott. Isn’t exposure bracketing via shutter speed the norm? What are the advantages of using aperture priority?

    1. To Scott and Josh,

      Yes it is more common to bracket on exposures. Truth be told though, I went with aperture to show the full stop range because I know those numbers better and was just feeling too lazy to look up the shutter speed increments in full stop values (and also was trying to remember whether 200 or 250 was the midpoint and gray matter interfered)! LOL As Scott said, the same technique applies though. Good catch and thanks for keeping me honest! 🙂

  6. Isn’t it more common to bracket on shutter speed, rather than aperture? Not that the same techniques wouldn’t apply.

  7. Great post Jason. Really useful stuff here. Pretty much ready to print this out and put in my camera bag.

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