Controlling depth of field in group shots.

• mrboswell

  Participant

  March 25, 2008 at 4:13 pm

  Hi all,
  I’ve noticed recently that my Canon 350D with 28-135 / f3.5-5.6 IS USM is giving my a very shallow depth of field in group shots from family events etc.
  I’ve been shooting in “P” or program mode with and without flash, ISO 200-400 depending whether indoor or out.

  Basically I’m wondering if it is due to the number of autofocus points on the camera – are there not enough to pick up all the subjects in the shot (think there are 7…) I know the other option is to set a higher f number but I’m wondering if anyone else has noticed a similar issue?

  Thanks,
  Colm
  Mark

  Keymaster

  March 25, 2008 at 6:55 pm

  I’d strongly advise switching to using Aperture mode then you’ll be able to control the depth of field (via F numbers).
  All you’ll need to do if keep an eye on the shutter speed to ensure that its fast enough to allow you to
  hand hold (1 / focal length used (eg 28mm) * the crop factor (eg 1.6) of your camera). Of course if you’re using a tripod
  then the shutter speed will be less of a factor although of course still important.

  You should also make sure that you don’t have Auto ISO set up. Switch it to be ISO 100 (best quality).

  If the light is low and to ensure a fast shutter speed is available to you, you can open up the lens, ie f3.5 instead of f8
  and/or up the ISO to say 400 (has same effect as letting in more light). Upping the ISO will reduce the quality of the
  image by introducing some ‘noise’ but you might find that it’s not noticeable.

  Of course you should practice using the camera in aperture mode before using it at an event.
  It’ll give you much more control over what you’re doing and will solve your depth of field (DOF) issue.

  Hope this is of some use :)
  Thorsten

  Member

  March 25, 2008 at 7:55 pm

  Good advice from Mark there.
  Mark wrote:

  Of course if you’re using a tripod then the shutter speed will be less of a factor although of course still important.

  One thing that’s worth mentioning in relation to this is that even though you might have your camera firmly fixed to a nice solid tripod, you could still end up with blurry images. Why? Because of subject movement. I’m probably stating the obvious, but it’s surprising how many people actually end up wondering why they still have soft portraits in spite of using a tripod. It’s a bit of a catch-22 situation – you want to get better front to back sharpness, so you change your aperture only to find out then that your shutter speed is too slow and you still end up with unsharp shots.

  Don’t be too worried about increasing the ISO. You certainly shouldn’t have any problems shooting at ISO 800, provided your exposure is correct. The noise on a 350D at ISO 800 is unlikely to be objectionable and certainly much better than a soft image due to camera shake or insufficient depth of field.
  mrboswell

  Participant

  March 25, 2008 at 8:12 pm

  Thanks for that folks. All points that I understand, but not necessarily used to practicing them!! Thought it might be that the camera can’t pick up everyone in the frame. I’m working with an 580 EXII so I didn’t really expect to have the problem with the flash…
  Have to point out that it’s usually the closest subject in the frame that is not the sharpest – so obviously the closer to the camera the subject is the more obvious any sideways movement will be.
  Thanks for the feedback,
  Colm
  jb7

  Participant

  March 25, 2008 at 8:27 pm

  You should be able to pick up an online depth of field computer, or widget-
  you might just be expecting too much to begin with-

  Entering values in the tables might tell you which apertures you should have been using-
  and maybe some of them just might not work out at all-
  especially as your focal length gets longer, and your front subject gets closer-

  It may have nothing to do with your ‘focus points’
  and more to do with the optics-

  j
  IOP

  Participant

  March 25, 2008 at 11:50 pm

  mrboswell wrote:

  Hi all,
  I’ve noticed recently that my Canon 350D with 28-135 / f3.5-5.6 IS USM is giving my a very shallow depth of field in group shots from family events etc.
  I’ve been shooting in “P” or program mode with and without flash, ISO 200-400 depending whether indoor or out.

  Basically I’m wondering if it is due to the number of autofocus points on the camera – are there not enough to pick up all the subjects in the shot (think there are 7…) I know the other option is to set a higher f number but I’m wondering if anyone else has noticed a similar issue?

  Thanks,
  Colm

  Colm, the 350D has a special “A-DEP” mode which is designed to be used in situations such as you describe. The camera basically tries to judge the nearest and furthest subject and works out the best aperture for the job. Have a look at page 88 in the 350D Manual for more info,

  Dave