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DOF advice

Discussion in 'Lens Lust' started by Mitchell, Jul 23, 2007.

  1. Well, I've gone and done it again. I left a fast lens open enough so that several people in a group shot are blurry. While I realize this was just a foolish oversight on my part, can anyone offer advice on how to reliably adjust the aperture so that all the people in the varying focal planes will be in focus at the widest aperture? DOF preview? I've never really figured out how to use this function.

    I've spoken to a professional photographer friend of mine who shoots all groups at f11 or higher!:eek:  While this may be practical with studio lighting, how do you reliably handle this when shooting in available light?

    This was taken at dusk with the 85mm, f1.4 at f2.5. I realize now that I should have increased the iso, but I generally hesitate to go above iso 400. Wife in focus, children quite soft.

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  2. eng45ine


    May 11, 2005
    Chicago, IL
    Good Morning Mitch,

    If I were shooting several people who were posed as you family is, I would set my aperture to f/8. This would allow for keeping them all in focus while still providing for a reasonably blurred out background. I can understand your concern about digital noise, but don't be afraid to bump up your ISO to maintain whatever shutter speeds you prefer. Just keep a prudent eye on your exposure settings and all should be just fine.
  3. Donzo98


    Nov 10, 2005
    Merrick, NY
    That is a great question Mitch. I always shoot at least 5.6 to insure that I will get focus sharp across the pic.
  4. Frank and Don,
    I appreciate your comments and advice. How did you guys arrive at these numbers? Trial and error or is there any science involved?

    Does this factor vary with which lens is used??
  5. The closer you shoot with a longer focal length, the smaller your DOF. Shooting a subject at 20' with a 50mm lens will give you a deeper DOF than shooting that same subject with a 200mm at the same aperature (say f/5.6). I don't have all the physics of it memorized, but it is based on science.

    You have to look at both the distance to subject and the aperature, and then think about the focal length that you're using. That's why the 200/2 is known for it's stunning bokeh.

    The DOF preview button is (on the D200) on the right side of the lens mount, it's one of those little black buttons. When you press it, you physically close down the lens (which does not happen when you spin command dials and watch numbers change in the screen). If you've chosen a small aperature (large f-stop), the viewing screen may get quite dim (f/16 lets in a LOT less light than f/1.8 or f/4). But you will be able to look and see what is (and is not) in focus.

  6. I was wondering about this too, as I often see this issue in my shots. I took some time to do an online seach and found these:

    Online Depth of Field Calculator

    Dudak's Depth-of-Field Calculator

    (Note: The second link let's you put in 5 settings at one time to compare the impact of your camera settings...)

    What's shocking is when I type in your set-up and guess that you were about 12 feet away..... At those settings you only get about 6 inches of DOF! I never would have thought it was that tight.

    I mostly shoot at 4 and 4.5, but based on the calculators (and what's been happening to some of my shots) I need go up a bit higher on those numbers....
  7. Mitch,
    In the studio, I will use f8-11 for the groups. Anything more open will cause problems. As for your question of how to do this with available light? The first would be to increase your ISO and if you could use a reflector to shine more light into the group, that would be best.

    I like using natural light, but many times it is not possible to get what you want.
    Thats when the flash comes in handy.
  8. eng45ine


    May 11, 2005
    Chicago, IL
    I arrived at this f-stop setting by some trial and error. Depending how far the subject matter is from the lens also matters, but f/8 seems to yield some very nice results.
  9. Butchdog


    May 29, 2007
    That's a good question and I appreciate you asking it. I've done the same thing and I bet many others have as well.
    I was recently taking some senior portraits and the mother asked if I would do a group shot of five kids. Guess what? Never changed the aperture. It's a reality check on how shallow the depth of field really can be.
    And quite honestly, in the digital age of photography, there's a lot to think about sometimes.
  10. ffb2t


    Jan 16, 2006
    Another thing you could have done besides increasing iso is lowering shutter speed (may now need a tripod) and/or use a shorter focal length.
  11. kgill


    Jul 25, 2007

    I am learning about depth of field also, and I often have these problems in BROAD daylight, so I have no excuse!!!! But someone suggested this program you can download: http://www.stegmann.dk/mikkel/barnack/ and play around with it. You can upload your picture to it and then fool around.

    It's still all a foreign language to me, and it takes a bit to understand, but it might help ?

  12. Ghunger


    Apr 2, 2007
    Seattle, WA
    I do the exact same thing all the time, opening my lens up for available light shots and ending up with small DOF that is. I'm slowly learning how to use fill flash. I still need a lot of practice to get consistant results though. Kind of tricky to make it look like there's no flash used.
  13. Billy Ng

    Billy Ng

    Jan 22, 2007
    Hartsdale, NY
    DOF Preview button ... it is your friend. What are you unsure about when using it? When you press it, it stops the lens down to your preselected aperture to show you how DOF would change when it came time to take the shot.

    The viewfinder will get considerably darker depending on how much you've stopped down. But make sure you concentrate on whether or not your subjects are becoming more/less blurry as you turn the preview on/off.

  14. Just downloaded that program--it's very helpful! While I believe I understand the theory involved (or I have myself believing I do) I don't always practice good dof behavior. I probably do for landscapes, but not for people shots and the like.
    Thanks the question and the responses, this has provided me much food for thought and the needed kick in the butt to be more--pardon the pun-- focused!
  15. Haibane


    Aug 14, 2006
    Smyrna, Georgia
    Guys, I know a lot of you think iso above 400 is satan, but its not. I shoot at 1600 quite frequently just expose it properly
  16. Also, don't forget that as a general rule, you will get more DOF behind your focus point than you will in front of it. I always try to focus on people mid-way through the group (rather than the ones in the back) so the people closer to the camera are also in focus.
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