Welcome to the forum!

As an adjunct to the Tangents blog, the intention with this forum is to answer any questions, and allow a diverse discussion of topics related photography. With that, see it as an open invitation to just climb in and start threads and to respond to any threads.

Help with focus/dof Issue

Hey guys,
In the attached pic I focussed on the girl using the leftmost focus point. She is sharp enough but the guy isn't  :(
24mm @f4 1/250s 400iso.
Any suggestions as to what went wrong?
Use f5.6 maybe?
I thought at 24mm dof would have been plenty.
Thanks
Iain
Tagged:

Comments

  • HoganHogan Member
    I'd guess because the camera back is not on the same plane as the people. Taken at an angle, the girl seems closer than the guy. You can tell this by the fact that the interior of the arch is more visible on the guy's side. To have them equally in focus at f4, you would need to ensure that both were the same distance from the camera (i.e camera back on same plane as subjects). Hope I've explained myself properly. Excuse bad diagram - exaggerated for effect 
  • dbrunodbruno Member
    Braveheart - If you could remember approximately how far away you were from the subject/subjects/center of composition, you could feed the info into a DOF calculator. I have some that I laminated and keep in my bag, because I frequently mess up, as I shoot a lot of indoor, low-light events (widen the aperture, let in more light, but unless I'm lined up correctly, shots of more than a few people are out of focus). Anyway, from my chart for F4 and 24 mm:

    Distance: 8 feet, Near-focus: 5.3 feet, Far-focus: 16 feet
    Distance: 12 feet, Near-focus: 6.8 feet, Far-focus: 49 feet

    Unless I've been interpreting these charts wrong, it seem like there should have been plenty of DOF at F4. Maybe something else is going on.

    Side note: from the picture you posted, it was really hard for me to see if the guy is out of focus, but if you say he is, he is. I probably should copy it and suck it into LR to really see it.

    Dave
  • CanonJayCanonJay Member
    I agree with what was said. Only three things can be happening here. #1 not enough depth of field or #2 the lens you used was soft on the outside edges. Last but not least, #3 camera shake. You did mention that is was 1/250 but a slight movement (by photographer) could still cause this. Probably the second or third I would assume as there should have been enough depth of field per say would be my guess. 

    -Jay 
  • BraveheartBraveheart Member
    edited June 29
    Thanks guys.
    I think Hogan is probably right, I had thought of that too.
    When I took picture, I was thinking along the lines of what Dave said.
    Definitely not shake, she is sharp. Lens is 17-55 2.8dx, top notch.
    I've noticed before in landscape pictures, if I use hyperfocal distance and then tilt camera up or down slightly, a similar effect occurs. Probably same effect here but in horizontal plane?
    Cheers  :)
    Iain
Sign In or Register to comment.