Depth of Field Preview

Discussion in 'Beyond the Basics' started by kkamin, Aug 25, 2009.

  1. kkamin

    kkamin TPF Noob!

    Joined:
    Aug 25, 2009
    Messages:
    514
    Likes Received:
    17
    Location:
    Minneapolis
    Can others edit my Photos:
    Photos OK to edit
    I just bought my first DSLR and then discovered its 'Depth of Field' preview feature. Initially I thought it was a weird work around for a digital camera to show you your depth of field, since I am without an f-stop ring on my lens, on my Canon DSLR it's all computer set.

    But then I went to investigate my analog SLR and realized, for the years I have been shooting, the aperture is always full open, and doesn't close down until you hit the shutter. If the aperture did close when I increased my f-stop, the image would dim. Panic took me over. I think for all these years, my depth of field hasn't been completely accurate. I always thought looking TTL was giving me an accurate picture.

    1. With my analog SLR, I was never getting an accurate depth of field by looking TTL, right? Kind of still in shock.

    2. How do analog SLR users get an accurate idea of their depth of field?

    3. When you look TTL, is the shutter positioned by default at the largest aperture or is it open even larger?

    4. My xsi lens doesn't have a focusing distance scale. If I'm in a tricky situation, like photographing a large group photo, how am I suppose to make sure everyone is in focus if I can't take a measurement with a tape measure, or even know what my depth of field measurement is--and if I use depth of field preview, it gets too dark since I am shooting at a high stop?
     
  2. PhotoXopher

    PhotoXopher TPF Noob!

    Joined:
    May 27, 2009
    Messages:
    3,475
    Likes Received:
    2
    Can others edit my Photos:
    Photos NOT OK to edit
    Aperture is always wide open until the shot is taken, or the DOF preview button (if equipped) is pressed.

    My Nikon N75 has one, so does my D90 - so they were available in the film days.

    I guess you either have to bring a calculator or download one of the many free applications for hand held devices, I have one on my phone for example (never use it, but it's there).
     
  3. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

    Joined:
    Dec 16, 2003
    Messages:
    33,817
    Likes Received:
    1,811
    Location:
    Edmonton
    Can others edit my Photos:
    Photos NOT OK to edit
    Same deal with any modern SLR. The viewfinder looks TTL with the aperture wide open. So you are only seeing an accurate DOF if you are set to shoot at the max aperture.

    By using the DOF preview button, by using the distance scale, by using a DOF chart (or calculations)...but I'd guess the most common way is just with experience.

    Yes, the problem with DOF preview is that because it stops down the aperture (if you are set at a smaller aperture) it dims the viewfinder. The smaller the aperture, the dimmer it gets. You can usually get your eye to adjust but sometimes it's just too dark. Also, back in the film days, viewfinders were often bigger, making it easier to see the image and ascertain the DOF. Higher end SLR bodies still have larger viewfinders but entry level DSLR bodies (like the Rebel series) have rather tiny viewfinders, which makes it quite hard to really see the image well enough to be sure of your DOF.

    Of course, you can take a test shot and zoom into the image on the LCD. Or just take several shots at different apertures, to be sure that you get one with the DOF you want.
    Heck, you can even take several shots with different focus points and combine the shots with what's known as 'focus stacking'.
     
  4. Garbz

    Garbz No longer a newbie, moving up!

    Joined:
    Oct 26, 2003
    Messages:
    9,713
    Likes Received:
    203
    Location:
    Brisbane, Australia
    Can others edit my Photos:
    Photos NOT OK to edit
    You were, assuming you were shooting wide open :p. TTL is through the lens. Didn't you ever look into the lens from the front and notice the lack of aperture blades?

    DoF preview isn't new. My Nikon FE from the early 70s has it. A friends Nikkormat has it too and that's even older. In the case of my FE the DOF preview lever actually physically actuates the lens's aperture blade release lever. My D200 does the same except via a computer inside the camera that drives a little electric motor and my haven't we complicated things in the last 50 years :lol:

    The shutter is totally closed at all times. That's what the mirror is for. You're looking past the shutter. The lens is open at it's max aperture. The aperture where the blades completely give way to all lens elements. There is no larger aperture since the glass isn't larger.

    Look into the front of your lens and hit the DOF preview button to get an idea for this.

    You can focus on the middle of the group and then use a Online Depth of Field Calculator. You can google Depth of Field charts too and print them out and carry them with you (quite handy, I keep a few in my camera bag).

    Or god forbid take a photo. It's digital. Look at the screen ;)
     
  5. kkamin

    kkamin TPF Noob!

    Joined:
    Aug 25, 2009
    Messages:
    514
    Likes Received:
    17
    Location:
    Minneapolis
    Can others edit my Photos:
    Photos OK to edit
    I'm glad you find some type of satisfaction in trying to make me feel unintelligent.

    I appreciate everyone else's replies.
     
  6. Goontz

    Goontz TPF Noob!

    Joined:
    Jul 17, 2009
    Messages:
    1,275
    Likes Received:
    2
    Location:
    Austin/Houston, TX
    Can others edit my Photos:
    Photos OK to edit
    Well I suppose that's one way it could be taken...:confused:
     
  7. JerryPH

    JerryPH No longer a newbie, moving up!

    Joined:
    Oct 14, 2007
    Messages:
    6,111
    Likes Received:
    15
    Location:
    Montreal, QC, Canada
    Can others edit my Photos:
    Photos NOT OK to edit
    I know garbz, and that was not what he was trying to do, he was asking you an obvious question if you never noticed the lack of aperture blades. Emotions are hard to convey in writing, but you need to grow a thicker skin if your intentions are to stick around here for more than 1 post. ;)
     
  8. robertwsimpson

    robertwsimpson No longer a newbie, moving up!

    Joined:
    Aug 3, 2009
    Messages:
    2,471
    Likes Received:
    30
    Location:
    West Palm Beach, Fl
    Can others edit my Photos:
    Photos NOT OK to edit
    I'm not certain that when you look through your camera you're seeing with the aperture wide open. With my 50mm 1.8, the DOF looks WAY deeper through the viewfinder than it turns out being after I take the picture at f1.8

    just sayin.
     
  9. bhop

    bhop No longer a newbie, moving up!

    Joined:
    Dec 10, 2007
    Messages:
    2,209
    Likes Received:
    236
    Location:
    Los Angeles
    Can others edit my Photos:
    Photos OK to edit
    My film SLRs have DOF preview.
     
  10. robertwsimpson

    robertwsimpson No longer a newbie, moving up!

    Joined:
    Aug 3, 2009
    Messages:
    2,471
    Likes Received:
    30
    Location:
    West Palm Beach, Fl
    Can others edit my Photos:
    Photos NOT OK to edit
    I can open and shut my aperture on my AE-1. there's a button right next to the lens.
     
  11. Sn00bies

    Sn00bies TPF Noob!

    Joined:
    Jul 4, 2009
    Messages:
    89
    Likes Received:
    0
    Location:
    Utah
    Can others edit my Photos:
    Photos NOT OK to edit

    Great point, now that you mention this, it makes sense... so what happens on the 50mm 1.8 then? *curious*:scratch:
     
  12. coreduo

    coreduo TPF Noob!

    Joined:
    May 4, 2009
    Messages:
    329
    Likes Received:
    0
    Make your shutter speed 4 minutes and your aperture f/45, you'll get a good DOF. I read it in a magazine that teaches basic photography. It arranges all arrays of f-stops and shutter speeds corresponding to each other under the title "Depth of Field". It is still available in bookstores although I forgot the title of the magazine.
     
    Last edited: Aug 26, 2009

Share This Page

Search tags for this page
automatic depth of field for large group shots
,
depth of field preview film slr
,
depth of field preview on film camera
,
dof preview on film slr
,

film+slr+dof preview

,
how to use aperture preview
,
how to use dof preview on film slr
,
nikon fe depth of field preview
,
nikon fe depth of field preview while taking photo
,
proper use of depth of field preview on film cameras