Lens with Depth of Field indicator. (For full frame [36x24mm] digital camera.)

Discussion in 'Digital SLR' started by Henry, Dec 13, 2009.

  1. Henry

    Henry Guest

    Before I launch myself into the wonderful world
    of search engines, which I understand little of, I
    thought I would be better advised first of all, to
    start by asking those who may know more about
    digital cameras and lenses it than I do. Some of
    you may have used such lenses, assuming
    they exist!

    Thank you for your time.

    Henry.
     
    Henry, Dec 13, 2009
    #1
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  2. There are lots of prime lenses with DOF indicators. AFAIK there are no
    zooms, because the DOF changes as you zoom in or out.

    If you know what a DOF indicator looks like, you can spot the lenses
    easily on sites like <http://www.slrgear.com>
    ..
     
    Robert Spanjaard, Dec 13, 2009
    #2
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  3. One-ring or "push-pull" zooms often have DOF scales, but such designs
    have fallen out of favor in the autofocus era. Here's a shot of one
    such lens, a 1980's era Nikon 75-150mm f/3.5E:

    http://wemightneedthat.biz/Images/dofscale.jpg

    (I took this snap with a 35-105mm f/3.5~4.5, which _also_ has such
    a DOF scale for 24x36mm.)
     
    Michael Benveniste, Dec 13, 2009
    #3
  4. Henry

    OldBoy Guest

    For Canon only:
    http://www.the-digital-picture.com/Reviews/Lens-Product-Images.aspx?Lens=403
     
    OldBoy, Dec 13, 2009
    #4
  5. The standard parameter is delightfully named the "circle of
    confusion," often abbreviated CoC. Basically it describes the
    smallest image element that retains identifiable details.

    While the _parameter_ is standard, an accepted _value_ for the
    parameter, alas, is not. For a 24x36mm frame, Zeiss and Leica use a
    value of 0.025mm. Another commonly used value is 0.030mm, and I've
    seen other values used ranging up to 0.033mm.

    The "right" value depends on some somewhat subjective judgments of the
    acuity of the Mark I human eyeball. It also assumes no cropping. For
    a crop, I suggest using the Zeiss formula of d/1730, where d is the
    diagonal measure of the sensor area used to make the crop.
     
    Michael Benveniste, Dec 13, 2009
    #5
  6. Ah, yes, I've seen those before. Thanks for the reminder. :)
     
    Robert Spanjaard, Dec 13, 2009
    #6
  7. If you have one. It's missing on some entry-level DSLRs.
     
    Robert Spanjaard, Dec 13, 2009
    #7
  8. Henry

    Bruce Guest


    There are plenty of older zooms with DOF indicators, however the zoom
    action must be of the push-pull type.

    The spacing of the DOF markings varies according to the focal length
    chosen, so the DOF lines are rather gracefully curved.
     
    Bruce, Dec 13, 2009
    #8
  9. I've been an "unbeliever" when it comes to DOF scales...
    Notice that when they exist on lenses (or in charts), they
    symmetrically place on either side of the "correct" focus
    point at a given aperture both the nearer and farther focus
    points within which a selected range of "misfocus" supposedly
    is permissible before the image becomes visibly soft - or the
    distance range around the correct focus within which all is
    supposed to be "hunkey-dorey". Baloney!;-) OK, here's why.
    Imagine (or shoot) a landscape with a tree with leaves at a
    great distance. Include the same type of tree much closer to
    the camera. Now, using DOF scales and aperture, select the
    distance setting on the lens that the DOF scale says will just
    produce both good sharpness for both trees and also equal
    sharpness for both trees. Print the image. You may notice that
    the more distant tree that was photographed doesn't look as
    sharp as the nearer one. In fact, it may look down-right fuzzy
    in comparison! This is easy to explain. The "blob" size used as
    a standard for "sharp point rendition" is the same in both cases,
    but for the distant tree, the "blob" size represents a much
    larger proportion of its size, making it appear softer. Beware
    of this effect when including near-infinity landscape features.
    "Almost-sharp" horizons and distant features generally don't
    look very good, and you may need to "fudge" the focus a bit
    toward infinity-focus and also use a smaller stop to really have
    good DOF coverage. BTW, I always considered that DOF
    indications cheated by about a stop..;-)
    --DR
     
    David Ruether, Dec 13, 2009
    #9
  10. Henry

    Paul J Gans Guest

    I'd agree. DOF indication is not only good for DOF, but for setting
    the lens to its hyperfocal distance -- and that's useful.
     
    Paul J Gans, Dec 14, 2009
    #10
  11. Henry

    Jeremy Nixon Guest

    I also don't use the DOF scales much. They seem to be a little
    "optimistic" compared to what I want to see.

    For landscapes, I never use hyperfocal; I focus on the most important
    part of the scene, then stop down as far as I can without losing to
    diffraction (f/11 for APS-C, f/16 for 35mm, in my experience). Then
    I just let the rest of the scene sort itself out. If there's nothing
    too close to the camera, f/8 works fine. In "weird" situations I
    rely more on experience (and possibly bracketing, if possible) than
    on scales.

    For medium or large format, working with a DOF scale would probably
    be more beneficial. (But I don't have the experience there to really
    say.)
     
    Jeremy Nixon, Dec 14, 2009
    #11
  12. Henry

    Henry Guest

    Thanks for the info folks.

    Henry.
     
    Henry, Dec 15, 2009
    #12
  13. Yes, of course, but you missed the point. The DOF marks on the
    lens ARE symmetrically placed either side of the focus indicator
    on the lens, and since the focus distance intervals are progressively
    smaller moving toward infinity on the focus ring, what you said is
    true (plus more, when choosing DOF hyperfocal settings), but what
    I was saying is that following this (or using DOF tables) results in
    visually incorrect results in the photo (nearer-infinity image parts
    look less sharp than closer-to-camera image parts). The reason for
    this is simple. The "acceptable" blur for rendering a point out of focus
    is judged by these methods to be equal for near and far subject parts,
    and therefore, supposedly using this method results in an equal sense
    of sharpness near to far in the image - but it doesn't perfectly in
    practice for the reason I gave (and "illustrated") --
    "Imagine (or shoot) a landscape with a tree with leaves at a
    great distance. Include the same type of tree much closer to
    the camera. Now, using DOF scales and aperture, select the
    distance setting on the lens that the DOF scale says will just
    produce both good sharpness for both trees and also equal
    sharpness for both trees. Print the image. You may notice that
    the more distant tree that was photographed doesn't look as
    sharp as the nearer one. In fact, it may look down-right fuzzy
    in comparison! This is easy to explain. The "blob" size used as
    a standard for "sharp point rendition" is the same in both cases,
    but for the distant tree, the "blob" size represents a much
    larger proportion of its size, making it appear softer. Beware
    of this effect when including near-infinity landscape features.
    "Almost-sharp" horizons and distant features generally don't
    look very good, and you may need to "fudge" the focus a bit
    toward infinity-focus and also use a smaller stop to really have
    good DOF coverage. BTW, I always considered that DOF
    [lens or tables] indications cheated by about a stop..;-)"
    --DR
     
    David Ruether, Dec 15, 2009
    #13
  14. Henry

    Wilba Guest

    Wilba, Dec 20, 2009
    #14
  15. Henry

    Wilba Guest

    That's a good description of the Object Field Method. I'm interested to know
    whether you learnt about that from someone else or worked it out for
    yourself.
     
    Wilba, Dec 20, 2009
    #15
  16. Henry

    Wilba Guest

    I had some discussion with the author about some of that stuff, and it kinda
    made sense at the time but I couldn't explain it now.
    I haven't really played with Barnack. I encouraged the cBlur guy to include
    object field theory, but he didn't get it.
     
    Wilba, Dec 21, 2009
    #16
  17. Henry

    Wilba Guest

    I'd start with Depth of Field Revisited
    (http://www.trenholm.org/hmmerk/DOFR.html), and The INs and OUTs of FOCUS
    (http://www.trenholm.org/hmmerk/download.html). The Shutterbug articles
    (http://www.trenholm.org/hmmerk/HMArtls.html) are good reading too.
    Merklinger explores how resolution of distant detail affects sharpness in
    the image (e.g. http://www.trenholm.org/hmmerk/Resintro.htm). He explains
    why hyperfocal shooting fails to deliver sharply resolved distant detail.

    I've played around with his stuff and come to the conclusion that distant
    detail appears at the sensor effectively blurred to twice the size of the
    circle of confusion, so to make hyperfocal deliver on it's promise you need
    to halve your COC (or just focus at double the standard hyperfocal
    distance).

    If you are focussing that far out, you may as well just auto-focus on the
    furthest thing you want to be sharp (with a small enough aperture to resolve
    foreground detail), and not bother with all that tedious mucking about in
    hyperfocal space.
     
    Wilba, Dec 21, 2009
    #17
  18. Henry

    Wilba Guest

    No, I don't recall the details, but I do know that that's about resolution
    at the sensor, not resolution in the object field.
    I'm sure they don't really mind.
     
    Wilba, Dec 22, 2009
    #18
  19. See my post, above (12/15/09).
    Maybe better yet, "fudge" the use of the DOF scale, maybe placing the
    farthest point of interest at the next-widest-aperture DOF scale mark
    on the lens for the selected stop, and checking to see if this also covers
    the nearest point (or, use the DOF scale markers for a stop one wider
    than you intend to use, and then fudging the focus a bit more toward
    infinity focus). And, "for good measure", you may want to stop down
    the aperture even one more stop (diffraction is the great "leveler"...;-).
    --DR
     
    David Ruether, Dec 22, 2009
    #19
  20. Henry

    MikeWhy Guest

    That's not at all better in any sense. That's just the same irrational
    system you've found to almost work enough of the time. It might give the
    same answer some of the time, in which case you would then still be
    satisfied, no matter how you arrived at the answer.
     
    MikeWhy, Dec 22, 2009
    #20
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