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  1. #1
    stradibarrius's Avatar
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    Critical focus question?

    On my manual focus cameras like my RB67 or Yashica 124G when I get to the "critical focus spot" where it seems to be in focus...a tiny bit more and it is still in focus and then it starts to go OOF again.
    My question is about the tiny spot of critical focus where, for me, it is extremely difficult to tell the difference, even with the loupe. I know that for the exact focal length of a technical piece of equipment the is "the" spot where it is perfectly in focus.

    How do you decide when it is focused correctly?
    This may seem like a silly question...but???
    "Generalizations are made because they are generally true"
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  2. #2
    Bosaiya's Avatar
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    Quote Originally Posted by stradibarrius View Post
    How do you decide when it is focused correctly?
    Part of this is knowing ahead of time what you want the final image to look like. It may be planned out to the tiniest detail or it might be impromptu (for example you know you want a shot of a model looking off into the distance over her shoulder but the exact expression and angle aren't exactly known, you just have a general idea). Either way I look through the viewfinder or on the ground glass and wait for the right moment when it all comes together. Philosophically there is a "click" where everything just seems right. The trick for me is knowing my gear and what I want to achieve so that when the magic moment appears I can act on it.

    Mechanically when the part of the composition that I want to be sharp is in focus I release the shutter. Not much to it.

  3. #3
    Christopher Walrath's Avatar
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    I can see this as a relevant arguement if a razor sharp focal plane is called for. However for general grade photography I think it's not quite so elusive. I just zero in. Focus through clear and then back through clear, see-sawing back and through until I get the focus sharp and where I want it as to DOF. Barring LF photography and movements, there's honestly not that much more to it.
    Thank you.
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  4. #4

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    You approach focus by going back and forth in ever decreasing increments until you think that moving the focus knob/ring more will only make it go oof.
    You'll never know for sure, unless you check and move the thing a tiny bit more and see what happens. If you were spot on, it will defocus (and you will have to guess how much to go back again). If not, you will have to guess whether where you are now is the best you can get, or ...
    It takes confidence, the believe that you have it nailed.

    Focusing aids help.
    A split image rangefinder, for instance, is very accurate.
    But it then too still depends on your judgement, on whether you believe your eyes.

    Yet, it is not a big problem.

  5. #5
    stradibarrius's Avatar
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    That is the method I use. I can get to the "focal point" quickly but I am always concern about razor sharpness. Maybe too much so? The RB in particular has such a beautiful viewfinder, almost 3D sometimes. I flip up the loupe and always fidget with the tiny-est detail. I am always concerned that the small scale of the ground glass will show up a mistake in the larger print.
    "Generalizations are made because they are generally true"
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  6. #6
    Bosaiya's Avatar
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    Quote Originally Posted by stradibarrius View Post
    That is the method I use. I can get to the "focal point" quickly but I am always concern about razor sharpness. Maybe too much so? The RB in particular has such a beautiful viewfinder, almost 3D sometimes. I flip up the loupe and always fidget with the tiny-est detail. I am always concerned that the small scale of the ground glass will show up a mistake in the larger print.
    It sounds like you are still uncomfortable with your gear. That will go away with time and practice. Learn your gear, learn what it does and how you interact with it until it becomes second-nature. Eventually all of that will just melt away and become invisible. Just keep working at it and don't change too many variables. Stick with one body and one or two lenses and learn how to use them so that they become a part of you. If you're thinking about your gear then you're not thinking about the shot.

  7. #7

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    If you only dwell on the plane of focus you will miss the more important issue of dept of field. You really need to think about the area of acceptable focus as a volumn, not just a plane. The visual focus point you refer to in your message is somewhere in the middle of that volumn. In your composition, it is up to you to decide what to bring into that volumn and what to throw out of it, but to do so you need to think about both the near and far boundaries, not just the plane of maximum focus.

    Denis K

  8. #8

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    Yet you have to focus, and the 'problem' arises.
    (I disagree, by the way, that depth of field is more important. Putting focus there where it should be is more important than - also important, but less so - deciding how the in-focus bit relates to the rest of the image 'focus/sharpness-wise'.)

    It's not a matter of being uncomfortable with your gear, i think. It's just a lack of a way to decide when you have reached the 'maximum' other than seeing it get worse again. And when you do, you know you're no longer there.

  9. #9

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    Quote Originally Posted by Q.G. View Post
    Yet you have to focus, and the 'problem' arises.
    (I disagree, by the way, that depth of field is more important. Putting focus there where it should be is more important than - also important, but less so - deciding how the in-focus bit relates to the rest of the image 'focus/sharpness-wise'.)
    I think an example to demonstrate my point is when taking a picture with the lens nominally focused at infinity. If you simply focus at an object at infinity, as you describe, then you will throw away a great deal of potential depth of field for the comfort of seeing a maximally sharp image (of infinity) in the viewfinder. From the standpoint of your composition this may be what you want, but I doubt it. I can't think of any simple way of boiling down the process of setting the focal plane of an image that does not come to terms with the near and far points of acceptable focus based on your estimate of the depth of field. Even if your strategy involves setting the focal plane at a fixed distance and hoping for the best, this strategy does not work well at infinity. I do, however, agree that this simple strategy will work if your objective is to maximally render a flat plane, such as the tombstone in one of the original posters portfolio pictures.

    Denis K

  10. #10
    MattKing's Avatar
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    Quote Originally Posted by stradibarrius View Post
    On my manual focus cameras like my RB67 or Yashica 124G when I get to the "critical focus spot" where it seems to be in focus...a tiny bit more and it is still in focus and then it starts to go OOF again.
    My question is about the tiny spot of critical focus where, for me, it is extremely difficult to tell the difference, even with the loupe. I know that for the exact focal length of a technical piece of equipment the is "the" spot where it is perfectly in focus.

    How do you decide when it is focused correctly?
    This may seem like a silly question...but???
    If you are having trouble determining critical focus, it would be worth your while to determine if the viewing system of the camera and your eyesight are matched to each other.

    There is a reason that eyeglasses are made for people, and correction diopter lenses are made for cameras .

    Matt

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