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Thread: ULF Minimal Focusing Discussion

  1. #21
    Corran's Avatar
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    Re: ULF Minimal Focusing Discussion

    I bring up reciprocity because that could be a major issue in some situations due to the increase in exposure length.

    We are talking past each other at this point. I have made contact prints from 4x5, 8x10, and a few 8x20 negatives now and see no difference in sharpness between all of them. The 4x5 is shot at f/22 or f/32 usually, so any differences in sharpness due to diffraction should be apparent when compared to the larger negatives shot at smaller apertures. All of them are very sharp and I would say are sharper than enlargements, but that should be expected due to less generational loss in the system.

    My opinion is that in many/most situations I encounter f/32 would not be sufficient for DOF, especially when considering a bit of a safety factor, and shooting such a relatively wide aperture would just be asking to get burned by lack of DOF.

    If I am wrong and your 8x20 contact prints are marginally sharper than mine, so be it.

    I am interested in other thoughts on this.
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  2. #22
    Randy Moe's Avatar
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    Re: ULF Minimal Focusing Discussion

    reciprocity

    wind

    forest

    time
    TIN CAN COLLEGE

  3. #23
    Corran's Avatar
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    Re: ULF Minimal Focusing Discussion

    Randy, I forgot to mention this earlier. I mentioned it to Michael in a PM but I calculated the exposure at f/32 and it would have been 1.5 minutes, so wind would still be a problem in general. Luckily it was a very calm morning.

    Shooting areas with larger swaths of moving water can be basically impossible with LF or ULF due to a constant low-level wind. Exposures have to be under 1-second to not have serious motion issues. In fact, the other 8x20 sheet I shot that morning was no good partly because of this. Lots of rhododendron and laurel leaves swaying in the wind at these places. I often watch the leaves and time my shutter release at the apex of their movement, and stop briefly.
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  4. #24
    Randy Moe's Avatar
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    Re: ULF Minimal Focusing Discussion

    A reason I dislike PM's as they exclude the rest of us.

    I always try to steer any PM Q&A back to open air.
    TIN CAN COLLEGE

  5. #25

    Re: ULF Minimal Focusing Discussion

    Quote Originally Posted by Corran View Post
    I bring up reciprocity because that could be a major issue in some situations due to the increase in exposure length.

    We are talking past each other at this point. I have made contact prints from 4x5, 8x10, and a few 8x20 negatives now and see no difference in sharpness between all of them. The 4x5 is shot at f/22 or f/32 usually, so any differences in sharpness due to diffraction should be apparent when compared to the larger negatives shot at smaller apertures. All of them are very sharp and I would say are sharper than enlargements, but that should be expected due to less generational loss in the system.

    My opinion is that in many/most situations I encounter f/32 would not be sufficient for DOF, especially when considering a bit of a safety factor, and shooting such a relatively wide aperture would just be asking to get burned by lack of DOF.

    If I am wrong and your 8x20 contact prints are marginally sharper than mine, so be it.

    I am interested in other thoughts on this.
    This is not about comparative analysis in any way shape or form. This is about a body of intellectual dialog toward a goal of providing an objective dialog to the current or future inquisitive participant relating to this topic. You as an individual have the right to choose your path toward the end result of your choosing. I wish you nothing but capturing your complete vision within your photography.

  6. #26
    Corran's Avatar
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    Re: ULF Minimal Focusing Discussion

    Regarding diffraction, I do believe that topic has also been discussed quite a bit on this forum, with much debate over whether it matters (even in smaller than ULF sizes). I don't have any handy links but could provide for good reading for those curious about diffraction.

    Having some experience with it as I mentioned earlier, as well as seeing/worrying about it in 35mm and digital imaging, I don't sweat diffraction for LF.

    I am still curious to hear from others shooting 8x10 or larger and what apertures they are using. I was under the impression that f/64 and beyond were de rigueur here in ULF land (if wanting maximum DOF) so if I am incorrect and all of you guys are shooting f/32 or wider I would be interested to know.
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  7. #27
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    Re: ULF Minimal Focusing Discussion

    Quote Originally Posted by Michael Kadillak View Post
    Great image. I could see a modest front swing being deployed in this image for myself intuitively given the orientation of the front two tree elements, but whatever you did you managed overall DOF very effectively.
    Actually, swing was not advisable -- the bush in the lower left is closer than the Redwood on the right. What I did manage fairly well was feeding three 4.5-year-old boys (Oct.2001) lunch on a blanket as I set the camera up and took the photo. Finished before the boys did, then they ran around -- sometimes between the tripod legs. Exposure was f/64 at 30 seconds. A G-Claron 355mm, I believe...on a borrowed homemade 11x14.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  8. #28
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    Re: ULF Minimal Focusing Discussion

    Quote Originally Posted by Corran View Post
    Oren, your comments on your 270mm is interesting. I will point out, since you mention aperture shape, that my 305mm GC is in an older shutter with many blades, creating a circular aperture. I do generally shy away from Copals that have 5 blades. However, at f/90, what was out of focus, to show the characteristics of such an aperture?
    At close range with normal-ish focal lengths for 8x10, even f/90 doesn't give you that much DOF. But the critical point was that I could see image character starting to degrade at the point of focus. Sorry for wording my comments in a way that left that unclear.

  9. #29
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    Re: ULF Minimal Focusing Discussion

    Thanks for the clarification Oren. I would certainly consider stopping only to f/64 in certain situations.
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  10. #30
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    Re: ULF Minimal Focusing Discussion

    Not to belabor this topic but I happened to find this interesting (and heavily math-focused) article with regard to DOF and a tilted lens:

    https://sites.math.northwestern.edu/...s/tilt_dof.pdf

    I took particular interest in the last paragraph of p. 10 on regarding sharpness at the boundaries of the DOF.

    Also this discussion on DOF and specifically diffraction could be helpful (again, very very math focused):

    http://www.largeformatphotography.in...DoFinDepth.pdf
    Bryan | Blog | YouTube | Instagram
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