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Thread: Circle of Confusion query

  1. #21

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    Re: Circle of Confusion query

    IMO CofCs are really only a sort of guidance. Calculating them is all very well but in reality few photographers have sufficient control over the final viewing conditions and detailed scrutiny to which prints are put, so they have to be used with a great deal of discretion. When shooting 35mm I tend to use the engraved dof scales for two stops wider aperture these days because people insist of examining images at much higher magnifications than they used to and because digital noise has reduced relative to film noise. Whilst this isn't so relevant to LF, viewer's behaviour has changed and more information is sought even when it can't exist.

  2. #22

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    Re: Circle of Confusion query

    Quote Originally Posted by pgk View Post
    Calculating them is all very well but in reality few photographers have sufficient control over the final viewing conditions and detailed scrutiny to which prints are put, so they have to be used with a great deal of discretion...
    Please see the context, this is about making a box camera with fixed "bellows draw" and no movement, not about managing CoC in the field. It is an interesting question to find what hyperfocal settings would perform optimally with what limitations.

    Probably, depending on what we mainly shot, different fixed parameters would be desired for the box...

  3. #23

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    Re: Circle of Confusion query

    As I said, it is guidance. The camera type is somewhat irrelevant unless you also know end usage parameters. If you want an 'infinity' landscape to be in focus and want to print 'large' then focus at infinity regardless. If you want to contact print and view at 'normal' 10"x8" viewing distances then a very different, old fashioned and defined dof can be used to calculate the accepted hyperfocal distance and the camera set accordingly. The 'problem' here is not defining output requirements, not the camera type. DoF and hyperfocal settings are part of a workflow which requires parameters to be specified throughout in oredr for any calculation to be meaningful. If you can't specify output requirements then the CoC can't be properly calculated.

  4. #24
    Jac@stafford.net's Avatar
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    Re: Circle of Confusion query

    Quote Originally Posted by pgk View Post
    As I said, it is guidance. The camera type is somewhat irrelevant unless you also know end usage parameters.
    The OP asked if it mattered for an 8x10 contact and I suggested that a CoC of 0.2 mm approximates the typical resolution limit of the human eye at normal viewing distance. So we have the degree of enlargement (none) and viewing distance so if one must use CoC then 0.2 mm is natural.

    To reiterate what ic-racer wrote: It best to have your important subject in-focus. DoF might work, might not.

  5. #25

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    Re: Circle of Confusion query

    It wasn't entirely clear to me whether contact prints were the only option for final output. I fully agree though that the point of focus remains critical and DoF (however calculated) should not replace precise focussing .....

  6. #26

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    Re: Circle of Confusion query

    Quote Originally Posted by Jac@stafford.net View Post
    To reiterate what ic-racer wrote: It best to have your important subject in-focus. DoF might work, might not.
    Perhaps it would be useful if the hyperfocal settings could be adjusted with a variable shim, perhaps in the film holder side... let's say that with just adding some rectangular frames in back (shimming the holder) we would have an optimal job for infinite, for say 20m and for say 3m. Just an idea, perhaps a weird one.

  7. #27

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    Re: Circle of Confusion query

    The recent posts tend to reinforce my feeling that I am in a circle of confusion.
    Peter Collins

    On the intent of the First Amendment: The press was to serve the governed, not the governors --Opinion, Hugo Black, Judge, Supreme Court, 1971 re the "Pentagon Papers."

  8. #28

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    Re: Circle of Confusion query

    Thanks everybody for your contributions. I think I understand CoC better than I did before, and what place it has in the formula to calculate a hyperfocal distance.

    It tickles me how replies amble gently off topic - my query wasn't about whether using hyperfocal focussing was worthwhile (although the practical experience from Oren is much appreciated), or the benefits of using a view camera and movements.

    For the record, I enjoy using my view camera as much as my 5x7 box camera. They are different, the box camera is primitive and delightfully simple (maybe just a step more complex than a pinhole), and quick to use.

    In the 10x8 box I'll be using paper negatives (oh no! Cue more hands up in horror!), so a relatively cheap experiment. If it doesn't work out I'll still have the lens and film holders to use elsewhere...

    I do love the breadth and depth of photography.

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