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Thread: Choice for the Circle of Confusion?

  1. #41
    Jac@stafford.net's Avatar
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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Tin Can View Post
    I can no longer trust what I see. Nothing is sharp...
    FWIW, my focusing eye is worthless. At some point is is good to ask ourselves for whom do we make images that we cannot experience. I am about done with it all.

  2. #42

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Emmanuel BIGLER View Post
    And this did make sense, because most often images were only contact prints of 6x9 cm size for the family album, viewed at a distance of about 30 cm.
    Yes.. the print size critical to find the optimal aperture.

    If I understand it correctly, if we know the print size (and viewing distance) then we know the aperture that starts damaging IQ in the focus plane, so we can extent DOF until that point without damaging the print.

    With the same viewing distance, as the print is larger we can stop less before we damage IQ in scene's the focus plane.


    But when we take a shot we may not know what print size we'll have... if the image is very good then we may want a big print.

  3. #43
    Tin Can's Avatar
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    Re: Choice for the Circle of Confusion?

    Never quit! i am working on set up for full blind LF photography.

    I lurk on Blind Ham Radio forums to prepare for the inevitable.

    Maybe 2 more years of day driving, unless something improves.

    No night driving for a while...

    I still shoot righty with my left eye...and my brother was opposite.
    Father confused us with his both eyes open approach. Which never worked for me. So I shot even shotgun with left eye. Which he considered idiocy. He was very good at knocking down 3 birds quickly. I stopped hunting with him. RIP

    Quote Originally Posted by Jac@stafford.net View Post
    FWIW, my focusing eye is worthless. At some point is is good to ask ourselves for whom do we make images that we cannot experience. I am about done with it all.

  4. #44
    Drew Wiley
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    Re: Choice for the Circle of Confusion?

    I can certainly sympathize with people still trying to do what they love yet with diminishing sight. It takes courage as well as some kind of plan. But there's a major museum dedicated to how Monet painted things as he actually saw them with impaired sight during old age. I'm not suggesting to do things the same manner, but that where there is a will, there is a way.

  5. #45

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    Re: Choirce for the Circle of Confusion?

    Quote Originally Posted by Bob Salomon View Post
    And how far away will it be viewed at?
    Details.

  6. #46
    Tin Can's Avatar
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    Re: Choirce for the Circle of Confusion?

    Most people crowd around one of my favorite paintings, so many do it's hard to see it at all. They go to the rope. Fools!

    But if I stop on the stairs just at the room entrance this 8X10 ft painting looks best at 30 ft.




    Quote Originally Posted by MAubrey View Post
    Details.

  7. #47
    Drew Wiley
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    Re: Choice for the Circle of Confusion?

    Was Seurat the inventor of pixels or grainy color film?

  8. #48

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Pere Casals View Post
    Yes.. the print size critical to find the optimal aperture. . . .
    The constant is the circle of confusion, on which the COC is based. As people back away from an increase in print size (to "better" see the print), the COC must also increase.

    What I'm suggesting is that, as the enlargement factor increases, one needs to decrease the circle of confusion proportionately. But if the viewer backs up proportionally to the increase in print size, then one needs to increase the circle of confusion by the same proportion. The decrease above in the COC offsets the simultaneous increase in the COC.

    Of course, this assumes that the viewer backs up in proportion to the increase in print size. As an approximation, I'm willing to make this assumption.

  9. #49

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by Emmanuel BIGLER View Post
    Hi Neil.
    You should not be uncomfortable with the idea of varying diameters for circles of confusion. . . .
    Emmanuel,

    Thanks again. This is interesting.

    I know that the COC needs to change as the format changes.

    But, I can also see adjusting the COC for different lenses. Although, I'm not sure how to evaluate a given lens to make this change.

  10. #50

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    Re: Choice for the Circle of Confusion?

    Quote Originally Posted by neil poulsen View Post
    But if the viewer backs up proportionally to the increase in print size, then one needs to increase the circle of confusion by the same proportion.

    Yes... the question is if we want a big print to be perfect at reading distance, or if it's enough if the print is seen perfect at the "ususal" viewing distance.


    If the print a at distance that we see it all, without moving head, then the print requires around 60MPix efective, not mattering the print size, so required circle on negative is constant. If we want to inspect the print at reading distance then, obviously, we require an smaller CoC in teh negative as print size increases.


    A human eye can see around 8MPix effective, but resolving power is very concentred in the fovea, so we can see aroung 60MPix effective if we don't move the head but we move the eyes exploring the field of view we can see without moving the head.


    To me a big print does not require the same perfection at reading distance than an small one, but LF allows to make monster prints that are perfect at reading distance, those prints are impressive !!!!

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