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Thread: DOF Question, non-mathematically

  1. #11

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    Re: DOF Question, non-mathematically

    Quote Originally Posted by Dan Fromm View Post
    ...that depth of field given how much the negative is to be enlarged...
    I'd add that it also depends on the CoC we want to tolerate in the print itself !!!

    We may want 6 lp/mm on a 2m print to view it with the nose on it, or perhaps we can tolerate 2 lp/mm because the print anyway has to be viewed from at least 1m far...

    Quote Originally Posted by Dan Fromm View Post
    Why am I mistaken?
    I guess this is a rethoric question

    It would be hard to find mistakes from you, Dan, possibly some are there, but they are well hidden !

  2. #12
    Jac@stafford.net's Avatar
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    Re: DOF Question, non-mathematically

    How many discussions regarding DOF do we need? The topic has been beaten to death for at least 100 years.

  3. #13
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    Re: DOF Question, non-mathematically

    Quote Originally Posted by Pere Casals View Post
    I'd add that it also depends on the CoC we want to tolerate in the print itself !!!
    How many photographers really measure resolution at the print level? I think none. Consider a camera lens with (an unlikely) 110 lp/mm projected through an enlarging lens with the same unlikely lp/mm on a paper with unknown metrics and what do you get?

  4. #14

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    Re: DOF Question, non-mathematically

    Quote Originally Posted by Jac@stafford.net View Post
    How many photographers really measure resolution at the print level? I think none. Consider a camera lens with (an unlikely) 110 lp/mm projected through an enlarging lens with the same unlikely lp/mm on a paper with unknown metrics and what do you get?
    Jac, it's not necessary to measure lp/mm on paper, I was telling it in numbers what it can also be told in words. Let me say it in another way:

    The way we consider what's in the DOF range depends on the enlargement we plan (as Dan pointed), but also it depends on how sharp we want the print, if a large print has to look flawless when viewed with the nose on it then we will consider DOF is narrower than if the large print has to look flawless from 1m.

    So in the first case the CoC is perhaps 1/3 on the one for the second case. Not necessary to make calculations, just we have a feedback from previous jobs. I used the 6 lp/mm value because it is the known required IQ from reading distance, and 2 lp/mm because it's an IQ of a flawless print seen from 1m, aprox.

  5. #15
    Jac@stafford.net's Avatar
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    Re: DOF Question, non-mathematically

    Quote Originally Posted by Pere Casals View Post
    Jac, it's not necessary to measure lp/mm on paper, I was telling it in numbers what it can also be told in words. Let me say it in another way:

    The way we consider what's in the DOF range depends on the enlargement we plan (as Dan pointed), but also it depends on how sharp we want the print, if a large print has to look flawless when viewed with the nose on it then we will consider DOF is narrower than if the large print has to look flawless from 1m.

    So in the first case the CoC is perhaps 1/3 on the one for the second case. Not necessary to make calculations, just we have a feedback from previous jobs. I used the 6 lp/mm value because it is the known required IQ from reading distance, and 2 lp/mm because it's an IQ of a flawless print seen from 1m, aprox.
    As I wrote "How many discussions regarding DOF do we need? The topic has been beaten to death for at least 100 years."

  6. #16

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    Re: DOF Question, non-mathematically

    Quote Originally Posted by Jac@stafford.net View Post
    As I wrote "How many discussions regarding DOF do we need? The topic has been beaten to death for at least 100 years."
    Personally I'm way more concerned by the OOF nature than by the DOF, IMHO some photographers try to focus everyting and play with composition and some play more with defocus.

    Perhaps any discussion about DOF can be shorter, because that's mainly a technical concept, while OOF (to me) delivers an array of powerful aesthetic resources that have a lot of flavours, and all those complexities deserve a rich debate.

  7. #17

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    Re: DOF Question, non-mathematically

    Quote Originally Posted by MAubrey View Post
    Sounds to me like Merklinger's illustrations contradict his data. The "trumpet bell" is indeed a more accurate image.
    Thank you, MAubrey. I write this belatedly, after the conversation has taken off into an entirely different direction from the specifics of my question -- which is fine; our forum is open an generous in this way. Perhaps your very concise reply is sufficient. I will keep it in mind as I continue my work.
    Philip Ulanowsky

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