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Thread: A question on hypefocal distances.

  1. #21

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    Re: A question on hypefocal distances.

    Quote Originally Posted by Helen Bach View Post
    Thanks for that. I also was wondering what you meant. You had written "Why hasn't anyone mentioned that HFD is a highly variable value..." and yet I had mentioned that it was an inexact calculation in the previous post to yours, including a mention of the variation in the value of the maximum acceptable circle of confusion.
    Yes, "CoC" gets mentioned almost every time people talk about HFD or DOF but that wasn't my point. The post you mentioned as well as the other posts at the time were trying to go in to great depth about HFD calculations. My post was merely trying to pointing out the fact that HFD values are so variable and therefore why anyone should nit pick that much to find out whether it's given from the film plane or the lens.


    Quote Originally Posted by Dan Fromm View Post
    G, vagueness is a sin.
    And the irony is funny Actually the term "variable" is quite well understood in scientific circles... of no confusion

  2. #22

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    Re: A question on hypefocal distances.

    Y'know, in the labs I've worked in we always spelled things out. My collaborators and I have always been as clear as possible. "x is a highly variable value" isn't very informative. "x is determined by y, z, ... " is.

    I've looked at your profile, see that you say you're "a scientist." That covers many fields with different standards.

    As I said, vagueness is a sin. It sometimes, but not always, reveals ignorance (see your question on extension at 1:1, posted earlier today, for an example of a question that reveals lack of knowledge) and attempts to mislead. Telling strangers about whom you know little "I'm a scientist. Shut up." is insulting. Unwise, too.

    No one knows everything. Trying to fill in gaps in knowledge and understanding is good. Trying to use credentials earned in one field to gain credibility in another isn't.

  3. #23

    Re: A question on hypefocal distances.

    Quote Originally Posted by Emmanuel BIGLER View Post
    However (and not kidding) we all know that the transition between sharp and unsharp play a very important aesthetic role. Hence let's experiment and see what happens ;-) I want my swirling bokeh ! Like a natural product, I do not want it to be modelled by a palmtop.
    Swirliness around the periphery because you want to exceed the covering power of your lens isn't the issue. Within the zone that is optically well-corrected, the difference between smooth defocus transitions that retain form and rough focus transitions where ni-sen turns everything to frizz throws all calculations to pot.

    Regardless of whether one is in a New-Agey frame of mind. ;-)

  4. #24

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    Re: A question on hypefocal distances.

    Quote Originally Posted by genotypewriter View Post
    The post you mentioned as well as the other posts at the time were trying to go in to great depth about HFD calculations. My post was merely trying to pointing out the fact that HFD values are so variable and therefore why anyone should nit pick that much to find out whether it's given from the film plane or the lens.
    I believe that point had already been made. The original question asked whether the distance given by a DoF calculator should be measured from the film plane or the lens. Simply saying 'you don't need to know because the calculation isn't that accurate' may not satisfy everyone's curiosity. Is it really 'nit picking' to explain that there are two different practices, and why they are different?

  5. #25
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    Re: A question on hypefocal distances.

    I think one does not need to know if the hyperfocal calculation if from the lens, or film because it does not make any difference. Say the hyperfocal distance is 65 feet. So what. No one is going to be measuring that distance. It is just an intellectual curiosity. If you were going to measure a focusing distance, one would just focus the lens.

  6. #26
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    Re: A question on hypefocal distances.

    Quote Originally Posted by genotypewriter View Post
    And the irony is funny Actually the term "variable" is quite well understood in scientific circles... of no confusion
    In the scientific circles in which I circulate, "variable" nearly always means "described by a random variable"--stochastic rather than deterministic. I don't think that applies to hyperfocal calculations. There are lots of factors in play, and it's hard to consider them all, with the result that calculations are usually imprecise. And they are based on a standard of sharpness defined by the user for a particular application, which might range widely. For example, DOFMaster, near as I can tell, is based on an 8x10 print. I routinely cut the circle of confusion values in half before using it for 16x20 target prints. That leads to much less calculated depth of field an a more distant hyperfocal point.

    What might be stochastic (because it is subject to a range of subjective factors) is what people interpret as appearing to be sharp. There is not some binary boundary between sharp and unsharp. A print made a bit too large might still look acceptable to most people, and some critical viewers might not accept any of the usual standards of sharpness (many of which originated in the Zeiss Formula).

    And that leads to the practical truth that outside the macro range, it probably doesn't matter whether the measurement is made to the film, lens, or tripod center column for that matter. And focusing at the hyperfocal distance is always outside the macro range.

    DOFMaster (with their 8x10 print assumption) claims that the hyperfocal distance for a 47mm Super Angulon on 4x5, at f/16, is 4.7 feet. A couple of inches (i.e., the distance from the film to the lens) one way or the other makes not much difference. At f/32, it's 2.4 feet--still more than an order of magnitude greater than the focal length. The hyperfocal distance they report for a 300mm lens on 8x10, at f/32, is 47 feet. The difference of a foot between the lens and the film is not significant. Stricter standards of sharpness as indicated by selecting smaller circles of confusion just make the hyperfocal distance that much greater with respect to the focal length.

    Remember, the thread was about hyperfocal distance, not more generally about depth of field.

    Rick "who has spent a big chunk of his career defining variability" Denney

  7. #27

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    Re: A question on hypefocal distances.

    So you don't think that it was worth mentioning the two different practices at all? I often ask myself if there is any real point in answering questions on the internet.

    Best,
    Helen

    PS The online version of DoFmaster allows you to choose your own max. acceptable CoC if you wish.

  8. #28
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    Re: A question on hypefocal distances.

    Quote Originally Posted by Helen Bach View Post
    So you don't think that it was worth mentioning the two different practices at all? I often ask myself if there is any real point in answering questions on the internet.
    I did not say that. I always enjoy detailed answers, and I've never believed a thread had to be limited to the conception of the OP. Your quote of the authors of DOFMaster was spot-on as far as I'm concerned.

    But those who said it didn't matter were not without justification for their point of view. Saying it doesn't matter in practical application, however, isn't the same thing as saying nobody is interested in the different approaches.

    Yes, as I said, I always cut the circle of confusion value used by DOFMaster in half. In the iPhone version, which I use, I select my desired C of C from the table, rather than choosing a format.

    Rick "just trying to keep things in perspective" Denney

  9. #29

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    Re: A question on hypefocal distances.

    Quote Originally Posted by Dan Fromm View Post
    Y'know, in the labs I've worked in we always spelled things out. My collaborators and I have always been as clear as possible. "x is a highly variable value" isn't very informative. "x is determined by y, z, ... " is.
    This is what's sad about online forums... once you point something out for the sake of others, someone comes and demands you to explain it like it's your duty. Good students go do their own homework.

    Quote Originally Posted by Dan Fromm View Post
    I've looked at your profile, see that you say you're "a scientist." That covers many fields with different standards.

    As I said, vagueness is a sin. It sometimes, but not always, reveals ignorance (see your question on extension at 1:1, posted earlier today, for an example of a question that reveals lack of knowledge) and attempts to mislead. Telling strangers about whom you know little "I'm a scientist. Shut up." is insulting. Unwise, too.

    No one knows everything. Trying to fill in gaps in knowledge and understanding is good. Trying to use credentials earned in one field to gain credibility in another isn't.
    lol... look up the term "false dilemma", Dan. Remember the time you were pounding your chest when I claimed that a 65mm lens gives half the field of view of 150mm lens and you were insisting that it's should be a 75mm?

    http://www.largeformatphotography.in...l=1#post762329

    But when I make a slip at 1.45am or something you go to say it "reveals ignorance".


    Quote Originally Posted by rdenney View Post
    In the scientific circles in which I circulate, "variable" nearly always means "described by a random variable"--stochastic rather than deterministic.
    I don't know which circles those are but variable != random. Random also doesn't always mean variable... in several senses.

  10. #30

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    Re: A question on hypefocal distances.

    Quote Originally Posted by rdenney View Post
    I did not say that. I always enjoy detailed answers, and I've never believed a thread had to be limited to the conception of the OP. Your quote of the authors of DOFMaster was spot-on as far as I'm concerned.

    But those who said it didn't matter were not without justification for their point of view. Saying it doesn't matter in practical application, however, isn't the same thing as saying nobody is interested in the different approaches.

    Yes, as I said, I always cut the circle of confusion value used by DOFMaster in half. In the iPhone version, which I use, I select my desired C of C from the table, rather than choosing a format.

    Rick "just trying to keep things in perspective" Denney
    Thanks for the reply. I often find it difficult to judge the appropriate way to reply to questions - is it too much, is it too little, is it too vague, does it require too much self-assembly...

    Best,
    Helen

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