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  1. Re: Curiosity testing for diffraction limitation -- very general

    Diffraction depends on the effective f-number, so it gets a lot worse in close-up work. I discuss diffraction in detail under “Diffraction” in...
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    Re: Use of Tripods on NYC street

    I’ve heard of people staring quizzically at a security guard and saying something like “You really don’t know who I am, do you?” Sometimes it actually works. One advantage is that there is no false...
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    Re: Use of Tripods on NYC street

    Somebody in City government ought to be able to answer this, or at the very least confirm or deny that it’s possible. I’d trust a typical security guard as far as I could throw him. Depending on the...
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    Re: Use of Tripods on NYC street

    So did you ask him why not?
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    Re: Use of Tripods on NYC street

    As Mrs. Iselin said to the senator, “Dear, you’re good at a great many things, but thinking just isn’t one of them.”

    The Washington Post recently suggested that the Park Police’s reputation is in...
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    Re: Use of Tripods on NYC street

    This gets at one of the more sensible provisions of NYC’s rules: § 9.01(b)(1)(ii), which requires a permit for photography that involves the assertion of exclusive use of more than one-half of a...
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    Re: Use of Tripods on NYC street

    Everyone knows—or reasonably should know—that a Smith and Wesson beats four aces. Or the Rules of the City of New York. Or the United States Code. Or the Code of Federal Regulations. Sad!
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    Re: Use of Tripods on NYC street

    I suspect the “regulation” would be difficult to enforce in some situations because there probably is no regulation. Ditto for the “bans” on photography of bridges. There were many stories—some of...
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    Re: Use of Tripods on NYC street

    Except for flash-bangs, tear gas, and rubber bullets ...

    At least in some of these jurisdictions, there is little authority for prohibiting tripods. Areas under the jurisdiction of the US Park...
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    Re: Use of Tripods on NYC street

    Rules for City property are given by the Rules of the City of New York, Title 43, §§ 9.01–9.03. It’s hardly a stellar example of legal drafting, but it was far worse before it was revised following...
  11. Thread: Spot meter

    by Jeff Conrad
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    Re: Spot meter

    I think the Pentax Spotmeter V and Digital use the same silicon photodiode, and both read well into the infrared (the brochures show the response juxtaposed with that of the 1931 CIE observer); the...
  12. Thread: Spot meter

    by Jeff Conrad
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    Re: Spot meter

    Ricardo,

    It’s been a while since I’ve been to a repair shop, so I’m not sure where I’d go for a meter calibration (San Francisco Bay Area) these days. The best I can suggest is to call a few...
  13. Thread: Spot meter

    by Jeff Conrad
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    Re: Spot meter

    Ricardo,

    Is there a camera-repair place that can check the calibration of your meters? It’s a pretty simple procedure with a proper calibration light source.

    One thing to bear in mind when...
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    Re: Ever felt in the minority?

    I think a lot of people conflate the zone system and religion ...

    I’ve always had a more prosaic view, treating it much like calibrating an instrument or something like a chart recorder: set the...
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    Re: Using blur calculations to estimate positioning tolerance in a machine vision sys

    A new version is posted. Because of the software issues mentioned above, it’s not elegant—I put an Erratum at the end of the paper, with a note linking to it next to Eq. (96). Hopefully, the...
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    Re: New articles by Jeff Conrad on DoF

    In this thread, it was pointed out that the expression for “relative blur” with an asymmetrical lens is incorrect. The error has been corrected; to avoid changing equation numbers for later...
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    Re: Using blur calculations to estimate positioning tolerance in a machine vision sys

    Sorry to be a bit slow getting back here—I had a few other things to take care of the last couple of days.

    On further thought, a simple diagram suggests that if magnification is to have its common...
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    Re: Depth of Field in Depth: Relative blur with pupil dilation issue?

    This is a new one for me. Admittedly, magnification of defocused objects isn’t a common topic; in fact, Merklinger’s discussion in The INs and OUTs of Focus is the only one of which I am aware, and...
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    Re: Depth of Field in Depth: Relative blur with pupil dilation issue?

    Magnification is determined by distances from the principal planes—not the planes of the pupils—so my Eq. (44) still applies to an asymmetrical lens, and Eq. (96) still holds.

    Despite the title of...
  20. Re: Restrictions on wheels in Wilderness Areas?

    As might be setting up a picnic table on the steps of the Lincoln Memorial, which presumably there is some means of preventing. But it shouldn’t be done by gaming definitions of “prop.” The NPS...
  21. Re: Restrictions on wheels in Wilderness Areas?

    There is an official definition of “sets and props” at 43 CFR § 5.12:


    Sets and props means items constructed or placed on agency lands to facilitate commercial filming or still photography...
  22. Re: Restrictions on wheels in Wilderness Areas?

    Wheelchairs are specifically allowed under § 507 of the ADA, codified at 4 USC § 12207:

    (c) Specific wilderness access
    (1) In general

    Congress reaffirms that nothing in the Wilderness Act [16...
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    Re: Dear god, pie holes are everywhere....sigh

    As long as they aren’t using models, sets, or props ...
  24. Re: Is your Internet speed and cost good enough?

    If speedtest.net is to be believed, I get about 40 Mbps down and about 11 Mbps up from Comcast—not great but not terrible either. Service has been OK; there are occasional outages, but they aren’t...
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    Re: Monkey owns Selfie Copyright!

    Slate and The Register address this pretty well. The complaint seems pretty ridiculous. I hope the court has the wisdom to throw this out on its ear, find it completely frivolous, and stick it to...
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    Re: Monkey owns Selfie Copyright!

    Doesn’t Slater’s UK copyright count? His infringement claim and PETA’s claim (whatever it may be) are of course separate pieces of monkey business.


    Especially since they say they won’t ... But...
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    Re: Monkey owns Selfie Copyright!

    PETA are notorious for flinging similar ... stuff, if perhaps from different openings. OK, perhaps a bit judgmental, but this case seems stretch, to say the least.

    PETA are correct that nothing...
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    Re: Monkey owns Selfie Copyright!

    Randy,

    What exactly did you see? The PETA lawsuit (Naruto v. David John Slater et al.) doesn’t look it’s even on the calendar yet.
  29. Re: New utility by Jeff Conrad: Sun/Moon calculator

    Alan,

    I’d much rather plan a shot on an iPad than on a smartphone—simply because of canvas size. Note that you need iOS 8.1 or later. If you have that covered, you should be fine. I think you...
  30. Re: New utility by Jeff Conrad: Sun/Moon calculator

    Alan,

    There may not be an advantage. But the only version of TPE that I’ve used is the desktop app (both old and new), so it’s tough to give a solid answer.

    It looks to me as if the Android...
  31. Re: New utility by Jeff Conrad: Sun/Moon calculator

    It’s arguably messy to have to manually set options for a programmatic invocation. I’ve added parameters to set several User Preferences at invocation; they have the same effect as setting these...
  32. Re: New utility by Jeff Conrad: Sun/Moon calculator

    It’s a user preference that needs to be set manually. It’s sticky, though, so at the next invocation with parameters, the additional times should be displayed. The new version clears any previously...
  33. Re: New utility by Jeff Conrad: Sun/Moon calculator

    Adding a parameter to suppress the Sun/Moon Calculator’s main form was straightforward, but setting things up so that a GET would produce readily captured output is not, mainly because of the way...
  34. Re: New utility by Jeff Conrad: Sun/Moon calculator

    The CIE method for determining sky luminance distribution is based on the luminance of the sky at the zenith. Although the formulas for this luminance vs. Sun altitude are quite simple, the...
  35. Re: New utility by Jeff Conrad: Sun/Moon calculator

    I don’t provide times for nautical or astronomical twilight, because they’re usually not relevant to terrestrial photography—at the end of evening civil twilight, it’s mighty dark. There are perhaps...
  36. Re: New utility by Jeff Conrad: Sun/Moon calculator

    Yincognyto,

    I see what you mean. To be honest, the URL parameter interface was an add on, done late late in the process at the request of one user. The implementation strove to minimize the...
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    Re: Forest Service: New Regulation/Fines?

    Dave,

    The regulations for the BLM, FWS, and the NPS are the same; they’re codified at 43 CFR Part 5. There are some additional regulations for the FWS at 50 CFR Part 27, Subpart G. You’ll need...
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    Re: Forest Service: New Regulation/Fines?

    Drew, I have absolutely no sympathy for people who break the rules and then whine about the consequences—and we’re likely thinking of some of the same people. Neither am I impressed when someone...
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    Re: Forest Service: New Regulation/Fines?

    Drew,

    Neither of us was there (and neither was Rowell), so who knows what really happened? Rowell was certainly known for sometimes treating rules (e.g., closed areas) as advisory, and...
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    Re: Forest Service: New Regulation/Fines?

    The section on still photography is a very interesting take, and one that’s slightly different from what’s in 36 CFR 251.50–51. Here the interpretation is the same as former 36 CFR 5.5(b) and similar...
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