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  1. #1

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    Optimum pinhole size

    Hi

    Looking over various pinhole math I get wildly varying
    Results
    What formula should I use

    I have a 21 mm focal length and will be using colour film lit with flash
    Subject distance will be about 5-10'

    What size pinhole should I use ?
    And why

    Thanks
    Robin

  2. #2
    Jim Jones's Avatar
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    I would use a 0.15mm diameter pinhole. This was calculated in Pinhole Designer with a user constant of 1.4, derived through research and experimentation. Pinhole photography is not a matter of mathematical precision; personal preferences are important. Different subjects may work best with slightly different diameters. In wide-angle cameras the diameter may be increased for improved off-axis performance with degraded center sharpness. Others may prefer slightly smaller or larger diameters based on other science or actual photography. The magic and mystery of pinhole photography may be frustrating to those who believe in exact answers to any question. To others, a little quirkiness adds pleasure to photography.

  3. #3
    RalphLambrecht's Avatar
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    send an email to rlambrec@ymail.com|(me)and I'll send you a free pdf,which may clrify the issue for you a bit.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #4
    Ken Nadvornick's Avatar
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    How powerful is your flash unit?

    A Vivitar 285HV on full manual (GN 120) using 400 speed film at 7.5 feet requires f/32.

    A Sunpak 622 Super on full manual (GN 200) using 400 speed film at 7.5 feet requires f/53.

    A Meggaflash PF200 type A-19 flashbulb (GN 420 at 1/30 sec or less) using 400 speed film at 7.5 feet requires f/112.

    A Meggaflash PF300 type A-23 flashbulb (GN 550 at 1/30 sec or less) using 400 speed film at 7.5 feet requires f/147.

    That last PF300 flashbulb option would seem to match up closely with Jim's recommendation for a 0.15mm pinhole size, since 21mm divided by 147 is 0.143mm. Unfortunately those PF300 bulbs sell at Cress Photo by the case lot (48 bulbs) for USD$630.00 per case, or $13.13 per bulb. Apparently scientists, railroad photographers and spelunkers are the major users of these still-in-production modern flashbulbs.

    The problem here is that for a pinhole camera 5-10 feet away is a lot (unless you have access to some big-boy studio flash units)...

    Ken
    Last edited by Ken Nadvornick; 10-28-2013 at 02:20 AM. Click to view previous post history.
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    — Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  5. #5

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    thanks for the replies guys

    I know there's a bit of trial and error
    but was a bit confused as to why the various online formula and calculators
    give quite different results
    as my pinhole to film is fixed in this instance
    I have ordered a collection of sizes and will see what works best
    I can't discuss the actual job but I'm sure you will all be interested
    when it's been signed off
    it's almost as crazy as the guy who did a wet plate stop Frame animation

    Ralph thanks for the offer I have emailed you

    Ken re. lighting

    I'm very fortunate to have over 60'000 j of lighting
    mostly made buy the English company Strobe
    I have 2 of their swimming pool lights that have 4x 5' 5000j flash tubes on them
    and various other 10'000j and 5000j lights
    I have only got 14'000j of flash packs to power them up with but I can borrow more if I need it


    we have run tests with tri x which came out great but a bit soft hence the initial question
    and portra 400 which came out very contrasty with odd colour and is clearly well under exposed
    and soft which I guess is down to the pinhole separating the wave lengths of different colours
    vs tri-x general ability to cope with everything
    we are testing again today so will use a lot more light as it's colour that we will ultimately be using
    probably kodak vision3 500t which has similar properties to the portra 400


    thanks

    robin

  6. #6

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    There are usually two different approaches for pinhole sizing, resulting in different apertures. The highest contrast is achieved with a slightly larger aperture than the aperture for highest resolution. They differ by about 30% in size, IIRC. The f-stops will be constant, meaning you have to calculate the diameter of the pinhole from the "focal length". I am not near my resources at present, but if you don't find help between the other posters here, drop me a PM and I'll scan and email you the relevant stuff. The higher contrast formula is usually favoured, as higher contrast is usually visually more appealing than lower contrast with higher resolution. It does depend a lot on taste and circumstances, though. For wide-angle, you may experience dark corners with the "optimum" f-stop, so using a larger aperture might help at the expense of resolution and contrast. What size negative are you capturing? 35 mm? Then how can you accommodate such a short register? Unless you use a rangefinder, probably. Still, 21 mm is very short, and you might battle to get even enough illumination. Colour neg film will be better than slide film, no doubt.

  7. #7
    RalphLambrecht's Avatar
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    i'll try to attach a pdf, but they are usually too big for APUG; TOO BAD.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #8
    Ken Nadvornick's Avatar
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    Quote Originally Posted by rbrigham View Post
    I'm very fortunate to have over 60'000 j of lighting mostly made buy the English company Strobe.
    Sounds like that'll do! You're good to go then. Let us know how the project turns out...



    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    — Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  9. #9

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    Quote Originally Posted by dorff View Post
    The highest contrast is achieved with a slightly larger aperture than the aperture for highest resolution.
    Me bad, it is actually the other way round, and the f-stops are not quite constant.

    The formula (based on contrast) is:

    d = 1.56 * sqrt (f * L)

    where f = focal length in mm, L = wavelength in mm, d = pinhole diameter in mm. For normal purposes, L is taken to be 555 nm, or 0.000555 mm.

    The "ideal" f-stop increases with focal length.

    In your case, with a focal length of 21 mm, the diameter should be 0.17 mm. This corresponds to an f-stop of 125, i.e. very close to f/128. For such a small aperture, the best would be to have it laser cut. If that isn't an option, consider a thin but sturdy metal foil. I have used copper tape with success. It can be found in craft shops, under stained glass consumables. Dent it with a ballpoint pen or other neatly round object, then pierce with a fine needle, against a slightly yielding backing such as hard rubber or wood.

    "Way Beyond Monochrome II" has a chapter on pinhole photography. If you do not have the book yet, it is an excellent resource and worth every dollar.

  10. #10
    Jim Jones's Avatar
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    I second the recommendation for Way Beyond Monochrome II. While it is about black and white photography, it covers the basics of photography that also apply to color, and is one of the most inspiring photographic books that I own. Its chapter on pinhole photography is more reliable than many other published sources. For much information on pinhole photography, look for Eric Renner's Pinhole Photography, available from http://www.pinholeresource.com/ and online booksellers. Two fine online resources are http://home.online.no/~gjon/pinhole.htm and http://www.f295.org/Pinholeforum/forum/Blah.pl.

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