Pinhole FL's for 4x5?

Discussion in 'Pinhole Photography' started by waynecrider, Sep 21, 2011.

  1. waynecrider

    waynecrider Member

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    So I played around over at Mr. Pinhole today trying to figure out a pinhole size for my Crown. While I prefer a longer lens like 210mm and above when out in the boonies, I read some hearsay that shorter is better when it comes to pinholes. Is there some sort of guideline concerning one factor or another or is it all b.s. and do what you want?
     
  2. John Koehrer

    John Koehrer Subscriber

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    Larger or smaller is dependent on format size. What is good for 810 is going to be way large for 120.
    Both extremes will give a softer image for different reasons, too scientific for the likes of me. I think there's a calculator on f295 also.
    If you like the 210 FL that's the FL you need to do the calculations for. Keep in mind, it will be optimal for 210mm not 150. It will be usable but the
    exposure will change because the relation between the FL and f stop has changed ie: f250 is no longer 250.
     
  3. Jim Jones

    Jim Jones Subscriber

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    It's true if image sharpness is the criteria. For pinholes optimized for best on-axis sharpness, blur in the center of the image will be proportional to the pinhole diameter. For example, I would use a pinhole diameter of .545mm for a focal length of 240mm, (f/440). At 60mm, the diameter would be .272mm (f/220). The shorter focal length would be two stops faster. However, if both pinholes were used on 4x5 film, the sharpness of the 240mm pinhole would be fairly uniform from corner while the corners of the 60mm pinhole image would be much less sharp and much darker than the center. The reduced illimination in the corners might partly mask the increasing unsharpness. Often esthetics is more important than sharpness.

    The topic of the most desirable pinhole diameter has been debated (sometimes hotly) for well over a century. A site with ongoing discussions of pinhole photography is http://www.f295.org/Pinholeforum/forum/Blah.pl. Another site with good information is http://home.online.no/~gjon/pinhole.htm
     
  4. DWThomas

    DWThomas Subscriber

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    I wouldn't argue that I was rigorously scientific in my approach, but my first pinhole efforts were done using a pinhole lensboard in my B&J Press camera, that allowed me to play around adjusting the lens-to-film distance with a given pinhole. I settled on a 0.46 mm pinhole at about 165 mm spacing (approx f360).

    More recently, I built an elaborate "box camera" to use a 4x5 holder. For that I used a pinhole of about 0.305 mm at a distance of 63 mm (approx f210) to produce a fairly wide angle of coverage.

    The joy of these beasties is that the variations appear to reflect very broad curves in the functions, and a wide range of choices can work pretty effectively. A variable most tedious to control is the quality of the pinhole itself. Ideally it has a knife edge and the opening is perfectly round with no ragged imperfections. This accounts for the popularity of laser-cut pinhole plates. But I must say this latest one of mine, built for last April's Worldwide Pinhole Photography Day and using a sanded dimple in one-mil brass shim stock, produced the best results I've had yet (maybe I just got lucky!)

    DaveT
     
  5. waynecrider

    waynecrider Member

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    Thanks guys, and nice pages there Dave.