20x24 Pinhole camera

Discussion in 'Large Format' started by brishen_hawkins, May 6, 2010.

  1. I was thinking of building a 20x24 pinhole camera, and using ortholitho paper as the negative.
    However, I have no idea how to do this. Any help?
     
  2. How about doing some research? Start by googling "pinhole camera." That will at least give you some idea how to do this.
     
  3. I have a basic idea of how to do it, but I have no idea as to the focal length, or the size of the box necessary to hold the paper.
     
  4. I think you should look into this site read it and if you still have questions ask. Some things I can probobly help you as I built 4x5 and 8x10 pinholes but my design always based on film. So I'm using backs from view cameras but using paper also works using holders. I think in that size using a holder would be very expensive. The only thing you got to figure out is how to load the paper and how to hold it in place. Also how to load on outside location as it would be to much job to run back to your darkroom to develop after each single shut.
    Here you go. and good luck
    http://www.mrpinhole.com/
     
  5. If you use a dime store =1.5 diopter lens (667mm ); or a +2 lens (500mm) +2.5 lens (400mm) 0r +3 lens (333mm) you will get a radically sharper image. This is many of us made some homemade rigs in the 1960's; using a big box and our spare scrap process camera films. A double boxed cardboard box can be used; or even wood if one wants to make a stronger one.
    We use to use ortho stuff and use thumb tacks or push pins to hold the film in place; the inside had a soft pice of cardboard or extra 1/4 plywood for the film. For a give box the distance in mm gives the lens toi use; one off a dime store pair of reading glasses. Instead of a dirts slow pinhole you can use a faster single element lens; with a stop cut out of black cardboard. If one varies the fstop by trial; the spot size on film will go thru a minimum maybe in the F32 to F128 range.
    With a lens you get a sharper image than a pinhole; or equal to one if the fstop is really tiny. If you want to really experiment in optics you can play with were the fstop is withj respect to the lens to get even sharper results.
    We use to glue a 35mm film can as the lens board; and one removed the cap for the shutter for many seconds; then placed the cap back on. The bottom of the film can is removed.
    ****None of this is new; it was taken out of a 1930's "how to article" in Pop Photo from a 1930's edition; back when folks had no money and were less afraid; scared about experimenting, Dime store lenses may not be exactly the focal lengths/ (diopter) marked on them; thus measuring some by the sun and burning some bugs is needed.
     
  6. head over to f295, great bunch of friendly, helpful folks and some are doing ULF,
    most build their own... http://www.f295.org
     
  7. I've decided to abandon this project for now due to certain constraints (time and size)
     
  8. hi brishen
    get a laser cut pinhole, it will save you trouble of making
    the right size poke in your shim. rule of thumb is about 3.5" * focal length
    is your image circle. laser cut holes have a known focal length, so it makes it easy.
    good luck!
     
  9. One can just use a piece of aluminum foil and a needle and make the pinhole for about zero cost.
    The time and cost to make a big pinehole camera is really about zero.
    All you need are a few cardboard boxes; discards from an item that is big; ie computer; TV; small dorm fridge, or you can buy one at a box store for less than 5 dollars.
    Where the film goes is just a piece of plywood; or more cardboard.
    You attach the film with pushpins of thumb tacks.
    The pinhole can be in a piece of aluminum foil from a gum wrapper; kitchen foil. If you do not cook you can bum off a piece from a neighbor; or knuckle down and buy some gum or a roll of foil at the grocery store.
    you cut a hole in the box and glue in a 35mm film can; the cap is your shutter; the foil pinhole is inside.
    The ones I built 30 years ago cost less than a dollar; today if one cannot find does not have a spare box or furniture store or office depot to get free boxes; one might have to spend 5 dollars at Uhaul/Ryder or a box store.
    Todays are more concerned with looks over function; plus most folks are alot richer tahtn in past eras; plus few folks build models.
    To build up a giant pinhole camera really involves nothing critical at all; here I could build up probably 6 of them this afternoon if I went into the garage and empted some boxes.
    In a way it is said to see how such a simple project like making a pinhole camera has folks buying pinholes or making the entire project cost 1000 times more than it has to be.
    making a pinhole camera is about as complicated as making a bird house or tying ones shoes or riding a bike; or cooking. You can make it as complicated as you want.
    You really do not need a store bought holes for a birdhouse or pinhole camera; if the hole is too big or too small you can find out with simple few tests.
    Back when folks were less rich than today making all ones stuff was the norm.
     
  10. The hole tolerance on a pinhole camera is radically less than a birdhouses; the pinhole can be within a factor or two and work OK and within 30 to 50 percent you will *NOT* see any difference on film.
    Rudolf Kinglake at Kodak Optics republished the pinhole criteria:
    D= 0.006 times the square root of the focal length in inches
    F= 4 inches gives a pinhole diameter D= 0.012 inches.
    F= 9 inches gives a pinhole diameter D= 0.018 inches.
    F= 16 inches gives a pinhole diameter D= 0.024 inches.
    F= 25 inches gives a pinhole diameter D= 0.030 inches.
    F= 36 inches gives a pinhole diameter D= 0.036 inches.
    F= 49 inches gives a pinhole diameter D= 0.042 inches.
    F is the distance from the pinhole to the film
    D is the diameter of the pinhole in inches
    The easiest way is to make some pinholes and just measure them!
    A dime store mm/millmeter ruler can be used to find one close to what one needs;
    remember a birdhouses hole tolerance is an order of magnitude more critical than this pinhole.
    Thus if your target pinhole is 1/2 or 2/3mm; just make some pinholes and get one in the ballpark.
    Colson in 1891 did some experiments with this pinhole stuff.
    With a dimestore mm ruler and a loupe one can select a pinhole close to the target size. Thus if the target size is 1/2 mm; a dime store ruler and a loupe can find one that is between 0.3 to 0.7mm in less time than reading this comment.
    With large piece of film like 20x24" one often has F in inches being large; and thus the pinhole is large and easy to make; easy to measure too.
    Folks have made big pinhole cameras out of cardboard boxes; foam core; plywood; old giant beer coolers; old dorm fridges; old small refrigerators; old 1950's TV cabinets; 5 gallon paint drum; garbage cans; whatever can be found that is really just old useless junk.
    In eras when folks built their own stuff; cost was a concern more than looks.
    Today it is the opposite; folks buying 50 buck pinholes like some how using a pin and some foil is rocket science.
    Even in laser optics here I often just make a mess of pinholes and sort them using a toolmakers microscope; thus the cost 1/1000 as much as a optical places ones.
    The hole size on a birdhouse is radically more of a issue than a pinhole cameras.
    A birdhouse poses radically more important sizing and tolearances; materials ; than a pinhole camera
     
  11. I think I get how to make a large pinhole camera now. Thanks
    The major cost is what kind of medium I'm going to use (ortholitho film). It gets pretty expensive around 20x24
     
  12. I remember emailing with a guy in Lake Tahoe years ago. He had some huge pinhole camera like your 20X24 idea. It was a one shot camera. He would load the thing at home and drive it out to location - the best part was that he used ski poles to determine the angle of view! I love that! Ski Poles for Criminy - HILARIOUS!
     
  13. brishen
    look for expired ROLLS of photo paper it might help your budget ...
     
  14. Just for reference the diameter of the pin hole is; The square root of the focal length in inches divided by 141. For mm you divide by 28 instead of 141.
     
  15. U-hull sells a box they call a "TV Box" that's 24.5 x 24.5 x 27.5 in for $9.75. It's very sturdy, double weight cardboard, and ready to use. All it needs is a pin hole and film.
     

Share This Page