pinhole-discussion:: RE: Making a 20x24 pinhole camera

From: George L Smyth <glsmyth_at_domain.name.suppressed>
Date: Sun 01 Aug 2004 - 07:22:21 PDT

Guy -

Thank you for the very complete explanation. I am thinking that in a case like this it might be helpful to build some apparatus that could be attached to it that would allow one to change the paper.

The exposure time, as we all know, will vary with the focal length, but at this sze we are talking about something much longer than using "standard" 4X5 film.

Cheers -

george

-----
http://www.GLSmyth.com
http://DRiPInvesting.org

--- On Sun 08/01, Guy Glorieux < guy.glorieux@sympatico.ca > wrote:
From: Guy Glorieux [mailto: guy.glorieux@sympatico.ca]
To: pinhole-discussion@spitbite.org
Date: Sun, 1 Aug 2004 01:45:49 -0400
Subject: [pinhole-discussion] Making a 20x24 pinhole camera

---- Original Message ----- From: "George L Smyth" > > The biggest I made was a 16"X20" out of foam core. The real problem with it was that it was rather unweildy, For those interested this is how I've resolved the problem: I've used 2-layered black foamcore to make my 20x24 camera. Each layer was precut and glued together with bookbinding glue. Once the box is finished, you could almost sit on it (well, sort of...) and yet it is very light (you need to hold it in place with your hands during the time of the exposure or to put a big book on top to hold it steady if you're outsdide and that it is windy. The drawing below shows more or less how it works, as seen from above the box. Let's assume that this is a 20x24 box with a 15 focal, but it could be 8x10 or 4x5.... The box is built with two layers of 1/4" black foamcore (BTW, single 1/4" black foamcore is not 100% light tight!). ___ ___ ___ ___ I s1 I I s2 I I s2 I
I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I I s2 I I s1 I I s1 I I s2 I_______________ ________________I s2 I I s1 I I s1 I I__________________I I____Front inner layer___I I s1 I I s1 I I s1 I I s1 I ___________________ Pinhole ____________________I s1 I I_______________________I Here I______Front outter layer____I The 2 layers (inner and outter) are dimensioned and fitted together at the joint in such a way as to become a light-trap in the form of a "staircase". Thgis acts also as a reinforcement for the box. Thus, on the Front side, the side with the pinhole, the inner layer is equal to 20" x 24", i-e the side of the emulsion (remember, it could be 8x10 or 4x5"...). The outter layer will be equal to these di
mensions plus 1/4" on each of the four sides to allow for the "staircasing". Hence it will be equal to 20 1/2" x 24 1/2". Glue the two layers so that the inner one is perfectly centered. Drill a hole before hand to fitt the pinhole between the two panels. Now, the vertical sides Right and Left. The inside panel " S2" is equal to 14 3/4" x 20 " (that is: the focal length of the camera _ minus 1/4" because the pinhole is fitted on the inside of the outter front panel _ X the side of the paper emulsion.). The outside panel "S1" will be equal to 15" x 20 1/2" (that is the focal length x the side of the emulsion plus twice 1/4" for the staircasing of the panels. Glue the panels so that the focal length side "staircases" in all directions except the side where the back of the box with the emulsion is fitted flush. The same principles apply when cutting and glueing the Top and Bottom sides of the box (they each will be 14 3/4" x 24" for the inte
rnal panel and 15" x 24 1/2" for the outter panel). Finally, the Back side, the one where the emulsion will be fitted on. I normally make it as a 3-layer contraption. One layer is 20"x24", exactly equal to the emulsion size (and also to the "internal" dimensions of the box when it is assembled). It will be glued to a second layer, this one equal to the outside dimensions of the box (that is 20 1/2" x 24 1/2") and on the external edges of this panel, a 2" strip of black foamcore will be glued (thus making it equal to 21" x25"). Then, a 21" 25" layer is glued on top of that second layer and a 2 1/4" strip is glued on the sides, thus "staircasing" the cover of the box. Note that when this cover is slipped onto the box, the first layer (that is the one that is 20"x24" slips exactly inside the box. The second layers becomes the light trap and the thisrd layer is there only to ensure complete opaqueness. The paper emulsion is held in place on the
firs
t layer by whatever method you feel is appropriate (blue gooe, two sided tape, etc...). There is no rule here and no simple solution. This being a single-shot-at-a-time, you load the camera in your favorite darkroom and go on location to shoot your picture after having made sure that you have worked out everysingle detail of your shot. If you happen to know a place where to remove the expose emulsion and refill the camera close to the shooting scene, consider how lucky you are, bring a lot of spare emulsion and use the darroom as much as you can... Regards, Guy _______________________________________________ Post to the list as PLAIN TEXT only - no HTML pinhole-discussion mailing list pinhole-discussion_at_spitbite.org FAQ at http://spitbite.org/pinhole-discussion/list.html

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Received on Sun Aug 1 07:22:58 2004

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