8x10 Pinhole in a Bag

[Taran of Caer Dallnem]

I am toying with the idea of building an 8x10 (18x24cm) wide-angle pinhole camera. Nothing difficult, basically.
But to decrease light drop-off in the corners, I would like to make a curved back.
As there is no such thing as a free lunch, that means I cannot use film holders.

That's why I'd like your expert opinions: Is it possible to change the sheets (I'll be shooting paper, not film) "in the field" with a changing bag?
Have you got any hints on the camera back design that would make loading it "by touch" easier?
I'm sure somebody has tried that, and I'd really love to hear their experiences.

The procedure I am thinking about is: Put camera and box for exposed film into bag. Take sheet out of camera and into the box. Open bag, take box out and put in box with "fresh" paper. close bag and load camera... etc.

BTW I'm thinking of a focal lenght of 90mm (almost 3").

I'd appreciate any input... Materials I can use are plywood and/or foamcore.

[Fred L]

I wonder if one could take a sacrificial beater holder and shape into a curve with the right amount of heat applied. If it could be done to fit a paint can, that would make life simple (aside from the shaping hurdle) using a paint can pinhole camera.

[SMBooth]

It would be very significant heat to soften the metal plate in the middle of the film holder.

I feel the OP pain, just need a big changing bag.

[Nigel Smith]

I have done the bag thing using my 5x7 pinhole. In public too! Even had the guard at the Shrine (in Melb) come down and ask me what the heck I was doing... he didn't unsling his rifle. :) I used 2 boxes. one for unexposed paper, one for exposed. That camera is slightly complicated in that it 'zooms' (variable focal length) and is comprised of a box within a box within a box! This means when you pull it apart in the bag, it doubles in size which makes it more difficult than if it had a simple back/front to remove. However the concept is the same and it's just a matter of taking your time to make sure you don't get the exposed and unexposed boxed confused. Sticking something with a different texture (felt/material/etc) to one box can help.

I have a curved back 7 & 7/8ths x 10 (stuff up in measuring... didn't allow for the thickness of the walls!) pinhole made of matt board. It has a simple lift off front held on with elastic. The film 'plate' is at the back of the box and the paper is held in place by the curve and a small bit of bluetak in the middle! Seems to stay in place ok as I haven't had any fall off during transportation, although I'm carefull to keep it upright. Haven't tried loading that in a bag, and don't think I could in my dark bag which is not very big.

[Fr. Mark]

I saw a youtube video once of a fellow who built a pinhole camera for 5x8 (8x10 in half) films/papers. It had a lid that came off in the changing bag and a section in the back of the camera that was light tight from the picture taking part and in there he kept his used and unused film with a file folder-like divider between the two groups of films. I built one like it out of foam core, but have not gotten the changing bag yet, so can't speak to how well that part works.

[Taran of Caer Dallnem]

Thank you! It certainly seems feasible. A great encouragement! I'll have to think of something that I can a) secure the paper well B) change it easily.... There must be something else than bluetack... But giving the boxes different textures surely is something I'll do, Nigel!

[John Olsen]

I built a curved-film pinhole camera for 4x5 film in a 6" coffee can. For 8x10 I expect you could just double sizes. The attached photo shows how much the film holder curved inside the can. I calculated that the exposure difference at the corners would be about 10%, and indeed, the film printed very easily. The film holder was hand-bent 4 ply black matboard. I would load it in a changing bag and fit on a blackened lid. The vignetting board across the middle avoids interior bounce light from reaching the film.
Good luck on a fun project.
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[Taran of Caer Dallnem]

I like the "top-loader" design and will try to use it in my camera. John, do you use a vignetting board only because the inside of the box is metal, or does it have its place in wood cameras, too?

[John Olsen]

I like the "top-loader" design and will try to use it in my camera. John, do you use a vignetting board only because the inside of the box is metal, or does it have its place in wood cameras, too?
If you had a larger box that didn't have the reflective sides so close to the film, then you wouldn't need to bother with a vignetting board. I don't know if it helped, but it seemed like a good precaution. In a normal LF camera, the folds in the bellows carry this function, so it seemed reasonable.

[Taran of Caer Dallnem]

Then what is the "bellows flare" I read about? Thank you for your explanation!

[scheinfluger_77]

You might find that 90mm won't cover 8x10 completely, even with a curved film plane. Eric Renner in his books on pinhole states that coverage is roughly 2.5 to 3 times the focal length, and that's still with light fall off. You may have better luck with something in the 150mm range. Experimentation is word of the day on this. Good luck.

[Taran of Caer Dallnem]

Thank you, Scheinfluger_77; when I look at pictures taken with the Harman Titan (f 125mm), there seems to be room to go a bit "wider". Fall-off is not that bad there. But you're right, 90mm is really pushing my luck, so I think of going for 100mm plus putting the pinhole on a lensboard, so I can vary the distance by putting shims under it etc.; plus Iam thinking of introducing some possibility of shifting it. Just to get the horizon straight.

[Taran of Caer Dallnem]

Just found this pinhole camera on ebay: Interesting concept, I believe!
http://www.ebay.de/itm/4x10-Large-format-Panoramic-Pinhole-Camera-/281519151278?pt=UK_Film_Cameras&hash=item418bd958ae
4x10" pinhole camera.
Focal lengh 105mm.
Pinhole diameter 0.5mm
View angle ~130°
This Camera has 1/4 Tripod Socket.
The camera will take 4x10" sheet film.

I hope it is lightproof,... I would prefer to fix that huge front panel at top and bottom, too.

[Fr. Mark]

Another thought about keeping film in place:
If building from steel, magnets.
Even if not building with steel, I've heard of people getting those magnetic strips similar to what people make magnetic business cards from and glueing two strips where the edges of the film go and then using two more strips to hold the edges of the film in place. For my recent pinhole cameras, I've either used a regular film holder or I've made a narrow slot/u shaped that the film slides into and once the top is on the box, the film is locked in place.

[JoeV]

Here's a link to that video of mine with the 5x8 camera (actually 5x7 image area with 5x8 sheets of paper, the extra 1/2" on each side for mounting via magnets) that employs a rear storage compartment. It also uses thin flexible magnets to hold the paper at the film plane.

http://youtu.be/LszigE3dzXM

Regarding the paint can camera, it would be simple to build a storage area behind the film for additional sheets of photo paper/film.

Cheers,

Joe

[JoeV]

I should add here that I've used one-shot box cameras for many years. Once, I hiked to the top of Delicate Arch in Arches NP with an 8x10 foamcore box camera, heavy Bogen tripod and backpack with changing bag and meter. The challenge is always finding a place to improvise a seating position, from which to load the box into the changing bag for changing out sheets of paper.

The next logical evolution is to build an arm sleeve onto the back or top of the box, where you can reload the film with camera still atop the tripod. Insert arm, open lid and swap out the film or paper. The trick here is doing so with a single hand. You can imagine something going wrong and the paper gets hung up on one corner, forcing you to having to figure out how to rescue the film with only one hand available.

An alternative is to build the box camera into a large changing bag, where you can insert both arms and reload atop the tripod. You'd have to rig a mounting plate that penetrates through the dark cloth, permitting the camera to be tripod mounted.

Cheers,

~Joe

[plywood]

I have made plans for a 5 by 12 inch curved film pin hole panoramic. Built a 3.5 by 10 inch version as a test of concept but the 3.5 X 10 inch prints are just too small. I intend to use Ilford MG IV RC paper that comes in 5 inch by 250 foot rolls. The paper is curved around a radius of 145 mm, that is the focal length, and covers 120 degrees. The paper is slid into groves about 1 mm wide on the top and bottom and the camera is loaded from the end. This is a late winter project and I don't expect to be able to have it finished until late February 2015. If my son will help me figure out how to post pictures on this site I'll use one of those digital things to record the building process. (Until someone walks me through it about a hundred times I have a hard time learning how to do anything with computers. I don't like them and they return the favor.)

[Taran of Caer Dallnem]

Thank you JoeV for the link to your video. I already knew the one about box cameras but not that one. I love the idea.

Well Plywood, a foto or sketch would be very welcome. "The paper is slid into groves about 1 mm wide on the top and bottom and the camera is loaded from the end." i.e. from one of the sides at the end?! Sorry it's late in the evening for me here and I can't quite imagine it yet!

[plywood]

Thank you JoeV for the link to your video. I already knew the one about box cameras but not that one. I love the idea.

Well Plywood, a foto or sketch would be very welcome. "The paper is slid into groves about 1 mm wide on the top and bottom and the camera is loaded from the end." i.e. from one of the sides at the end?! Sorry it's late in the evening for me here and I can't quite imagine it yet!

Yes, the box will be about 11 in. long, 5.5 in. high, and 7 in. wide on the outside. The grooves are made with 1/8 in. hobby plywood. I use a compass to mark the radius and then a power scroll saw to cut along that circle. The edges are sanded just enough to make them smooth and the pieces are glued to the inside top and bottom of the box carefully leaving a 1 mm gap. This forms the groove that I slide the paper from the end into the camera. (The other end is closed) I then put the cap on and secure it with a rubber band. Of course it has a tripod socket and the outside top is flat so I can lay a 'bullseye' level on it to make sure the camera is level before making an exposure.

I was looking at the FAQ for uploading pictures to the forum and I think I'll take a few photos of the prototype I built and when the missus wakes from her nap (SHE! who must not be disturbed) then I'll see if she can help me upload to this thread.

Plywood plays with plywood.

[jp]

Photo paper rolls are a good idea... I'd probably trim down 14x17 xray film into 17" strips and try to get three exposures out of that with a takeup spool.

[wilper]

I attached the darkbag to the top of the camera. Inside the camera there are two compartments, one for taking pictures, and one behind that for storing paper.

When I change the paper I can lift it upwards into the extra space granted by the darkbag, place it in the storage compartment, and then draw a new one, lift it over the film holder area and slide it down.

In the storage compartment I keep the sheets in a dark plastic bag, just in case some light should slip through the sleeves of the darkbag.

http://photofying.wordpress.com/2014/08/07/building-a-e25-large-format-camera

My camera is built for 5x7 paper, then it is possible to do the operations one handed with a single sleeve dark bag. If I were going larger I think I would prefer to have two sleeves.

[Taran of Caer Dallnem]

That's an interesting concept!

Wilper and plywood: any inside/detail pics?

[Fr. Mark]

You might also look u the Afghan Camera Project. This is relatively small format photography with lenses where the camera box is also a box with one sleeve for handling film or paper and developing. They made and processed paper negatives and then copied camera type procedure to make positives. Sorry no time to hunt down the link. Merry Christmas to all.

[wilper]

That's an interesting concept!

Wilper and plywood: any inside/detail pics?

Not much to show. It's just an lid-less box, spray painted black on the inside, where I have drilled a hole in one end and taped an achromat to the inside wall.

Since I didn't build a pinhole camera I needed some way to focus, so there are strips of cardboard taped vertical along the side walls. There are tiny gaps between the strips so that I can slide my film holder/compartment divider into place from above. That way I can change the focusing distance in the field.

The camera works well enough, that I plan on building a larger one for 11x14 size papers, just so I can say that I can join the ULF club. :-) I'll get a lens with a longer focal length for that project, to get a reasonable chance at having full coverage of the paper.