Author Topic: 6x24 (or 56x230) curved film plane pinhole? Another bottle case camera (Read 24073 times)

Ezzie · « **on:** February 08, 2014, 08:33:55 PM »

I am so lucky as to have a friend who sends me all sorts of film in return for feedback on exposure and development. As I have been known to experiment with this and that, in both departments.

Last time he sent me a package of maybe 30 films, packaged in a wine bottle case, with a piece of cardboard covering up the front opening with a drawing depicting a pinhole and an f-stop of 128. I took this as a hint and set about making a camera out of the case. This was about a week ago.

This is what I had to contend with:

Ezzie · « **Reply #1 on:** February 08, 2014, 08:57:15 PM »

After covering up the hole with a piece of 3mm plywood, I measured the depth of the box, I found I had a focal length of maybe 82-85mm to play with. I already have a 6x17 pinhole, this case is wide enough (long or tall depending), for more than that. But since the image circle of a 85mm pinhole is maybe 170mm, in order not to lose the extra width to vignetting I thought I would curve the film plane. But a half circle with 85mm in radius, gives 267mm in circumference. 230-240mm film plane would mean that the field of view would have to be almost 165 degr. Not sure the pinhole would cover that either. So I made a curved film plane which is 85mm in the middle and 105mm towards the edges. Semi-anamorphic you might say.

The internals are made out of what I suspect may be foam core, just something I picked up at a hobby shop a long time ago. Oh, I forgot to mention. This camera was to be made from things lying about in the cellar, purchases forbidden.

The film gate is an insert, rather like the 6x17 I made. The lid and bottom of the insert extend out and past the spool holders and function as tensioners. The spool holders are 5mm screws. The bottom just stick up into the spool, the top have had the heads filed flat so can advance the film, and are sprung loaded/retractable to enable spool loading.

Film guides are made out of 5mm threaded rods clad in heat shrink.

Ezzie · « **Reply #2 on:** February 08, 2014, 09:06:45 PM »

A bit if staining, a 0.500mm pinhole (a bit oversize maybe). two clasps to keep it shut (hinges dispensed with) and bit of light sealing flanges, a foot that is shaped like a quick release for my tripod, and a shutter made of cardboard.

rotarysmp · « **Reply #3 on:** February 09, 2014, 08:18:49 PM »

Nice work.

Ezzie · « **Reply #4 on:** February 10, 2014, 10:11:03 AM »

Thank you indeed.

Ezzie · « **Reply #5 on:** February 10, 2014, 11:58:36 AM »

For those who have seen these in another thread, I apologise. I just thought I'd conclude this thread by showing the end results, the camera and test shots.

6x24 Pinhole by Eirik0304, on Flickr

Frozen river by Eirik0304, on Flickr

Power substation by Eirik0304, on Flickr

Alan · « **Reply #6 on:** February 10, 2014, 02:35:32 PM »

brilliant ! simple solution's ! looks great.

the curved film plane works great to minimise the dark edges.

well done

Ezzie · « **Reply #7 on:** February 10, 2014, 06:25:00 PM »

Thank you Alan. I tried to keep it as simple as possible. Taking some care to detail, but not so much as to make it a longwinded project. Design, or trial and error as the case may be, and building took maybe 15 hours in total. My Vermeer 6x17 inspired me to use a curved film plane. It saves space, and it gives a more even exposure, without having to resort to longer focal lengths, and unlike optical lenses (I hate the term, as there are no other kind, but as opposed to no lens at all), a pinhole needs no correction if film plane is curved. The biggest caveat is the horizontals will be subject to barrel distortion, when off centre. But that can either be used to accentuate the panoramic effect, or avoided (for landscapes at least) if camera is kept dead level.

Terry · « **Reply #8 on:** February 10, 2014, 08:43:56 PM »

I like the way you manufactured nearly everything--especially the film winding knobs! And I like the idea of curving the film plane; the way the image brightness falls of at the sides is a good effect and you've used it well in composing these shots. I recall that my Horizont camera (now Nigel's Horizont) had a bubble level built into it; now I know why!

Ezzie · « **Reply #9 on:** February 12, 2014, 08:02:38 AM »

Thank you Terry.

Ezzie · « **Reply #10 on:** February 12, 2014, 08:04:28 AM »

I made a hasty description of the film holding and winding mechanism. Both ends are the same, so I tension the film if need be, either that or wind back if I missed a frame.

Chalky · « **Reply #11 on:** February 17, 2014, 01:11:57 PM »

some of the film plane technicalities are beyond me, but that is a very impressive bit of work, very nicely done. Might have to try my hand at building a pinhole myself when time allows. great stuff.

Sandeha Lynch · « **Reply #12 on:** February 17, 2014, 08:27:00 PM »

Hehe, brilliant. I really like the idea that nothing was purchased and no parts were photographically related.

I must find me a box.

stevesegz · « **Reply #13 on:** March 01, 2014, 06:42:37 AM »

brilliant! missed these on Flickr

Ezzie · « **Reply #14 on:** March 01, 2014, 07:35:10 AM »

Thanks Matt, Sandeha and Steve.

Second roll of film hanging to dry. Hope to post an image or two tomorrow.

Ezzie · « **Reply #15 on:** March 02, 2014, 03:42:50 PM »

Made a few adjustments to the film gate, it was a bit wonky. Better, but still could use with some cleaning up. Anyhow, it works quite well none the less.

Søndre Bjørkhaugen #3 by Eirik0304, on Flickr

Bustokkelva #2 by Eirik0304, on Flickr

Bustokkelva #1 by Eirik0304, on Flickr

FrankE · « **Reply #16 on:** March 02, 2014, 04:01:32 PM »

that camera works great
those are nicely composed images

how do you make the actual pin hole and get the focal length correct so that the film is in focus

I am really impressed

Ezzie · « **Reply #17 on:** March 02, 2014, 06:16:05 PM »

Thank you Frank.

There is a bit of theory behind size, focal length and "sharpness" or circle of confusion (CoC). I usually skip it and use a calculator on the net. Mr Pinhole for example. Why? well read on and you will see.

In general however, a pinhole doesn´t focus or have a focal plane as such. Any size (as long as it small enough compared to the film/paper format and focal length) will work. However the so-called CoC is relative to the pinhole size, so a smaller pinhole will normally give sharper pictures. However you do get diffraction with pinholes too, so you need to make sure the material you punch a hole in is ideally no thicker than the diameter of the pinhole, preferably much less. Also, a smaller hole will give longer exposure times, so there is no easy way out. Another issue is the focal length and coverage. A shorter focal length has less coverage. Two of my cameras have focal lengths of 85-90mm. This will have an image circle of less than 170mm. Which is one reason one gets vignetting, the other being that since there is no optical correction, the edges of the frame will get less light, (in effect have a different focal length than the centre) and therefore experience fall-off. Curved film plane will help a lot on the latter, and a bit on the former).

A calculator will give you a size relative to the focal length. The shorter the focal length the smaller the hole. 90mm focal length, a hole of 0.300mm to 0.400mm is normal. The f-stop is a factor of focal length over aperture. So 0.300mm will give an f-stop of approx 300. That is 7.5 stops slower than f16

So I upped mine to 0.500mm Not as sharp, but an f-stop of 170 approx is two stops faster, which helps.

How to make a hole? I use a soft drink/soda can. I put a small dent in it with a ball head hammer, then I sand the dent down as far as I dare (600-1200 grit). Then find a small needle and rotate it whilst putting pressure on it centre of dent. Sand a bit more, and repeat. Eventually a hole will appear. Make sure that there are no burrs. I measure the size and just how much it resembles a circle with a scanner. I set it to a factor of 2541dpi (1x254i or 2x2541, 3x or 4x - depending on scanner resolution). But lets say I use 2541dpi. 2541dpi equals 100 pixels pr mm. So a hole 50 pixels across is 0.500mm.

This is the scan of the pinhole in the pano camera:

Francois · « **Reply #18 on:** March 04, 2014, 09:22:56 PM »

I think this is the best example of how the size of the pinhole affects the image quality.
It came from an old Time Life photo encyclopedia.

Andrej K · « **Reply #19 on:** March 05, 2014, 04:45:10 PM »

Thanks for the bit of theory Eirik. I've been thinking about a curved plane pinhole for some time now, on and off... Rollfilm panoramas are nice but not having a LF enlarger does not make enough encouragement to actually make the thing happen.. But I have one project in drawings... The basic idea is a curved plane one shot camera using 7x17 inch XRay film... That would make a nicely sized negatives and hopefully some nice prints... Still quite a long way to go but this thread is very helpful..

Sent from my i9300 using Tapatalk

Ezzie · « **Reply #20 on:** March 05, 2014, 06:42:53 PM »

With negatives that size all you need is a good contact printing setup Andrej. I know Roger Hicks is a big fan for 5x7 for that very reason.

6x17 and 6x24 are a bit small for that. And for the former you need a 5x7 enlarger, the latter an 8x10, both way too big for my intended darkroom - house even. So negatives of these formats are bound to get the digital treatment. I have however considered hybrid processing, scan, process, then print a smaller negative that will fit a 4x5 enlarger. I need to build my darkroom first

Francois · « **Reply #21 on:** March 05, 2014, 11:12:50 PM »

There's also the photograph the negative in fine grain 35mm duplicating film and enlarge.

Andrej K · « **Reply #22 on:** March 06, 2014, 10:28:30 AM »

Quote from: Ezzie on March 05, 2014, 06:42:53 PM

With negatives that size all you need is a good contact printing setup Andrej. I know Roger Hicks is a big fan for 5x7 for that very reason.

6x17 and 6x24 are a bit small for that. And for the former you need a 5x7 enlarger, the latter an 8x10, both way too big for my intended darkroom - house even. So negatives of these formats are bound to get the digital treatment. I have however considered hybrid processing, scan, process, then print a smaller negative that will fit a 4x5 enlarger. I need to build my darkroom first

I know.. Currently I'm quite capaple of very fine prints from 5x7 and 8x10 negatives, but a format that large (7x17 would indeed require a whole lot of DIYs, not just the pinhole cam - printing frame, UV light source, etc...
Anyway, it should be fun!

Ezzie · « **Reply #23 on:** January 03, 2015, 09:35:25 PM »

A few shots from this spring.

Portra 400, 6 minutes exposure, more than enough time to wander into the frame

Wistful thinking by Eirik0304, on Flickr

Ezzie · « **Reply #24 on:** January 03, 2015, 09:38:09 PM »

Tri-X, ND8 filter, 30s

The wier by Eirik0304, on Flickr

k.hendrik · « **Reply #25 on:** January 04, 2015, 10:10:07 AM »

thanks for this inspiring topic! great camera & very fine dreamlike images. the encyclopedia must have been French because of the appearance M. Maigret ?

ManuelL · « **Reply #26 on:** January 04, 2015, 12:10:58 PM »

Really like the images Ezzie! I always find it hard to get a good composition with the wide format, but you nailed it.

Ezzie · « **Reply #27 on:** January 05, 2015, 07:49:01 PM »

Thank you both. I thought I would warm the thread up in readiness for some recent shots. Camera now can use one Lee-type filter at a time - I chose an ND grad for these. Gave a little definition in the sky, if not much.

Took these a few feeks before X-Mas

Pond by Eirik0304, on Flickr

Flood by Eirik0304, on Flickr

6cmsquare · « **Reply #28 on:** February 24, 2015, 04:35:05 AM »

Wow! really inspiring, I just finished my first pinhole conversion on an old Ansco "Sure Shot" box camera, 6x9cm negative, - your shots make me want to modify the guts and fit a curved plane in there. -although, with a width of only 9cm, I don't suppose it would be a very deep curve? -Probably time to build another!

Ezzie · « **Reply #29 on:** February 24, 2015, 06:11:29 AM »

Thank you Mike. Yes 6x9 is probably a bit on the short side for a curved plane. 6x12 may be enough. It really depends on the focal length you choose. If you want a perfect semi-circle, the long edge of the film needs to be less than pi x radius (which is also focal length). In my case it wasn't, which is why my curve is not a semi-circle, but more convex in shape. Vignetting is more pronounced towards the edges, but still better than a flat film plane camera.

02Pilot · « **Reply #30 on:** February 26, 2015, 02:14:39 AM »

FWIW, my pinhole-converted Kodak Flash Six-20 (6x9) from the 1930s came from the factory with a curved film plane, so there must be some tangible benefit.

Ezzie · « **Reply #31 on:** February 26, 2015, 07:32:47 AM »

You are right of course. The principle is to try to make sure that all points along the horizontal plane are equidistant from the pinhole. This should ensure equal amounts of light to the whole frame, and minimise vignetting. However, the wider the frame the more diffraction will play a role, unless of course you are capable of finding brass stock for the pinhole, that is just a few microns thick.

Sid Dongre · « **Reply #32 on:** February 26, 2015, 10:38:03 AM »

Such an interesting project! And amazing results. Thanks for the detailed explanation(s) too!

02Pilot · « **Reply #33 on:** February 26, 2015, 03:25:56 PM »

Quote from: Ezzie on February 26, 2015, 07:32:47 AM

However, the wider the frame the more diffraction will play a role, unless of course you are capable of finding brass stock for the pinhole, that is just a few microns thick.

I've always used brass shim stock for pinholes - it's readily available through hobby suppliers, or just check Amazon.