Drop Guillotine Shutters and hefty glass - making the "Spitfire Camera"

I've had a monster lurking in my darkroom for some time now.  It's a huge lens made for World War II reconnaissance work; A 36" (900mm ) f/6.3 Dallmeyer, originally fitted to a special camera mounted in a Spitfire for photographing targets, battlefields etc.  It was made to cover 5x5in or 7x7in negs on roll film (in 150 foot lengths!) but the coverage is quite a bit more than that. The problem is that at over 20kg it's ridiculously heavy and difficult to mount on a conventional camera.

F/6.3 is very fast for such a long lens so there's potential for wet-plate or calotype work. The bokeh is very beautiful and the depth of field is tiny, even at long distances.  I've an idea it will suit the scanner-back camera too.  I decided it was worth building a simple camera for it.

Quick and Dirty Prototyping

While I suspect this lens has a properly big image circle, mounting it on the Behemoth 20x24" camera would require quite a bit of hacking about and make an already huge and heavy camera twice as unwieldy. I decided a simple sliding-box design would be quite adequate. If I made the back plate a replica of the one on my LSC folding 10x8" I could use its backs- allowing both wet-plate and conventional film holders to be used. I'd also simplify the build process a lot.

To get some rough dimensions for the boxes I knocked up a prototype from cardboard boxes and tracing paper.  The good news was that the lens is a true telephoto design, needing only about 21 inches from flange to film to focus on infinity. Quite a reduction from the 36" I was expecting. To accommodate the LSC backs it needed to be just over 12" square at the back.

cardboard prototype with lens installed

Note the shredded paper focusing screen thanks to my "assistant" Algernon who burst through it while playing with the box.

The Boxes

I made the boxes from cheap 5.5mm plywood from Homebase.  It's pretty awful stuff, imported from China and warped all over the place even if you pick and choose your pieces but it's hard to find anything which is much better, short of full-on certified marine ply which is ruinously expensive. To keep the weight down and to make it as close as possible to an original 1840s Calotype camera as possible I comb-jointed the pieces together. This is time-consuming and fiddly as all the slots need cutting on a router with a specially made jig but the result is very strong and needs no bracing.- Important as the boxes need to be a close fit.

I made a custom lens board so the lens could be easily demounted for transport. The camera box accounts for only about a quarter of the total weight.  The boxes are a close sliding fit, with a felt flap on the inner box edge to act as an extra light trap. 

Once glued up, stained and varnished,  the boxes received their fittings to take the lens board and focus screen/film backs. The base has the same 'keystone' plate fitting as the Behemoth so it will fit on the heavy duty tripod.

Testing

A quick test using RC paper confirmed that the camera's lightproof. I made a simple filter holder from foamboard as grade 00 is usually needed to cope with the subject brightness range.

Ilford Multigrade no. 00 filter installed behind the lens. The are 6" square acetate.

Mk 1 Spitfire Camera completed. Chief Assistant Algernon providing scale. He is quite a large cat too.

Paper is around ISO 1 with the filter giving an exposure time of 8 seconds at f/16 which is typical. Film will need faster shutter speeds, particularly as the aperture only goes down to f/16.
The next stage was to make a drop or "guillotine" shutter.  These are very simple: A plate with a slot in it is dropped in front of the lens. The width of the slot controls the exposure.

Shutter

While a wood and brass shutter would be nice, it was more important to build something which would work quickly, easily and cheaply while ironing out the bugs of the design. I made another QAD prototype from black foamboard and card, starting with the biggest slot (8 inches) I could get out of the card. This will define my slowest shutter speed. Faster speeds are achieved by making smaller slots.

A useful reference is Bill Kumpf's article on largeformatfphotography.info - While quite heavily technical it gives the maths necessary for calculating speeds for different slot widths.  I calculated my 8" slot should give a speed of about 1/11 second. Testing it against the excellent Shutter Speed App developed by Lukas Fritz I confirmed a reasonable match: 1/10.3.

From here it was a simple, if tedious job to plot out the slot widths for standard shutter speeds: 1/15, 1/30, 1/60. 1/125 and 1/250 are all possible by reducing the slot width. I've made a variable-width slot with a second piece of card held in place by velcro:

Slo-Mo filming

Another test revealed an unexpected problem: By filming using the iPhone camera's "slo-mo" function. This records at 240 frames per second so it allows the operation of the shutter to be watched at around 1/10 normal speed. Theoretically you can count the frames too as a check of speed but this isn't too easy or accurate. What it did show was a hell of a bounce when the shutter reached its stop:

The shutter plate was bouncing so much it was re-exposing the last part of the image!  This was easily cured with bit of foam to act as a buffer.

Images.

I really want to use this with direct positive colour paper prints but the events of this year have made that unfeasible (the colour machine at Farnham was drained down before Easter and there's no access to chemistry for the time being at least. Most of the B&W workshop images I've given away but this one is nice:

As soon as some semblance of normality returns I'll lug this out again and we'll get to grips with it...

1

2

3

4

1 blue

2 blue

Sorry they're not very straight and 3 is upside down.

Here are the virus models I made.  I decided that sitting and thinking about it all was not too healthy and a bit of a waste of my time, instead I decided to cobble together some models from old bits and bobs.  I had a bunch of flowers a few years back that had some shiny gold baubles on sticks in it(? - probably Christmas) I kept them. I found a pack of kids modelling clay in a bin and kept that too.  Cocktail sticks, hot glue gun and some white chalk paint (coz that's what I had).

I got to spend the day still thinking about the virus but I also spent a happy day practicing wet plate.

It was a good day:)

Contact Printing Frame Designs

In response to a couple of recent queries, here's a video showing some different designs for contact printing frames. If anyone has any other designs, improvements etc. please let us know.

Key things for a good contact frame:

1)  FLAT BACK.  The back board must be flat or it won't press evenly on the glass.

2)  RIGID BACK. The back shouldn't flex when clamped up.  If it does, the clamp bars may crack the glass.

3)  SOFT SURFACE Almost every one I've seen has a felt or baize surface to absorb minor imperfections and avoid creasing papers. Some of the 1960s-80s ones use foam rubber. If making contact prints of thick objects eg. plants this might be a good idea.

4) HEAVY FRAME - for the same reasons as 2) This includes the glass. Thin 2mm picture frame glass is unlikely to take the pressure except on very small frames.

5)  SPLIT BACK - to enable opening the back to check exposure without losing register. Traditionally split 1/3 of the way across.

Here's the video: apologies for the poor sound quality - I'm still learning this stuff!

https://youtu.be/NuD_OQoaDlk

https://youtu.be/NuD_OQoaDlk

A cheap LED exposure box for ultraviolet processes.

[If you're reading this during the UK lockdown and have no access to tools or facilities note that it's entirely possible to buy the LED sets and just stick them inside any old box - no need for fancy stuff!]

There's nothing like necessity for driving projects.  Both my UV exposure units are on semi-permanent loan to UCA. They spend most of the time in the finishing room where everyone can use them and I only bring one back home when I need it - only now, of course I can't!  They are languishing in the UCA Photo dept, left there in the lockdown.

I want to make use of some of this time to do some serious testing of the carbon print process, particularly working out a useable contrast curve for digital negs. While it may seem odd in these days of glorious sunshine, testing processes like this requires an artificial, and therefore 100% consistent light source. - I need a UV box!
While mine use fluorescent tubes from home sun-tan units I've seen people online who've made them from long strips of UV LEDS.  These are cheap and generate almost no heat. I've toyed with building one as an experiment for a while but now necessity means I'm finally getting round to it:

The light source.
Accepted wisdom online (see links to sources at the end of this article) says the LED strips to use must be SMD 5050 type, 395-405nm wavelength.  (Don't use the lower-powered SMD 2835 type) I bought two rolls of 5 metres with UK 240v power supplies. (NB: you don't need the versions with waterproof outdoor-spec LEDs or remote controls (!?) These cost me £16.99 each from China via Ebay.

Layout.
The strips are 10mm wide and carry 300 LEDs in each 5 metre length. The strips can be cut with scissors at every three LEDs at marked points where there are solder pads. Mine (possibly because they were cheap?) were made up from ten 30 LED / 500mm lengths, soldered together. As this was just the length I was going to use anyway it was easy to un-solder them at these points.
Twenty lengths of LEDs spaced 10mm apart means a light panel 500mm x 390mm. (around 20" x 16") This is a good size, roughly equivalent to my current ones.  You could, of course build a smaller, high-intensity version by putting the strips closer together.

closeup of LED strips. Arrows show the cut points.

Each strip is backed with double-sided tape. They should stick to most surfaces and as they don't get hot you can use things like plastic or cardboard boxes to support them. I wanted to make something a bit tougher (it'll probably end up at UCA like the others!) so I used Dibond.  This is a sandwich of thin aluminium sheets with a plastic centre. Very flat and rigid, with the advantage of being reflective (every bit of brightness helps).  I was slightly concerned the aluminium would short-circuit the LEDs but the sticky backing seems to insulate it OK. I added extra strips of electrician's tape at the ends to be on the safe side.

Power and current distribution.
LEDS are terrific things but they are a bit fussy about the way power is supplied to them. They need the right voltage of course but also a carefully controlled amount of current. Unlike old-fashioned lightbulbs, unless the power is regulated, LEDs will consume more current than is healthy for them and burn out.  They therefore need the correct power supply for the application. This is why it makes sense to buy a matched power supply at the same time.
The strips are supplied with pre-soldered wires on both ends and a plug to connect to the power supply. While they do work with just one end connected, the resistance of 5 metres of strip means that the ones furthest from the supply are noticeably dimmer than the nearest: - Not good for making an even light source. The answer is to wire the strips in parallel like this:

one set of ten strips of 30 x LEDs wired to power supply

It's a bit of a fiddle to solder lots of little jumper wires but it means that the current is much more evenly distributed.
As I was running two sets from two power supplies I arranged them so the second set was powered from the opposite end of the board. This ensures that even if there is a little drop-off in brightness it's evened out.  Here's the first set of ten 500mm strips (total 5 metres) installed:



- And the second. It is possible to run just one set of lights, giving half-power but why you'd want to I don't know. - also the lighting is unlikely to be as even with wider spacing.  I offset the second set a little to get the most even pattern of lights possible.

the finished array.  See below for the schematic of the wiring.

the second set of ten strips of 30 x LEDs and power supply interlaced with the first.
Note no electrical connection between the two sets!

- and it works! LEDs are hard to photograph as digital sensors seem to react oddly to them. In reality they look almost disappointingly low-powered but that's hopefully because they are mainly emitting invisible UV light.

The only way to assess the brightness is by testing.  I propped the panel up on some scrap wood,  made a couple of  pieces of cyanotype paper and ran some quick test strips. Maximum density is achieved at around 5-6 minutes with the paper 120mm away.  This is much the same as the fluorescent UV units.

Wiring and safety.
The LED power supplies come with standard 'kettle lead' wires with three-pin plugs. The problem with these is that the plugs have no fuses, which I think might actually be illegal in the UK. - At any rate it's a bad idea. The fuse is to protect you in case of an electrical fault in the power supply box, cutting the power before the thing catches fire or electrocutes you.  For this reason I'm ditching the supplied cables and fitting proper leads with fused plugs. - I should have checked before I bought the cheapie sets!

'kettle lead' fitting and un-fused 3-pin plug

Making the box.
The panel can be used any way convenient. Gavin Lyons (see link below) put his into a plastic crate which is a super-easy and quick way to house it. I've built a simple box from scrap wood with a hinged lid and an opening flap on the front:

The finished box. the flap at the front hinges down and the top opens too. Note I'm running the lights off an enlarger timer.

I like the way it looks like a Las Vegas casino in there!

Verdict.
The LED option does require a bit of electrical expertise, soldering wires and ensuring the power supplies are connected safely. However, if you are confident in tackling that part, there are several benefits over the fluorescent tube tanning lamps: The light panel is compact, weighs very little and generates negligible heat. It uses very little power, can be left on for long periods and almost any size of panel can be made. I'm happy with this set. - I could add two more sets of LEDs and double the power - though I'll look for fused plugs next time.

Links:
Gavin Lyons excellent video on making a very similar lightbox using a plastic crate:

https://www.youtube.com/watch?v=L7-NVZ7oWSQ

Large Format Photography forum article by Eric Biggerstaff:

https://www.largeformatphotography.info/forum/showthread.php?122508-LED-UV-Light-Box-Build-Your-Own-for-Under-150

Greg Brophy: a photographer in the US who has made his own UV box:

http://gregbrophy.com/blog/how-to-make-a-uv-led-exposure-box

I've been walking dogs in my local area for the past 2 years, I quite enjoy it, I have 4 of my own dogs anyway and the money's good, well better than I can get from photography!  I've just quit my final furry friend so that I can dedicate more time to my photography practice (whatever that turns out to be?)

To make a start I thought I'd have a rummage around in the studio to see if I can make the space a bit less cluttered and maybe have a go at fathoming a work flow of sorts.  I definitely have started to notice what's working and what's in the way.

I really need to start putting the plates away on a daily basis now as I'm starting to get them muddled up.  It's also not very good to have them all over the place.  With that in mind I've started to wax/varnish then scan them all...Boooorrriiinggg!

I made 2 larger plates a few weeks ago that have both peeled.  This one though has lifted in one piece so I'm going to have a go at lifting and re-siting it.

Learning through play!

I bought this little camera at the car boot sale along the A3 in Guildford about 3/4 years ago. I paid £90 as that's all I had. The man selling it was keen for someone that wanted to use it to have it rather than a dealer.  I was very excited, got it home, poked it a bit and not really sure what to do with it promptly forgot about it! Anyway, last week I rediscovered it sitting on a shelf (with all the other old cameras I've accumulated). With my new found invincibility I thought I might have a go.

I didn't do anything to it, not even clean the lens so these plates are just made for fun, to test me, the camera, lens etc.  I had to cut the plates down,  I did this with scissors and it was ok, maybe a bit rough but it did the job.



I made 3 plates (quarter plate) The exposure was much faster than the MPP I've been using. It's possible there's a light leak and the lovely dark slides are a bit shitty on the inside.  Anyway, who cares!  It works and I got some lovely little plates so I'm calling it a success ;)

I've set some traps locally and hope to snare a few victims this weekend, I'll let ya know what I'm up to soon.

1.

2.

3.



Found these 3 plates in the drying rack, I made them a week or so ago and would have written notes in my little book about how they were made.  My little book has been 'borrowed' by one of my offspring so I have no recollection of any of the info, can't even remember exactly when it was made!  I'm considering finding a way to connect the mains electricity to the doorhandles of my studio :|

THERE ARE NO RULES - JUST MAKE PICTURES!

Sometimes I think I'd like to do something; maybe go for a walk, go shopping or maybe...photography.  But I have that nasty little monster self doubt, spewing it's poison in my brain.

'Get someone to come with you, to guide you, to hold your pathetic little hand' it says.  So I ask friends to come along.  As soon as the task begins I find myself wishing I was doing it alone!

What the fuck is that?  I'm pretty sure it's some kind of fear of the unknown.  Some potentially crippling lack of self confidence.  FAILURE?

The last of my children left home last week so for me, it's now or never!

I leapt of the cliff blindfold.  I took the keys, a coffee and some tunes down to the studio and set my stuff up.  All that talking, planning, hand-holding and dreaming comes to nought if you won't lake that leap.  I made some plates (wet plate is my thing).  They were beautiful rubbish as it turns out but it was easy and I didn't die!

I had a couple of things that I'd forgotten and usually I'd ask Peter but this time I just got on and worked it out for myself.

In that lovely moment my confidence returned I remembered how capable I can be.  I'm in my studio writing this while I wait for the chemistry to reach room temperature.  It's exciting to see where I might go with the work I'm starting and I can't believe how easy it is just to have some fun again.  Realising that there aren't any rules is very liberating. (if you can kick the fear of the unknown in the balls!)

To the friends who listened to my many reasons and excuses, thanks for keeping in touch.  To anyone else who might be wandering alone in the creative darkness that can come after uni...Make some pictures, anything.  Just keep making for the fun of it, something good will come!