​The nub of the issue is that to keep the circuit cheap, most designers at the time relied on the fact that a mercury cell gives a nearly constant voltage all its life before dying suddenly, so the meter could rely on the battery to give a fixed known output. The electronics could then consist of nothing but battery, LDR (light dependent resistor - the light-sensitive CdS or CdSe cell), meter and one resistor, all wired in series. It’s that simple!
So what other cells give the constant voltage we need and are still available? Several, is the answer, but easily the best for us is a silver oxide cell which gives a nearly constant 1.55V. You can put one of these directly in a meter but it is likely to read too high by several stops, and be non-linear. We need to reduce the battery voltage by 0.2V, and the way to do that is a suitable diode (a Schottky diode) which creates a voltage drop of 0.2V, that itself is also constant; a resistor would give a voltage drop proportional to the current flowing, which would not do at all. The diode is wired in series with the battery.
This is the conclusion reached by Frans de Gruijter, and is the basis of his conversion kit – which I have tried and can recommend. But maybe we can slim it down even more? Here goes.

​The slimline adaptor is a paper disc with a conducting layer each side, with the diode soldered to the edge of each layer. This slips under the battery, with the diode near the edge of the compartment, where the shape of the battery leaves a little space. The pad itself is less than 0.5mm thick and should not cause any clearance problems in the instrument. If your device needs two batteries, you also need two adaptors.

Tools needed:
Most of the job can be done with readily available hand tools – a craft knife and scissors are useful, tweezers, small snipe-nose pliers, and a fine-tipped soldering iron. The trickiest part is probably the punching out of neat discs of paper and backed copper foil, best done with wad punches. These can be bought individually, or as a set of punches with a common handle. You need two sizes – either 3/8” and 7/16” or 10mm and 11mm would do. Expect to spend around £20 if you need to buy these. I happen to have a small hand-press which does a good job of punching out these materials. But usually you would use a block of wood and a hammer, and you need to give the punch a surprisingly meaty thump even when just cutting paper.

Construction sequence:
Cut a piece of the red card to approximately the width of the foil tape, and stick down a length of the copper foil, to cover one side.
Using the larger punch, punch out as many discs as you like. A piece of material 8”x1” should make 20-odd discs. Each disc should be completely covered with copper on one side, and bare card on the other.
Using the smaller punch, punch out the same number of discs directly from the copper foil plus its backing paper. This should give you a set of discs with the copper on one side and still on backing paper.
Using the tweezers, lift the copper from these smaller discs one by one, and stick them to the bare card side of the larger discs, trying to keep an even margin of red showing all the way round. I call this side of the card the positive side. You need to be sure not to get a short-circuit between the copper pads on the two sides of the card.

Now for each disc:
With the soldering iron, make a little dot of solder just at the edge of the positive pad.
Take a diode, and note the black ring round one end. Trim that lead to about 6mm long. Hold the lead with fine-pointed pliers, butted up to the diode, and bend it about 70°. The reason for the pliers is not to do the bend at the actual end of the diode body, which is fragile.
Hold the diode by the other lead, so that it is positioned on the edge of the disc, over the red rim, roughly parallel to the edge, and with the end of the short lead over the little solder dot you made. Solder lead to dot (only a couple of seconds contact at most, so the diode doesn’t get overheated).
Using the thin pliers as before to protect the diode body, bend the second lead up and around the edge of the disc, so it lies flat and in close contact with the edge of the negative pad. Trim off the excess lead and solder in place, rapidly as before.
That’s it done.

Continuing to use Kodak Aerographic 2645, as I have been doing some comparative testing of twin-lens reflexes that use 127 film (yes, I know, why would you?) In due course I hope to have a comparative report here so you can decide which to buy.
Meanwhile a note on developing. As well as the late Patrick Gainer's ascorbate developer, I am trying his PC-TEA formula. You can read all about it here.
P=phenidone, C=Vitamin C, TEA=triethanolamine. Thus PC-TEA.
Now triethanolamine is an interesting liquid, because it is both an organic solvent and an alkali. That is to say, if you dissolve your developing agents (ascorbic acid=Vit-C and a pinch of Phenidone) in neat TEA (not tea!), they are not exposed to any water. The theory is that rather like rusting iron, for the developer to go off it needs to be in the presence of both air and water. So a stock solution of developing agents in TEA should have a very long shelf life. When you want to use it, 8ml of stock solution + 392ml of water makes 400ml of working developer, used 1-shot. The clever bit is that the TEA, having so far worked as the solvent, now becomes the alkali and activates the developers. The benefits are several - a very dilute working solution, so minimal environmental or health risks, long shelf life, cheap to make and use. And the actual performance is fine, with developing times similar to other brews.
Vitamin C is safe to handle, TEA is a common ingredient of cosmetics (though it should not actually be drunk), and the phenidone content of the working solution is only 50 milligrams per litre.
If there is a snag, it is that TEA is viscous at room temperature, so I find it best, when I make up a batch, to dose it into little screw-top tubes each containing 8ml (enough for 1 tank of working developer). While it is still hot, once you have dissolved the developing agents, it is easy to measure it into the tubes with a 10ml syringe.
​Here is a picture taken on Aerographic 2645, developed in PC-TEA. Camera - Yashica 44LM

Update some months later:
Storage life is looking good so far. The PC-TEA concentrate is pale straw colour when first made. After about 5 months, in little individual sealed glass tubes (10ml tubes containing 8ml of concentrate), the liquid has darkened to near-black, but still works as normal!

I am enjoying trying out an assortment of TLRs that make 4x4 images on 127 film. But I am not keen to pay about £12 per roll of film, especially as some of these first trials are more likely to produce lists of problems to fix, than artistic pictures.
​
In the back of a cupboard I find several rolls of Kodak Aerographic film, 240mm wide and 20m long. Packed in an amazing cassette, like a 35mm cassette but huge. If cut down to 610mm long and 46mm wide, that is really a huge number of 127 films, just for the trouble of cutting it up and sticking to the backing paper of used rolls of 127, or even backing paper from 120 suitably cut down and marked with frame numbers by hand.

This is the film I am using - a sealed box just opened. Made in 1990 and used in 2018, and not kept refrigerated, so will it be OK? And how to use it? The web contains almost nothing about this particular Kodak film, though there is plenty on other varieties, most of which seem to have extended red and reduced blue sensitivity; a bit like having a yellow filter on the lens, permanently?

​After a preliminary trial of developing conditions, I fixed on 8 minutes at 20°C in Gainer's Ascorbate developer, something I have using a lot recently. Here is a result:

Exposed at 50ASA in this case. Exposing at 200ASA produced a less dense but quite usable negative, so this film has good latitude. Taken with a Koni-Omega Rapid using Aerographic film hand-cut down to 60mm wide and mounted on recycled 120 backing paper.

​How does it compare for resolution with other films? I have not done a comprehensive survey, but here is an example:

Conclusion so far - very promising, and the film is still excellent after 28 years of cupboard storage. I shall be taking some 127 pictures soon!

I bought an odd roll of 127 film for 50p from Doug Palmer's lovely shop in Bridport a few weeks ago. Needing to try out a new (old) camera, I unwrapped it and found myself with a roll of Agfa Superpan Supreme, no less, which from what I can gather would have been made during World War 2. I peeled off the tape and found this little notice, which clearly says that if I am not fully satisfied I can send the negatives to a New York address for a free replacement roll. I reckon that at the time of exposure it was about 75 years old, and had not been stored in a chiller.
I loaded my camera - a Minolta Miniflex - exposed the film at a guessed 50ASA and developed it in Gainer's developer, which is basically vitamin C with some alkali and a tiny pinch of phenidone. Wonders will never cease, I got pictures of reasonable density and no fog! On closer inspection, though, there were two problems - the grain is very squidgy and what should be even tones are uneven, plus the frame markings on the backing paper have printed across into the emulsion and can be seen on each picture.
​Can I send it back?

A recent purchase by my good friend and colleague John Wade (www.johnwade.org) brought back to mind a camera I'm quite fond of, and mentioned here - the Toyocaflex-35. The Tougo-do company split in two during the war, leaving two different Tougo-do companies for a while thereafter. In 1955 the Toyohashi Tougo-do factory launched the Toyocaflex-35. This is one of the very few designs anywhere of 35mm twin-lens reflex. It is clearly a descendant of the wartime Meikai, but better made and now using standard 35mm cassettes instead of little packets of sheet film in the No-Need-Darkroom system. It is 60% heavier than its predecessor and works quite smoothly. The taking and viewing lenses are both Owla Anastigmat 4.5cm f/3.5 (taking lens in NKS shutter, 1-200 & B, which looks just like a Compur rimset). And sadly the Meikai's top-plate magnetic compass has gone. To compensate for this, a neat feature is the matching lens caps, the larger one embossed “Toyoca” and the small one “35”.

When I got it I had to do a thorough service -  complete strip, replaced leatherette, cleaned all optics and outside, replaced the reflex mirror. Reattached A/R knob which had fallen off. It has knob wind, a body release, and is interlocked in such a way that if you forget to cock the shutter before firing, the body release is locked, and you have to fire it from the lens. Focusing is by a quadrant lever that moves both lenses in and out. Loading and winding film is easy, and the frame counter is clear. The direct finder is actually rather poor, but the reflex finder is quite good as a finder. There is now a focusing magnifier, but it’s not really much easier to focus than the old Meikai - fine focusing is impossible. I find it easiest to set the distance scale as usual. Rewinding is straightforward, if a bit tedious. The shutter is quiet, and the quadrant lever focusing is quite nice to use. The camera produces good sharp usable negatives.
​
What brought all this to mind is that John bought a Hulda 35, which is the same camera but with a different and much less common nameplate. Compare the pictures and you will see they are more or less identical. Why there were two names I don't know, perhaps for different retailers. It is something Tougo-do did with many other models too.

A small puzzle revolves around the various serial numbers:
                         Body      Taking Lens   Viewing lens
Toyoca            55430        542210        55053
Hulda               56631        55200         55380

See, the Toyoca taking lens has an extra digit in what is obviously a common numbering series across both name badges. I suppose it must be an engraving error!

Sugiyama's Collector's Guide to Japanese Cameras gives the Toyoca 4 stars for rarity (5 stars is the maximum) and doesn't mention the Hulda at all - these are not common cameras!

If you have read my previous post, you will know that I had in mind a two-month anthotype exposure using paper coated with spinach juice. I found a place to clamp up the 5x4" Arca Swiss monorail camera where it could watch a scene which is often sunlit but immobile (my house) and also sheltered from the rain. Once again the lens was a totally uncorrected f/2. I prepared and loaded the paper, and the exposure ran from August 3rd to October 3rd 2017. This should be a good test of my sensitometry and the possible occurrence of reciprocity failure. Over the two months we had a good amount of sunshine, but of course there is now a lot less each day, so the season for such experiments is over.
​
The moment of truth came this afternoon.

Not what I was hoping for!

On the positive side, it is easy to discern the masked edges of the paper, so the system does have some photosensitivity. The result is also attractive, in an abstract colourful kind of way. That was the good news.
Instead of a photographic image, I have created a little garden of fungi of several kinds. Although the camera and its bellows seemed dry and unharmed by their outdoor experience, the sensitised paper felt damp when I took it out, and had obviously managed to attract moisture and provide a food source for these little local denizens. I tried to match up the result to the scene I hoped for. Did different coloured fungi grow in areas of different brightness? - now that would be quite some colour process! But sadly no, I can't discern the expected scene hidden in this colour field.
I remain fairly confident that in the dry conditions of a desert island, the result would have been very different. The climate of the Devon coastal regions is mild and can be damp, and a future experiment needs to be in a different kind of camera - sealed to keep out the moisture, perhaps with a big bag of silica gel to keep it so.

Autumn and winter are coming now, so further experiment will need to await the return of plentiful sunshine next year. That gives me time to design and build a better camera, at any rate!

A week before a July 2017 meeting, I had a phone call asking for a short talk on “What camera would I take if I were stranded on a desert island?”
My first thought was that photography on a desert island without any of the supporting infrastructure that we’re so used to would be impossible. Film? Processing solutions? Electricity? I might take stuff with me, but once I’ve run out, what do I do?
However, when the going gets tough, the tough get going! In the circumstances, we need to keep it simple. For a start that means no enlarging, so the first requirement is that the camera should produce images at the final size – which in turn means that I should not be too demanding about the size of my pictures; my gallery is anyway going to be a small hut made of banana leaves.
My island, I have discovered, is deserted but by no means a desert. Although I am the only human, there is lush vegetation, small animals and birds, and fish in the lagoon. The essentials of life should therefore only take me a few hours a day, leaving ample time for exploration, photography, and sampling the fine wines which I shall learn to produce. The climate is subtropical, everything seems ideal, but unfortunately there is no silver mine; photography will have to be based on other chemistry than silver halides.
This raises a big problem, because nothing else is so fast. I shall have to be patient, and only photograph things that don’t move. I shall be happy with pictures 5x4”, so there is plenty of choice of cameras. I need something that packs reasonably small, and is very robust as I shan’t be able to get spare parts. A Gandolfi perhaps? – but I think there might be termites, so it needs to be metal. In a box I find an Arca Swiss monorail not being used for anything else, so there’s a good basis – strong, well-made, aluminium construction. I hope it will survive.
Now back to the speed problem. The easiest of processes to manage in the jungle would be cyanotype. Just two solutions to mix and paint on to any surface. If no paper, then leaves, wood, leather. A contact print or photogram in sunshine takes maybe 5-10 minutes, which is faster than most other non-silver processes such as dichromated gelatin. Processing is just washing with water. So when I first arrive I can bring the camera and some cyanotype ingredients, at least to get going. However, a 10-minute contact printing exposure is equivalent to a couple of days behind an f/2 lens in a camera! So no need for a shutter, fortunately for reliability.
Undaunted I set up the camera, but where to get a lens? The fastest affordable proper lens of about 20cm focal length is perhaps a Petzval Portrait at about f/3.5, but if we relax on the boring subject of aberrations, a large plano-convex lens (once part of a condenser) from the optical bits box is about 20cm f/2. Chromatic aberration is not a big problem as only blue/UV light affects the paper, but all the geometric aberrations remain. A 2-day exposure with this would alternatively need 4 days with the Petzval, over a week with a well-corrected lens such as a 210mm f/4.5 Xenar.
So here we go, and with a week’s notice for my talk I had only a couple of opportunities to get it right. The first exposure (1 day) was quite successful but a little underexposed. For the second (0.5 weeks) I allowed for the “chemical rays” by shortening the camera by 2% (4mm) after focussing visually, which probably didn’t help – and the sun got in and burnt two small holes in the paper! It was better exposed though, probably 2 days would be about right.
And when my chemicals run out? The longterm solution may be anthotype – juices from flowers, leaves or berries are painted on paper, allowed to dry, and exposed. For photograms exposures can be as short as 6 hours in sunshine, more commonly a few days. I haven’t tried it in the camera yet, but I should be able to get an image in as little as two months!

Is this the future of desert island photography? Anthotype photograms of Enchanter's Nightshade, made with spinach juice (6 hour exposure) and Italian red wine (5 day exposure). The faster of these might produce a direct positive in the camera in a couple of months.

As I write this, we are just at the beginning of a new photography season on BBC4 which I am finding fascinating. It is wonderful to see photography, and the history of photography, being given a prominent place in the schedules, and therefore in the public consciousness.
We started with Eamonn McCabe, the Guardian’s sometime picture editor, with a three-part series on the history of British photography. The first episode was a lightning tour through the 19th century concentrating very specifically on British photography. We were thus introduced to Fox Talbot, Frederick Scott Archer, Hill and Adamson, and Julia Margaret Cameron. It was remarkable how little it was possible to say about the daguerreotype and still make sense of the early history of photography! To most of our readers there was probably little here that you didn't already know, but if you want to introduce your friends and family to the fascination of early photography then it looks as if this series will be a good way to begin.
The second program I watched was called "The Man Who Shot Tutankhamun", and told the story of Harry Burton, who was Howard Carter’s photographer in the Valley of the Kings. Not just in 1922 when he discovered Tutankhamun’s tomb, but for another decade afterwards as well, whilst they were doing the detailed excavations. It was really worthwhile to concentrate on the quality of the photography, done under fairly difficult conditions and to a very high standard, technically and artistically. What made a real difference was the involvement of photographer Harry Cory Wright. Cory Wright is an experienced large format photographer who brought along his 1950s Gandolfi to replicate as closely as possible the experience that Burton would have had. The original photographs were taken on 10x8 glass plates, so that is what was used for the modern experiment. Interestingly, the professional archaeologists still working there are using 10 x 8 cameras themselves for some of their work, albeit using sheet film rather than glass plates. Why? – right now, you can still get better resolution that way than with any digital solution, though eventually even that will change, no doubt.
To do his trial, Cory Wright needed to coat his own glass plates using liquid emulsion and a brush. Although no fuss was made about this, serious brushmarks were visible in at least one of the resulting negatives!
The team also contrived to get access to an adjacent tomb in which Harry Burton had actually done his own negative processing. What was very clear was that Burton was achieving far higher standards of cleanliness in the dusty and dirty conditions than Cory Wright could. By this time in his career Burton had been photographing in the Egyptian desert for many years, and had undoubtedly refined his technique.

The other day I came across a very weird mathematical thing. It’s called Benford’s law, and it describes how numbers generated by more or less any process form themselves into the same pattern. Suppose you made a list of the populations of all the towns in Britain, or a list of the individual sums you paid for all the cameras you’ve ever bought. You might suppose that the first digit of each number in one of those lists would be equally likely to be anything from 1-9, but it turns out that is not so. With any large sample of numbers you find that about 30% of them begin with a 1, 18% with a 2, right down to 4.6% starting with a 9. This was first discovered in 1881, but it took until 1996 for a statistician to work out why. The reason is too complicated to go into here, and anyway need not trouble us.
It turns out, though, to have real practical applications. For example, it has been used by forensic accountants to root out fraud, where financial figures don’t follow Benford’s law, and millions of pounds worth of fraudulent expense claims or rigged sales figures have been detected. It can be used to detect any reasonably large set of data that does not follow the natural or expected pattern, having been subjected to some sort of manipulation.
So I thought, I know a set of data which has probably been manipulated more than most by manufacturers over the years, and that is the serial numbers they engrave on the items we buy. We know, don’t we, or at least we reckon, that manufacturers don’t start their counting at one, they leave gaps in their sequences, all sorts of tricks mostly aimed at inflating the apparent number of items sold. So as I have a little database in my computer of all the photo-historical things that I own or have owned, it was time for a little experiment.
It turned out that I had records of 655 serial numbers which start with digits (some of them start with letters and I left those out), relating to cameras, lenses, shutters, accessories and so on. That seems to be a large enough random sample to use Benford’s law to see if the world’s manufacturers of photographic goods do indeed cheat when it comes to setting serial numbers. And they do.
Looking at the first digits of my serial numbers, the digits 1, 2, 5, 6 & 7 do indeed turn up with a frequency reasonably close to what Benford’s law predicts. However, 8 shows up 16% too often, 4 is 18% too rare, 3 is 21% over, and 9 is an enormous 37% in excess. I don’t know how much you can make of the specific ups and downs, but it’s clear in particular that too many of these numbers start with 8 or 9.
So I have demonstrated statistically what we already knew, that over the years manufacturers have indeed used their commercial skills to tweak their serial numbers for their own ends!