Rescue and Modification of a Ricoh Auto Half

I’ve restored this cute little Japanese half-frame 35mm camera with a metering conversion from selenium to CdS, and the addition of adjustable focus. Here’s the story.

My collection includes different cameras for different purposes or moods. Sometimes it’s great to slow the process down, and agonise over the precise technical details of every shot. Other times it’s more appropriate to just go snap, snap, snap and capture the moment. This tiny Ricoh is great for the latter. It was introduced in 1960, and featured clockwork motor wind that’s good for a dozen or more shots in one go. Being half-frame, it allowed you to snap away for up to 72 portrait-format exposures.

On most versions, the focus of the 25mm f2.8 lens was fixed. The shutter release was initially on the front of the camera, and fires the shutter at about 1/125s when there wasn’t a flashgun connected. Automatic exposure metering used a selenium photocell behind the familiar ‘bubble window’ around the lens, driving a hidden exposure meter and trap-needle mechanism that controlled the opening of the 2-bladed aperture.

Later versions added all sorts of bells and whistles. The shutter release was moved to the top plate, a self-timer was added, and there were multiple fancy coloured finishes from Ricoh and several other licensed brands. A few got fiddly-to-use zone focus, adjusted by turning the front of the miniscule lens rim with downwards pressure from your fingertips. The top-of-the range SL model got a much bigger f1.7 lens with proper zone focus, and battery-operated metering with a CdS sensor, but if you can find a working one it’ll be eye-wateringly expensive.

I got my camera cheaply on eBay earlier this year, in nice cosmetic condition and undeclared functionality. It’s the first version, 1960-63. Unsurprisingly, the metering didn’t work. Disassembly and investigation showed that the selenium plate produced only a tiny flicker on the metering needle when exposed to bright light. All of my efforts to improve it failed.

I didn’t want to give up though, so I looked for alternatives. Some people have had success replacing a selenium plate with a solar panel out of a calculator, and re-calibrating the circuit. Not really an option here, because all the panels I could find were much too wide to fit in the narrow housing under the lens.

The next option was to make a battery-powered CdS system to drive the Ricoh’s meter. I had some CdS photoresistors from defunct SLRs in my spares box, and the very simple 1.5 volt circuit diagram used by the old screw-mount Praktica SLRs is available online. Before long I had rigged up a test circuit, using potentiometers mounted in an old takeaway tub, and a CdS sensor placed in front of my calibrated LV light source. In the camera I removed the viewfinder for access and placed a piece of masking tape next to the meter needle path. That enabled me to mark the seven positions that produced apertures from f2.8 to f22 when the trap-needle was operated.

Circuit testing. Power supply & voltmeter on the left, then my light source which is calibrated for LV.

Now I could experiment to determine what changing the resistor values would actually do. It was an iterative process of trying a set of resistance values and noting how the aperture value in the camera changed as the sensor was exposed to varying light levels. Plotting the results in Excel enabled me to see how the resistances in the circuit changed the gradient of the graph, and its vertical offset. After a bit of fiddling, I had a set of resistor values that should work.

Getting it to fit was the next challenge, because this is a palm-sized camera. I designed and 3D-printed a new front housing that is slightly wider than the original, as far as possible while still being symmetrical around the lens and not interfering with the shutter release button. The CdS sensor sits above the lens, behind an enlarged viewfinder window made from an old CD case. The circuit and battery are in a compartment below the lens, behind a sliding cover.

This is a tiny camera, so the electronics are a tight fit.

The other practical addition it needed was an on/off switch, to prevent the battery draining when the camera is not in use. There really wasn’t any room for it below the lens. In the end I built one into the camera, so it operates with the shutter lock mechanism. When button on the outside of the camera is slid forward to unlock, the other end of the see-saw locking lever moves backwards to disengage from the shutter release. That end now touches against a springy brass electrical contact I made, and completes the meter circuit. Sorted.

The brass contact (top left) is connected to the white wire, and grounds the meter when the shutter is unlocked.
Note the pencil marks against the meter, from f2.8 to f22.

Adding front-element adjustable focus wasn’t too difficult, because the existing housing for the front element screws in and out. It’s set to a distance of about ten feet at the factory, and locked with three grub screws. I removed the grub screws, and glued the housing into a 3D-printed lens hood, which has a decent grip and a focusing scale. A removable brass tab inside the circuit compartment is used to set the infinity stop, and also prevents the lens being unscrewed more than one turn.  Due to the lack of space, I had to add a white-painted metal pin to a recess in the front housing to indicate the focus.

The focus scale as-seen when in use, visible through a recess with a white needle to indicate the centre.

The only tricky bit is that there is no ‘B’ setting, which would make focus calibration easier. Instead I worked out where I needed to shove a little sliver of plastic into the shutter release mechanism, to jam it mid-cycle with the shutter open. Then calibrating the focus was simple enough, using an old SLR split-prism focusing screen held against the film rails.

Assembling and testing the camera seemed to indicate that it worked, as the aperture opening changed according to the light level.  That justified fitting some new light seals on the rear film door, which is removed completely when loading film.

The rear film door is fully removable. Shutter lock is on the right hand end of the camera.

I loaded a roll of Ilford Delta 100 into it and took it on a couple of photo walks — one around Norwich, and one around the North Norfolk coastal village of Burnham Overy. It’s not really suitable for covert use, because the quiet click of the shutter release is followed by a ‘ZZZZZZUUP!’ noise as you release your finger and the clockwork winder does its thing. Winding the spring uses a silent ratchet though. I got 79 exposures out of the film, and could have got 80 if I’d have loaded it in the dark.

Elm Hill, Norwich.

The famous Norwich Keyboard.

Mannequin on Norwich Market.

Boat at Burnham Overy Staithe.

Millstream, Burnham Overy.

Tower Mill, Burnham Overy.

The results were pleasing. Exposures were pretty close to the mark, although it’s still sensible to use a negative film with decent latitude. Being able to focus the camera allowed for a lot more picture opportunities than would have been the case with fixed focus. All the detail is there, and it’s a very usable camera to keep in your pocket.

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About The Author

22 thoughts on “Rescue and Modification of a Ricoh Auto Half”

  1. I’m utterly in awe of what you’ve managed to do here, far exceeds my ability, and the end results are great, both in terms of the camera and images.

  2. Absolutely amazing. I’ve had one of these cameras for many years and sadly the once working selenium is now dead… whether I could do what you’ve done is another matter!
    I also tried fixing a later Auto Half to use in the rare underwater housing – and that refused to play ball either – maybe I should send it to you for a makeover and restoration?!

    1. Thanks Timothy, I appreciate your confidence in my abilities. The minicule scale meant that it was quite a stressful job carried out over several months. Nice that it worked out OK, but it’s not really one I’d want to do again if I could avoid it.

  3. Nicely done Stuart! I like the Ricoh Auto Half for its clean aesthetics and good quality lens. You managed to modify it for better functionality without compromising the original look. And nice photos too.

  4. Uli Buechsenschuetz

    I‘m thoroughly impressed by the job you‘ve done here. One thought crossed my mind: when you printed the front element housing, have you added a filter thread in there?

    1. Thanks Uli. I haven’t added a filter thread, and I think my printer would struggle to print a 27×0.5mm thread accurately enough. I suppose I could have cut the female thread off a 27mm filter and designed a recess at the front of the lens hood to glue it into. It wasn’t really a priority though.

    1. I have a box full of dead cameras in the loft, that didn’t survive my ham-fisted attempts to repair them. It serves as a reminder of my limitations, because learning how to repair cameras is a long road of success and failure.

  5. Amazing work. I fix old cameras occasionally and have been known to build one or two, but I’ve never even attempted to modify the electronics on one. Really fantastic. Thanks for sharing.

  6. Very nice work! I had an idea to do the same thing for a Trip 35, perhaps putting the electronics in a housing on the hotshoe, the circuits for these things are so simple, just have to find the voltage needed to move the needle. Perhaps one day doing this in bulk would be worth the effort to save these otherwise perfectly functional cameras.

    1. Thank you! There’s loads of room inside the base of a Trip 35 for the circuit and a battery, no probably no need to mount anything externally. You might even be able to fit an LR44 battery compartment with a flush screw cap, if you can find an old SLR with a suitable one to use. Obviously the photoresistor would be mounted in place of the circular selenium plate. It’s been a while since the last time I took my Trip 35 to bits, so I can’t remember how the ASA selection affects the circuit. As it’s on the end of the lens it must be electrical, but on the Ricoh it works mechanically on the meter itself. The Trip 35 is such a great and popular camera, you’re right it’s ripe for a mass commercial solution.

      1. I took apart a Trip 35 before to fix a stuck aperture, the ISO selection is not actually electrical, it’s a series of different size holes that uncover set amount of the selenium meter. The circuit goes up to the needle and resistor under the top plate. That is also when I had this idea, beyond just fixing it, we would be able to extend the metering to use higher ISOs. The 25 and 50 ISOs see very little use these days.

        1. Ah – I stand corrected! It could still be made to work in a similar way when there’s a small CdS sensor instead of a large selenium plate. The ASA selector could move a disc with different sized Waterhouse stops (calibrated holes) that vary the amount of light able to reach the sensor. You could choose your preferred ISO range and select hole sizes / resistor values / labelling to suit.

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