Fujica ST701 Information |
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Fujica ST701 Information |
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I got my camera at a garage sale along with a basic 55mm f/1.8 lens, a 55-135mm zoom, a 2x teleconverter, a few filters, and a shutter release cable all for $35. At the time I didn't know anything about the camera, but at only $35 it seemed like a good deal for a simple camera I could use for basic astrophotography. This page is intended to help people who, like me, have obtained these cameras second-hand.
The ST701 accepts 42mm screwmount lenses which are still fairly easily found on the used market. For example, search eBay for "screwmount", "lens" and "-leica" or search for "Takumar" and look at the listings to see which lenses fit the Pentax Spotmatic line, which also take the screwmount lenses (these lenses are often referred to as "Pentax screwmount". Through eBay I have added a 28mm wide-angle lens to my collection and replaced my original garage-sale ST701 that started eating film.
The best solution seems to be to use a zinc-air button cell from Wein called the MRB400 ("MRB" for "mercury replacement battery"). A Google search for "Wein" and "MRB400" should turn up some sites that sell this battery. The price seems to run between $4 and $6 each (you'll need two).
Other solutions involve using the more widely available and somewhat cheaper silver oxide button cells available at most large discount department stores or Radio Shacks. This is a less than ideal solution because these cells deliver 1.55 volts while the original battery (and the zinc-air replacement) deliver 1.35 volts. The difference means the light meter will be miscalibrated -- you can be in a dark room with your lens closed all the way up, some slow film, and a 1/1000 second shutter speed and the meter will still tell you there's enough light. Some people have claimed that the silver oxide batteries are also bad because the voltage they deliver is not constant over the life of the battery like it is for the mercury battery and the MRB400 with the result that the meter will be off by different amounts as the battery ages. However, a check of the technical information at Energizer's web site seems to indicate that the voltage discharges is, in fact, very constant.
It may be possible to add a diode to the meter circuit to drop the voltage down to the correct level. The battery compartment cover seems like the easiest place to add the diode. You will need knowledge that I don't have to figure out the proper diode to add to the circuit.
The easiest solution seems to be to simply deal with the miscalibrated meter somehow. One way is to set the meter for one film speed slower that what you're using. This did not seem to work for me. My solution was to figure out what the light meter's new "correct exposure" range is. I've detailed by whole process for testing the meter, installing my batteries, and calibrating the meter below.
If you have suitable tools lying around, it may be a good idea to test the meter before you start running around town buying batteries or making modifications. I used a AA battery holder I had lying around and a couple lengths of wire (vindication for keeping all kinds of scraps of things). The wires had about 1/4 inch of insulation stripped off one end of the wires and about 1/8 inch off the other. The battery holder I had held 4 AA batteries, but 2 gives the proper voltage (more or less), so I had to trace the wires in the holder to find two electrically adjacent compartments and where the negative end of the resulting arrangement would be and where the positive end would be. I stuck a the long end of one wire between the coils of the spring at the negative end and installed one AA battery there. I installed another AA battery in the adjacent compartment and managed to get the other wire stuck between the last two coils of the spring adjacent to its positive end. Using a multimeter I was able to check the connections and see that I did in fact have a circuit delivering about 3.0 volts.
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After connecting the batteries you should set the camera up so the light meter will indicate overexposure so you can see the needle jump when you activate the meter. Completing the circuit and pressing the meter button is a little tricky with just one person, but it can be done. I managed to get the short end of the negative wire to lean just right against the threads of the battery compartment cover. With one hand I was then able to press the end of the positive wire against the round plate marked "+" at the bottom of the compartment. With the other hand I pressed the meter button as I crouched down to look through the viewfinder. If the meter jumps then you can proceed, otherwise recheck the settings, connections, and configuration of the batteries. If everything is OK but the needle still won't do anything then your meter is probably stone-cold dead.
If you have a multimeter that uses two AA batteries for testing resistance, you may be able to use its probes to supply electricity to the meter instead of the rig I set up.
Many types of battery should work. The correct diameter is 11.6mm, but you may be able to get away with smaller batteries if you can make some sort of spacer. (There is actually a zinc-air Energizer, the AC312, that is 7.8mm across which may be easier to find than the Wein cells.) Since the spring on the battery compartment cover is so big there's a lot of leeway with the thickness. Anything between 2.6mm and 3.6mm ought to work fine and you may even be able to go outside that range. The Energizer 387S fits the bill and has been suggested elsewhere as an option. My local Wal-Mart didn't have those so I opted for the thinner Energizer 389. Other choices include the 344, 350, and 390.
You may have trouble getting a good connection between the bottom battery and the contact at the bottom of the compartment. I solved this problem with a very small scrap of aluminum flashing with a dimple poked in it with a phillips head screwdriver. I put this scrap over the contact with the dimple pointing down and then put the two batteries on top of it. Later, I experimented with a small ball of aluminum foil smashed into a disc; that worked too.
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With this all in place the meter responds to light, but is miscalibrated because of the voltage difference. I decided to live with this and figure out where the needle is when the exposure is correct. To do this you can use the "sunny f/16 rule" -- on a bright, sunny day, the correct shutter speed at f/16 is the one closest to the reciprocal of your film speed. Go outside on a sunny day, focus on a well-lit subject, stop your lens down to f/16, and then select the correct shutter speed (for example, 1/250 for ASA 200 film). When I did this, the needle was somewhat higher than it would normally be for the correct exposure (see the illustration to the left). For other subjects in different conditions, I tried to set the exposure so the meter read the same level. Some results are below; they seem satisfactory. |
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