The original Photomic was designed to use a single PX625 battery. The battery compartment is in the side (unless it's been removed and lost, an incident metering diffuser is screwed into and stored on top of it).
The later Photomic heads use two PX625 batteries, stacked.
Original 1.3 volt PX625 size mercury batteries they use are no longer available.
ALKALINE PX625 will fit and will work.... but won't work well. There is no voltage stabilizer in the meter's power circuit, so using a battery with a steep power curve like alkaline have will make the meter skew differently throughout the life of the battery. It's near impossible to calibrate. Alkaline batteries are also the most prone to leaking and causing damage to cameras.
ZINC AIR and SILVER OXIDE batteries are a much better choice, but are generally not available in the corrects 625 size. Most of them come in smaller diameter 675/SR44/303/357 sizes.
One exception is "Wein" Zinc Air 625s... which are 675s modified by having a shim added. They're pretty expensive at about $5 apiece.
Widely available and much cheaper "hearing aid" Zinc Air 675s can be used by going to a hardware store and buying a 20 cent rubber o-ring to serve as a shim on the outside of the battery, so that it remains centered in the battery compartment. (Take the camera and battery with you to test fit o-rings... I forget what size I bought, but they were cheap and work fine in many cases.)
Both types of Zinc Air are slightly low powered when the seal on them is first removed, but they come up to around 1.4 volts in 15 to 30 minutes, then remain at that power level for 2 to 3 months, before dying. The Wien supposedly last a little longer. But neither have anywhere near the life of the original mercury (which could last for years). Also, once unsealed, a Zinc Air battery will die after its short life span, even if removed from the camera and resealed. (Mercury, Alkaline and Silver Oxide all will stop draining to a large degree, extending their life, once the meter is turned off or the battery is removed from the meter.)
Silver Oxide are a bit more expensive but have a life span much more similar to the original Mercury cells. Often Silver Oxide will last a year or more in normal use. Common sizes are SR44, 303 and 357, which are similar to 675 and require similar o-ring shimming "trick" to keep them centered in the battery compartment. When first installed, Silver Oxide tend to be a little high powered, but most settle down to a steady 1.5 volts after a half hour or so, which they maintain for the remainder of their life span.
Both Zinc Air and Silver Oxide have a flat power curve.... maintain a fairly steady voltage through most of their useful life, then drop off rapidly at the end.
I've used both Zinc Air and Silver Oxide in vintage cameras and meters. The slightly higher voltage of the modern batteries skews meters slightly (less with ZA 1.4v, a little more with SO 1.5v). You can set a false ASA to compensate for this. Some meters also have enough adjustability to be professionally calibrated for the newer batteries. Other meters without sufficient adjustability can be calibrated professionally by adding components to the power circuit to reduce the voltage slightly. However it's done, once adjusted for a modern voltage, batteries of the same type and voltage need to be used in the future, unless the meter is re-calibrated again, for a different voltage.
When I just want to test a camera with a few rolls of film, I'll usually use the cheap Zinc Air batteries. Those work fine for the short term and have lower voltage that doesn't skew the meter as much. For longer term use, I use Solver Oxide instead.
None of these batteries should be left in a camera for long term storage, as there's some risk of leakage and damage. However, of the different types the Zinc Air are pretty safe... very unlikely to ever leak. Silver Oxide rarely give any problem, too. Alkaline batteries are the riskiest (as were the old Mercury that were originally used).
You actually don't need to use a battery or meter at all, to shoot with the F. It's a purely mechanical camera, so can be used without any meter (or taking readings with an external, hand held meter and using those settings on the camera). This is true of many of the SLRs and rangefinder cameras of the 1970s and earlier. In the late 1970s and the early 1980s when cameras began being fitted with electronically controlled shutters, which offer greater accuracy and a wider range of speeds, but are "battery dependent". Of course, that dependence has only increased and all modern digital require a power source of some sort.
I had one years ago. If you decide to sell it. Let me know the price. I am interested. Thanks Bill
mainonite (new user) Joined: Mar 4, 2019 Posts: 2 Loc: Maine
I had one years ago. If you decide to sell it. Let me know the price. I am interested. Thanks Bill
I am looking forward to firing it up and run some film through it first
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