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Original voltage without modification: Zinc-air batteries (type 675) drop to ~1.35V under the minimal load of a CdS meter—exactly the voltage of the original PX625 mercury cell. Flat discharge curve without drift: your light meter will measure accurately again.
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One adapter for all contact types: The conductive plastic establishes contact regardless of the geometry, whether your camera draws power from the side, bottom, or top. No trial and error.
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Runs on type 675 batteries from drugstores: Available at dm, Rossmann & Co. and online, in packs of 6 for under EUR 3, instead of a discontinued specialty cell.
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Ready to use right away: 2 adapters + 6 batteries in the standard set—unpack, insert, and take photos. No additional purchase needed.
Compatibility
Suitable for various cameras, including:
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Canon: Canonet series (QL17, QL19, 28, G-III), F series (F-1, FT, FTb, FX), Demi / Dial series [...]
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Nikon: F series (F, F Photomic, FTN), Nikkormat / Nikomat series (FT, FTN) [...]
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Minolta: SR-T series (100-303, MC, SC, Super), SR series (1, 7, 100-505), Hi-Matic series (7, 7S, 9, 11) [...]
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Olympus: OM-1 series (OM-1, MD, N), 35 series (RC, RD, SP, DC), Pen series (F, FT, D2, EED) [...]
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Pentax: K series (K2, KM, KX), Spotmatic F, H series (H1a, H3v) [...]
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Rollei: 35 series (35, 35S, 35T, Classic), SL35 series (SL35, SL35M, SL350), XF35 / A26 [...]
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Praktica: MTL3, super TL / super TL 1000, MTL5, LTL / LTL3 [...]
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Leica: M5, CL / Leitz Minolta CL, Leicaflex series (Standard, SL, SL2), MR / MR4 light meters [...]
Are you unsure whether the battery fits your camera?
Here is a complete list of all cameras compatible with the PX625 battery type.
Scope of delivery
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Standard: 2x PX625 adapters, 1x battery pack (type 675)
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Double pack: 2x standard sets (4x PX625 adapters, 2x battery packs, type 675)
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Set: Standard + 1x light seal set Universal including mirror damper
Technical details
- Material: Conductive technical plastic
- Compatibility: Replaces PX625 / MR-9 / PX13
- Battery system: Enables the use of PR44 / 675 zinc-air batteries (1.4V)
- Fit: Universal (side and bottom contacts)
Description
This PX625 adapter, also known as an MR9 adapter, replaces the PX625 mercury battery that was standard in many analog cameras from the 1970s through the 1990s. It holds a standard 675 zinc-air hearing aid battery, which drops to ~1.35V under the low load of a CdS light meter—exactly the voltage of the original PX625. Suitable for, among others, Canon Canonet and F-1, Nikon F, Minolta SR-T, Olympus OM-1, Pentax Spotmatic F, Rollei 35, Praktica MTL, and Leica M5 and CL.
The adapters are made of conductive plastic and therefore work in almost all cameras, regardless of whether the battery contact is made from the top, bottom, or side. Since the EU ban on mercury cells, there has been no direct replacement. Alkaline (LR44) batteries provide 1.5 V, which is too high and fluctuates, while silver oxide (SR44) batteries are stable at 1.55 V but are also too high.
Practical tips
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Activation: After removing the protective film, wait 1–2 minutes before inserting the battery. The cell needs oxygen to activate.
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Storage: Unopened batteries last 2–3 years. Only remove the film when you actually need the battery.
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Battery check: Some cameras (e.g. Olympus OM-1, Minolta SRT) have a battery-check function calibrated for exactly 1.35 V. With zinc-air batteries, it may sometimes indicate “weak” even though the battery is fully charged. This is normal. The light meter still works correctly.
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Replacements: Type 675 batteries are available at any drugstore (dm, Rossmann & Co.), in pharmacies, and online. You are not tied to a specialist supplier.
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Leica M5: The M5's battery compartment is narrower than those of other PX625 cameras, so the screw cap often will not close with an adapter installed. In the M5, simply insert the Type 675 cell without an adapter: The cap screws in far enough to make secure contact with the smaller cell.
Frequently asked questions
“How can a plastic adapter provide the correct voltage?”
The voltage comes from the battery, not the adapter. Under the tiny load of a light meter, the Type 675 zinc-air cell delivers around 1.35 V—exactly the value your camera is calibrated for. The adapter merely brings the smaller cell to the size of the old PX625 and establishes contact. To make this work with contact from the side as well, it is not made of ordinary plastic but of a conductive material. The current flows through the adapter.
“Zinc-air batteries dry out. They only last a few weeks, right?”
Correct: Once you remove the protective film, the cell starts working. In a hearing aid (which has a consistently high power consumption), a 675 cell lasts 5–12 days. In a camera, consumption is orders of magnitude lower: a CdS light meter draws microamps, and only while actively metering. This means the batteries last 2–3 months. At a unit price of under EUR 0.50, that is an acceptable trade-off.
“1.4V isn't 1.35V—will my exposure meter give incorrect readings?”
1.4V is the nominal voltage under standard load. Your camera's CdS exposure meter draws so little current that the voltage drops to ~1.35V. The difference from the original is no more than 0.05V. This corresponds to approximately 1/3 of a stop. Negative film tolerates 3–5 stops of overexposure without any visible loss in quality. With slide film, 1/3 EV is barely noticeable in practice.
“Can moisture from the zinc-air battery damage my camera?”
Zinc-air cells use oxygen from the air as the cathode and contain a small amount of electrolyte. The theoretical possibility of moisture release exists, but in practice it is irrelevant when used in cameras. Hearing aids sit directly in the ear canal and are much more sensitive to moisture than a camera's battery compartment. Thousands of photographers have been using this solution for years without any problems.
“Why not just insert an LR44?”
It works, but not without consequences. A 1.5V alkaline battery in a CdS meter calibrated for 1.35V results in systematic underexposure. With some cameras, by up to two stops. Alkaline voltage also fluctuates significantly over its service life (1.6V when fresh, 1.2V when empty). This makes meter readings unpredictable. Silver oxide (SR44, 1.55V) is more voltage-stable, but still too high. Zinc-air, on the other hand, has a flat discharge curve like the original mercury cell, with no drift over its service life. The zinc-air adapter is the only passive solution that delivers the correct voltage.
“What about Wein-Cells and other cells in the PX625 format?”
There are zinc-air cells manufactured directly in the PX625 format (e.g. Wein-Cells), using the same chemistry as hearing-aid batteries, just in a different housing. The advantage of our solution: You can get Type 675 cells everywhere (drugstores, pharmacies, online) and pay a fraction of the price per cell.
Want a rechargeable solution?
For anyone who doesn't want to keep replacing disposable batteries: we developed the PX625 rechargeable battery with USB-C charger (V80H). A NiMH rechargeable battery with an operating voltage of 1.25–1.30V, rechargeable via USB-C. Buy it once and use it for years.
Want to learn more about voltage and exposure metering?
In our FAQ article about batteries and adapters for analogue cameras, we explain all the alternatives in detail, including voltage comparisons and when each solution is the right choice.
