Replacement options for mercury batteries

Cameras designed and manufactured before 1975 very often use coin shaped Mercury Oxide batteries to power the CdS cell in charge of metering – the most common being the PX625 aka PX625 / PX13 / MR9 Mercury Cell.

Three substitutes for the PX625 battery – Wein Zinc-Air (left), Exell Zinc-Air (right), Alcaline (center)

The chemistry of those 1.35 V. batteries is based on mercury oxide. The sale of mercury batteries was banned in 1996 because of their toxicity and environmental unfriendliness, and, unfortunately for the owners of camera of the early 70s, there is no perfect substitute. For all of their drawbacks, mercury oxide batteries had two big advantages – they delivered a constant 1.35v tension across their lifespan, and if not used, they kept their charge for a very long  time (at least 10 years).

Three substitutes for the PX625 battery – alcaline (top), Wein Zinc-Air (right), Exell Zinc-Air (right) – Note the little vents on the two Zinc-Air batteries

The most common cameras using the PX625 battery were launched between 1970 and 1975: Pentax Spotmatic F, Olympus OM-1, Leica CL, Leica M5, Nikkormat FTn, Canon FTb and Canonet GIII QL, … . The battery looks like 3 coins of different diameters stacked above one another, and is rather large and thick (Diameter: 15.6 mm. Height: 5.95 mm).

The dimensions of the two Zinc-Air batteries are not exactly similar to the alcaline (or to the original PX625). The Exell in particular can’t be inserted in the Leica CL

Older cameras (like the original Pentax Spotmatic, for instance) use a smaller button (or pill) shaped Mercury Oxide battery, and more recent models (practically any camera designed and launched after 1975) use silver oxide or lithium batteries in many shapes and forms.

Possible Replacement:

  • alcaline – (LR9 or V625U) – this battery has one big advantage – it’s the same shape and dimensions as the PX625 – but it has two limitations – its nominal voltage is higher at 1.5v; and it loses voltage progressively, which makes it unfit to provide power to the meter of a camera, unless some voltage compensation circuit is built into the camera. The meter of some cameras will not work at all (Leica CL), and for most other cameras the metering will be unreliable.
  • Silver oxide –  it delivers a constant voltage across its lifespan, and can last for a few years when not in use. But unfortunately, its voltage is significantly higher at 1.55v, which again will promise unreliable metering results unless the camera or the battery container itself is designed with a voltage compensation circuit. There are three options:
    • the S625PX – I believe it’s been discontinued – it had the same shape as the mercury PX625 battery, but delivered 1.55v – it will only work as a substitute for a PX625 if the camera has a built-in voltage compensation circuit,
    • a silver oxide “386” battery (a “button” cell), inserted into a adapter with its miniaturized voltage reduction circuit – the adapter is rather expensive ($35 to $40.00). It would be an ideal solution for photographers willing to use the camera regularly- but there are fakes on Amazon (products without the voltage reduction circuit presented has products with). Only buy from a seller you trust.
    • a Silver oxide 386 battery (a “button” cell), inserted into a adapter without any voltage reduction circuit – some of the “adapters” are as simple as a rubber gasket – again, it will only work if the camera has a built in voltage compensation circuit.
Three substitutes for the PX625 battery – alcaline (left), Wein Zinc-Air (right), Exell Zinc-Air (center). The Exell does not seem to be manufactured as carefully as the Wein.
  • Zinc-Air batteries have three big advantages – they’re  used for hearing aids and are sold in every drugstore/pharmacy in the US, they release the same voltage as mercury batteries; and the voltage remains constant over the life of the battery;
    You can buy a Zinc-Air button cell and insert it in the battery compartment of the camera (it may work with some cameras). A more reliable solution is to buy a PX625 substitute assembled by a few vendors who integrate third party zinc-air cells in a container shaped as the original PX625. The best know product is the so called “WEIN Cell” but there are alternatives available on Amazon.WEIN cells are packaged in individual blisters, and are cleanly assembled. They fit physically in all the cameras I tested.  When the WEIN cells were more expensive than they are now, I had bought “compatible” cells from Exell on Amazon – they worked, but didn’t look as nicely finished and assembled as the WEIN cells – and could not fit in the battery compartment of a Leica CL. Currently,  the “compatible” cells are more expensive than the original WEIN. So why bother?A Zinc-Air batteries are powered by oxidizing zinc with oxygen from the air. Therefore, the shell of the battery has small vents that let the air enter the battery. Batteries are stored and shipped with a removable membrane that “seals” the vents and deprive the battery from the air’s oxygen. To activate the battery, you remove the membrane – but once the zinc-air reaction has started, the life of battery is limited to a few weeks at best.  Some people remove the battery from the camera after each photo shoot and reseal them, but I’m not convinced that it really helps extend the life of the battery.

As a conclusion…

The WEIN cell worked on every camera I tested. It’s a relatively expensive solution if you want to use cameras designed for Mercury Batteries on a daily basis: because of the short life of the battery once you’ve activated it,  you will have consumed a significant quantity of batteries by the end of the year.

If you’re absolutely determined to use a Leica CL or a Leica M5, I’m afraid there is no real substitute to WEIN cells. That being said you could also shoot with a Minolta CLE or a Leica M6, the experience would not be very different, and those cameras rely on Silver Oxide batteries (*).  Up to you.

Paris – A school visit at Le Louvre – Leica CL – 40mm lens.

(*) – I did not find a more modern substitute to the Canonet using silver oxide battery. The models that immediately followed (the Canon A35F and A35 Datelux) were sold well into the eighties, and still used a mercury battery. Cameras launched after the A35 are motorized autofocus compact cameras – a totally different experience. If you like cameras in the style of the Canonet, Zinc-air cells are in your future.

Storage – Netgear ReadyNAS RN 214

I’m not a professional tester of IT equipment. And this blog is primarily about film photography. But I can’t avoid addressing the issue of digital image storage: unless you develop your film in a dark room, use an enlarger and get large prints the good old way, the images on your film will be digitized at some point, will be consumed digitally, and will have to be stored and archived on digital media. Because Adobe Lightroom is more flexible than the proverbial cardboard shoebox.

Over the years, I’ve been using consumer grade storage systems from brands like Buffalo and LaCie, until I settled on a Network Attached Storage system (a NAS) from Netgear. The RN104, that I purchased in 2014, fulfilled his duties honorably until last year, when it started to misbehave: the disks got corrupted  (probably because of an unstable supply of power) and I had to restore the data from a backup on Amazon Glacier. More recently a power spike (probably due to a bad connection between the external power brick and the NAS enclosure itself) fried the motherboard and gave me an opportunity to reconsider my allegiance to Netgear, and to consumer grade NAS in general.

netgear system page
Netgear – the system admin page (overview)
Netgear ReadyNas 214

What I’m asking is pretty simple: I don’t want to store Terabytes of images on a single laptop equipped with a single drive – I want to store my pictures (RAW and jPEG) on a device accessible by the computers (PC, Mac, iPad) connected to my wireless LAN. That device has to be local – I’m using Lightroom to catalog, upload, edit and print my images, and a broadband connection would be far too slow if I used some form of cloud storage as the primary location of my pictures. That perfect device should also act as a Time Machine target for the backup of my Macs. And of course, because hard drives are inherently fragile, I want the device to offer some form of disk redundancy – ideally, it should be also be able to backup its data on a low cost, on-line archival service.

Most of the recent NAS devices (from Netgear and from competitors) meet those basic requirements. They can also stream video (they take care of decoding) and, because their OS is generally based on some Linux distribution, they can be used as multi-purpose servers (not only as file servers, but also as application servers to run Drupal, Joomla, php, or Python applications, for instance). I have no use for those features and they’ve not been part of my evaluation criteria.

Netgear – some of the applications that can run on the system
  • So, what I’m looking for?
    • a NAS,
    • solidly built (case, power supply, connector)
    • with removable drives – that can be moved to a SAN enclosure of the same family, without losing configuration or data (in case the original enclosure dies, or a capacity upgrade is necessary)
    • with good data protection (RAID 5 or better)

The Netgear RN104 met the requirements for the most part:

  • most of the issues I have encountered with my old RN104 have been power supply and power supply connector related – with dreadful consequences for the data on the disks and ultimately for the chassis itself.
  • until the big crash last year, the NAS was configured with RAID-X, the proprietary implementation of RAID in Netgear’s devices. With RAID-X one disk is reserved for parity, the other disks store data (it’s more or less equivalent to RAID 4). With Raid-X, volumes are easy to expand, but if you lose more than one disk, you’re dead in the water.
  • the Western Digital RED 1TB disks  that I bought separately for it (the Netgear chassis can be purchased diskless) proved flawless

When the RN104 chassis finally died, I considered buying a Sinology or Qnap enclosure, but I would have had to reformat the drives and restore everything from the Amazon Glacier backup, again. Sinology and Qnap are well considered on the marketplace, but seem to use the same type of external power supply brick as the Netgear, and maybe even the same dreaded power connectorUnfortunately, chassis with a built in power supply are much more expensive. 

netgear volumes page
Netgear – all 4 disks healthy – it’s configured with Raid 6 (too many drawbacks with X-RAID in comparison)

Ultimately, buying a new Netgear NAS device appeared to be the lesser evil. The RN214 unit I bought accepted my old Western Digital drives and recovered its configuration automatically from them. It was on line in less than 15 min after I had received it. Performance seems to have massively improved during the last 5 years. The new units  have a quad core ARM processor at 1.4 GHZ and 2GB  RAM, as opposed to a single core processor at 1.2 GHz and 512 MB RAM for old  model. The power brick and the connector are the same, but being new, everything clicks reassuringly and I hope they will age better than their predecessor.

netgear services
Netgear – services enabled on my system

The operating system is the same  as before (Netgear 6.10), the unit accepts the same additional applications (plus a video streaming app that could not have worked on the old unit). As before, the unit can connect to a few external cloud storage services to backup its data (but not to Amazon Glacier, unfortunately) and the Web user interface is reasonably pleasant to use. I did not have to configure this unit (the config information is stored on the disks and moves to a new enclosure when you swap the drives) but my recommendation would be to read the manual carefully if you want to configure a unit from scratch (the factory defaults are not always the best, in my opinion).

I paid $250.00 for the diskless unit (it’s discounted at the moment). Netgear also offers models pre-populated with disks. There is a good warranty on the hardware, but tech support is only available as an extra-cost subscription (storage issues can be vexing,  hard to diagnose and time consuming to fix, and I understand Netgear can’t offer free support on a device  sold for a few hundred dollars). But Tech Support won’t get your data back if your disks are too badly corrupted, so a good backup is your best friend.

Back to photography, now…

One of the oldest pictures on the Netgear – Shot in 2002 – scanned and copied from system to system ever since – Pornic – France – Minolta Vectis S1




The most read Posts of 2019

Screen Shot 2020-01-03 at 8.16.44 AM
The typical WordPress dashboard…

There is little to add:

    • I did not devote much attention to CamerAgX last year, but still had 27,000 visitors who read almost 40,000 pages. Thank you for your fidelity.
    • Stating the obvious, most (75% approximately) of the visitors were directed to CamerAgX by a search engine, predominantly Google. The rest followed links posted by contributors in forums dedicated to photography (including DPreview, surprisingly).
    • anything related to the Angenieux 28-70 f/2.6 lens or its Tokina cousins hits the top of the charts (and has been doing so for years).
    • I must have become a specialist of the Fujica 35mm SLR  cameras of the  seventies and early eighties – Fujica related pages are #2, #3, and #9 on the list of most read blog entries – truth to be told there is very little written about those cameras over the Internet – people interested in the subject have little choice outside of this blog.
    • Two of my favorite brands (Nikon, Olympus) round up the top ten. Canon cameras are not represented – I only started writing about Canon film cameras rather recently, and the field is so crowded it’s difficult to be noticed by the search engines
    • Lastly, most of the visitors of this site live in the Anglo-Saxon world – with readers from Non-English-Speaking European countries (Germany, Italy, France, Netherlands) rounding up the top 8.

Your comments are appreciated as always.

Happy New Year


Paris –  Shot from the Pont Neuf -Minolta 7xi – Angenieux zoom 28-70 F/2.6 – Fuji Velvia (July 1992)

The iPhone 11 and the power of “computational photography”

Photo and Video have become major differentiators in the world of smartphones – and the three-way competition between Google (Pixel), Samsung (Galaxy) and Apple (iPhone) has led to huge improvements in the last few years. Each new generation is markedly better at making pictures than the previous one.

A few weeks ago, I could not resist any longer, and took advantage of a promotion of my favorite carrier to buy the brand new iPhone 11 for $350.00 – I just had to surrender my old iPhone 7 in exchange. The truth is, I needed more internal storage, but I also wanted to see whether the new camera was as good as promised.

iPhone 11 – sunset at the pool

And I was not disappointed. The photo section of that thing is incredible. Simply having access to any focal length between the ultra-wide (13mm equiv.) and the wide angle (26mm equiv.) at full resolution, with a digital zoom to bring you a bit closer to the subject if you need it – is literally a game changer: how often have amateurs access to a  13-35mm zoom lens on their full frame digital camera?

Of course, with a 12 Megapixel sensor and a “normal” lens limited to the equivalent of a 26mm wide angle, it can’t beat a medium format digital camera for large prints, or a DSLR with a fast telephoto lens for sports photography. And because of the way Apple has tuned noise reduction and HDR, the pictures are a bit light on contrast to my taste, but that’s nitpicking.

For subjects which are considered “normal” for an amateur photographer: selfies, family shots, portraits, street photography, urban landscapes, interiors, and for the “normal” destination of most of today’s pictures  (instant messaging, social networks, on-line photo galleries, prints up to 11x 8) it’s so good that I doubt I could get better pictures out of camera with any of the digital cameras I own.

Even if I spent big money on the latest and greatest full frame mirrorless camera, bought more lenses, and dedicated a lot of time to practicing and testing in order to seriously step up my technical game, I’m still not sure I would get significantly better results out of camera than what this iPhone gives me effortlessly. (*) (**)

So is the power of “computational photography“…

Very high level, an iPhone takes many different versions of the same shot (just before and just after you press the shutter release), with different focus and exposure settings, and uses artificial intelligence to decompose the image in sections (main human subject, background, sky, …). Each segment of the image is then optimized (exposure, contrast, noise reduction, focus, white balance…) and integrated into the “final picture” presented on the phone’s LCD. They call that “semantic rendering”.

All of this happens in a fraction of a second – the iPhone’s processor is a 64 bit / 6 core chip with a “machine learning accelerator”, and it can process 1 trillion operations per second.

Canon, Nikon and Sony don’t disclose many details about the architecture of the electronics of their top of the line cameras – but I doubt they have anything that even remotely compares to the processing power of the best of the smartphones.

iPhone 11 presentation – the processing pipeline of an image – segmentation is what’s new.

Ultimately, “amateur photography” is about the pleasure of taking and sharing pictures.  I’ve been so pleased with the iPhone’s pictures that I’ve not used any other camera (digital or film) since I bought it. The novelty will wear off, and at some point, I’m pretty sure I’ll get tired of a “neural engine” making “semantic rendering” decisions for me. I’ll want my pictures to be really mine, not a quilt of segments massaged by an algorithm running on a chip with 8 billion transistors. Maybe I’ll just go back to black and white film, and process the images in a dark closet at home.

In the meantime….

Happy New Year.

Out of the camera pictures taken on the iPhone 11 – minor adjustments in the iPhone’s photo app.

Florida – Sunset at the pool – iPhone 11


Las Vegas – the Paris – iPhone 11 – with the 13mm equiv. Wide Angle lens


Las Vegas – Night scene (iPhone 11 with optical image stabilization, handheld)
Las Vegas – Mandalay Bay hotel. Interior Photography – iPhone 11
Las Vegas – Street Photography – iPhone 11
iPhone 11 – portrait mode. at night, at the terrace of a restaurant
Florida – Landscape at sunset – iPhone 11 –


(*) Of course, the key restriction here is “out of camera” – with the help of Lightroom, and a set of Lightroom plug-ins, a recent full frame digital with a good set of lenses beats an iPhone – but we’re not in the realm of candid amateur photography anymore.

(**) I don’t do videos. But I’ve read multiple comparative reviews of the iPhone 11 opposed to good mirrorless cameras: for still images, a dedicated camera will ultimately yield better results than Apple’s latest smartphone (think large prints, action photography, …) – but for videos there is no discussion that the iPhone – because it has enough processing power to enhance each individual frame in a real time – is the better widget.

More about Apple and computational photography

DP Review’s preferred “analog gems”

After Thom Hogan’s list of Nikon Classics, another list, this time coming from no other than dpreview.

The “DP” in dpreview stands for “Digital Photography” of course, and the site was launched in 1998, at the beginning of the digital camera craze. And they’ve never reviewed a film camera. As far as I know. But over the years, they compiled two lists of recommended,  “excellent and affordable” film cameras, the first one in 2017, with a follow up in June 2019.

A few of the cameras listed as “analog gems” by DPreview have been presented in this site over the years (the Nikons FE2, N90, the Olympus OM-1 and the Canon T90). Very often, my preference goes to other models of the same family (I prefer the Olympus OM-2 to the OM-1 because its battery is much easier to find, the Canon AT-1 to the AE-1 because I’m not a fan of shutter speed priority automatism, and the EOS-620 to the EOS-5 for its simplicity).

Nikon FM
Nikon FM

I’ve never been a fan of compact cameras in the days of film (poor viewfinder, not enough controls for the photographer). Their only advantages were their small size and their ease of use, but a film SLR with a pancake lens was not much larger and delivered much better images. And today, why would you spend money on film and processing to use a compact camera which will give you less control over your images than a good smartphone?

My absolute favorite? The ones I would bring on the proverbial desert island (assuming the desert island has no electricity, no Internet access but a huge stack of film cartridges waiting for me)?

Canon T90 – the ergonomics of an EOS camera with an FD lens mount
  • a compact, mechanical, semi-auto SLR – not the Olympus OM-1, not the Pentax MX, but the rugged and supremely reliable Nikon FM. The FM2 is probably an even better camera, but it’s also more expensive.
  • the most elaborate pre-autofocus SLR, the Canon T90, for the looks, the ergonomics, the crazy exposure system, with no concern for its questionable reliability or its mass, because I would always have the Nikon FM as a backup.

And of course, when I would be back from the desert island, I would reconnect with my cherished Nikon FE2…


“La Maison aux Bambous” – Bed and Breakfast – Vinay (France). Canon T90 – Canon FD 24mm – Fujicolor 400.

Thom Hogan’s preferred Nikon “classics”

Thom Hogan has been on the Web forever, it seems. He’s a pro photographer, has a background in marketing and product planning, and he also teaches, I believe. He’s been  publishing very detailed user guides for Nikon cameras for ages, and his collection of Web sites (;, is always an interesting read, not only for users of Nikon equipment, but also for anybody who wants to understand the market forces shaping the photo equipment industry.

A few months ago, Thom wrote a short piece about future Nikon classics (collectible cameras that are still usable and will hold their value in the future):

He has much more experience of Nikon cameras than I do, and my tastes have been – at least in part – formed by what I read in his books and Web pages over the years. So I won’t say “I’m right, he’s wrong”. Let’s be honest: if there’s such a thing as being right in photography, the odds that he is are much higher than mine. But sometimes I simply beg to differ.

Film Era:

Thom’s list includes some cameras that grace my personal collection, even if they’re not my preferred in Nikon’s range. The F90/N90 is extremely efficient, but a bit too automatic for me, and the F4 is really too heavy to be used anywhere but in a studio. I never used the F100 or a F5 (too modern for me – I tend to like my film cameras with a conventional user interface – you know, knobs instead of LCDs and control wheels).

Which leaves us with the last entry of his list, the FM3A.

The FM3A is an evolution of the FM2/FE2 cameras, with a dual shutter control mechanism (electronic and mechanic) – which offers the best of what the FM2 (mechanical) and the FE2 (electronic with On the Film TTL flash control) can offer. I don’t own a FM3A, but two of its direct ancestors are at the top of my list: I use my old FM relatively often – because it’s a rugged camera and I know it’s going to work no matter what. The FE2 is a peach (it oozes quality, and it’s so pleasant to use) – one of the  very best film cameras ever.

Nikon FE2
Nikon FE2

Digital Era

You can collect “classic” cameras for their beauty and  for their importance in the history of the industry or a brand, but to me, a camera I can’t use to take pictures doesn’t qualify as a classic – it’s at best a “curiosity”.

In my opinion, early digital cameras are not really usable anymore, primarily because of their very limited dynamic range and very low resolution. If I brought one to cover a photo opportunity, I would most probably end the day disappointed and frustrated for having missed what could have been a great shot because of the technical limitations of the camera. Or I would have put it back in the bag, and used an iPhone instead. That’s why there is no early digital camera in my collection.

I recognize the importance of cameras like the D1h or the D100 in the evolution towards modern digital photography, but I will not add them to my collection. On the other hand, I believe that cameras like the D3 and D3X are still perfectly usable, but because they’re so big and heavy, I would ignore them, and buy their little brother,  the D700 instead. Admittedly it’s still a big and heavy camera,  but its performance is still exceptional, and with it I can use all the  Nikon (and Nikon-compatible) lenses I own.

Because I’ve been using Nikon cameras for so long, I find the D700 very intuitive and rewarding to use, and even today, the quality of the pictures that the 12 Mpixel sensor produces is incredible (in particular in low light or high contrast situations).

Nikon D700 – a classic

It may be too early to add a D850 to a collection of classics, but it will most probably be the last enthusiast / pro DSLR from Nikon – the future is clearly mirrorless. They may launch a D6 for the Olympic Games next year (who knows) but I doubt they will keep on developing the D800 series beyond the D850.

Atlanta – World of Coke – Nikon D700
My always available and patient models – the performance of the camera in low light and with multiple light sources of different color temperatures is simply incredible. Nikon D700 – Nikkor 28-70 f/3.5-4.5 AF – 3200 ISO.

Back to the keyboard…

I have not abandoned this blog – I’ve just been pretty busy lately (a new job, a house renovation going on, and my Netgear ReadyNAS RN104 crashing again – I simply hope I won’t have to restore 2 TeraBytes of images from Amazon Glacier again).

The review of the Canon AT-1 that I published yesterday had been in the works for six months, and there will be more Canon related pages in the coming weeks (I found a restored Canonet QL17 in an antique show – maybe it’s going to make me more comfortable with rangefinder cameras – I brought my old Leica CL back in service to have a point of comparison). I added two old mirrorless (digital) cameras and a strange pancake lens to my Fujifilm arsenal, and I’m trying to spend more time with my favorite SLR, the Nikon FE2 and with Kodak’s Porta 400 film.

Rottenwood Creek, Atlanta –  Canon AT-1 – Lens Canon FD 24mm f/2.8

So… compact rangefinder cameras, Nikon SLRs and dSLRs, early Fujifilm mirrorless cameras, Kodak film, you’ve got an idea of what I’m working on.

Please come back regularly, or follow my updates on twitter @xtalfu.

Miami- Wynwood  -Street art – Unknown tourists – Leica CL – Fujicolor 400.