Canon F-1 and batteries- MR-9 adapter or modification?

I've recently acquired two original Canon F-1 bodies and I'm trying to decide which route to take. I've heard good stuff about the C.R.I.S. Camera MR-9 adapter, but I've also read that it leaves the battery cover sticking out. I'd also read that the F-1 couldn't be modified for 1.5v batteries but then I read elsewhere that a resistance diode can be added to drop a 1.5v to the 1.35v required. Can anyone weigh in on either option, which is best etc.? My gut feeling is that an adapter would be better than camera surgery but wanted to hear from folks with more knowledge than me!

If the modification is indeed possible, is it reliable long term? (interested in the long term reliablility of the MR-9 too!) And does anyone know of any reliable camera techs performing it? Ideally I'd get it done at the same time that I have the bodies CLA'd.

Also, if anyone can report on the MR-9 adapter, does it indeed stick out of the bottom plate? and if so, how much? Thanks to all in advance!

A search should come up with several options.

When I got my F-1n, I did the same search and settled on buying hearing aid batteries (675) and using a rubber o-ring to hold them in place. I seem to be replacing the battery a couple of times in the run of a year, but the batteries are cheap and didn't require any modifications. The battery cover fits the way it should.

So the hearing aid battery is a 1.35v then? What o-ring did you use...size etc.? I think I saw a mention of that option but what I found didn't go into enough detail to tell me much!

Aah, just looked 'em up. Have you found any difference in the metering accuracy with the 1.4v 675 vs a 1.35v battery such as the Wein Cell (an option that I've ruled out due to reports of a very short lifespan)

The battery is 1.4V and works fine. For o-rings, I just went to the store and bought a package that had some small o-rings in it. It was a repair kit for Moen faucet. If you have a plumbing store that sells loose o-rings, just get the smallest that fits over (around) a 675 battery.

Jon Goodman (interslice on eBay) sells an adapter which takes the 675 hearing aid battery and exactly mimics the shape and size of the 675 housing. This is an advantage over the 0-ring approach for cameras that have unusual locations for the contacts.

Jon is really helpful - his main claims to fame are his camera light seal kits.

No connection, just a satisfied customer, etc., etc.

EDIT: The hearing aid batteries use exactly the same battery technology as the Wein cells. Jon's adapter or the o-ring approach give you what is essentially a Wein cell with interchangeable very cheap hearing batteries. They give relatively short life, but it's easy to find them and a dozen are often less than one single silver oxide cell.

Do those batteries require drilling a hole in the battery cover? I read that the technology of those batteries required air for the battery, and read that some had drilled holes in their battery covers.

I wrap a 675 hearing aid battery in a metal split washer of the right size. It works great. Much, much better than Wein cells, which IME are terribly inconsistent, short-lived, and expensive. My meters never matched between camera bodies or my hand held light meter when using Wein cells. They always do with the 675's. I have two F-1's and two FT-bs, and they have never matched so well since the discontinuation of the proper batteries. You can get large multi packs of the 675's for very little money.

FWIW, I didn't make up this technique or read it on the Internet. The way I learned of it was from my camera repair person, when I asked him to modify my cameras to take 1.5V alkalines. He said there was no modification necessary. The only drawback is shorter battery life (about 6 months).

However, I feel that the battery issues with the PX625's are a blessing in disguise. The batteries are not needed at all for the mechanical bits of the camera to work properly; they are only needed for the light meter. Not having an in-camera meter will force you to think about lighting constantly, and to rely on experience and/or external meters, which will give you better results by far than any in-camera meter ever made, IMHO. I keep the batteries in as a backup, though I really have not used the camera meters all that often. I check them on a grey card against my spot meter every now and then to make sure they are still fine, so I can rely on them if I need to. They always are, until they aren't, then I replace them for cents, rather than dollars like with Wein cells.

I'd suggest investing in a good incident meter instead of worrying a lot about the ones in your cameras.

It is interesting that the 675 batteries are also zinc-air, or whatever it is called. I had nothing but [expensive] trouble with Wein cells, and no trouble whatsoever with the 675's.

Sounds like the Wein cells are definitely out! I do have both a reflected/incident and a spot meter than I can use for off-camera metering, but I do often use in camera metering...when I want to travel light or I'm trying to grab a fleeting shot.

mtngael said:

I've recently acquired two original Canon F-1 bodies and I'm trying to decide which route to take. I've heard good stuff about the C.R.I.S. Camera MR-9 adapter, but I've also read that it leaves the battery cover sticking out. I'd also read that the F-1 couldn't be modified for 1.5v batteries but then I read elsewhere that a resistance diode can be added to drop a 1.5v to the 1.35v required. Can anyone weigh in on either option, which is best etc.? My gut feeling is that an adapter would be better than camera surgery but wanted to hear from folks with more knowledge than me!

If the modification is indeed possible, is it reliable long term? (interested in the long term reliablility of the MR-9 too!) And does anyone know of any reliable camera techs performing it? Ideally I'd get it done at the same time that I have the bodies CLA'd.

Also, if anyone can report on the MR-9 adapter, does it indeed stick out of the bottom plate? and if so, how much? Thanks to all in advance!

Click to expand...

I don't mean to hijack the thread, but this is a related question. May I ask if anyone knows if the same battery issue happens with the A1 (not an ae-1, but the A1)? I ask because shots I take on my Pentax K1000 generally have a correct exposure but I'm finding the shots I take on my Canon A1 to be generally brighter than those taken on the K1000 in similar conditions. If so, would someone be so kind as to point me in the direction of how to compensate or adjust the camera? Thank you!

The A-1 (like the AE-1) uses a PX-28 battery. The PX-28 is a currently available battery. There are a number of versions available - alkaline, silver oxide and, I believe, lithium. As I understand it, the Canon A series cameras will function equally well with the alkaline and silver oxide variants, with the silver oxide version lasting much longer. The lithium version didn't exist when the A-1 was being manufactured, so I don't know whether they are compatible.

When you refer to your A-1 shots being "brighter" I'm assuming that you are referring to prints or scans. The differences between the cameras may be due to your metering technique and/or the differences between the metering sensitivity patterns for the cameras (e.g. the Pentax may be metering more of the sky than the A-1). Alternatively, one or both of the cameras may be out of calibration.

You can adjust the exposure by adjusting the ISO (ASA?) setting on the cameras. To make your prints darker on the Canon, increase the ASA setting. You will need to experiment to find the right amount, but if you wish to use the Pentax as your target, I'd suggest using both cameras to take reading off something like a blank wall illuminated by the sky on a cloudy day, and then adjust the ASA on the Canon to make those readings match. Then note how many "stops" you have adjusted the meter for.

I'm glad I bought a box of Mercury cells while I still could. Still have some still in package and they still work... Must still be some more around.

The Wein 625 is a 675 with a washer on it as mentioned. If you can't find the correct sized metal washer, you can buy a Wein 625 and take the washer off when you are done. The 675s can be found frequently for less then a dollar a piece.

MattKing said:

The A-1 (like the AE-1) uses a PX-28 battery. The PX-28 is a currently available battery. There are a number of versions available - alkaline, silver oxide and, I believe, lithium. As I understand it, the Canon A series cameras will function equally well with the alkaline and silver oxide variants, with the silver oxide version lasting much longer. The lithium version didn't exist when the A-1 was being manufactured, so I don't know whether they are compatible.

When you refer to your A-1 shots being "brighter" I'm assuming that you are referring to prints or scans. The differences between the cameras may be due to your metering technique and/or the differences between the metering sensitivity patterns for the cameras (e.g. the Pentax may be metering more of the sky than the A-1). Alternatively, one or both of the cameras may be out of calibration.

You can adjust the exposure by adjusting the ISO (ASA?) setting on the cameras. To make your prints darker on the Canon, increase the ASA setting. You will need to experiment to find the right amount, but if you wish to use the Pentax as your target, I'd suggest using both cameras to take reading off something like a blank wall illuminated by the sky on a cloudy day, and then adjust the ASA on the Canon to make those readings match. Then note how many "stops" you have adjusted the meter for.

Click to expand...

Thank you for your kind reply. That tells me *exactly* what I need to know-- it's not an issue of mercury vs silver oxide cells. I will do just that and try to figure out the compensation necessary now that I understand it is not a set factor related to voltage output of the battery. My apologies to any and all for the momentary derailment of the thread.

John

The A-1 also has an exposure compensation dial that can be used to temporarily increase or decrease exposure without changing the ISO setting. In fact, that should be on the highlighted "1" arrow for normal use -- is it?

DWThomas said:

The A-1 also has an exposure compensation dial that can be used to temporarily increase or decrease exposure without changing the ISO setting. In fact, that should be on the highlighted "1" arrow for normal use -- is it?

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It is indeed. I think it's overexposing slightly. Ektachromes shot in both the Pentax and the Canon show a difference-- Pentax is more pleasing to the eye at the same settings as the Canon. Underexposing with the Canon by 1/3 to 1 stop produces similar results, but I haven't done a more exact test to determine the difference between the two. My friend suggested using an external light meter and testing comparing the readings between the two cameras to the reading of the light meter. I will try that with the knowledge that the results from the Pentax are what I'm shooting for. Maybe I can devise a mathematical equation to equate the exposures and if necessary have the Canon calibrated to match the readings of the Pentax. Thank you as well for your reply. I really appreciate the help!

John

Interesting that the extra .5v of the 675 batteries doesn't make a difference in meter accuracy but one more volt does! I found 675s at the local supermarket at $10.99 for an 8 pack. Definitely more economical than the Wein cells!

Am I correct in believing that unlike the old mercury batteries, which maintained a steady voltage till death, that the 675s would gradually fail, and thus start giving meter inaccuracy with the dropping charge? I'd probably just replace them at a set interval anyway but my geek side is interested.

Thanks for all the info!

Good morning, Mtngael;

There is one characteristic about the Silver-Oxide battery that makes it the best choice generally as a replacement for the old Mercury battery -- the voltage discharge curve as it goes from new to fully depleted or used up. The old Mercury battery had a very flat discharge curve; it stayed at the same voltage as it was used up, right until the very end, where it had a sharp "knee" and the voltage suddenly dropped from its standard 1.35 VDC to going down to the bottom at zero. The Silver-Oxide battery has a very similar flat discharge characteristic, but a slightly higher voltage of about 1.50 to 1.55 VDC. This 0.15 VDC difference can induce an error in many of the older light meter circuits which expect to see a constant 1.35 VDC power source at a very low current draw. The MR-9 Battery Adapter adds a Schottky Barrier diode in series with the Silver-Oxide battery. The normal V(sub f) or Forward Voltage Drop rating of the Schottky Barrier Diode at this current level will be around 0.15 VDC, so it provides almost a perfect compensation for the higher nominal voltage of the Silver-Oxide battery for the light metering circuit.

The only real criticism I have about the MR-9 Battery Adapter is the $40 price. When you have a lot of old cameras, this can add up. One cost effective way to work around this is to just get some small Schottky Barrier Diodes of almost any voltage rating -- we are going to be using it in its forward biased mode in a very low voltage circuit -- and putting the diode in series with the terminal on the battery holder in the camera and the wire that was going to that battery holder terminal. If you can do this yourself, it will save you a lot of money by then just putting in the Silver-Oxide (Ag-O) battery in the camera battery socket with any required additional mechanical positioning ring to hold it where it should be. The anode end of the Schottky Barrier Diode should go toward the Positive or Plus Terminal of the battery, or the cathode end of the Schottky Barrier Diode should go toward the Negative or Minus Terminal of the battery. The opposite end of the diode not connected to the battery terminal should go toward the light metering circuit wiring.

I have the MR-9 for my F-1n and the silver oxide battery and it works very well for me.

mtngael said:

Interesting that the extra .5v of the 675 batteries doesn't make a difference in meter accuracy but one more volt does! I found 675s at the local supermarket at $10.99 for an 8 pack. Definitely more economical than the Wein cells!

Am I correct in believing that unlike the old mercury batteries, which maintained a steady voltage till death, that the 675s would gradually fail, and thus start giving meter inaccuracy with the dropping charge? I'd probably just replace them at a set interval anyway but my geek side is interested.

Thanks for all the info!

Click to expand...

The 675 hearing aid batteries are zinc-air technology, so they too maintain a steady voltage until discharge.

The difference is that they don't nearly as much capacity as the mercury batteries, and they have a tendency to lose capacity even when not under load. So they don't last as long.

I have been using F-1 cameras for about twenty years. When I ran out of mercury batteries, I went to the CHRIS MR-9, and my meters stayed accurate, across the scale.

Later I had Ken Oikawa, former Canon technician and F-1 specialist, tune up an F-1n body. He converted the camera to use a 1.5 volt 625 battery. This is the standard conversion that Canon recommended. But this left the meter accurate only in the middle of the scale. It called for underexposure in high light values, and overexposed in low light values. Ken then studied an MR-9 converter with the camera, adjusted the meter for that, and concluded that in fact the meter was indeed more accurate across the scale with the MR-9 adapter.

So I have concluded that for me it is totally worth the price of an MR-9 adapter to provide an accurate, dependable meter on such a fine camera.

jmcd said:

So I have concluded that for me it is totally worth the price of an MR-9 adapter to provide an accurate, dependable meter on such a fine camera.

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I would agree if I had only one camera to fill with batteries. But with the number that I would need (sometimes I shoot three cameras at once of I am on a trip), I could buy an excellent light meter (or two), and get better exposures to boot.

I don't even really bother to fill my old Canons or Nikons with batteries any more. Every now and then, I decide I should go ahead and put batteries in. But most of the time, if I decide that I would benefit from an in-camera meter, I just bring my compact and lightweight AE-1P, and use that to meter for all the cameras. (I also carry a 4x5 gray card with me.) I got two AE-1Ps for $45 shipped, each with a clean 50mm f/1.8 lens. That is as much as one of those adapters.

If the battery adapters were $10 instead of $40, I'd get at least five of them. And if I only had one camera that I used regularly, I'd pay the $40. But neither of those are the case.