Oh! Now I understand. You are right, the correct comparison would be to check the voltage with and without the adaptor, but always with the 10k ohm resistor.
MR-9 Adapter 1.55V to 1.35V
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Oh! Now I understand. You are right, the correct comparison would be to check the voltage with and without the adaptor, but always with the 10k ohm resistor.
Yes, but as I noted upthread a bit, a few tenths of a volt one way or the other isn't going to make much difference. These old meters are not all that accurate in the first place and they are also notably nonlinear - they don't track perfectly at very low- or very high light levels.
For example, I've used these adapters and/or have recalibrated old Luna Pros so they can use modern batteries. In both cases the top of the low light scale does not match the bottom of the high light scale no matter what you do. Similarly, the old Yashica 124G meters were never great in the first place. Their end of scale error will be far greater than a small battery variation.
Probably the best meters I've seen (that I've used these adapters with) are the Nikon F Photomic FtN heads ... when they work. Some of them need cleaning and some of them need brand new resistor rings.
Even with modern meters, you get a vary degree of variation in accuracy. If I compare a Nikon F3 meter, a Pentax spot meter, and a Sekonic handheld Spot/Incident meter - all very good metering systems - I get as much as a stop variation. So ... you have to calibrate your exposure discipline for your own particular meter. As long as it is "off" by a consistent amount, you can correct for that by dialing in an appropriate amount of ASA offset. Some cameras even have +- correction you can permanently set to account for metering.
I shoot a lot of sheet film and those old leaf shutters are all over the place in accuracy. So in addition to correcting my meters, I have to account for slow shutters speeds.
The point is that a few tens of a volt simply aren't going to mean all that much in the scheme of all the thing that influence exposure calculation. Just be sure to use silver oxide batteries (which fail all at once, not by slowly dropping voltage like an alkaline ..... which DOES affect light measurement).
You can also look at something from this guy. I have done business with them an bought several of his cube meters and they work fine. One nice feature is that they have an offset adjustment so you can make that meter read the same as a known good meter. I set that immediately to match my other meters:
https://www.reveni-labs.com/
I use 2 of these adapters (the CRIS ones) with silver oxide cells in (a) a Rollei 35 and (b) a Metrastar exposure meter. In both cases the indicated exposure is identical (within 1/3 stop) to that indicated by my Leica M6, across a wide range of light conditions.
Since we are now five days into our M9 adapter adventure, why don't you take a risk and insert the battery and adapter in your camera, and compare the meter readings with one of your other cameras or a light meter. Let us know what you find.
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I agree, just use the adaptor, instead of tieing yourself in knots worrying about it, because I have been using 2 of these with my 2 Canon F 1n cameras for over 10 years and they work perfectly.
If the adapter is not working properly he will know by comparing it to his other meters/cameras with built-in meters. Just seems easier and less expensive than getting a better voltmeter and pile of different resistors as some have suggested.
On the basis of this thread, I took a new MR9 and battery to confirm what I already knew - that the voltage does not drop to the proper level until the adapter is under load. I simply put a resistor across it to force current through the device, and, voila, the voltage jumped right where it needed to be.
There is a diode in an MR9 that essentially does nothing until current flows through it. When it does, the diode's semiconductor properties will deliver the necessary voltage drop.
But here's what the real takeaway should be. No two built in meters will have the exact same current draw, and that draw will vary slightly with lighter- or darker subjects. So no matter what we measure at the adapter, it really isn't that important.
What's important is to use the adapter across a variety of lighting situations and compare the results against a known good meter. (They will likely differ somewhat because these older meters that need the MR9 were not super accurate when new.) Then adjust your exposure discipline accordingly.
With this kind of stuff, we do not seek accuracy, we seek repeatability.
There is a diode in an MR9 that essentially does nothing until current flows through it. When it does, the diode's semiconductor properties will deliver the necessary voltage drop.
But here's what the real takeaway should be. No two built in meters will have the exact same current draw, and that draw will vary slightly with lighter- or darker subjects. So no matter what we measure at the adapter, it really isn't that important.
What's important is to use the adapter across a variety of lighting situations and compare the results against a known good meter. (They will likely differ somewhat because these older meters that need the MR9 were not super accurate when new.) Then adjust your exposure discipline accordingly.
With this kind of stuff, we do not seek accuracy, we seek repeatability.
" A man who has one clock always knows the time, a man with several is never sure".
Considering that these adapters have been in use for a couple of decades, it’s great to finally get confirmation that the designers knew what they were doing and the device works!
But what makes you think “these older meters” weren’t super accurate when new?
Accuracy is important, but not that important. I mean if your adapter only drops voltage to 1.40V instead of 1.35V, you need to be able to deal with that constructively, i.e., ignore it. I mean the difference is only some small fraction of a stop. You are only going to be able to change shutter speeds in one stop increments. There are a couple of cameras that you can set shutter speeds continuously between stops, but you don't know exactly where. And shutter speeds are not dead accurate. The faster shutter speeds can be up to 30% slow and still meet spec. And, depending on the lens, you only have click stops for full stops, half stops a third stops. Of course, you can set the aperture between stops, but you really don’t know where. Get things reasonably accurate and get on with it.
All of that plus ... these meters were never that accurate in the first place. It wasn't until the advent of digital spot meters that light metering got to be more linear and absolutely correct, and even those can show errors against a standard in some cases.
As I've said before, the OP should put the MR9 into use, compare it to a known reference and call it a day. Hand wringing over the exact precision of an inherently imprecise measurement instrument is a waste of time. It's like people doing "math" with inputs that have one digit of precision put publishing results out to 9 decimals ...
Because they weren't. I have 4 different Nikon bodies with meters built between the mid 1950s and 1973. I have a Yashica MAT 124G with its original meter. I have three Luna Pros that I've recalibrated for new batteries or use with MR9s. All of these are less sensitive, and less linear that modern meters. Even when calibrated against a known standard, they can disagree by over 1/2 stop ... which, given modern film latitude is usually fine.
2 days ago, I shot with my very clean Nikon F2 and the built in metering system disagreed with my Sekonic digital spot meter by nearly a full stop. This is normal.
You have to understand the instrument to learn how to get consistent results. Asking analog meters designed 40-60 years ago to be super accurate is a fool's errand.
And because of that whenever I have a camera that requires mercury battery I simply use it without the battery. My estimation of the light is about as good as these old meters.
Wow! Do you use Sunny 16.0000 or Sunny 11.0000?
Sunny 16 is much more reliable than any of these old meters. However, you don't always get the sunny 16 condition. You may be in shade, cloudy, rain, indoor with artificial lighting etc.. this is where it's more difficult to estimate the lighting condition but yet I would fair about equal to the the old meters.
funny
At the risk of seeming confrontational, which is not my intent, and pendantic, whcih happens at times... like you, I've been using meters for a long, long time and found "professional grade" meters, especially, back in the good old days to yield exceptional exposure advise. Back then I shot an awful lot of transparency film so didn't have the latitude of color neg or b&w film to rely on. The Weston meters I used back then wre great but cannot perform the same task today. The Luna Pro I used back then still performs splendidly with a voltage converter, including at low light levels as it was originally touted as excelling.
It seems that a lot of people judge the original engineering by the condition these meters are in after half-a-century (or more) of aging and use/abuse. Or, they simply don't know how to use their meter. (Can't count the number of times someone complained about a bad meter only to find out that they didn't know the impact something like sky has when using a general coverage meter.) Plus there were some different design philosophies, both between manufacters and within, like what K or C factor were used in the calculator, that can yield different results irespective of potential accurancy issues.
I agree, these vintage meters today can be a crap shoot but it may not be that the original engineering was faulty or the orginal capabilities were inconsistent. They became that way over time. But there are many more factors to consider than just when it was designed and judging a design by old equipment is, as you phrased it... a fools errand. Bottom line, thouh, we completely agree taht one needs to understand the instrument to get consisent, wheter that is accurate or precise, results.
Yes, very funny it was!
By the way it can be sunny 16.0000 but not 11.0000 because it's 11.3137.
My older Nikons mostly have very good working meters that are well matched to my newer meters. It's not their age that is the issue. It's just that the design of the meter is very simple and isn't as linear across the range of light a modern meter is. Moreover, even with Photomic center weighting, you still are getting an average of the scene that may not actually be right for the lighting conditions.
I have several Luna Pros that I've personally taken apart, cleaned and recalibrated against good meters. Their sensitivity to low light seems better than the old SLR meters, but they still exhibit a lack of linearity across their ranges. The top of low light doesn't agree with the bottom of the high light scale.
And ... none of this matters. I know how these meters work and I compensate accordingly. Even with a brand new Revini reflected meter (which has a large angle of acceptance), I have to meter carefully and repeatedly to establish what the actual range of light is, before deciding on the exposure.
As I keep saying - knowning how to use the equipment in a repeatable manner is far more important than absolute accuracy.
I have the same problem with the adapter as the OP. Testing the adapter with a 10k load it works fine but my OM-1 presents around a 16k load. In the camera it doesn't drop the voltage sufficiently and the meter is about a stop and a half off. I confirmed this by testing the adapter on the bench with a 15k load and sure enough it doesn't regulate properly. Perhaps Olympus changed the circuitry over the years and the adapter works with some cameras and not others. Testing a suitable diode to get the voltage drop at 15k shows that to work fine so I will likely use that option instead of the MR-9 adapter.
Exactly. Like just about everything else (lens, film, developer, etc.) TEST IT YOURSELF. Pretty easy. Meter a gray card, etc. with & without that adapter and see if it reads the same -- or close enough. It might work with some gear and not others. K.I.S.S.
Yep, same here....using the adapter in my Olympus 35 RC, I find it is about a stop and a third off, over exposing.
When I shoot 400 speed film I use the 800 setting and they turn out mostly alright, but slower speeds I can compensate better.
When I shoot 400 speed film I use the 800 setting and they turn out mostly alright, but slower speeds I can compensate better.
Which adapter are you folks using?
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