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.
Right. And, a better quality meter wouldn't hurt. We're talking about a few tenths of a volt here. You need good accuracy.
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.
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.
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.
With this kind of stuff, we do not seek accuracy, we seek repeatability.
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.
But what makes you think “these older meters” weren’t super accurate when new?
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?
Wow! Do you use Sunny 16.0000 or Sunny 11.0000?
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.
funny
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.
All I can re-iterate to the original poster is stop tying yourself in knots, just put the adaptor into the camera and shoot with it., I can assure you it will give you correct exposure.
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