sweat100 Posted March 18, 2022 Share #1 Posted March 18, 2022 Advertisement (gone after registration) I would like to calibrate my M5 light meter as it is off by 1 stop. How should I go about calibrating it? I have have seen a YouTube video listing a linearity and total adjustment variable resistor. I am not sure which I should adjust. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Quote Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/330808-leica-m5-meter-calibration/?do=findComment&comment=4403059'>More sharing options...
Advertisement Posted March 18, 2022 Posted March 18, 2022 Hi sweat100, Take a look here Leica M5 meter calibration. I'm sure you'll find what you were looking for!
giannis Posted March 18, 2022 Share #2 Posted March 18, 2022 What batteries are you using? If you're not using the correct batteries (i.e. ones with constant voltage even when discharging, namely zinc air (available) or mercury (discontinued) ), there's no way to calibrate the meter across the brightness range, since, say alkaline batteries, change their voltage as they slowly discharge. If you're using the appropriate batteries and the meter is still off by one stop (across the range, i.e. one stop off when metering something dark and the same one stop off when metering something bright), then you adjust the total response. 1 Quote Link to post Share on other sites More sharing options...
sweat100 Posted March 19, 2022 Author Share #3 Posted March 19, 2022 11 hours ago, giannis said: What batteries are you using? If you're not using the correct batteries (i.e. ones with constant voltage even when discharging, namely zinc air (available) or mercury (discontinued) ), there's no way to calibrate the meter across the brightness range, since, say alkaline batteries, change their voltage as they slowly discharge. If you're using the appropriate batteries and the meter is still off by one stop (across the range, i.e. one stop off when metering something dark and the same one stop off when metering something bright), then you adjust the total response. I am using mercury PX625 and MR9 battery adapter with a diode which I use with silver oxide battery. Using these batteries, I noticed there is one stop off. I noticed at bright outdoor conditions (EV 11-15), it under exposes by 1 stop. At indoor conditions (EV 5-8), it meters correctly. Quote Link to post Share on other sites More sharing options...
Hintsalae Posted March 19, 2022 Share #4 Posted March 19, 2022 You are not supposed to use mr-9 adapter with mercury batteries. Mr-9 allows you to use higher voltage batteries that original mercury cells (1.35V). Either remove mr-9 or buy silver oxide battery with your mr-9 adapter. 1 Quote Link to post Share on other sites More sharing options...
TomB_tx Posted March 19, 2022 Share #5 Posted March 19, 2022 The M5 uses a CdS cell for metering, which (as I recall) has high resistance in dark that lowers with light intensity. If these cells get moisture penetration as they age it lowers the ultimate resistance, and the response also becomes more non-linear, often beyond the range that can be adjusted by the built-in linearity adjustment. This has happened to a few of my old cameras, so they could be adjusted to be correct in either bright or dim light, but not both. Luckily my M5 still meters correctly, as replacement meter cells for it are nearly extinct. My Leicaflex SL was affected and after trying to adjust to compensate, DAG replaced the cell back when he still had some stock. The M5 cell is very unique, so difficult to fit something else. At one time I believe Sherry Krauter was tying to source replacement cells for some Leica models, so you might check with her. I also use the MR-9 adapters in these cameras with silver cells, and they work quite well. 2 Quote Link to post Share on other sites More sharing options...
a.noctilux Posted March 19, 2022 Share #6 Posted March 19, 2022 (edited) M5 meter system "CdS based" is unique, however in my use, comparing to more modern Silicon based meter can give false ideas of "accuracy". Linearity is one of them, why there are adjustments for low/high light. When I compared (long ago) the values with artificial lighting, M5 meter can be very different than Silicon based meters. So the "color response" is different between CdS and Blue Silicon cell. In practice, I learned to "adjust" the M5 metering with the right color for example "neutral gray" as close as can be to 18% ... With Kodachrome, that was my way of using M5. The good thing we can do is the nice feature of M5 (not available before in any M), every half speed between two "conventional settings", so following appreciating the analog index is quick to learn to use, with 1/2 EV, isn't it nice. the tricky lighting can be a success "story" when we know well the meter behavior Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Edited March 19, 2022 by a.noctilux 3 Quote Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/330808-leica-m5-meter-calibration/?do=findComment&comment=4403599'>More sharing options...
sweat100 Posted March 20, 2022 Author Share #7 Posted March 20, 2022 Advertisement (gone after registration) On 3/18/2022 at 11:58 PM, giannis said: What batteries are you using? If you're not using the correct batteries (i.e. ones with constant voltage even when discharging, namely zinc air (available) or mercury (discontinued) ), there's no way to calibrate the meter across the brightness range, since, say alkaline batteries, change their voltage as they slowly discharge. If you're using the appropriate batteries and the meter is still off by one stop (across the range, i.e. one stop off when metering something dark and the same one stop off when metering something bright), then you adjust the total response. Apologies if I was not clear. I do have mercury batteries (1.35V) and MR-9 adapter which I use silver oxide batteries with. Both types gives me 1.35V voltage sources. However, I need some guidance on how to start calibrating the light meter. Which should I adjust first as the baseline and fine tune? VR1 (battery test adjustment), VR2 (total response) or VR3 (Linearity). What is the light value I should be using for bright and dark scene? Quote Link to post Share on other sites More sharing options...
a.noctilux Posted March 20, 2022 Share #8 Posted March 20, 2022 In your shoes, I would NOT adjust anything. This is for repair person job who has skills and well equipped with required tools. As side note, had you pushed the "test lever" to see if the battery in use is right ? 2 Quote Link to post Share on other sites More sharing options...
250swb Posted March 20, 2022 Share #9 Posted March 20, 2022 (edited) Adjust the meter reading by compensating with the ISO until a technician can adjust it. Edited March 20, 2022 by 250swb Quote Link to post Share on other sites More sharing options...
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