Metering Differences

[dreilly]

Okay, here's my question.

I have three meters here. An old Leica M meter (still works though it looks like it was field tested in the Korean War), a Weston Euromaster, and the spotmeter on the CL I just got back from DAG (adjusting the meter, etc.) Is it normal for a two stop disagreement between the two?

For example, the two selenium meters give me 500/2, the CL gives me 125/2. It seems fairly consistent. Is this the difference between a spot and averaging meter?

Is it possible that both selium meters are bad in exactly the same increment?

Doug

 

[TimF]

Give me a slap if you want Doug, but the meters are set to the same film speed I take it.

I have found that my Weston Master V can give reflected readings that deviate considerably from a TTL meter. Eventually I put it down to the weston having a wider angle of acceptance, as the difference disappeared when I took a reading closer to the test subject.

 

[Biber]

There is no difference between a spot meter and an averaging meter if the metered surface has the same reflectance. Make sure that the averaging meter doesn't catch anything outside of your test area.

 

[FrankS]

Make you readings fairly close (2 meters or so) from a blank light coloured wall and see what happens.

 

[dreilly]

Slap! 🙂

Yep, they are set to the same ASA. But, this pointed me in the right direction. The Weston wasn't zeroed!

Now those two agree fairly closely.

The Leica M (properly zeroed) now reads accurately at the lower end of the scale, but is about a stop off at the higher end.

thanks!
doug

 

[VinceC]

I'd try pointing all the meters at a large brick wall in the shade (or whatever else is handy with an unvarying surface brightness and uniform color ... side of a barn, parking lot, cloudless north sky in daylight, uniform low-hanging clouds on a cloudy day, Wall Street Journal or Financial Times taped to a wall). The meters ought to more or less agree. You can also double-check approximate accuracy with Sunny 16 -- if ISO is set to 500, then the meter ought to be showing roughly 500th of a second @ f/16 when pointed to a typical sunlit scene ... green grass in the open sun is particularly good fo this test. Make sure the sun is to your back and the grass blades are fully lit. Midmorning or midafternoon works best. (If you live near the Arctic or Antarctic Circles, disregard Sunny 16. However, if you live on the moon, it works quite well, because the moon is a sunlit object).