testing spot lightmeter

[quigon]

Hello, I want to test my lightmeter. Is there a forum where the topic was already dealt with?
Thanks
Luigi

[BrianShaw]

Testing for what aspect of spot metering - accuracy, precision, correct exposure recommendation? Which spot meter?

If I'm checking out a new-to-me meter I "test" by comparing meter readings with trusted meters on a large surface and not worrying about minor differences. But most often, I shoot a roll of film and look at the negatives. If the negatives are reasonably exposed then the meter is reasonably accurate. Others might be more scientific about testing and demand higher criteria than do I.

[quigon]

Thanks for answering
It's a Pentax digital spotmeter. I cannot test by comparing because I have no other trusted meters.

[BrianShaw]

Thanks for answering
It's a Pentax digital spotmeter. I cannot test by comparing because I have no other trusted meters.

I'd suggest shooting B&W film in "normal" circumstances and look at the negatives to see if they appear "normal". For me this works best with general coverage and incident meters. With a spot meter you'll need to be careful that your spot metering technique does not abnormally skew the exposure.

Some people find comparing meter readings to "Sunny-16" to be a good way to assess a meter. That depends on how accurate Sunny-16 is in your location, though.

Did it once work correctly or is this a meter of totally unknown accuracy?

[quigon]

It still works, but now and then I get mistakes (the problem may be with me). I've gone through a couple of papers which made my doubts increase (Ctein, Post Exposure and Exposure Metering by Jeff Conrad here they demolish the myth of 18% reflectance calibration).

[Bill Poole]

If you have a smart phone, you can download MyLightmeter Pro ($4) or other metering app and use it to compare with the Pentax. In my experience, the My Lightmeter ap agrees with my several other meters. Hope this helps.

[ic-racer]

Adjust the ASA dial so that a film renders a photograph of a uniform target 0.1 density when underexposed 4 stops.
BTW 0.1 density is 1/3 of a stop. So you can use the meter to check the negative.

[Ulophot]

Two things, depending on your preferred subject matter and light levels for photographing, and how detailed you wish to be.

Meter linearity is an important characteristic to test. That is, is it accurate throughout the range? If not, resulting anomalies may drive you batty. Therefore, I would add to the "test in normal situations," that you test your target in direct sunlight, exposing it by the reading and three stops over (to put it in the domain of textured white, Zone VIII in the zone System); in open shade, ditto, and either indoors (if applicable) or outdoors in very low light.

The film speed test mentioned above is also important, and I am attaching the notes I have on this, copied from where I don't recall.

Spot Densitometer.pdf

Feel free to post back with further questions.

[xkaes]

No need to get fancy. Some people on this board have a tendency to go overboard.

It's easy to figure out if it's functional -- i.e., working CLOSE to correctly.

Meter off a gray card in sunlight, a northern blue sky, or put a white, Styrofoam cup over the front and point it at the sun.

That won't tell you if it's PREFECT, but it will tell you if it's defective -- if it isn't close to the f-16 rule.

[Lachlan 717]

Accuracy of your shutter(s) will be a much weaker point in your process than your meter.

Perhaps look at calibrating them first.