Couple of New Toys (lightmeters)

[xpatUSA]

After 40 years of [only] using the camera metering, I've started studying ISO in it's various forms, for which I needed to figure out the sensor exposure on a camera. I did have one of these to hand:



Said to be 5% accurate, even with that tiny little dead-flat window (arrowed). But it has no 'hold' button and it's not really a Photography Tool, eh?

So I splurged a whopping 49 bucks on this fine little machine - deliberately choosing one with ASA and footcandles, just for the fun of it:



I do like those 'analog' functions much as I love my high-quality vernier caliper, my Jepperson flight computer, etc. BUT . . readings from these two meters are wildly different - in spite of the Seller saying that the Sekonic was recently calibrated. (Yes, it's a selenium cell and, yes, it's very clean, not crazed, etc, etc.).

So, what's a body to do but spend more money, $29 this time on a used TES-1334 . .



Nice and simple. When it gets here, what's the betting that all three will read different . .

[Shadowman]

Nice, I have a very old one that has the ASA measurement and it usually read about 0.5 to 1.0 stop below my camera.

[pnodrog]

If you get 10 of them you can discard any readings that are way out then average the rest....

[xpatUSA]

Nice, I have a very old one that has the ASA measurement and it usually read about 0.5 to 1.0 stop below my camera.

What model is yours, John?

My CEM reads about a stop below the Sekonic under cheap and warm LED strip-lighting . .

[Shadowman]

What model is yours, John?

My CEM reads about a stop below the Sekonic under cheap and warm LED strip-lighting . .

Ted,

It's a Gossen Scout.

[rpcrowe]

I used this type of light meter for my cinematography for years.



No battery needed. I would slip in the grid with the ASA (now called ISO) I was using into the meter and then I could read the f/stop directly off the meter dial with no need to move any part of the meter.

Every couple of years and I would send it in for a rehabilitation and the Spectra folks would drill out the holes in the slides so that the meter would be accurate.

It was an amazingly tough and sturdy meter. I kept it on my belt through many difficult combat situations. It never failed me even though the film I normally used (Kodak 16mm Commercial Ekltachrome Reversal) had very little exposure latitude (It was ASA 25 under 3200 K. tungsten and ASA 16 in daylight with a Wratten 85 filter). This gave me a normal f/11 to f/16 exposure at 24 frames per second in bright sun. I would send the meter back to Spectra whenever I would not get f/11 to f/16 in bright light outdoors. The Spectra folks would redrill the slides free of charge.

This was my own personal meter. The Navy issued me a Gossen Luna Six meter which I carried along on jobs as a back-up but which I never needed to use...

I mostly use my camera's internal meter and have not experienced any difficulties. However, I own an old Sekonic L-718 Digimaster meter which can measure both ambient light (incident and reflected) and flash. It doesn't have the bells and whistles of a more modern meter but, it does measure the light accurately...

[miatab]

Exposure meters- wow, what a blast from the past they are! My first was an old Bertram Standard I pinched from my brother when he left it behind on moving out. He had no use for it as a fellow traveller stole his Voightlander Vito11 from him when staying at the YMCA. It opened like a flip phone and a spring loaded cell jumped up like a jack in the box. It had a very complete depth of field table that taught me everything I needed to know then and now. It's gone to a grave known only to God. I still have an external meter somewhere, an underwater model I used SCUBA diving, but it used mercury cells, and so it is retired without hope of resurrection. I presented my old Western to somebody, somewhere, some time. My Df 's meter does a better job.

[xpatUSA]

Interesting, thanks for posting!

Er, what's a "Df"?

[edit] . . . anybody? . . [/edit]

[tao2]

Hi Ted,
What d'ye mean by "sensor exposure on a camera"?

[xpatUSA]

Hi Ted,
What d'ye mean by "sensor exposure on a camera"?

Hullo Boab,

I'll expand on that a bit.

I own several Sigma cameras. Elsewhere, controversy has raged as to what is 'base' ISO for the so-called Merrill models.

So, I'm trying to figure that out by measurement and comparing the result to the many ways of defining ISO.

Part of the measurement involves knowing either a) the luminance L of the target in cd/m^2 or b) the exposure H at the sensor in lux-sec.

By "sensor exposure on a camera" I meant b) but stayed with less pedantic terminology because the task in hand had little to do with the post other than as background.

HTH

[Tronhard]

With so many meters, by the time you have consulted them all the light will have changed or the subject will have moved (even if it is a landscape!)

If you get 10 of them you can discard any readings that are way out then average the rest....

[Acorn]

Whatever happened to the Weston range? In the days of film they were pretty accurate. Remember them?

[miatab]

What I remember about the Western were the high price and the high reputation. They were the Leicas of meters. Ha ha.

[mikesan]

My CEM reads about a stop below the Sekonic under cheap and warm LED strip-lighting . .

Just a couple of random thoughts. First, I don't think it is a fair comparison. The Sekonic meter (I believe) was originally supplied with a flat disk (Lumidisk) which replaced the sphere (Lumisphere) for unidirectional measurement of incident light. I would guess that the former would better replicate the measurements (and the sensor geometry) of the CEM meter. Second, Sekonic has a long established reputation as a manufacturer of precision instruments. For that reason alone, I would be inclined to rely more on the Sekonic than upon an inexpensive lux meter.

None of the above explains the discrepancy between the incident meter readings and those of your camera's reflective metering. I think that deserves a second look. I would try a more uniformly reflective surface in preference to the tree. How about the time honored gray card? I am sure you have one of those around (or a reasonable substitute).

Cheers,
Mike

[xpatUSA]

Just a couple of random thoughts. First, I don't think it is a fair comparison. The Sekonic meter (I believe) was originally supplied with a flat disk (Lumidisk) which replaced the sphere (Lumisphere) for unidirectional [not "unidirectional" - cosine response instead of cardioid response] measurement of incident light.

I used the Lumidisk. What made you think I did not?

I would guess that the former would better replicate the measurements (and the sensor geometry) of the CEM meter. Second, Sekonic has a long established reputation as a manufacturer of precision instruments. For that reason alone, I would be inclined to rely more on the Sekonic than upon an inexpensive lux meter.

Mike, My Sekonic L-398 is old, used and was an eBay purchase. It has a selenium photocell, not noted for their longevity.

My lux-meter (albeit a multi-purpose meter) was brand new and has a silicon photo-diode with a CIE response filter.

Which would you be more inclined to rely on now?

None of the above explains the discrepancy between the incident meter readings and those of your camera's reflective metering. I think that deserves a second look. I would try a more uniformly reflective surface in preference to the tree. How about the time honored gray card? I am sure you have one of those around (or a reasonable substitute).

My first tests were indeed done inside with my 8x10" Kodak R-27 card under warm LED (shock!) lighting. Time for you now to tell me how that lighting does not match CIE illuminant 'A'.

Since my original post, I have had a good few successful shots with the Sekonic set at 40 ASA and my camera set at 100 ISO.

[Cantab]

Ted, I've nothing substantive to add to the discussion. But I've now had a closer look at the photo of your lux meter in post #1 and to my surprise see that it really is multi-purpose: light, sound, humidity and temperature! Does it measure more things if you turn the meter over and use the reverse side?
They've probably been around for some time but it's the first I've heard of such a meter.

[xpatUSA]

Ted, I've nothing substantive to add to the discussion. But I've now had a closer look at the photo of your lux meter in post #1 and to my surprise see that it really is multi-purpose: light, sound, humidity and temperature! Does it measure more things if you turn the meter over and use the reverse side?
They've probably been around for some time but it's the first I've heard of such a meter.

They're Chinese:

http://www.cem-instruments.com/en/About/index

I had a quick look but mine is no longer made, by the looks of it. Nice facility though . . .

[mikesan]

I used the Lumidisk. What made you think I did not?

Perhaps a too hasty conclusion; because the photo shows the meter with the sphere in place.

Mike, My Sekonic L-398 is old, used and was an eBay purchase. It has a selenium photocell, not noted for their longevity.

My lux-meter (albeit a multi-purpose meter) was brand new and has a silicon photo-diode with a CIE response filter.

Which would you be more inclined to rely on now?

Well it was just a thought; I bow to your decision.

My first tests were indeed done inside with my 8x10" Kodak R-27 card under warm LED (shock!) lighting. Time for you now to tell me how that lighting does not match CIE illuminant 'A'.

Since my original post, I have had a good few successful shots with the Sekonic set at 40 ASA and my camera set at 100 ISO.

I have no quarrel with the illuminant. To the best of my (admittedly limited) knowledge the observed differences between meters is not significantly influenced by the illuminant. I have confidence that your better controlled indoor test has given you a good basis for correcting the reading of the Sekonic by shifting the ISO (ASA).

Thanks for your reply.

Cheers,
Mike

[xpatUSA]

Perhaps a too hasty conclusion; because the photo shows the meter with the sphere in place.

Well it was just a thought; I bow to your decision.

Sorry, that was indeed misleading. In my rush to post, I just linked to the eBay image, as I recall.

I have no quarrel with the illuminant. To the best of my (admittedly limited) knowledge the observed differences between meters is not significantly influenced by the illuminant.

Cheers,
Mike

Thanks for sharing your experience with illuminants which I find greatly encouraging. And sometimes lack of correctness has less effect when a comparison is being made.