Exposure Meter testingany affordable devices available,or any shops still doing this

Ira Rush · Apr 30, 2009

Exposure Meter testing any affordable devices available, or any shops still doing this?

While I know that the common sense low-tech approach to test a meter might be the Sunny f/16 rule, that can be somewhat less than truly reliable (time of day, time of year, pollution on and on), and extremely subjective oh yeah, thats a f/16 day all right.

Another common sense, low-tech approach would be to shoot a series of transparency at indicated meter reading and then increase/decrease in ½ stop increments to +/- 3 stops and compare frames.

Better, but still somewhat subjective

Still another low tech way, the good old grey card test.... on and on:rolleyes:

What I am really getting at is there a more precise-objective method for testing the accuracy of a meter, such as there is for shutter speed testing?

Years ago Calumet sold a shutter speed tester, thats long gone now, but search the web and youll find tons of do-it yourself plans to build your own.

Is there an affordable device out there for exposure meter testing?

I know that some web site out there has some plans, but you seem to have to build a known light source first, then the tester then something else, starts to gets a little complicated.

So, any such self contained device out there, any shops still testing meters at a reasonable price, or any other low-tech ideas that might work?

Thanks in advance

Anscojohn · Apr 30, 2009

Sounds to me that one of the "kids" could come up with a way to do meter testing using a computer screen.

I know for one, I use a very low-tech approach to viewing negs and trannies without hunkering my arthritic spine over the light table: I just go to my word processing program, open a blank page, and use that instead of a light table.

ic-racer · Apr 30, 2009

Anscojohn said:
meter testing using a computer screen...

Here you go : http://www.robertsuomala.com/5.html

(link points to an article about calibrating a restored SEI using a DSLR and a computer screen)

RJS · Apr 30, 2009

I am fortunate in that I had a copy of Dr. Richard Henry's book, Controls in Black and White Photography in which he describes using an ordinary light bulb as a standard. He listed the make, wattage etc. of the bulb along with his results testing his Pentax meter. I purchased two of the bulbs and got almost exactly the same readings he did. I also sent my Luna Pro meter to Quality Light Meteics for repair and calibration. It does not read the same as my Pentax. Since my readings using Dr. Henry's procedure agree with his exactly, I trust his procedure. At this date I'm afraid the bulb in question has been changed. It is a GE Longlife white lamp bulb 100V 1585 lumens. For those interested, check Dr. Henry's book for precise directions. He has a considerable section on light meters and their calibration but I have no idea how to calibrate my LunaPro so it is usable. I sent it back, they said they checked and it is fine. Sent me my money back, but the meter does not agree with my Pentax. I 'm not sure where to go from here, as the Pentax gives me fine negatives, confirming my calibration. I have owned two SEI meters, from back when AA was writing about them. I never could get consistent measurements - the color of the comparison spot was a problem for me so that one time I would get a good reading, then an obviously ridiculous one. So I gave up on them and bought to first Pentax Spot.

felipemorgan · Apr 30, 2009

Section 2 in this article (Dead Link Removed) lists a method that might be helpful.

Ed Sukach · May 1, 2009

Having calibrated many different typs of photometers, I'll toss a couple of comments into the fray:

1, "Sunny 16" - is it "good enough" to use as a standard for calibrating ordinary run-of-the-mill exposure meters? It can be surprisingly close. However "surprisingly close" is just that - a really "close" value constitutes a "surprise". There are MANY environmental variables that will affect the results - time of day, latitude, particular content of the air ....
Final answer: No.

It may be of interest to consider our procedure (simplified). We would take a Standard Lamp (an IntrAlaboratory Standard) calibrated by the National Bureau of Standards, place it on an optical bench in a controlled atmosphere, power it up using an ampereage-contolled power supply and, from the light emitted, do our thing with the subject meters.

2, "I sent my meter to --- for calibration. When it returned, I compared it to my other meters and it didn't agree with them."

No kidding. So you think it reasonable to assume that the recent calibration was in error?
If it was me, I would suspect all the others.

RJS · May 1, 2009

The procedure using a "Standard Lamp (an Intralaboratory Standard) calibrated by the National Bureau of Standards" sounds very much like the procedure used by Dr. Henry except he was able to obtain ordinary bulbs which GE assured him were consistently producing the stated value. These were the lamps I used calibrating my Pentax and yes I think it reasonabe to assume Dr. Henry's procedure, which I followed using a volt meter to be sure the lamp was receiving proper voltage, is accurate. And that a meter calibrated I know not how which disagrees grossly is in error.

Where can one purchase a "Standard Lamp"?

If you read Dr. Henry's book it seems that light meter calibration by the manufacturers, i.e. their standards, are somewhat variable and a bit quirky.

Ed Sukach · May 1, 2009

RJS said:
... ordinary bulbs which GE assured him were consistently producing the stated value.

To accept "assurance by those at GE" as being superior to calibration by NBS is to me, a gross error. Of course GE will try to produce all lamps within design parameters ... but those parameters are no where near error limits in NBS calibration.

We had a motto: Right or wrong, the NBS is always RIGHT!

These were the lamps I used calibrating my Pentax and yes I think it reasonabe to assume Dr. Henry's procedure, which I followed using a volt meter to be sure the lamp was receiving proper voltage, is accurate. And that a meter calibrated I know not how which disagrees grossly is in error.

Well ... One of the basics is that "amperage drawn" affects light output three times more severely than voltage - and the problem is more of stability than knowing the amount of current drawn at any point in time. What appears to be great at the moment may be unacceptably out-of-whack three minutes later. Those power supplies are sophisticated and expensive. Out of curiosity - what voltage meter were you using?

BTW ... you do NOT want to "take" a belt from the primary power to a cascade photomultiplier system. I did, once ... and I'm convinced that was sufficient.

You write that you would trust what you did more than the results of - you know not what procedure. I can only suggest that you contact whoever did that for you and ASK them. I'm sure that, if it was anything other than poking the meter out of the window (at 2:00 PM ??) on a sunny day, they would be happy, if not proud to discuss it with you.

Where can one purchase a "Standard Lamp"?

I have *NO* idea - I never bought one.

If you read Dr. Henry's book it seems that light meter calibration by the manufacturers, i.e. their standards, are somewhat variable and a bit quirky.

Impossible to deny. The question is whether the "quirkiness and variable-ness" is greater or less than that of "ordinary" lamp manufacturers. I'd personally (wild guess) go with the meter manufacturers.
They have more of a stake in the game.

BetterSense · May 1, 2009

I just bought for our lab a $20,000 calibrated solar spectrum simulator for testing solar cell efficiency. I plan on putting a grey card on the test fixture with the simulator on the standard AM1.5 test conditions and calibrating my homemade exposure meter to EXACTLY sunny 16!

RJS · May 1, 2009

I think if you read Dr. Henry's book you will find that he presents his information in a way which makes it possible to replicate his procedures. My 'scientific' training was in the social sciences rather than the physical sciences and while I am aware of general methodology used in the sciences I barely know a volt from an amp from a watt. That said, I get the impression you are not familiar with Dr. Henry's book. The variability and (my term) quirkiness in the manufacturing of light meters I am referring to lies in their apparent varying of standards from one manufacturer to another. As far as trusting repair shops; again I would refer you to Dr. Henry's book which, added to my own experience, leads me question the accuracy of the work performed by some. There are many excellent shops, but there are also many operating with obsolete uncalibrated instruments. Again, I must fall back on Dr. Henry's instructions. I used a meter purchased at Radio Shack.

By way of correction: I did not say I thought GE's assurances were superior to the NBS. Au contraire. I would certainly trust the NBS. But I have absoloutely no idea where to obtain a light source certified by the NBS. And since, when I replicated Dr. Henry's procedure and obtained exactly the results he obtained, it leads me to believe his methodology was correct.

I'm not sure what a 'primary power source' would be (my concept would be the wall plug) and I wouldn't know a cascade photomultiplier (some kind of fancy abacus?) if one was sitting next to me.

You sound as if you worked in the photography and/or electrical business wheras I spent my life working as a psychologist. I can lay claim to being friends with some famous photographers (all, sadly, gone) but to the best of my knowledge none were schooled in the physical sciences. Whereas Dr. Henry was a research chemist.

I look forward!

Anscojohn · May 1, 2009

RJS said:
I am fortunate in that I had a copy of Dr. Richard Henry's book, Controls in Black and White Photography in which he describes using an ordinary light bulb as a standard. He listed the make, wattage etc. of the bulb along with his results testing his Pentax meter. I purchased two of the bulbs and got almost exactly the same readings he did. I also sent my Luna Pro meter to Quality Light Meteics for repair and calibration. It does not read the same as my Pentax. Since my readings using Dr. Henry's procedure agree with his exactly, I trust his procedure. At this date I'm afraid the bulb in question has been changed. It is a GE Longlife white lamp bulb 100V 1585 lumens. For those interested, check Dr. Henry's book for precise directions. He has a considerable section on light meters and their calibration but I have no idea how to calibrate my LunaPro so it is usable. I sent it back, they said they checked and it is fine. Sent me my money back, but the meter does not agree with my Pentax. I 'm not sure where to go from here, as the Pentax gives me fine negatives, confirming my calibration. I have owned two SEI meters, from back when AA was writing about them. I never could get consistent measurements - the color of the comparison spot was a problem for me so that one time I would get a good reading, then an obviously ridiculous one. So I gave up on them and bought to first Pentax Spot.

*****
It is my understanding the Luna Pro is calibrated to ca 36% grey, rather than 18%. If true, that might account for your variance.

Anscojohn · May 1, 2009

Thanks for the links. No reason why I cannot duplicate my prior procedures using this crt screen. In the past, I have just kept it kind of low tech. Grey card, open shade on a sunny day with no clouds. Check them all.
Tomorrow: I have two Weston Master Vs calibrated by Quality Light Metric. I can use them to check the reading of my figital camera. Then I'll check all three against every camera with built in meter; then see if my old Luna Pro still reads one stop different. Phew. Whatever happened to Weegee's "F/11 and bein' there?"

mike c · May 1, 2009

John, it all depends what "it" is,ask ex Pres. Clinton.I have two meters and use both but not at the same time,One is fore the fast printing of negs the other fore when I'm not in a hurry when I print.

mike c.

archphoto · May 1, 2009

The most easy way is to have a reflective lightmeter that you know is good and aim it at a spot on your wall.
Measure with both lightmeters.

I used this method for the past 20 odd years: a Gossen ProfiSix as reference.
Works great !

Peter

Anscojohn · May 1, 2009

archphoto said:
The most easy way is to have a reflective lightmeter that you know is good and aim it at a spot on your wall.
Measure with both lightmeters.

I used this method for the past 20 odd years: a Gossen ProfiSix as reference.
Works great !

Peter

******
Far too simple, Peter!! This is the modern world, dontcha know!? If it ain't complicated, do one's best to complexify it; then, perhaps, hire a consultant.

Anscojohn · May 1, 2009

mike c said:
John, it all depends what "it" is,ask ex Pres. Clinton.I have two meters and use both but not at the same time,One is fore the fast printing of negs the other fore when I'm not in a hurry when I print.

mike c.

******
Sorry, I have no idea what you are talking about. What am I missing?

RJS · May 1, 2009

Quality Light Metric are really nice, honest people. Over the years they have repaired several meters for me. Unfortunately I have this Pentax spot meter and Dr. Richard Henry's book and I followed his directions very carefully. The Pentax checks out using his methodology and my Luna Pro agrees with it wonderfully at very low light levels, but then diverges until at the high end it is two stops different.

Maybe the best way is to throw away one of the meters?

Anscojohn · May 1, 2009

RJS said:
Quality Light Metric are really nice, honest people. Over the years they have repaired several meters for me. Unfortunately I have this Pentax spot meter and Dr. Richard Henry's book and I followed his directions very carefully. The Pentax checks out using his methodology and my Luna Pro agrees with it wonderfully at very low light levels, but then diverges until at the high end it is two stops different.

Maybe the best way is to throw away one of the meters?

*****
Throw it my way.

mike c · May 1, 2009

The" it " part was when Clinton was in court testifying in the Monaca L. thing, he had brought up the meaning of the word " it " as having maybe more than one than meaning,spiting hairs you could say. You could use a meter for 20 years and not notice anything wrong with it until you compare it to another and find a two stop deference between the too meters. You take your meter in have it calibrated find out its two stops off,but you were doing fine with it for twenty years. So all the personal flim speeds have to be worked out to make the adjustment to the newly calibrated meter. That is what I was referring to about the fast printing and slow printing, if you had two meters one a stop or two off from the other. Sorry John I not a good writer.

mike c.

erikg · May 1, 2009

I've had Quality Light Metric do a Weston meter for me and it is working well, although I don't use it all that often. I also had Richard Ritter do my pentax/zone VI spot meter and it is the one I trust most, I use it mainly when shooting transparencies and the proof is on the light table as far as I'm concerned.

Anscojohn · May 1, 2009

That is what I was referring to about the fast printing and slow printing, if you had two meters one a stop or two off from the other. Sorry John I not a good writer.

mike c.[/QUOTE]'

Ahh, now I understand. Well, my meters all read a grey card, open shade, sunny day with no clouds, pretty much the same. I print the negs exposed with them beginning at minimum exposure for max black through clear film of each negative. So I guess that is slow printing. I find that the key is having an accurate meter set for my EI and metering a known tone in the scene; then souping in my usual soup, with a standardized procedure. Totally low tech.

RJS · May 1, 2009

Yes, I think transparencies would be a good measure. Not a great deal of latitude in exposure. But then, if using other, not electronically regulated shutters, that can confuse things (I am easily confused). Fortunately - or not - I have one of the old Calumet shutter testers. I think I heard there were problems with them with focal plane shutters but I'm not sure. Perhaps someone reading this knows?

mike c · May 1, 2009

Yes ,I have two meters all so luna pro and a capital spot meter, all though the lunna has the last say when I 'am uncertain.

mike c.

RJS · May 1, 2009

Capital spot meter is new to me. I have Pentax, I know of Minolta and Soligor and SEI and attachments to make the Luna Pro a spot meter. What is 'Capital?'

Arvee · May 1, 2009

RJS, remember, when comparing the two meters mentioned, one is a CdS and one is a silicon photocell.

They have very different color responses. Both meters can be in calibration and give very different readings.

Somewhere on the net is the chart Pentax publishes for adjusting the exposure depending on the predominant color of the subject, up to a stop and half, IIRC.

-F.

Exposure Meter testing any affordable devices available,or any shops still doing this

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Exposure Meter testingany affordable devices available,or any shops still doing this