How To Test Light Meter Film Camera

I take an one-time Gossen Luna-Pro F meter and I am trying to make up one's mind if I need to replace it.
I take tried metering a scene with different cameras and the Luna-Pro and comparing the readings but I can't seem to draw any conclusions.
I demand a meter when I shot my RB67 and I am nether the impression that I will get more accurate readings with a hand held meter than a TTL camera meter????
Is there a method to test the Luna-Pro that is not and so complicated that I need a degree in physics to utilize?

I take been looking at the Gossen Digi-Pro F or the Sekonic 50-308S but why spend the money if my sometime Luna-Pro is simply equally accurate? Maybe I just practice not know how to utilise it correctly???
One testway is to shoot a roll or ii in a diversity of situations using the meter "ordinarily" and encounter if the results friction match your expectations.
If the shadows and neutrals fall "in the correct spot" it's probably working fine.

This assumes a "standard" is used when you develope and print too.
A very rough cheque of reflected light meters is to hold the cell confronting a flourescent light. The reading should approximate the "sunny sixteen" exposure. A better check is to compare the meter in question against meters known to indicate the right exposure. TTL meters can certainly be as accurate as most hand-held meters under boilerplate conditions. My offset camera with TTL metering, a new Nikon F Photomic T, exposed Kodachrome a trivial more than accurately than the Weston Master 3 I'd relied on for some fourth dimension.
I definitely don't have a physics degree. You could endeavour reading off a matte black carte du jour, 18% gray card and a bright white bill of fare and compare the readings. Use the xviii% gray bill of fare reading and set your camera to that and photograph each of the cards. Pick a scene or subject field that has a decent range of tones and have an incident reading and take shadow, mid-tone and highlight readings adjusting for the zone each falls in. Develop the film and contact print the negatives -- see what you get. You could also exam by photographing the gray card having over and under exposing by one-half stops up to say 2 1/2 stops each way as well as the gray carte du jour reading. Embrace the lens and click off a couple of frames which will give clear negatives plus the pic fog. Make a test (step) print from the clear neg. see where it turns black and utilise that for your printing fourth dimension. Cut pieces of print paper and print each negative at the same enlarger summit, fourth dimension and lens opening (having labeled which stop of the movie it was). Then see which ane of the prints is the very closest or hopefully right on matches the grey card. That will be the ISO for that meter, picture, camera and chemistry.
I'thousand sure there are more scientific means to do this but this is simple and doesn't have long to practise. It could be repeated for other films. All of course B&W. Information technology should requite y'all an idea of the equipment'south accuracy because it takes in to consideration the meter and camera. Which volition carry over to color (I think). For color y'all could accept transparencies once you have the accuracy of the equipment established and if they expect right no worry.
http://www.jeffreyglasser.com/
All you need is a grey carte and a cell telephone. Hold the grey card up in front of a subject and shoot it in black and white. Find a comparable tone with the grey card and meter both that function of the subject area and the grey card and see what yous get. Yous can then meter up and down zones and see how they fall by comparing to some sort of zone strip. You could make ane of those by stride printing in the darkroom or just buy i on the cheap.
Take information technology outside and set it for ISO 100 and cheque the reading. It should be 1/100 or 1/125 @f16 in bright sunlight.
I tested my Luna-pro F against my F100, FM3A and F65 using a grey card, making sure the cameras and the low-cal meter were the same distance from the menu, from the aforementioned spot, and that the calorie-free isn't changing betwixt readings. Make sure the lenses on the cameras lucifer the bending on the lite meter (I think the angle on the Luna-pro matched an 80mm lens). Make sure all the adjustments on the meter are prepare to zero. After a lot of fooling around I was satisfied that the meter was very shut, but in that location was fifty-fifty a small-scale difference in the readings between the cameras so no readings matched upwardly exactly.
It wouldn't have to exist a grey card, a towel would practise just as well.
When it comes to using a light meter to create an accurate exposure regime, out and out accurateness is non as important as consistency.
A light meter may be "inaccurate" past one or more stops and yet be perfectly good plenty to create an operable exposure regime for a specific photographic camera. It would simply kickoff to go wrong if you attempted to apply the same exposure regime to the camera using a dissimilar (mayhap accurate) light meter.

Creating an accurate exposure regime for a specific camera/light meter combination is, in effect, setting upward a closed loop ; modify ane element and the loop breaks...

Regards
Jerry
I have used a Luna Pro-F and have used it for years. The meter has ever performed flawlessly. I accept tried to cheque information technology against other meter with limited results. You take to use a uniformly lit surface with a compatible color. The Luna Pro-F seem to accept a pretty broad angle of view and that makes it hard to compare the reading with other meters. I got a Vari-Angle attachment which turns the meter into a semi-spot meter with a 7 & 15 degree angle of view. Since getting the Vari-Angle it has made comparing much easier, you know exactly what the meter is seeing. I have compared the meter with my Sekonic Fifty-558, F100, N80, D300, D50 & 645ProTL and they are all within 1/3 finish of each other. (all those cameras have spot meters)
I thing you demand to practice is null in correctly, if you don't it volition be off. Download the manual from the link below it tells you how to zero it.

http://www.butkus.org/chinon/flashes_meters/luna-pro_f/luna-pro_f.pdf
Pardon my ignorance, my sensation is that the Gossen Luna-pro existence a lightmeter with silicon blue sensor and integrated circuits, if it works, it should piece of work only as mill new. Electronics don't "decay" with years. Selenium meters might lose sensitivity, I don't think SBC metres will evidence whatsoever kind of disuse. So basically you lot are just checking for damage (needle out of calibration, "lens" displaced, who knows) that would put reading sensibly off.
Anyway, for testing any lightmeter, I would just do this:

- Find a big surface of uniform neutral colour: a white or a grey wall, that is, in shade (you must be in the shade likewise). ("neutral" colour because CdS metres respond differently to different colours. SBC light meters should not have this trouble, or take it very much reduced. Neutral is neutral anyway).

- Measure reflected light from a altitude of at least a metre, paying attention to the angle betwixt lightmeter and wall. Go on it orthogonal to the wall.

- Repeat measure with other cameras, and lightmeters, you have, from the aforementioned distance, paying attention to the angle.

Yous need a uniform wall because this way, the larger or the smaller the angle of reading, you can compare readings;
Y'all need to exist a bit distant, let's say at to the lowest degree 1 metre away, so that modest differences in the bending of incidence does non play a role, and and so that pocket-size lack in uniformity in the wall do not crusade two different readings with two dissimilar lightmetre having a dissimilar angle of reading.
You lot need a neutral wall then that you tin can apply CdS metres for comparing.
Y'all need a wall in the shade and then that it is more uniform, and there is less parasite light inbound photographic camera viewfinders (obviously you lot must exist in the shade yourself).

All that said, you should have the same reading from all lightmetres, and maybe from all cameras. You might come across small differences betwixt lightmetres, but no more than one/3 EV. I would be more careful in comparison readings from cameras, as those can exist influenced by lens vignetting or lens flare (you can have slightly unlike readings when you change your lens) and by parasite calorie-free entering the viewfinder if yous take the dominicus at your back.

I would not use grayness cards, equally a reading from a grey bill of fare is influenced by the angle formed past sunday - carte - camera. Grey cards are tricky, basically not very reliable, objects, unless you lot mount them on a tripod, stick them to a wall etc. and then that you make the readings with exactly the same angle of reading and the same bending of incidence of the low-cal. Besides be conscientious not to project a shadow on the grey card if you use this method. With grey cards, a small movements in the card, changing the angle of reflection of the calorie-free, changes the lite that is measured and this is possibly why comparing lightmetres is unreliable with gray cards, yous tin hands go pocket-size random differences.

A wall in the shade is more reliable because it is in a stock-still position, so you only have to bank check that the bending of the lightmeters-cameras that you compare is e'er the same.

That's what I would do.

Fabrizio
Not to be a total snot here simply I've been seeking the respond to this for several years at present and I've almost given up on it! I really fail to run across, here in the 21st. century, how we take very uncomplicated, precise, and accurate means of measuring virtually all concrete quantities, but no user-friendly means of checking the accuracy of a light meter!
For distances we have rulers and meter sticks. For mass/weight nosotros have scales and balances. For fourth dimension we have stopwatches accurate to the femtosecond! For temperature nosotros have thermometers. Yadda yadda!

It's really difficult to believe that the only fifty-fifty-close-to-satisfactory answers to checking the accuracy of a light meter fall forth these lines:

ane. Transport information technology to a calibration lab for $$$ many times more than the meter is worth.
2. Purchase a $$$$$$ laboratory standard light source.
3. Compare it to a meter or camera which you believe is accurate.
4. Go outside on a sunny day with a grayness/white card or whatsoever.

For all other quantities it seems like information technology'southward like shooting fish in a barrel to trace to a known standard and verify measurement well within a fraction of a per centum.

Why is this so {f-bomb}-ing difficult with a light meter?

(Aye I know, b*tch b*tch b*tch!)
OK I'll bite, whats the cell phone for....
The easiest way is to check it against a meter of known accurateness. If one is not available:
As a first approximation, fix the ASA at 125.
On a sunny twenty-four hours point the meter at a field of green grass or an 18% gray bill of fare. The meter should read f/xvi at 1/125sec. White peel should read f/22 at 1/25 sec on such a day.

If it passes that test and so expose a roll of 35mm colour transparency film using the meter readings, bracketing exposures by one/3 and 2/3 stop and recording your settings and meter readings.

You should terminate up with a meter calibrated to an accuracy of 1/3 finish WITHIN THE LIGHT RANGE Yous Accept USED FOR CALIBRATION. If you lot want to use the meter for, say, night exposures, yous will have to calibrate once again for that.
Why non merely send it in for calibration and KNOW that it's accurate? I like George at Quality Lite Metrics, I ship meters to him regularly, I retrieve he charges about $60, 2 or 3 day turnaround.
In that location'south very niggling to a Luna-Pro: a CdS prison cell, a meter and some resistors. So while information technology *may* exist slightly out of scale, it'south still worth having calibrated. You can even adjust it to apply silverish oxide cells in place of the unavailable mercury cells: http://world wide web.graphic-fusion.com/lunapro.htm
Camera and Luna Pro both aimed at an evenly lit blank wall. Apply a pair of incandescent lamps on a dimmer to light the wall evenly.
Compare readings. I bet it's all the same pretty authentic, the used one I bought was. But, there are places that will recalibrate information technology for you.
All your other examples are a macro measurement. But a light meter is measuring a phenomenon down in the quantum range.
If the low-cal source was intense plenty to oestrus a pail of h2o, you could measure the temperature easily. But that'south a pretty intense light axle. Probably EV 5673 or something preposterous.

Last edited by a moderator: Jan 13, 2011
If you lot are not using information technology correctly, whatever examination you do is going to neglect. Practice yous have the manual? In that location are manuals at http://www.butkus.org/
(I will acknowledge that a friend got a Lunapro F, and fifty-fifty with the transmission, I had some difficulty showing him how to employ it; its not the easiest meter to figure out. Its a good meter but its most like trying to show a beginner how to use an SEI ).

Last edited by a moderator: Jan thirteen, 2011
To test any reflected meter for accuracy, you can get outside on a sunny and entirely clear solar day, near the middle of the 24-hour interval. Meter a greyness card in direct sunlight, with the card at a 45 degree angle to the Sun; make certain the card is free of glare and shadows. Fill the metering pattern entirely with the card. The reading should be close to existence half a stop brighter than a sunny xvi exposure (i.e. the meter volition tell y'all to utilise 1/2 f cease higher than what sunny xvi sez).
In other words, to get the right exposure from a grayness carte du jour when actually shooting, yous take the reading and open up half a finish. In this case, the meter should read f/sixteen-i/2 when shutter speed is set one/3 stride above EI (east.g. shutter of '500 with 400 movie).

Better yet, so yous don't take to monkey with a greyness carte du jour and the 1/2 stop adjustment off of it, just use your Luna Pro as an incident meter. Point the dome at the dominicus in the same conditions I described higher up. You should go a reading that says pretty much exactly '500 at f/xvi with a 400 film, '125 at f/16 with a 100 film, '60 at f/16 with a 50 flick, etc.

Last edited by a moderator: Jan thirteen, 2011
Actually nosotros have a fantastic ways. Meliorate than a 'standard candle' and better than the sun.
Movie! Yep, the ISO of every batch of Kodak film is exactly tailored to a specific ISO (the one on the box) with trimming dyes (per info from our own PE).

I calibrate my sensitometer with Kodak film.

Since yous demand a camera to expose film, you are right in that you can't easily calibrate the meter and camera separate. But since you usually use them together, that should non be a trouble to calibrate them every bit a system.
CPorter Fellow member

Joined:

Feb two, 2004

Location:

Westward KY

Shooter:

4x5 Format

I accept the Luna Pro F, it's a good meter.
First, cheque that the meter is properly "zeroed". Note, adjacent to the three stops "UNDER" designation, notice that in that location is a small green mark. Remove the battery and check that the needle rests on that dark-green marker. If information technology does not, you need to turn the zero adjusting screw on the back of the meter until information technology does; the screw has a curved line above it with pointer marks on each terminate. Use a small screwdriver.
Galah Member

Joined:

Feb 4, 2009

Location:

Oz

Shooter:

Multi Format

I have a boxfull of "erstwhile" meters (also as many cameras with built-in meters).
The but two which actually agree with each other are my Gossen Lunasix-3 and my Gossen Lunasix Pro-F .

Despite this, most of my exposures are quite acceptable.:lol:

Mod (negative) films are amazingly tolerant.
It's been said before in other threads only, whilst the 'sunny 16' method works well in some climates, it doesn't concur here in the united kingdom (and, I'd guess, the rest of northern europe).
Of course, non intending to disparage a technique that conspicuously works well in places like Oz and the US. Only a heads upwards for anyone from northern europe thinking of trying information technology.

********

It's non a technique I'd use merely, if y'all must calibrate a meter, I similar i-c racers suggestion of using the picture to 'backwards calibrate'.

It reminds me of something said to me past 1 of the boffins at Ilford, during a get together of the 'Ilford Main Printers', when I asked him a question virtually making film speed tests towards a zone organization... "Why on globe do you want to do that? If you develop our films according to the instructions, they're already accurately calibrated."
Not sure I fully agree with him, because each photographer works under slightly unlike conditions, but it certainly gave me pause for thought...

Regards
Jerry
Doesn't fifty-fifty work all over the Us, Sunny 16 for me is Sunny eleven.
Don't give upward too soon on that Luna Pro. I have used a Luna Pro F for years, and love it. I actually prefer using it to my L-608. I got enamored a while back with digital readouts, spot metering, and AA Zones and paid a bunch of money for the Sekonic, and I'k lamentable I did. The Luna Pro F's instant analog F-finish under/over exposure indication and ability to see the entire range of available optional apertures and speeds at one glance is then simple and fast to use it puts the fancy 50-608 to shame, at to the lowest degree in cogitating manner. Smashing meter. Mine reads less than one/3 stop dissimilar than the L-608 under quick and dirty reflective utilize, which is how I commonly meter with old cameras anyway. And in the reflective way information technology's FAR easier and faster to utilise than turning the L-608's cumbersome eyes sideways and pushing buttons right and left, and then turning the matter dorsum and studying a readout to meet what happened. Angle of view is pretty wide, but so what? Unless you really need spot metering for zone work or do a lot of studio work and need automatically accumulated and computed flash readings, the Luna Pro F is enough of meter.
If you lot accept a local photographic camera repairman, he should accept a gizmo that puts out a known light value and can quickly test the accuracy of your meter.