View Full Version : Spot meter calibration
Any one know of a company in the UK able to calibrate my Pentax Spotmeter V light meter?
On a weekend shoot with others, my meter seemed to be 2 stops out compared with others.
I have phoned a local photoshop who can send it away, but they are quoting £80-£100, which was a bit of a shock. Is this what I can expect to have to pay? Alternatively, is there a way I can do it, though I guess it would me taking the meter to bits, as well as having the appropriate gear.
Here is an article by photographer Alan Ross, taken from www.AlanRossPhotography.com. This article was copied and pasted as its original text. I thought this might be of some use to you, so I pulled it up. Hope it helps! At the cost of getting it fixed thought, you might be better off purchasing a used one that works correctly.
According to Ted Orland’s poster Photographic Truths: “No two light meters agree.” Sadly, that does seem to be pretty much the truth – unless you do something about it.
For years I had a pair of supposedly “matched” Pentax digital spot meters that were never closer than 1/3 of a stop from each other - so I had to remember which meter I used for film tests and which one I had in the field. One of these meters had an accident and got sent off to its maker for a rebuild – and came back 2/3 of a stop away from where it had been, now 1/3 higher than the meter it had been lower than! So I sent the other meter off to its maker and after two months got it back about the same as when I had sent it. Which meter was right? I then got a dandy little “Pocket Spot” from Metered Light which sometimes agreed with one Pentax and other times, the other. The Pocket Spot was the only really “linear” meter of the three, yielding nearly identical densities on a roll of 35mm film exposed randomly on plain targets ranging in brightness from about 1 EV up to 18. Last spring I had had it with the three-meter dance and decided to finally standardize on the work of a highly competent, pro-savvy company in Hollywood. Quality Light Metric does the meter calibration for the film industry, and those folks don’t have the time to mess around with equipment that isn’t right. I sent both meters off to Hollywood. The calibration was done in two days at substantially less cost than the “other” place, and both meters now agreed exactly with each other, and while they were still 1/3 stop different from the Pocket Spot, they were now, at least, perfectly linear. The final answer? I sent the Pocket Spot and one of the Pentaxes off to Metered Light and had them tweak the PS to match the Pentax. I now have three meters that all read the same!
My students, naturally, have all varieties of meters in their kits. Sometimes they agree with mine and sometimes not. We can tell pretty quickly whether their gear is linear, and if it is then we know they can rely on the readings, they’ll just have a different film speed than I use. But they’ll wind up with the same exposure!
If you have multiple meters and want to put an end to calibration frustration, just have them all set to the same standard, and make that your own. Contact George Milton at Quality Light Metric, 7095 Hollywood Blvd., Hollywood CA 90028. 323-467-2265. If you Google them, you’ll come up with a bunch of different addresses and phone #s. This is the current info for mail order work.
I was wondering what batteries you use to replace the g-13 mercury cells.
Also I presume that the battery check reads OK............
How do you know your meter wasn't "right" and theirs wasn't "off" by two stops? What do your negatives and prints look like?
Apart from that, even if your meter is "off" by two stops as long as it's consistently off by the same amount you don't have a problem, just take that into account when metering.
My understanding is that the sun is a consistant, known light source.
Also that on a bright sunny day that the LV is 15 which matches with EV 15 on the pentax spotmeter.
Therefore, a grey card should read 15 (zone V) on the spotmeter, and the palm of your hand will read 16 (zone VI) ...
My analog pentax spotmeter does read these values... therefore I trust it.
Thanks for the responses so far. They have been informative and reassuring.
I guess I panicked (what with the purchase and processing costs of 5x4 Velvia) when two other digital spot meters agreed with each other and not with mine.
Ryan - thanks for the very full and useful information.
Gerald - I had thought that a low battery would either work or not work, but you infer that it might initially present as inaccurate readings, a point I had not realised. I have checked the batteries (G13's) and they are fine going by the battery tester on the Pentax.
Brian - Outnumbered two to one, I assmumed my meter was the inaccurate one. The Velvia has gone off for processing today, half exposed on the Zone system by my Pentax readings, and half by my Gossen, used in incident mode, when I thought my Pentax was misbehaving. Will feed back on the outcome. I accept your point about working with the inaccuracies of the Pentax (if indeed they are), but just felt that was one more thing to remember when making an exposure, and one more step at which a mistake can be made if forgotten!
WC - I will try your recommendation in the next flush of sunshine here in the rainy north of England!
I would appreciate any other observations, and especially any ideas of who to approach in the UK, if it comes to servicing and calibration, though at the first quote I have received, it could be more economical to look for another, if it is way out of line, as suggested above. I hope not 'cos I am really quite attached to it, and the newer digital versions of meter look rather more cumbersome to use for the Zone system. I have stuck a curved piece of paper around the dial with Zone steps marked at 1 stop intervals, which makes easy work of placing the EV values where you wish them to fall.
John: Please look at this site - it has very good and useful information for you.
Check Dr. Richard J. Henry's book "Controls in Black and White Photography". He describes a very simple (three neutral density filters and a light bulb) method of checking spot meters. You can check against his results (I did) and it works perfectly! Simple, easy and accurate! And I can attest, practically foolproof.
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