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Contradictory meter exposure data


robb_reed
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Hi there...

 

While in the Sierras last week I inadvertently discovered that there

was a difference of 2.5 to 3.5 stops between the Sekonic hand held

meter I use for 4x5 work and the in camera lens in my pentax 6x7! I

wound up running them both against a standardized output light in

Phillips Camera down in Bishop, hoping that one of the two would

suggest an exposure of f8 @ 1/125th. Neither was calibrated with the

light source. The hand held was providing for about 1.5

stops overexposure; the in-camera lens was providing for 2.0 to 2.5

stops underexposure.

 

I've developed some of the 6x7 rolls and they are indeed

underexposed...to such an extent that zone 3 is now zone 1! I'm not

as worried about the sheet film since at least the detail will have

been caught.

 

Anyone relate to this? I'd be interested to hear your strategies for

dealing with the problem. Prior to this trip I never had a problem

with either meter. The handheld had been used in incident mode in the

studio the week before and it provided perfectly exposed negs....

 

Thanks, as I am gnashing my teeth...

 

Robb Reed

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Start with new batteries in both. If there's an adjustment pot (most hand helds will let you calibrate with a pot inside the battery compartment) adjust to a "known." Never adjust without fresh batteries though. All else fails, junk them both and get a new Minolta Spotmeter F.
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No two meters ever agree perfectly, but it's usually a matter of a half stop or less. Yours is definitely a major malfunction.

 

People used to talk a lot about Cds meter cells being temporarily binded by direct exposure to the sun, or also developing some sort of temporary memory. Gossen SBC Blue cells were supposed to be the solution.

 

And then there is increased ultra-violet light at high altitudes which some films and meters see very differently from others.

 

I would let both meters rest in the dark for a week, install new batteries, calibrate them using the sunny/16 rule with a new graycard, then run an exposure/development test.

 

Some sort of factory repair may be in order for this extent of anomoly.

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Robb, it seems odd to me that both meters would go on the blink at the same time, especially considering neither acted up before. I would be more concerned with consistency throughout the range of the meter rather than showing f whatever at whatever at whatever speed rating. You can always adjust the film speed to fit what the meter says if the meter is linear.

 

I think your situation warrents looking for more clues. Now that you are back home, how do your meters read?

 

At the risk of sounding like a broken record, I will offer my exposure advice again. It is a minority opinion on this forum. I think the best way to use a light meter is to leave it in the camera bag until after you set the exposure. The very best way is to actually expose a sheet of film. At that point, bring out the meter as a second opinion. You will soon develop a tuned sense of judging light. You should be able to work without the meter. I do quite often. In this case, you would have noticed the meters were reading off early on.

 

I wouldn't junk either meter until you investigate further. Be aware of the situation in the future. These things happen....like the time in East Berlin when I incorrectly loaded the film........

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Interesting advice, Ken.

 

Reminds me of the time during the 60's when I once assisted Tom Kelly in Hollywood (the guy who did the famous nude of Marilyn Monroe) during a location car shoot up in the hills.

 

He asked for a reading from the Spectra he had handed me to use. After I gave it to him, he questioned my reading. So I read the light a second time.

 

Tom then grabbed the meter and threw it into the bushes. He exposed the 8x10 ektachrome the way he wanted instead. Needless to say, it came out right on the money.

 

Ahh, those were the days...

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This is an easy one. I would be shocked if they DID read the same because you never bothered to have them calibrated.

 

Yes, you can become so familiar with a particular film with lighting that you do not have to meter and get professional results, but you have to shoot a pile of film to get this familiar with the particular emulsion. With 35 and 120, this is not that hard. Process the whole roll the same because that is the way that it is done. You can figure it out pretty damn quickly.

 

Shooting large format is a different ball game for the very reason that we want to contract or extend development for optimal results -WHY? Because we can. Lazy metering practices can surely defeat the whole process.

 

Best recommendation I can give you if you are serious about results. Buy two identical spot meters (or any kind that you use) of the brand that you like and immediately send them both to get calibrated by a professional and reputable company. Leave one in the closet (less battery) as a backup and every four months or so take the one that you regularly use and check it against the one that has been sitting in your closet. When it deviates more than 1/3 stop in any difection from the idle meter, send it immediately back for a calibration. Then the process starts again as the meter that comes back calibrated is now the user meter that checks the other one.

 

The meters that you really use if you do get out and photograph consistently MUST be calibrated every year and it should be a standard part of your equipment maintenance plan. If you travel on an airplane, microvibrations that we do not really feel can play hell on electronics as can bouncing in the back of your pickup truck on the weekends to shoot. Play it safe and look at it as insurance. Until the laws of physics are changed, light that is carefully measured should read the same with each and every meter that reads it every time. I can't tell you how many times I hear that "things are not looking as consistent with my negatives" and the blame immediately goes to chemistry or any number of potential processing shortcomings when the answer is very likely assuming that the meter should work for a career as it came from the factory. Spectra, unquestionably the most respected name in measuring light for years also recommends that their meters be calibrated each and every year. Good Luck

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I agree with Ken on this as well. If daylight is your primary light

source, it doesn't take much experience to know the light levels

easily within one stop and a little more practice will have you within 1/2 stop. You would notice an meter off by 1-3 stops in a hurry.

(I work in a similiar way to estimate exposure, then check

with a meter,,, _then_ I expose) Most daylight situations are within

6-7 stops of full sun. This is only a 6-7 stop range you need to learn. The Sierras were quite sunny this weekend, making it even easier. ....Much easier than carrying 3 or more meters.

 

To start, think in terms of absolute light levels relative to full

sun, or EV's @ ISO 100: full sun = EV15, shade is EV11-12, etc.

 

For much more on the method, give this a read:

 

http://www.fredparker.com/ultexp1.htm

 

This whole problem started when meters quit giving you (and

photogeraphers quit using) EV's. It's hard to think in terms

of actual light levels when you are only dealing with a bunch of shutter speed and f/stop combinations. Set your scale with

'Sunny 16' as the reference point. Most hand held meters give you

an EV readout: use it. For in camera meters it's a bit more tedious

but just reference from F/16 at the sunny 16 shutter speed.

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On my recent trip to Yellowstone, I carried a Rollei 35 pocket camera to make some color snapshops to show my wife. (in addition to the 4x5 with Tri X) On the inside of the lid, the Great Yellow Father had included the "sunny 16" suggestions. However, for the alledgedly 200 speed film, the recommendation was f11 at 1/250. This doesn't invalidate the sunny 16 concept; just be prepared to modify it somewhat.

 

The old Weston Master meters had a very nice feature. I don't remember the exact scientific term, but the meter read in some sort of foot candles. The neat thing about this was the foot candle reading worked out to be the shutter speed when used at the square root of the film speed (f8 at ASA64).

 

On the other hand, I think Michael makes a very good point. He presents a very solid, professional working technique. I think the best combination would be to set the exposure by eye, and then use the precisely calibrated meter. If the eye and meter disagree, shoot two sheets and compare.

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