Calibrating Spot Meter

mrh

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• Mar 26, 2004

• #1

I had to replace the batteries in my Pentax spot meter (analog), and the unit now seems to be out of calibration. I know there is the test button and adjustment screw to calibrate. I think I once read that when holding down the test button one should adjust the screw so that the needle is pointing to a certain EV value and then it's good to go.

Is that correct and if so, is that EV value '12'? Is there anything else I can do to verify accuracy?

Many thanks,

Matthew

 

Bruce Osgood

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• Mar 26, 2004

• #2

mrh said:

I had to replace the batteries in my Pentax spot meter (analog), and the unit now seems to be out of calibration. I know there is the test button and adjustment screw to calibrate. I think I once read that when holding down the test button one should adjust the screw so that the needle is pointing to a certain EV value and then it's good to go.

Is that correct and if so, is that EV value '12'? Is there anything else I can do to verify accuracy?

Many thanks,

Matthew

Click to expand...

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I have the Spotmeter V which I think is the same as yours.

The test button is to test battery life. When pressed if the needle falls within the black bar running from about 11.5 to about 14.5 your batteries are ok. The 11.5 to 14.5 does not tell you anything about the quality of your batteries. The simple fact that the needle is in the black bar tells you: Good. If outside the black bar: Bad

The set screw above the test button is to adjust the needle farthest right to within the black dot to 'null' the meter. No buttons should be pushed.

 

OP

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mrh

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• Mar 26, 2004

• #3

Bruce, that's great. Thanks!!

 

mobtown_4x5

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• Mar 26, 2004

• #4

I have this meter as well.
I'm wondering if you are aware of the battery issue with these?

The meter is designed to use the old (no longer generally available) 1.35 V mercury cell, apparently, replacement with a regular alkaline battery will screw up calibration.Just changing the offset or "null" will not fix this if the linearity compensation of the unit is designed around the load of the original cell.

There are a bunch of threads around on this on various forums, and there a few options are available (adapter, Wien cell, etc.).

If you are aware of the battery issue and think your calibration problem is unrelated please disregard-

Matt

 

Bruce Osgood

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• Mar 26, 2004

• #5

My Spotmeter V runs on three button batteries.

One happens to be a Sony, an LR 44 as best I can read it.

The other two are Everyready 357.

I'm not aware of any battery issues.

 

lee

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• Mar 26, 2004

• #6

There are two versions of the Spotmeter V out there. The older meter has one scale for low values and one scale for high values. To change to the lower scale you use the trigger button on the handle under the lens. The high scale is always on if I remember correctly. The newer analog meter has one scale period. You activate the meter with that same trigger. It is the older meter that uses the 1.35 volt battery that is not available any more. Someone mentioned some kits for batteries but I have heard that these really eat batteries, but you can buy a lot of batteries for what a new digital meter costs. I had one of the older meters and sadly I killed it one day on my driveway by dropping it on its little head.

lee\c

edited for content one time by l\c

 

mobtown_4x5

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• Mar 27, 2004

• #7

thanks for the clarification lee, I was unaware that there was a newer analog version of the "V" between my old one and the digital incarnation-

luckily I have a stash of 2 unopened mercury cells in the fridge so mine should be going strong for a few years at least!

anyone else out there still using the old one? what are you doing for batteries?

Matt

 

grahamp

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• Mar 27, 2004

• #8

My old Soligor spotmeter takes mercury cells, but I invested in a couple of C.R.I.S. adapters for silver oxide cells. This is a pricey solution - four of these little things would buy you a used Pentax spotmeter - but I have some other equipment that can share them.

Performance seems to be on a par with the original batteries. I rarely use it for low light work which is where any non-linearities would really show.