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08-28-2009, 06:25 PM   #1
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Honeywell Pentax 1/21 Meter

Anybody is still using light meter?

Just picked up a circa 1966 Honeywell Pentax 1/21 spot meter:



It is well-used, but seems to be operational, at least the "low light level" part of it. It is about 1/3 - 2/3 stop off toward underexposure compared to a much younger Minolta IV F. Is that acceptable? If not, is calibration a DIY job? Sending it out for professional calibration probably does not make economic sense.

I don't have the proper battery (1.35V mercury) to test the "high light level" metering. Not sure what to do about that.

I don't think the meter has much practical use, at least for me, but it is sure fun to play with.

08-31-2009, 12:22 AM   #2
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Don't you hate it when you reply to your own post, or worse yet, answer your own question

So here's the initial status:

- I insert a 1.5V alkaline battery cell in the batter chamber (with some other things to take up the spare space). The 'low level' meter matches with the Minolta IV F.

- But the 'high level' meter is 1 stop slower than what it should be (e.g. it recommends F/8 when the correct value should be F/5.6).

So I open the meter up to take a peek. To my surprise, there is no potentiometers to adjust. The circuit board is pretty simple, with only 4 resistors.

By trial an error, I find that if I add a 1 KOhm resistor in parallel with one of the 4 resistors, the 'high level' meter becomes correct. The 'low level' meter remains correct.

So now I have a working 1-degree spot meter. It has limited usefulness (unlike films, photos are essentially free) but is fun to play with.
09-01-2009, 09:30 AM   #3
D W
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It is good to have to actually understand the contrast range of your scene. Since we can't alter the development time/contrast ratio of sensor some of the usefulness is not there anymore.
Like you mention, there is no added cost to bracketing a scene.
09-01-2009, 12:02 PM   #4
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QuoteOriginally posted by D W Quote
It is good to have to actually understand the contrast range of your scene.
Yup, DW.

I forgot to mention that the spot meter is a fantastic educational tool. My son is having fun with it. And I take this opportunity to give him more info on contrast range, EV, .... (he already knows about f-stop and aperture and ISO).

It sounds good, right? Wrong, according to my wife. Now my son needs a K-7 body so that he can use its HDR feature. His birthday is coming, you never know

11-20-2009, 04:52 PM   #5
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QuoteOriginally posted by SOldBear Quote
Anybody is still using light meter?
I use it all the time. I have the Pentax Spotmeter V. I use a WLF on my Pentax 67 and Hasselblad 500C/M so this meter is very useful. And I like it better than the digital Minolta Spotmeter F I also have. The dial on them is quicker to finally decide on the scene's exposure.
08-20-2010, 02:43 PM   #6
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SOldBear,
I just picked up a Pentax 1/21 spot meter myself.

It had an alkaline cell in it with a little juice left and I threw in a 9 volt to see if it works. It seems to; at least the needle responds to changes in the light but it's a little shy of the bar when the check battery button is pressed.

Can you elaborate on where you placed the resistor so that the meter works with the 1.5V alkaline cell?

Thank you,
Andelps
04-05-2013, 11:48 AM   #7
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I just picked up a 1966 vintage 1/21 series spot exposure meter in perfect shape with manual, but I need battery advice please. I ordered the 625A battery but the 9v battery it uses does not seem to be our normal standard 9v transistor radio battery. The manual does not list product numbers for either of the batteries and the photo seems to show a 9v that has contacts on the base as well as on the top. A standard 9v is too tall as the door won't close. Any help would be appreciated. Thanks.

04-06-2013, 09:01 AM   #8
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The Pentax Spotmeter is both a very useful tool and a 'fun' tool (especially if you're one of those guys that always wanted one when they first appeared and you couldn't afford one ).

Search for "mercury battery replacement" on-line. There are voltage-equivalent options and some DIY projects too. Don't disregard the possibility of building an "outboard" battery pack wired to the original battery contacts - that offers many options for replacement batteries; ICs and simple diodes can be used to tweak the voltage. In some cases you can simply stack 1.2-volt button cells and a coil spring in heat shrink tubing to find a temporary solution.

Hardware calibration is possible, but I've found that simply building a calibration card taped to the meter is much more flexible and can be tailored to customize the use for different situations as well.

I learned long ago to calibrate all my meters, including my first Spotmatic TTL meter, against a clear blue sky and/or a grey card. depending on the use.

There's much to be learned from spot metering a scene and comparing the results with the various in-camera metering modes and the matrix mode EV graphic in PhotoMe.

H2
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