Spotmeter V Delirium

[Arvee]

Hi All,

I recently inherited a Pentax Spotmeter V in the box in perfect condition. It has a peculiarity that has me wondering if it needs repair.

When taking a measurement holding the meter perfectly vertical and aiming it at the horizon (perfectly level) there is about a third of a stop of needle 'jitter.' If I elevate or depress the meter aimpoint by 5 degrees the reading stabilizes. If I rotate the meter a few degrees away from vertical while still holding aimpoint level, the reading stabilizes.

The readings are deadly accurate but has this weird behavior when perfectly vertical and horizontal. It seems gravity stabilizes the reading.

Any other Spotmeter V owners seen this? Is this normal operation? Pentax thought this was probably okay.

Fred

 

[Kilgallb]

The Spotmeter V uses a d'Arsonval meter movement. The jitter is normal, but the lack of jitter when off of vertical is not. It indicates the meter indicator is not seated in the jewelled berings correctly. There is a mechanical zero adjust that could be misadjusted. you would need to open up the meter and with no power applied adjust the screww in the midle of the meter movement for zero then back itoff slightly. I am not sure if the screw is actually accesible. (I have only taken mine apart twice)

 

[pentaxuser]

Isn't the horizon the area where light values suddenly change? Is even 1 degree spot at this distance accurate enough to exactly split the horizon without a slight deviation/oscillation in the holder's hand. I can't explain why when aimed at other than straight ahead from the user it should still fluctuate except to ask: Can you be sure it is still aimed at exactly the same horizon/ ground dividing point without fluctuation of its level when you do this?

Just some thoughts

pentaxuser

 

[Arvee]

I see this jitter when the subject in the 1 deg. circle is mixed tonal content. Solid tones seem to be stable. Is the sensor so specific that it will dither a mixed tone? Does the circle not integrate the tonal content within the measurement area?

 

[jovo]

If you want to have it checked out and/or repaired and calibrated consider sending it to Richard Ritter. Among his specialties is Pentax and Soligor spot meter service. Superb work, a fair price, and not a long wait.


Here's a link: http://www.lg4mat.net/

 

[Arvee]

Jovo,

Thanks for the tip. Talked to Richard and he says the jitter is normal as the pivot points are subject the least amount of friction when held perfectly vertical/horizontal. Going off axis changes the amount of friction and suppresses the jitter.

Fred