Pentax Digital Spot Meter Questions

[Pover]

So I just received a used Zone IV modified Pentax Digital Spot Meter and have a few questions for you guys. I have been comparing it to my roomates sekonic 508 and everything seems to be in order except when I comes to very low light readings (around EV 1-4). On these readings the Sekonic won't give me an exposure at all but with the Pentax I can get a reading only if I hold down the trigger for a few seconds for EV 3-4 values. To get anything lower I have to first meter something in the EV 6-7 range and then with the trigger depressed pan it to the shadow areas to get EV 1-2 exposures. Is this normal? If not would it cost much to fix? I got the meter for a pretty good price and am wondering if I should return it. Any help would be greatly appreciated.....Thanks

[Donald Miller]

It appears as if your meter is functioning the same as the Pentax that I had several years ago.

Donald Miller

[Jeff Conrad]

My Zone-VI-modified Pentax Digital behaves the same way. In most cases, I can eventually get an indication by directly reading the actual low-luminance area, but it takes a long time, perhaps 20–30 seconds. The values seem to be the same whether I wait forever or first read a higher-luminance area, though my testing here has been cursory at best.

[RichardRitter]

Meter is working right. At low light levels you can speed up the reading by first pointing the meter at a brighter area holding the tirger then the low area. Has to the do with how the analog to digital conversion happens in the meter. Think of it as filling a bucket at high light levels it happens fast and you don't notice it, at low levels it happens slowly.

[BetterSense]

I have a homemade digital spotmeter and for increased dynamic range I programmed it in such a way that it is slower to take a reading at low light levels than at higher ones. The "filling a bucket" analogy is apt. Perhaps the Pentax is designed the same way. However in my mind I cannot reverse-engineer any scheme in which pointing it a higher light levels and then lower light levels would increase the reading speed without also effecting the accuracy. My hunch is this technique only causes it to "work" because it is averaging the higher brightness scene with the lower brightness scene.

[tgtaylor]

Interesting. I never thought about pointing it first at a bright source in low light situations. I have noticed, however, that it will read a value as low as 1/3 EV off moonlight reflecting on water. Maybe I pointed it at the moon first.