I have been using Minolta Spotmeter F for years. While the spotmeter worked great and consistently, I was eyeing the Pentax spotmeter due to its dial exposure calculator. With Minolta, I had to push too many buttons to get the required shutter speed. Minolta only works in time priority mode and I use aperture priority for B&W landscapes. Well, I finally got the Pentax digital spotmeter and would like to share my first impressions and ask a couple of questions..
When first comparing the two, I noticed that the Pentax viewfinder is about 1 stop dimmer than Minolta. This came as a surprise, since the lens diameter seems to be the same as for Minolta and the magnification is less than for Minolta. I also noticed that the spot circle is much easier to see in Spotmeter F: it gets dark with bright background and somehow it shines when there is a dark background. With Pentax, it is difficult to see the circle with background at EV 5 or less.... I read many forums before buying the Pentax, but no one mentioned this issue, I wonder would there be variations between the Pentax digital spotmeters (serial number on my is 117752 and it is zone VI modified)?
Second observation is that the Pentax reads about 1 EV less than Minolta. Using a spotmeter on a digital camera, the reading was the same as for Minolta. Now I wonder would this be due to zone VI modification, plus better glare handling of multicoated Pentax spotmeter? I made a hole on white cardboard and put it in front of shoe-box that had black wrapping paper inside. Measuring the reading of the hole and comparing it to the reading on the white cardboard, I got about 3 stops less on the hole with Minolta and about 3.5-4 stops less with Pentax (the white board gave ~ EV 17). Both of them gave too high EV, but Pentax less so (reading off the wrapping paper from behind the white paper gave about EV 9).
My third observation was that Pentax drained the battery much more than expected. I was using 6V silver oxide battery, which was supposed to hold 6.1 V for long time. However after only a few hours of playing with the spotmeter, the voltage dropped to 5.7 V (the temperature was about 15 C). I went to measure the current drain of the battery: it was 18 mA when measuring with lid on the lens and about 23 mA with lid removed from the lens. Without metering, the current was zero. I gather there may be a problem with my spotmeter, draining too much of the current. This current would correspond to effective circuitry resistance of 300 Ohms, way too low....In comparison, Minolta spotmeter drained only about 0.2-0.3 mA (on 1.5V battery). I wonder if anyone else had a similar experience with Pentax spotmeter??
Overall, the Pentax spotmeter is nicer to handle than the Spotmeter F, even though it is difficult to locate the spot circle in dim light. Pentax feels better in hands and is less fiddly to use. However, the battery drain is a concern... I suspect a battery may have leaked in the past, living a conductive path inside the meter.