[Alt-photo] LightMeasure UV meters - First impressions

Jacques Kevers jacqueskv at gmail.com
Mon Dec 11 13:33:02 UTC 2017


Hi,
Several of the Picto Benelux members purchased the PPM2 from the first
production run.
I have been collecting their first impressions and made the following
summary:
....
The meter is neatly stowed away in a handy case. Easy to set up and to put
into operation. It is rather small, and therefore easy to place in the UV
light box.

The sensor with the extension cords seems a bit fragile. But if you remove
the plug carefully and do not pull on the cable, it will certainly last for
years.

The display is simple and clear, it shows the time (in seconds), the
instant intensity and the accumulated amount of UV energy. Everything very
simple but efficient.

For one of the tests, the sensor was placed in a lightbox (face tanning
lamp), and only then was the light switched on. This highlighted how those
bulbs works: the light intensity shows a continuous and almost stable rise.
After 3 minutes the lamps were still heating up, which means that their
frequency and thus their output continued to change. After letting the lamp
warm up first for 5 min., and then exposing for 3 min., the intensity was
still increasing during these 3 min. by about 3%. All this shows also the
high photosensitivity of the device.

The most important thing about such meters is repeatability. The same
numbers should be obtained, for example, with repeated identical
exposures/measurements. That was the case here (5x exposure/measurement
cycles).

When comparing two meters with each other, they won't give quite the same
values. That's normal, and the manufacturer mentioned that the units are
not calibrated in engineering units of luminous flux. The difference
between different meters was around 4%, but these 4% remained constant. For
our use, as one usually only works with one and the same measuring device,
this is absolutely no problem.
But if you want to exchange exposure information (when discussing a process
with other photographers, for instance), you have to keep in mind that
there may be small differences.

The sensor must be well placed. If it is not exactly aimed at the light
source, there will be immediately a difference in the results.

Other uses
- Measuring the light distribution of the light box. One can see how the UV
light illuminates not only the center, but also the corners, and how
important is the fall-off.
- René Smets, a prominent member of our group, used it as a light meter for
his wet collodion and daguerreotype outdoor shots, placing the sensor on
the camera lens, and is delighted with it. Once the target dose for his
plates is determined, sun variations during exposure are easy to handle.

So, the general impression is very positive and the buyers are very
satisfied. In short, they consider it as a good and useful tool.

I tought this might be of interest for the list members. I'm sure that, if
the information about the devices' qualities could be widespread enough,
Ian should be able to get enough orders for further production runs...

Best regards,
Jacques

Jacques Kevers
Beau Site
Première Avenue 7
B-1330 Rixensart
Belgium
+32 2 653 56 02


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