Frequently Asked Questions
1. How will this meter be useful to me in my artwork?
If your artwork uses UV light to expose the medium, this meter will allow you to ensure a consistent exposure. Examples include: platinum/palladium printing, cyanotypes, kallitypes, photopolymer gravures, vandyke browns, solarplates etc. The meter works by measuring the total dose of UV that your artwork receives and is sometimes called an 'integrator'.
If you work with a UV light source that has variable intensity this meter will ensure that you expose accurately every time. For example, if you use the sun to expose your prints, you can work on a bright summer's day, or a dull winter's day and be certain that your prints will be equally exposed.
Additional uses include: monitoring the uniformity of studio lamps, measuring the UV density of negatives, or monitoring the ambient UV levels in your studio.
2. If I do all my work in the studio using an exposure lamp, do I need this meter?
If your studio lamp is stable and you have already established your exposure times then you really don't need this meter. You already know the dose that works best for your prints. If, however, your lamp intensity varies, or if you have several similar lamps in your studio that have different intensities, you might find it useful.
3. How do I establish the correct 'target dose' for my work?
The target dose is easily established by making test strips in the normal manner for establishing your optimum exposure. Simply note the 'dose' that you give for each test strip. Once you have identified the best dose this becomes the 'target dose' for future work. You don't need to make any more test strips - simply use the meter to monitor the UV during the exposure step and stop when you reach the target.
4. I already established the target dose using my studio lamp, but I now want to start using the sun for my exposures - do I need to find a new 'target dose'?
The short answer is 'yes'. Most likely the emission spectrum for your studio lamp will be very different from the solar emission spectrum - some wavelengths will be much more intense and others much less. Your artwork medium will respond differently to these different spectra, so you will need to establish a new target dose for the sun. But again, you only need to do this one time (see Q.3). For the same reason, if you change your studio lamp (maybe you replace your mercury halide source with an LED source) you will need to establish a new target dose.
5. Why would I want to use the sun for my exposures when I have access to a studio lamp?
The most obvious reason is if you want to do some large format work for which your lamp is too small or for which the intensity is too non-uniform. Also, the sun doesn't take up valuable studio space. The meter will allow you to make prints using the sun and ensure perfect exposures every time.
6. The intensity of the sun can vary considerably - is this a problem?
Not at all, in fact this is the very reason we designed the meter. Please see Q1.
7. I have a target dose for my cyanotypes, will it be the same for my platinum prints?
Generally no. And this applies to most types of media - different media respond differently to light, even to the same type of lamp. Some media (e.g. SolarPlate) respond only to UV wavelengths within a narrow range, whereas other media are sensitive to the blue/green part of the spectrum as well. This is a consequence of the chemistry that takes place in your medium during the exposure process. So you will need to determine the correct 'target dose' for each medium.
8. Which is the best meter for my work?
Both the PPM-2 and PPM-3 meters have the same spectral response and can do the same job of enabling you to get the correct exposure, so your choice should be based on your intended use. If you work in the field, using the sun to expose your work, or you are just looking for a simple-to-operate unit for your studio, the PPM-2 may be a better choice. If you work primarily in the studio, and desire consistent, controllable exposures, with the ability to remember settings and perhaps the ability to automatically switch lamps on and off, the PPM-3 might suit you better.
9. Are the sensors calibrated?
They are calibrated in the sense that they will not change from day-to-day so you can be sure that the 'target dose' you established last week will still work today. But they are not calibrated in engineering units of luminous flux. Adding such an engineering calibration would add unnecessary cost to the meter, without adding much benefit in most cases. The majority of artists simply need to be able to monitor the dose for their artwork, and the units are not important. We simply present a unitless 'dose' number as a convenient and reliable number for the artist to target.
10. I tested my meter inside my house but it doesn't register any UV light. Is it working?
Readings made indoors under normal house-lighting conditions will register almost zero intensity since household bulbs are designed to emit little UV light. In contrast, the midday sun measured outdoors (not through a glass window) will have an intensity level of several hundred units, and a studio lamp may be even brighter.