I have a metal halide 1000 watt vacuum unit.
I am very accurate with my exposures using Ryonets WDP emulsion but I have recently started to look at photo polymer emulsions like Saati PHU or HiFi. Over been doing research and I see people commenting that it takes them "160 light units" to expose. So please can someone school me on what the measurement stands for in regards to time? And how I can put that into perspective on how my unit would work with a certain emulsion.
Thank you
Andre
Metal Halide exposure time in light units?
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Re: Metal Halide exposure time in light units?
Basicaly a "light unit" is a unit of measurement used by the light integrator. Only exposure systems that use a light integrator use this. The light integrator is a device that uses a photocell to determine how much light (in the proper wave length) is seen during the exposure. When a integrator is calibrated (fresh bulb and fresh photocell) one light unit equals to 1 second. As the bulb ages the amount of UV the bulb emits will decrease (even though it is still bright to look at). The photocell captures this information and feeds it back to the integrator which will compensate for this uv loss and extend the total time. So after 6 months 1 unit wont equal 1 second anymore it may equal 2.5 seconds (this example is just a simple explination and may not reflect your actual measurements). A properly calibrated integrator will help maintain a consistant exposure over the life of the bulb (typically 1000hours of use).
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- Joined: Tue Jul 24, 2012 7:02 pm
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Re: Metal Halide exposure time in light units?
Thank you for the response.