When Donald previously asked a related question I wrote a long reply with my analysis of enlarging to Azo: http://www.photo.net/bboard/q-and-a-...?msg_id=004T4K. Someone thinking of trying this should study Sandy King's article on UV light sources at http://unblinkingeye.com/Articles/Light/light.html, the sensitivity curve of Azo in Kodak's publication G-10 at http://www.kodak.com/global/en/profe.../g10/g10.jhtml, (with the curve at http://www.kodak.com/global/en/profe...009_0106ac.gif), with the transmittance curves for enlarginging lenses, e.g., http://www.schneideroptics.com/photography/photo_enlarging/apo-componon_hm/pdf/apo-componon_hm_40_150.pdf.
Note that the vertical axis of the spectral sensitivity graph for Azo uses a log scale.
From comparing the sensitivity curve of Azo with the transmission curves of enlarging lenses, one wants is light of about 400 nm. An interesting new possibilty would be to use many near UV LEDs. LEDs are less efficient than incandescent bulbs in terms of light per input electrical power, but when only a narrow range of wavelengths is useful the calculation changes. The semi-surplus seller Marlin P. Jones, Inc. has 400 nm LEDs for $2.99. It would be interesting to try a couple of these, and if they seemed promising, to make a 4x5 head with LEDs densely spaced over the negative.
If your light source needs a shutter, you could always make an independent support to hold it a few mm in front of the lens. This way any vibration of the shutter wouldn't effect the lens or the image. Probably this wouldn't be necesssary because the amount and time duration of vibration would be very short compared to the exposure time.
From's Donald's description, it sounds like the 400 W source is a mercury vapor or metal halide lamp rather than BLB fluorescent. Also, Sandy King explains why a BL fluorescent bulb would be slightly better than the more common BLB.
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