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Technical Evening January 15th

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Technical Evening January 15th

The first evening kicks of on January 15th 2018 with a technical evening.

Please bring with you a camera (!), tripod, lens with biggest aperture possible (f1.4 / f2.8 etc) and a flash (if you have one).

Will will be looking at bokeh and use of light.

Many thanks,


Tech Evening

Hi All,
I hope you found the Tech Evening instructive. Unfortunately I didn’t manage to join the bokeh fun. I did, however, find out other things. Using the light transmission meter borrowed from an optician I found that modern so-called UV filters may not be.
Two UV filters from a Braun Super Paxette IIB film camera of 1958 vintage had UV transmissions of 62% and 58% with visible light transmissions of 90% and 91%. This makes sense.
A 58 mm “UV filter” which fits my Canon cameras has a UV transmission of 90% and a visible light transmission of 92%. Clearly the “filter” doesn’t. Trying this test on a few Members’ “UV filters” showed comparable results, i.e. they did not filter UV out.
This is probably no problem for digital cameras which are not as responsive to UV light as the film in a film camera can be.
Interestingly my polarizing sunglasses stopped 100% UV (0% transmission), and my two PLC filters had UV transmissions of 19% and 0%. Your polarizing sunglasses, clip-on or integral, are probably UV absorbant as well.
This does not mean that “UV filters” for digital cameras are of no value since they will protect the camera lens against rain, dust, dirt and fingers with minimal reduction of visible light.
If Members would like to check their UV filters, or other filters, I can arrange to borrow the meter again.
Much fun was had with polarizing film and filters, resurrecting Brewster’s angle and my version of Pepper’s Ghost using Alan (images available).


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