Here after having previously tested that with a quartz / fluorite achromat, now about using this focal reducer method to change the focal length of a Noflexar f3.5/35mm lens, a very well used lens for UV photography, to widen the field of view. This is also known as telecompressor in astronomy and it is the opposite of a (negative) Barlow lens. Here a positive (quartz in that case) element is used which achieves a 0.86x reduction, hence the lens now behaves as a f3/30mm lens. Here some results using some Phalaenopsis orchids.
[click on image to see a larger one]
no reducer full format:
no reducer 100% crop:
0.86x reducer full format:
0.86x reducer 100% crop:
As you may see, the image quality is hardly affected, even by this simple solution. Focus shift is a little increased, but hardly visible. Next step would be to try out a larger reduction factor. The visible vignetting is caused by a too small reducer lens and will disappear once I have a larger quartz reducer lens one on hand.
P.S.: Just made a test with another quartz focal reducer lens, achieving a) a 0.78 reduction factor and b) the vignetting is gone. That now makes a f2.7/27mm lens out of the Noflexar f3.5/35mm.
Stay tuned, more will follow on that fascinating subject...
More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos