Thursday, December 12, 2013

EADS SODERN CERCO f4.1 94mm vs Coastal Optical Systems Inc. 105mm f/4 UV-Micro-Apo lens for reflected ultraviolet photography

Today about two specialized UV lenses, the EADS SODERN CERCO type 2085 f4.1 94mm and the Coastal Optical Systems Inc. (COSI) 105mm f/4 UV-Micro-Apo apochromatic quartz fluorite lenses. In lack of a flower with UV pattern, I'm using a African violet hybride flower for that test as well as my "work horse" UV filter, the Baader-U filter. Light source was Xenon light. All shots were done at f5.6.

[click on image to see a larger one]

Diptych image CERCO 94mm (left) vs COSI 105mm lens (right), Visual light:
 

Diptych image CERCO 94mm (left) vs COSI 105mm lens (right), reflected UV using Baader-U filter (approx. 320-395nm, peak approx. 350nm):
 

Diptych detail image CERCO 94mm (left) vs COSI 105mm lens (right), reflected UV using Baader-U filter (approx. 320-395nm, peak approx. 350nm):
 

The comparison images clearly show that both lenses work exceptionally well for reflected UV as for visual photography and deliver sharp images rich in contrast and detail. I had to adjust the camera position to equalize the focal length differences, so this is not a scientific lens test, but the view of a user. Both come in Nikon-F mount, but the COSI lens covers full format sensors, the CERCO only about the smaller APS-C format (25mm image diameter).

P.S.: The images were not re-adjusted in focus between UV and VIS shots, to show that there is no focus shift between VIS and UV.

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