Mold on a gourd: reflected UV photography

Today about mold on a gourd and making that visible using reflected UV photography using my "work horse" UV filter, the Baader-U filter. Lens used was an older enlarger lens. Light source was a modified for UV high power Xenon flash.

Here now some results: [click on image to see a larger one]

visible light image using UV/IR cut filter:
 

UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm):
 

Differential image VIS - UV:
 


Well, as one can see, UV and visible image contribute differently to that mold, UV bounces off right from teh surface, while visible light penetrates a bit deeper, which the differential image makes quite visible.

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

Deep UV reflected photography - Uranus-U filter

Today again about that Phalaenopsis orchid, but this time used as a target for deep UV reflected photography. Usually I use my "work horse" UV filter, the Baader-U filter, but this time also the Saturn-U (300-350nm, eff. 325nm) and Uranus-U (300-325nm, eff. 313nm) filter, the latter newly introduced here now. Lens used was the 94mm CERCO quartz fluorite lens. Light source was a modified for UV high power Xenon flash.

Here now some results: [click on image to see a larger one]

visible light image using UV/IR cut filter:
 

UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm):
 

UV image using Jupiter-U filter (approx. 280-385nm, effective peak approx. 365nm):
 

UV image using Saturn-U filter (approx. 300-350nm, effective peak approx. 325nm):
 

UV image using Uranus-U filter (approx. 300-325nm, effective peak approx. 313nm):
 


Interesting to notice, how the visible details change when the used wavelength gets shorter and the appearance of that turquoise color. I'm looking forward to testing this with flowers having more prominent UV patterns, once spring is here...

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

Quartz lens for reflected UV photography?

Today about using a quartz lens for reflected UV photography. I'm using quite rare Quartz Takumar f3.5 85mm for this and one of the few flowers available, a Phalaenopsis orchid, as well as my "work horse" UV filter, the Baader-U filter. Light source was sunlight and a Nichia UV LED (365nm). The questions was, how the image quality would turn out, knowing that such lenses should only be used for a quite narrow wavelength band (literature states between 10nm and 20nm depending on source), as these lenses are not chromatically corrected. All shots were done stopped down to f8, which is a usual working aperture to get enough DOF and sharpness.

[click on image to see a larger one]
Here some results:
visible light image using UV/IR cut filter:
 

multispectral image (i.e. unfiltered) and sunlight:
 

UV image using Baader-U filter and sunlight:
 

UV image using Baader-U filter and sunlight + 365nm UV LED:
 

Findings:
1) There is a substantial focusing difference, here 5mm between the UV (95mm) and the VIS image (100mm between front and camera mount), resulting in a 5% different image size when focused both (UV image is smaller). Distance orchid - camera was 700mm.
2) When white light is being used for visible photography, the 400-750nm band is quite broad, i.e. 350nm, which leads to quite visible CA (around edges), soft image and loss of contrast.
3) When white light is being used for multispectral (i.e. unfiltered ca 300-1100nm) photography, that band is even broader, leading to even softer images and loss of contrast.
4) Also the UV image taken in sunlight using a Baader-U filter (320-395nm i.e. 75nm bandwith) leads to rather soft images, but a bit better as the band is narrower, only 75nm wide.
5) The UV image taken in UV LED light at 365nm (ca 20nm bandwith) using a Baader-U filter leads to the best image, as here only the narrow 20nm bandwith of the UV LED around 365nm plays a role. The image is crisp, sharp (see structures on petals) and has a rather high contrast.

Conclusion is, that only if quasi monochromatic photography is being done (either using narrowband UV filters or narrowband UV light), acceptable results can be expected. For broadband UV photography, chromatically corrected UV lenses are required, such as quartz fluorite lenses.

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