Friday, 31 August 2012

Pano processing and UV photoing

This morning I processed a pano. Then I looked online for UV flash power info. Unfortunately I couldn't find any specific information. I think that probably my camera isn't as sensitive to UV as converted cameras (despite my camera being designed for UV work).

I went out and picked some dandelions. Then I took some test photos. These are all at ISO 320. The first photo is with the flash a few centimetres away from the flower and at full power. So I think really I need about 3 flashes at least, that way I can use f/8 and lower ISO, or have the flashes further away from the subject.

This next photo is holding the fresnel lens from the (Vivitar 283) flash in front of the flash. (Since I removed the fresnel lens from the flash as that is recommended for UV photography). As you can see, the recommendation of removing the lens is 100% correct. If the fresnel lens was still installed in the flash normally, this image would be completely black. Obviously it does a very good job of blocking UV.

The next photo is taken quite a while after the previous one, and the Dandelion had started to wilt. (I did have it in a pot of water, but I guess that wasn't good enough for it). The long delay between pics is that it took me ages to find my 52-67mm step up ring needed for the Vis photo. This photo below is not the visible light one, but a full spectrum photo taken with natural light only (1/20s).

Photo below is visible light only (B+W 486). 1/15s.

And this last photo is NIR only (Hitech infrared). 1/10s.

For these photos I adjusted the exposure in ACR slightly. I set the white balance on the white pot the dandelion is in. For the UV photo, the WB adjustment does not go far enough. So I played the hue adjustments on the camera calibration tab to make the pot as close to neutral as I could.

In the evening I cut out a piece of plastic as a replacement for the flash's fresnel lens.

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