Posted August 30th, 2014

Teardrop of a Zucchini Leaf

While examining a zucchini plant with a magnifying glass to check for spider mites, I observed a number of these curious, tiny protuberances on the undersides of some of the leaves. The spherical extrusion on each of them looks like a drop of liquid but seems to be solid; I presume it is dried sap. Perhaps these are injuries from a previous mite infestation? The plant has been unproductive since that occurrence in spite of having deep green new foliage, so it is not fully back to health.
Photographing this minute feature was quite challenging. The combination of the reverse mounted lens on my full set of extension tubes produced a magnification factor of about 17x on the sensor (further cropped by almost another 50% in the final composition). At this magnification, just positioning the tripod mounted camera to frame the subject and find focus is difficult. Depth-of-field is razor thin and precise focusing in live view is critical, but live view is noisy and unstable with this setup. The slightest vibration through the floor or a draft that invisibly stirred the leaf resulted in a blurry image. I was probably pushing the old lens beyond its capabilities in this application and even my best captures were soft with very poor contrast and contained multiple dark spots that must have been dust on internal glass surfaces. Heavy tweaking in software was required to compensate for these issues and produce this final image, which closely represents what I saw through my magnifying glass. It doesn't stand up to viewing at large size but I think it is good enough and interesting enough to qualify as my latest Feature Photo.
Pentax K-5, SMC Pentax A 28mm f/2.8 reversed on 68mm extension tubes, 1/6 sec @ f/9.5