Thursday, March 24, 2016

Springtime - With A Vengance!

Yes, we see the calendar - we're a couple days into Spring, but Tucson never really had a Winter! A quick check of the National Weather Service data shows that all Winter, every month had some days over 80F (27C). We've already broken 90F (32C) on 17 February, and the local NBC affiliate has started the contest to name the time the official temperature reaches 100F - grand prize is a $7500 central AC unit! The "normal" date is mid-May, but with 90F broken already 5 weeks ago they are being cautious. And even though it was supposed to be an el Nino winter with above-average rain for us, since the first week of January, we've had under .3" of rain, so we've already taken to occasionally watering the native desert plants to keep them from stressing so soon. So with the higher than normal temps and lack of rain, we didn't get many wildflowers, but the cacti are starting to bloom, seemingly the smallest ones first!

Recently I was reminded to shoot some springtime shots - I was complaining to my bloggin' buddy Ken Spencer on a recent post where his shot of tree buds was mostly out of focus. He should have combined a few frames with slight focus change between them and combine them in Photoshop to "focus stack" and extend the range of sharpness. So I should lead by doing, so here we go... Down at the end of the street, our neighbor Mike has a few potted cacti and has some nice little mammallaria cactus covered with flowers and buds. Since the biggest is less than a cm across (less than 1/2"), time to break out the macro and extension tubes for some ultra-closeups! At left is that 1cm blossom with a 12-frame focus stack, where 12 exposures were combined with slight focus shift between them to keep everything of interest in focus. For comparison, at right is one of the single frames, which were all shot at F/8. Make sure you click on the image to examine the full-size version to see the finest details available. At this magnification, only a narrow range of the flower is in sharp focus - that is why the focus stack is such a powerful technique.

This next one used the same technique on a similar blossom atop the cactus, so the flower was seen more in profile. Again, a dozen frames were combined to make the image - interesting how it takes about that many for these shots... Now someone might ask that instead of taking a dozen shots and spend the 10 minutes on the computer to do the focus stack - can't you just stop the lens down to a smaller aperture to increase the depth of field? Good question and yes, you can! A smaller aperture extends the focus range, but there must be drawbacks - well, yes there is that. With stopping the lens down, the exposure is correspondingly longer. These cacti are pretty sturdy, and since I was shooting with a tripod, there wasn't an issue with using a tenth of a second exposure (at F/32) compared to 1/250 second at F/8 for the others. There is another drawback - at the smallest apertures, the laws of optics fight you and diffraction effects start fuzzing out details again. At right is shown the comparison at full camera resolution, showing the single shot at F/32 with the focus stack at F/8. While the stopped-down exposure does extend the focus range the focus stack wins hands down with incredible sharpness down the pixel scale.

With the mammillaria cactus well-covered, I moved the 40 yards closer to home. My neighbor Susan's prickly pear was forming flower buds - another natural subject. I like the "shooting into the sun" angle, making the needles look almost translucent. While the plant has a few big showy spines, the truly dangerous ones are the multitude of little spines that are hard to spot should you brush against it. On a hike in the wilderness, you nearly need magnifying glass and tweezers to remove most of them. Still, it can be a long-term painful experience! On the right, our Indian Hawthorne in our front planter is almost in full bloom. Interestingly, these plants get almost no direct sunlight, being under the north eave of the house, depends on me for occasional watering, yet has survived for the nearly 30 years I've been in the house. Not really a desert plant, it is likely the constant shade that has allowed it to survive. The flowers are short-lived, but for a couple days are a nice accent to the front of the house. The prickly pear buds were a 9-frame focus stack, the Hawthorn a 12-frame.

While the above pictures would likely have been enough for an early-Spring post, I wanted a little more, so went in search of denizens of the yard. On the Rhus Lancea tree in the back yard, I spotted some aphids and moved in close! These little sap-suckers are small and tough to spot, only about 1mm across. With the maximum 50mm extension tubes on the 100mm macro, the front of the lens was only a couple inches from the little guy. The shot at left is a 12-frame focus stack of a sprig on the tree where the new growth is soft enough for the aphids to take in the sap. I was surprised to only find the one on the higher sprigs (easily accessed without getting down on the ground). After taking this sequence, I looked harder and found a whole herd of aphids being attended by ants. Reading up on the phenomena, it turns out to get enough protein, the aphids take in a huge amount of sap and literally "poop" sugar water, which the ants love. Ants watch over the herd of aphids, moving them to different parts of the plant where there is new growth. Since the ant was so active, a focus stack wasn't going to work, so I went to some effort to get everyone in the same focal plane, and used the flash to freeze the ant's motion. Again, at right is a full-resolution blow-up of the ant watching over the aphids, the left image is a 12-frame stack.

And of course, it wouldn't be a "flora and fauna" post without some 3D images! So get out the red/blue anaglyph images for the following images. Macro shots are a little harder to get good 3D - they are very sensitive to scale, and the baseline between the image pairs are smaller than your eye separation, otherwise the 3D effect gets uncomfortably large and tough to focus. The little mammallaria cactus at the start of the post was a great subject, with only about an inch baseline between images. Shown at left, it is a great stereo shot, but the flower color is close to the glasses filters color and weird shifts occur! The flowers come out a blue/purple - interesting, but totally alien in appearance! So go to the top images in the post and imagine THAT color in the anaglyph at left. At right is the only non-macro shot today. I think it is a mesquite or palo verde tree whose flowering branches would make a good 3D image. It was taken with the kit lens and has a stereo baseline of about your eye separation, so should look pretty natural.

So that is what I've got so far this Spring. I'm keeping an eye out and will continue to see what looks interesting...

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