Archivos de diario de noviembre 2022

01 de noviembre de 2022

Exploring underfoot: Point Defiance Park, Fort Nisqually

On Sunday, I visited Point Defiance Park, which is densely forested and not managed for logging - quite a lot of snags and also many older trees. Good place to see pileated woodpeckers, but I was there to look down, not up.

I observed at several spots close together, and with the iffy GPS reception, I'm not sure there's much point trying to differentiate. If I wanted to be more methodical, I'd have to keep better records of what I observed where. I did notice that the beetle mites (which were very common) were mostly associated with locations containing decaying wood.

I observed mostly on and near the bluffs above the water, so these were fairly exposed locations. On another day I'll see what I can find near the center of the park.

I found different springtails here than I found at the other locations, and I was able to observe several different varieties. That was exciting! I also saw a couple interesting-looking snails and some very cool mites. My favorite observation of the day, however, was a little purple globular springtail - I suspect of a cosmopolitan species - who displayed very actively, seemingly in response to my camera. I have to admire the pluck. Imagine challenging the Death Star to a duel...

The springtail must have won, because my camera and I departed.

Publicado el noviembre 1, 2022 01:17 MAÑANA por wildnettle wildnettle | 20 observaciones | 0 comentarios | Deja un comentario

28 de noviembre de 2022

Single-shot imaging of living Collembola in the field with existing equipment

I've been trying to achieve acceptable detail on springtails at high magnification without spending $1000 on the lens that springtail photographers prefer (that I don't even have a camera body to match anyway). The goal is to be able to clearly and unambiguously distinguish morphological details such as individual ocelli and setae, even on specimens of 1mm or less, when they are in focus. Additionally, the depth of field must be sufficient to locate the springtail, focus the image, and get at least an entire eye (cluster of ocelli) in focus at once. Preferably, it should be possible to achieve reasonable focus on both the eye and front lateral plane in a side view, but that will depend on the size of the individual being photographed.

This won't permit identification of all spp or even all families, but it should at least permit identification of some of the more easily identifiable spp, genera, and families, and should be sufficient for me to start learning more about identifying living springtails in the field without a compound microscope.

I'm also enjoying photographing mites and other small critters, but the springtails are really the focus of this project.

The images associated with this post were taken at Point Defiance Park in the Rhododendron Garden. There were quite a lot of springtails about!

The field of view is about 3.6 mm across, and the depth of field achieved is at least 100 microns. Features of 10 microns or perhaps smaller can be recognized if they're in focus.

Yes, I decided I should try to focus a 100 micron (1/10 mm) depth of field handheld. BECAUSE I'M LIKE THAT. I did it though! A lot of breath-holding was involved.

The "lens" is around 200mm long (but not very heavy) and it is not remotely water resistant. Using this in the field is... a life choice. That I made. For some reason.

Technical details:
I used a 4x infinity microscope objective mounted on a reversed Raynox DCR-150 tube lens, identical to what is often used for focus stacking at high magnification in the studio. However, in order to get some actual depth of field, I added an aperture disk in between the microscope objective and the lens. I spent $10 to buy a set of aperture disks intended for a Lensbaby Composer. This set doesn't have anything between f/5.6 and f/8, so I widened the holes in the f/16 and f/22 objectives to fill the gap. Then the disk is simply taped to the opposite side of the adapter that holds the microscope objective. Black gaffer's tape would be ideal but I just used electrical tape because that's what I have, and it's facing away from all the light sources anyway.

I'm astonished and thrilled that I was able to manage remotely acceptable results with this technique. Did I mention the lens typically used for this task costs $1000, which is $1000 more than I have available to spend on this project?

Publicado el noviembre 28, 2022 04:57 MAÑANA por wildnettle wildnettle | 5 observaciones | 0 comentarios | Deja un comentario