Tuesday, November 29, 2011

Microsnail Microphotography #1 - Reversing a Lens

The technique I've landed on for photographing microsnails is reversing a prime focal length lens. After testing close-up filters I feel the quality and magnification are better by reversing a lens.

Note that this math seems to only hold true for reversing a prime lens (non-zoom). Also, the reversed lens should be set to it's widest aperture and both lenses focused at infinity.

The math for how much magnification you get reversing a lens is a simple forward lens focal length/reversed lens focal length. So, if you have a 200mm lens and you reverse a 50mm you are enlarging 4 times. It's handy-to-do, uncomplicated math.

Now I've got two choices as to where to reverse a lens. I own a Nikon D90 dslr camera and just purchased a Panasonic Lumix FZ150 digital camera. They are both 12 megapixels. This means the bigger sensor is less crowded for better images. Thus, the D90, being a dslr, has an edge on image quailty.  Still, both produce usable images. The FZ150 I'd likely keep to ISO 100, maybe 200. The D90 I can shoot to 400, maybe 800.

The key, however, to enlarging these 1 to 4mm snails is sensor size. The D90 has a sensor size of 23.6mm x 15.8mm and the FZ150 has a 6.16mm x 4.62mm. So you can imagine which camera it's easier to fill with an enlarged portion of light projection.

The lens I own for the D90 is a 90mm macro. Forward it's a 1:1 lens. Useful for full frame if I'm photographing one of the larger polygyrids. With a 50mm lens reversed it's 1.8x enlargement. So let's say I want to photograph a 1.1mm Punctum minumissimum. Saying the snail is evenly round it projects a 1.98mm image onto a 23.6mm sensor. It's not very big, only 8% of the sensor height.

The FZ150 has a built-in lens ranging from 4.5mm to 108mm. This is equivalent to 24mm to 600mm in 35mm terms, but you can't use that measurement, only the real focal length. Reversing that same 50mm lens you get a 2.16x enlargement. It's not that much more than the dslr with a 90mm lens but the key is where it's being projected. Now the snail is 2.376mm on a 6.16mm sensor or 38.5% of the image height.

If I wanted to fill as much of the frame as I could with that same snail I'd just need to use the short measure to reverse engineer it. It needs to just about fill 4.62mm, so for easy math let's say I want to enlarge it to 4.4mm on the sensor (remember, it's 1.1mm), that's 95%. Good enough. Desired enlargement size/actual size is 4x magnification. Forward lens/ magnification is 27mm. I don't know of any 27mm lenses but 28mm lens are pretty common. If I were to get one my P. min. would now take up about 92% of the short measure of the image. The long side only gets about 70% but I would suppose an apical view with an even measure. That's still a lot of image on a 12 megapixel camera.

But what if I really wanted to use that D90 ? I could always use extension tubes. I've got about 58mm of extension tubes, add the 90mm lens for 148mm, reverse a 28mm lens is 5.28x enlargement. The snail is now 5.8mm out of the short measure (15.8mm) so a little over a third. I've never tried this but that seems like it would be the math. I could be wrong because of where the back of the forward lens is in. If I'm assuming I'm doing the math right, what if I added in a 2x teleconverter. It would go directly behind the forward lens but not between camera and tubes. It's now a 180mm lens and 58mm of tubes--238mm. Supposing this is all right, we're now at 8.5x magnification. Our snail is 9.35mm of projected image. I'll leave you to the math of what lenses/tubes/teleconverters/alchemy to use to try to fill the frame. Needless to say there are a ton of possibilities. But these possibilities generally add up to more of a cost that just the digicam and a prime lens or two.

As you see, it's easier to work with the small sensor for these small snails. Plus ultimately cheaper if you're starting from scratch. Another bonus is that the digital camera, although big as far as digicams go, is still lighter and compact thus more likely to go on a hike with me.

The biggest gotcha I've found with reversing a lens is that some lenses/combinations/focal lengths will be seen on the periphery of your image. I only have the 50mm lens and on the FZ150 I can use it from 76.5mm to 108mm without seeing any of the reversed lens. I'm not sure if a shorter lens would allow me to zoom out more or exacerbate the situation or keep it about the same. I'll have to give it a try if I can get my hands on a shorter lens.

One last thing. If you want to get really fancy you an just reverse the lens without a lens in front of it for various magnifications. I didn't do the math and I'm super tired but as a for instance I made a makeshift extension tube out of a Pringles can and then reversed a 50mm lens at the end of it. It would up giving me about 8x magnification (I shot this with the D90 since you can't remove the lens of the FZ150). Not bad for a 99¢ can of chips (although I find the inedible) and a lens I got on ebay for about $20. I already had a macro reverse ring to attach to a camera but you could also modify a body cap from the camera to connect it if one was so inclined.

Next headaches: Depth of Field, Lighting, Camera Shake.

Wednesday, November 23, 2011

Pupoides albilabris : White-lip Dagger

Found: Under debris along the railroad tracks, Salt Point, Lansing, NY, Nov. 2001
Sympatric: Gastrocopta armifera, Pupilla muscorum, Vallonia costata, Vallonia excentrica/pulchella, Hygromia striolata

Working on macrophotography for the microsnails. Right now just trying to handle magnification, that's why the lighting is less than wonderful in these photos. This little fella measures 4.45mm (shell height), still on the large size of the snails I want to photograph. These are crops taken with a reversed lens on an dslr where the snail's height took up about 50% of frame height.

Tuesday, November 8, 2011

Updated Pupillid Info

Big score tonight when I happened upon this:

Pupillid land snails of eastern North America

by Jeffrey C. Nekola and Brian F. Coles

It's basically an updated key to the the Pupillid (Pupilidae, Gastrocoptidae, Vertiginidae) Snails. That's about as hot as it gets. Relatively speaking.

This seems to be a busy team as they also wrote a few more papers available online:

A discovery of a new Vertiginidae snail in 2007- Vertigo malleata

A paper on acidic preferences of land snails

And one with Ulfar Bergthorsson on the Evolution of the Vertigo gouldi group using DNA testing

Thursday, November 3, 2011

Introducing Ithaca

Of a pretty big disappointment to me is how much the terrestrial mollusk fauna in the Ithaca area is non-native. I guess, however, this is to be expected in a developed area-- even one that seems like it's known for it's natural areas (Ithaca is Gorges). Still, I'm spoiled by some good snailing back home in PA.

Here are some of the non-native species I've encounted:

Discus rotundatus

Photo by Aiwok: http://commons.wikimedia.org/wiki/File:Discus_rotundatus_2.JPG
Probably the snail I was most pleased to see out of the non-natives only because there are so many Discus Catskillensis where I live in PA. I found some of these near the Equestrian Center in Ithaca (can't remember what it's called, some sort of orchards).

Limax Maximus : Leopard Slug

Photo by Jonathan Feinberg http://commons.wikimedia.org/wiki/File:Leopard_Slug_Somerville_MA.jpeg
As far as the non-native slugs go, this is pretty cool the first time you see it. It's absolutely huge. Another species I've never encountered back in PA. I've found this slug in Sapsucker Woods and Monkey Run.

Trochulus hispidus : Hairy Snail

Photo by James K. Lindsey http://commons.wikimedia.org/wiki/File:Trichia.hispida.jpg
This could be a wrong identity on my part as Trochulus striolatus (Strawberry Snail) as juveniles of this species have periostracal structures as well. I've only found 2 alive and a ton of empties. I'll have to check inside the umbilicus of the many shells I found this week for hairs with a microscope when I go home to PA to see if I can confirm these as T. hispidus. Either way, I've seen Trochulus species at Sapsucker Woods and Salt Point.

Carychium minimum : Herald Thorn

Photo by snailmail http://commons.wikimedia.org/wiki/File:Carichium_minimum.jpg

I only found empties of this snail in stream drift from Buttermilk Falls. However, I read a paper about the snail being naturalized in wet areas around Beebe Lake on the Cornell campus. This is a tiny snail-- somewhere between 1.6mm and 2.2mm.

Other species about:

Cepaea nemoralis- around the Lab of Ornithology. Rose and yellow variants, as well as spiral lined. There may also be C. hortensis mixed in. That or it's some C. nemoralis juveniles reaching to about C. hortensis size and not yet developing the brown lip. I'll have to check harder next year. I tend to gloss over non-native species, not giving them the attention I do natives.
Oxychilus allarius- possibly. Cayuga Heights and near Lab of Ornithology
Arion species- Definitely subfuscus and possibly distinctus. Never pay much attention to ugly Arion slugs.
Deroceras reticulum- another ugly alien slug, everywhere.

Tuesday, November 1, 2011

Vitrina angelicae : Eastern Glass-Snail

I've said it once, and I'll say it again, the northeast region of Pennsylvania is fairly understudied (or at least under-reported) when it comes to nature, which is funny to think about, as it's located a short 2 hours from either Philadelphia or New York City. Multiply an understudied class of organisms by an understudied area and you've got a void of knowledge. This reason is why it's exciting (alright, let's talk in relativities) to be interested in snails and live, at least part-time, in Northeast PA. My sightings get to actually add to the knowledge base with new records.

Which brings me to Vitrina angelicae, the Eastern Glass-Snail. Also I've seen a common name of Transparent Vitrine Snail, but that name is pretty lame. According to Pilsbry, the genus name stems from the the latin word vitrum, which translates to glass and the species name is traced to the plant, Angelica archangelica, near which it was originally found.

According to the records, this snail is only known to reside in Western, mostly Northwestern, Pennsylvania. Also, according to what is known, the snail is an annual species--becoming active in October and dead by the spring. You can read about it at http://www.carnegiemnh.org/mollusks/palandsnails/vi_ange.html.

I also found information at http://www.livinglandscapes.bc.ca/cbasin/molluscs/vitrinidae.html which is an account of the related species Vitrina pellucida (the Western Glass-Snail). According to the website, Vitrina pellucida is carnivorous, and it's only difference with V. angelicae is anatomical. To test a little theory that then V. angelicae is also carnivorous I have it in a jar with what is likely prey, Cochlicopa lubrica-- which was found in proximity to the snail-- and Zonitoides arboreus.

I should also mention that I have found empty shells in two locations in Luzerne County. The first the island of trees and rocks in the turnaround at Nescopeck State Park where also present were plenty of Stenotrema hirsutum, and during the summer while taking my younger daughter through the Butterfly Garden at Frances Slocum State Park. I have also found the shells in the woods adjacent to the Butterfly Garden, though not very far into them.

From now on, instead of attaching an image to the snails known Pennsylvania counties I'll be just linking to my interactive known distribution map. To autoload Vitrinia angelicae go to http://kevinripka.com/pasnails/?snail=113.