Smithsonian Magazine on Snowflake Photography

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bralex
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Smithsonian Magazine on Snowflake Photography

Post by bralex »

An article on snowflake photography in Smithsonian Magazine. Light on technical details - almost everything described is stuff I've done myself, barring cooling my camera and using sapphire slides - I took my pictures out in the cold, so melting wasn't an issue! I suspect there's more to it, just the details are not included in the article. For example, they don't actually note what the “highest resolution snowflake camera in the world" can actually achieve. Nice photos though.

https://www.smithsonianmag.com/innovati ... 180976710/

Lou Jost
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Re: Smithsonian Magazine on Snowflake Photography

Post by Lou Jost »

I bet this is forum member nathanm, who often posted excellent ground-breaking posts here, driven by his desire to photograph food.

Charles Krebs
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Re: Smithsonian Magazine on Snowflake Photography

Post by Charles Krebs »

If you would like technical details let me know what you are curious about. I worked with Nathan and a small "crew" building this microscope, and photographing in Fairbanks and Yellowknife.

physicsmajor
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Re: Smithsonian Magazine on Snowflake Photography

Post by physicsmajor »

From the article image Image:

Looks like a Mitutoyo M Plan Apo 10x is the objective given the yellow ring and lack of a HR-style coned tip. Thus I'm not sure if the article step size quoted is incorrect at 1 um or not; I think 8 um steps should be appropriate for the Mitutoyo 10x. So either the step size is quite small or that's perhaps not the only objective used.

CCD on top is not a repurposed camera and may be lab grade, possibly custom mated to the optical system. It could be monochrome, with color backgrounds applied to some of these in post?

Clearly set up as a Z-stage. There appears to be water block cooling of the stage with the actual specimen in center allowing transilumination, presumably off-axis. Not seeing a lot of reflective light sources.

How close am I, Charles? I'd be mildly curious about the rigidity of the stage and its control (open or closed loop, if closed how the feedback operates) and the step size resolution possible.

Edit: on second read-through I caught the comment about some esoteric Japanese cold-LED flash system which is far brighter and faster than conventional flash. I'd really love to know what that is, I have potential applications.

Charles Krebs
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Re: Smithsonian Magazine on Snowflake Photography

Post by Charles Krebs »

physicsmajor,

It does make use of Mitutoyo objectives. Typically 5X, 10X (used most often), and 20X. The camera back is a medium format Phase One IQ3 100Mp Digital Back. There is a cooled stage that utilizes 4 Peltier coolers. The heat is removed with a cooling system utilizing computer liquid cooling components and a very low temperature heat transfer fluid (Dynalene HC-30). The "slides" are sapphire disks mounted in copper rings that seat into the cooled stage top. The stages cooling is adjusted to prevent frost by integrating a dew-point meter into the controlers.

The entire frame is made from carbon fiber components. A thermal flexure Nathan designed is attached to this frame to further minimize any expansion/contraction issues for the optical components.

The linear stage is a beauty... made by Zaber. It incorporates a linear motor, and a magnetic counter-balance (to accommodate the vertical weight). Highly accurate to 1 micron steps. (As you surmised, the 10X did not use 1 micron steps... more in the 5-7 micron range. Don't remember what we had programmed.)

The lighting can be from above or below. The lighting unit below consists of a central disk with a larger ring that is outside the field of the objectives view. Different interchangeable filter disks and rings are used to get, in effect, brightfield, darkfield, and Rheinberg illumination (or any mix thereof) with this lower light.

The LED components are from a company called "CCS". We use their CCS Control Unit PF-A16048-4, along with a variety of their high power strobe LED light units. Duration is very short (IIRC considerably less than 500μs). You can pump lots of amps through these units, but only for a very brief time!

mawyatt
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Re: Smithsonian Magazine on Snowflake Photography

Post by mawyatt »

Nice article, and images. Really like the portability of the setup, well done!!

The LED high source utilized from CCS, what's the ball park cost for the LEDs and driver power supply?

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

Charles Krebs
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Re: Smithsonian Magazine on Snowflake Photography

Post by Charles Krebs »

Mike,
There's a brochure here:
https://www.ccs-grp.com/ecsuites/media/ ... L_PF_e.pdf

And you can check prices at a distributor for their products here:
https://pyramidimaging.com

The control unit is about $2.1K and the high power light units vary a great deal depending on size and type... $1.2K to $3K for ring-lights from 36-100mm.

mawyatt
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Re: Smithsonian Magazine on Snowflake Photography

Post by mawyatt »

Charles,

Thanks for the information. Kind of what I thought, these are industrial units intended for those type applications and thus somewhat expensive for limited use I had in mind.

I've got some core LED strobe controller electronic designs completed, PCB designed, tested and utilized but not at higher peak currents and short duration of these devices. So looks like I've got some designs tasks ahead!!

Thanks again,

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

physicsmajor
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Re: Smithsonian Magazine on Snowflake Photography

Post by physicsmajor »

The same company's "slower, conventional" solutions - both LEDs and controllers - are much more available on the used market for about 1/10 those prices and I may experiment a bit with those. Their superfast stuff is trying to freeze motion on assembly lines and such. Their "slower, conventional" LED pulse durations are in the vicinity of 50-60 us instead of 4 us. Properly triggered a 50 us pulse is the equivalent of a 1/20000 shutter speed. Even if the output is somewhat lower it still has interesting potential.

mawyatt
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Re: Smithsonian Magazine on Snowflake Photography

Post by mawyatt »

The controller we developed awhile back can handle ~100us at up to 10A, although the LED COB we presently have can't handle that high a peak current. Considering a design for 10us at >20A capability which doesn't require a high voltage external power supply. Would operate from any 12~36VDC input and supply LED COBs up to 60V in constant current strobe pulsed mode, have variable current level as well as pulse width control. Also have a much lower variable constant current "modeling" mode similar in use to studio strobes.

Had the concept dancing around for awhile but never seem to have enough time to actually start the design process, simulations and PCB design (why I was curious about the CCS cost since this wouldn't involve any detailed design). We are forming a new company at the moment for doing some advanced semiconductor research work, so available time will diminish. Maybe later this spring we'll have some time to get started on the design process.

Anyway, go JPL, NASA and Perseverance, what a remarkable achievement =D>

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

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