Wednesday, November 29, 2006

On Assignment: Zebra Fish and Zygotes

For whatever reason, I tend to get sent into laboratories on assignment pretty frequently.

Maybe they have taken a good, long look at my sports photography and decided that scientists might be easier for me to get in focus. I dunno.

About a month ago, I was assigned to photograph a scientist who was studying zebra fish zygotes to gain insight into their brain formation.

It was pretty cool, actually. The little suckers are not only completely transparent at this stage of their lives, but you can modify specific genes to fluoresce so you can track the genes' positions in the various developmental stages.

Along with the typical shots of the scientist and her assistant working in the lab, I wanted some close-ups of the cute little fishies and their new new little bundles of joy. At least the one the parents didn't eat.

But these guys are pretty small - an inch or so - as an adult. So you can imagine how small they are just 22 hours after conception.

In the process of figuring out a bootstrap solution, I came across two techniques that I will definitely use again. And I wanted to pass them along just in case there were any other zebra-fish-zygote-shootin' photographers out there.

The photo at top was lit with a off-camera Nikon SB-24, synched with a Pocket Wizard. I tried various ways of lighting the aquaria from the back, as the containers were blue and had a cool look when backlit.

They were all failures. The fish were too backlit and showed up as being too dark. If I had brought a second light with me, I would have had no problem. But I was on a college campus and parked the better part of a mile away.

(Boy, I do not miss those days.)

Besides, it was raining cats and dogs. So we were just going to have to do this one with one strobe.

After deciding I really needed a broad, close-up light source from the side, I set about creating one that would not reflect from the side of the aquarium. After scratching my head for a few minutes, I realized that I could make the side of the aquarium into a light source.

I took the sheet of paper on which my assignment was printed and slipped it between two aquaria, like this:


Then I used it to diffuse the light from the strobe by shooting through it. Presto, the aquarium becomes its own soft box. Here's a shot of the same scene with the light going off, adjusted for the proper flash exposure:


You can see how much better the fish are defined. In addition, the flash gave me all the aperture (and depth of field) I needed to keep the little buggers in focus as they swam around.

This last part was harder than it sounded. So I used what I call the "direct mail" approach. I just fired off a couple hundred frames - no kidding - in the knowledge that I would get good focus and positioning on several of them. Simple math.

The flash was pumping plenty of light out at even 1/16th power on manual, so shooting a gazillion frames was not a problem for the flash head overheating. Nor was I limited by recycle time - even with just AA's as my power source.

Having an acceptable shot of the adult fish in the can, the zygotes were next in line.

The scientist had them set up under a stereo microscope, and I hoped she had a Nikon adapter ring for shooting specimens with a camera.

She didn't. Oh, well. I didn't really expect the solution to be that easy. But I always ask. You never know.

So I took my lens off and gently tried to line my bare camera up to the eyepiece. (I have had success like this with telescopes on astronomy assignments.)

Close, but no cigar.

Next, I removed the eyepiece and tried the same thing.

Nope. Not even close.

On a whim, I replaced the eyepiece and put on a 50mm lens. Then I sloooowly lowered my camera down until the front element of my lens gently rested on the eyepiece glass.

Bingo:


I couldn't believe how clear it was. I don't know if it was the specific optical designs of my lens and the scope's lens, but it sure worked.

I'll remember this technique for later, too. If you try it, just be careful not to screw up your front element.

As it happens, I would be back in the lab within a couple of days, this time to photograph something even smaller: E. coli bacteria. (No biggie - tastes like chicken.)

But that's a different assignment, and will be the subject of a future post.


Next: Stainless Steel and Cookies


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12 Comments:

Blogger Patrick Smith said...

Nice Idea! Do you have a copyright period where you cannot use your assignment images from The Sun before you use them here? Just wondering because you said you shot this a couple weeks ago.

Also, nice tip on firing off a bunch of frames. I would have been following those suckers around! I know that wasn’t point of the post, but it’s the little things that sometimes get me.

November 28, 2006 9:44 PM  
Anonymous Lee said...

David you continue to amaze me. You are indeed the MacGyver of off camera flash photography.

Pleasssse keep em coming.

November 28, 2006 11:14 PM  
Anonymous John Dohrn said...

I like the first photo, but it helps illistrate "be prepared". Also, you may wanna look into digiscoping if you're interested. It's basically what you did with the microscope, actually, it's the definition

November 28, 2006 11:42 PM  
Blogger Chris Parker said...

I'd say this whole thing sounds a little fishy, but that would just be in poor taste, but it is nice to know that there are other paper shooters out there who'll just load up their whole card and figure that they've got to get a couple cleans ones! I've done that on more than one occaision.
Chris Parker

November 29, 2006 12:41 AM  
Anonymous Captoe said...

I'm reminded of this photo set on flickr:
http://www.flickr.com/photos/ophis/254462908/

The photographer constructed a temporary shooting aquarium of two 4"*4" plates of glass sandwiched around a length of 1/4" tubing.

November 29, 2006 12:59 AM  
Anonymous Ted Leung said...

The piece of paper is awesome. Reminds me of the time my wife used the back window of our van as a fisheye lens...

November 29, 2006 2:57 AM  
Anonymous Anonymous said...

Hi David - You might want to look up some of the astrophotography "how to"s. IIRC your microscope solution is termed "eyepiece projection".

HTH,

Mark

November 29, 2006 6:15 AM  
Anonymous Tim Kerby said...

I do that a lot with microscopes and magnified viewers for electronics. The only thing ro remember is not to touch the lenses as a small separation is usually ok if you have focus controls on the microscope and camera. Your eyeball doesnt have to touch the eyepiece lens so your 50mm standard lens shouldnt have to either as its field of view is similar to that of the eye.

A little distance also allows autofocus on the camera. If you have a lens with a moving or rotating front element, touching glass to glass would be a really bad thing as it would likely break the glass or grind the lenses when the af moved

November 29, 2006 6:58 AM  
Anonymous Joris said...

For the E. Coli photograph:

It might be worth asking if they have any recombinant E. Coli in the lab, that express Green Fluorescent Protein (just say 'GFP').

You might need a tripod, but it should look more interesting. (example of fluorescin secreting bacteria, and google 'GFP').

November 29, 2006 8:05 AM  
Anonymous WideSpred said...

Turning your 50mm lens backwards and holding the front element to your bayonet ring is the easiest way to do a macro. You lose any depth of field control, but hey...

A 28 backwards will get you close too, if you have one handy.

-wsp

November 29, 2006 3:23 PM  
Anonymous Stefan Julius said...

Thanx for the hint at Pro_Blogger.net

November 30, 2006 5:27 PM  
Blogger dillon said...

I actually ran into the same problem while I was out at sea on a US Navy destroyer. We were cruising around with USS Enterprise and I was thinking, "Man, it would rock to get a good shot of her hauling rear around the Atlantic and landing F-18s under the stars." So what did the ship I was riding have to see her in the pitch black??? and I mean PITCH black... no light pollution hundreds of miles out to sea like there is here in DC. They had night vision telescopes. So I dutifully hooked up my best light-grabbing lens, the wonderful el-cheapo Canon 50 f/1.8. I pushed it up to the night-vision telescope and voila:
http://members.cox.net/dillonallen/images/nvgent.jpg

Oh yeah, like the other guys said, don't press the lens to the scope if you have a rotating barrel during AF. Stick with manual focus for this kinda shot anyway.

April 23, 2007 11:24 PM  

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