Microscopic Photography Tricks: Side-lighting

Photographers have amazing skills to make their images look exactly how they want by changing the lighting.  Simply changing the direction the light is coming from, for instance by having an external flash, can make the world of difference in how your pictures turn out.  With Aaron visiting this week, I was inspired to steal some of the same techniques he uses to take his beautiful macro shots and translate them into the Foldscope.  Manu has already documented a number of different lighting techniques, most notably reflective mode (https://microcosmos.foldscope.com/?p=1515), and Matt has shown how to make a simple dark-field setup (https://microcosmos.foldscope.com/?p=7042).  Jumping off from that, I wanted to look at samples that were a mixture of opaque and translucent.  Often, opaque samples just appear as shadows on the Foldscope, which can be highly disappointing when you know that there is incredible structure hidden there.  I made a simple side-light module and was very surprised by the results.

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Picture of a fly with normal light-module illumination (3 layers of diffuser tape and a condenser lens) on the left versus a picture of the same fly with the side-light illumination.  Note that the compound eye is now visible, when it was previously hidden in shadow.

 

Methods:

I took a coin battery, a small LED (3mm, with a hemispherical top) and a switch and soldered them together to form a simple circuit.  This was a little tricky, since the switch I used was so small, but that meant that the module was only a few millimeters tall, which helped a lot when inserting it into the Foldscope.  I used a small piece of double-stick tape to attach the module to one of the Foldscope paper slides.  The switch peeked out the corner, which allows you to switch between natural light and side light.  See the picture below for the arrangement.

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Next, I sandwiched the sample slide between the light module slide and a couple of blank paper slides.  Because the side-light module was thicker, the sample was forced closer to the lens, so I had to add some extra slides on top (rather than on the bottom like normal) to get it in focus again.  IMG_0301

Image of the opened Foldscope with the side-light and the fly sample.

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Image of the closed Foldscope with the side-light.

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Goldfish Scales have very different coloration with normal light module illumination (left) versus side-light illumination (right).  Even though there isn’t much more insight into the structure, the image still looks very different.

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This is one of Tom’s samples of coralline algae that has always just been a shadow on the Foldscope with light module illumination (left). With side-lighting, the pink color comes through much better, and you can even see some of the cellular structure!  (unfortunately, my picture didn’t come out perfectly in-focus).

I think a big part of the change in the pictures is related to how the camera on the iPod Touch that I’m using auto-adjusts light levels.  So playing with those settings will probably also have a significant effect on the images.  I encourage everyone to try different light settings!

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More zoomed-in images of the fly with side-lighting.  Some of the pictures look very similar to dark-field.

Check out Aaron’s posts here!

https://microcosmos.foldscope.com/?p=8128

https://microcosmos.foldscope.com/?p=7722

-Marie

10 Comments Add yours

  1. laksiyer says:

    Marie. This just solves so many things. This is just fabulous. Oblique illumination is also super cool for transparent samples, giving some kind of 3D effect. I just got myself a few light module parts after Matt’s post. Cant wait to assemble it all. The only thing is that I havent soldered things in 35 years, the last time I did it was in secret past midnight and made a big mess.

  2. Manu Prakash says:

    What an incredible post @Marie. Love the colors – biology is a master of colors and what we see through transmission is so different from this side illumination.

    Now; what’s brilliant about your design is the fact that the light is implemented not in the microscope but in the slide. So j can make many of them and use different one for different illumination.

    Absolutely brilliant. What a fantastic solution.

    Cheers
    Manu

  3. Manu Prakash says:

    @laks: soldering is easy – just keep the hot end away from your hand 🙂

    Secondly, you could just break open a simple LED flash light and steal parts from the same (some key gains with LED would be the best bet); and see if you can hack something without soldering.

    Cheers
    Manu

  4. mherring says:

    Laks, I’m also not that great at soldering, so this clearly doesn’t need perfect execution to get useful results 🙂 In fact, for the first iteration, I just stuck the LED leads under the clips on the battery. I look forward to seeing what you do with your light module parts! I think there are a lot of options 🙂

  5. Saad Bhamla says:

    Awesome post @marie.
    The images just look spectacular!!

    Saad

  6. laksiyer says:

    @Marie. What wiring material did you use to make the circuit?

  7. mherring says:

    @Laks I didn’t use any wiring material. The battery I used (CR2016) had clips that were able to be soldered to the leads of the switch and the LED.

  8. Matthew Rossi says:

    Marie, this is amazing. I’ve got a sample of urchin eggs and algae in my place right now, and I’m definitely going to have to dive in and try looking at them side lit…I’m so excited to see what comes.

  9. mherring says:

    Wonderful Matt! Let me know how it goes! I haven’t tried it with any wet samples yet; I was hoping to figure out how to make the glass slide itself into a light guide but I haven’t done that yet. If you do figure out a way to make it work, please post your set-up, as I’d love to see your approach 🙂
    -Marie

  10. Great post!! I will definitely try this technique. Thanks for sharing it!

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