Monday, 15 January 2018

Going from from Micro to Macrophotography with Melolin

Multiple layers Melolin dressing taken though the microscope
Recently, I've had a play with macro-photography. I'm comfortable photographing through the microscope, creating panoramas and stacks but wanted to try capturing subjects more in the centimeter size range and ended up reading around and just experimenting.

I was trying to capture almost a whole specimen on a microscope slide. Initially I tried using my camera with its usual lens but with a lot of extension tubes (66 mm).  The sample was also between tow polarisation filters for colour effects. This worked reasonably well, especially when I took a range of images at different focus and combined them. However, when you look more closely at the image (Full screen), you could see a softening of the image around the edges.

Melolin membrane using 50 mm lens with 66 mm extension tubes
This bugged me, so the next day I thought, why not simply use a low power microscope objective as the lens for the camera?  Cutting some card and and using blue-tac I finally bodged the arrangement  below. Note that the camera is also mounted on a Newer two way rail which I am quite impressed with!

Using a low power microscope objective on the camera
Taking another stack of photos at focus through the slide, I generated a much more satisfactory image as shown below.

Melolin membrane between crossed polars, with low power objective attached to camera.
Trying the same method on a different slide with several layers of melolin membrane on top of each other gave this beautiful coloured image, created by the interference of the polarised light passing through the different filters.

Multiple layers of melolin membranes between crossed polars, taken with low power objective on camera
Of course, the final question is, what is Melolin membrane? The membrane is used in Melolin dressings. Melolin is a trademark of Smith & Nephew http://www.smith-nephew.com/uk/products/wound_management/product-search/melolin/.

As you can see from the image of the single layer, the membrane has numerous very small pores. It is made of poly(ethylene terephthalate) and can be applied to lightly leaking sutures, abrasions or wounds without sticking to them. Dressings can be provided with absorbant pads over the filter, so that the exudate passes through the filter and is absorbed on the pad.

There is a simple beauty in a practical everyday object, that makes even more sense when you know how it works.

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