Fern Scales

Cactusdave · Post by **Cactusdave** » Thu Nov 01, 2012 3:35 pm

We have the Victorian microscopists to thank to thank for uncovering many unlikely sources of beauty under the microscope. Who would have thought for example that the molluscan tongue (radula) would be an object of surpassing beauty, but under the polarising microscope it is. Another source of unlikely beauty is the humble scale on the stem and leaves of ferns. I came across an article drawing attention to this as an object for the polariscope and the attention it had received from Victorian microscopists http://www.microscopy-uk.org.uk/mag/ind ... rfern.html I resolved to try to acquire a slide of my own, but passed on the few I came across as clearly they were going to 'collectors' for exaggerated prices. I was lucky finally to acquire a slide simply labelled 'Scales of Acrostichum'. Now Acrostichum is a small Genus of tropical ferns, the Mangrove fern Acrostichum aureum being the best known. I awaited this slide with anticipation and was not disappointed. The slide has five scales arranged in a rough star shape, and the mounter is unnamed, but the style suggests the 1880s-1890s. Under polarised light with a simple retarder made from two thicknesses of Sellotape on a glass slide, these scales fairly glow. I wanted to create an image which would do justice to the entire slide. This required low power, I used a Zeiss X6.3 0.20 Neofluar objective on my Nikon Diaphot and took 105 individual images to create a large stitched composite. The magnification at camera was X16. The retarder produces a magenta/purple background which I didn't think showed the scales to best advantage, and I replaced the magenta background with a black one during processing.

This image suffers from the constraints of the forum image rules, but a larger 33 Megapixel zoomable version is hosted here http://photosynth.net/view.aspx?cid=86e ... 5c88a2b8e3

Now subjects that look good under polarised light often look great when viewed by DIC, which after all employs polarised light in the creation of contrast which it so dramatically achieves. Unfortunately the lowest powered DIC objective I possess is X10, and though I was tempted by the thought of a heroic stitch of the entire arrangement, I opted for the more practicable single scale. Total magnification at camera is X25 and this image is a stitch of 49 images. As you will see from the previous picture the scales are rather entangled at their bases, and I had to do a bit of careful 'disentangling' in Photoshop to isolate this single scale.

A larger 26 Megapixel zoomable version is here http://photosynth.net/view.aspx?cid=46d ... 537f9de93d

I have done a couple of crops from these images, but I'll post those tomorrow.

curt0909 · Post by **curt0909** » Thu Nov 01, 2012 9:15 pm

Wow. Nice job Dave. I especially like the idea of changing the background color to black. Gives the false coloring greater contrast.

RogelioMoreno · Post by **RogelioMoreno** » Thu Nov 01, 2012 10:28 pm

Dave,

The second one is amazing!

Rogelio

Cactusdave · Post by **Cactusdave** » Fri Nov 02, 2012 1:49 am

Thanks Curt and Rogelio. Setting a background to a different colour can be tricky, to do it successfully requires a reasonably homogenously coloured background in the first place, as well as adequate contrast between the new background and the outline of the subject. Fortunately both these criteria were met this time.

I promised a couple of crops from these images. First a crop from the X6.3 image.

Now a couple of crops from the X10 DIC image. I have tweaked the colour cast compensation for these compared with the original composite image to remove a little more yellow.

The extraordinary 'tiling' of the individual dead cells that make up the scale really shows up in the last image.

gpmatthews · Post by **gpmatthews** » Fri Nov 02, 2012 7:18 am

Absolutely splendid!

Cactusdave · Post by **Cactusdave** » Fri Nov 02, 2012 8:31 am

Thanks Graham.

Pau · Post by **Pau** » Fri Nov 02, 2012 9:47 am

Interesting subjet and great images. I most like the DIC one.

Cactusdave · Post by **Cactusdave** » Fri Nov 02, 2012 2:10 pm

Thanks Pau.

curt0909 · Post by **curt0909** » Mon Nov 05, 2012 12:28 pm

There is a PS program called on-one mask that is great for this type of job. You really need to use the interactive zoom on photosynth to do this work justice. Its amazing to see the details you've captured on such a large image.

Cactusdave · Post by **Cactusdave** » Tue Nov 06, 2012 4:36 am

Thanks Curt. I recommend Photosynth for hosting large detailed images. The zoom tool is very nice. I have used the Topaz masking tool ReMask for situations like this, and it's pretty good, but I don't like to do so much with images that they become totally unrealistic of what was seen through the microscope.

Walter Piorkowski · Post by **Walter Piorkowski** » Tue Nov 06, 2012 8:32 pm

Enjoyed these very much Dave.
Walt

Cactusdave · Post by **Cactusdave** » Wed Nov 07, 2012 1:08 am

Thanks very much Walter, your comment is very much valued.