Hiking With A Field Microscope
Copyright © 2004, Wayne Lanier, PhD
Little-known Techniques of Field Photomicrography
TABLE OF CONTENTS
Secrets of a San Francisco Deck Garden
Giant Bacteria Found in Golden Gate Park Flowers...!
Cryptobiotic Soil Unearthed in Utah
Revealing Films of Life in a Cliff-side Seep
A Hard Life Out in the Salt Flats
Beneath the Tufas in Mono Lake
Professionals in well-equipped laboratories have access to tools usually unavailable to amateurs. Described in this chapter are low-cost protocols that will enable you to create photomicrographs with some of the features found in journals.
REFERENCE BARS not only make your photomicrographs look more “professional”, but really are necessary if you use a digital camera with a zoom and change the size of the image to fit a page. Stating the magnification means little if we do not know how much the image was enlarged or reduced.
First, you need a slide of an object of exactly known dimensions. In the “good old days” photomicrographers made a standard Reference Bar of a carefully fixed, stained, and measured diatom. You can actually buy sets of diatom slides from Carolina Biological Supply Company [see ORDERING STUFF] at the end of this chapter.
An easier and more accurate solution is to use a slide with a grid or scale etched on it. You can buy such slides new [see ORDERING STUFF], but they are often costly. You can usually borrow one from a laboratory or find a used one. For my Reference Bars, I used an old Hemocytometer, which is a grid slide intended for blood-cell counting.
Here is a photomicrograph of my Hemocytometer, taken with my Nikon Coolpix 885 at a fixed optical zoom setting intended to prevent vignetting. Zoom beyond this value is actually an “electronic zoom”.
The counting field in a Hemocytometer is 1-mm X 1-mm, very accurately ruled into the glass. This square is cut into 25 major squares, each 200-micrometers on a side. Each of those squares is cut into 16 minor squares, each 50-micrometers on a side. At least one of a set of Reference Bars of these dimensions will fit most photomicrographs taken between 40x and 800x.
First, you need to take photomicrographs of your reference object at various magnifications and repeatable zoom settings. With my Nikon, I can reliably reproduce zoom settings of 1x, 2x, 3x, and 4x beyond my anti-vignetting stop.
Then you need software tools to crop, paste, color, write text on, and combine photographs. I use PhotoImpression [free software that comes with many digital cameras] and ACDSee [freeware from the Internet]. With ACDSee, I crop a row of minor squares from the Hemocytometer image and save the cropped part as a JPEG file. With PhotoImpression, I can color this image and write text on it. I pasted some results back in the image of the Hemocytometer, above. As long as you do not reduce or enlarge a specific Reference Bar image, its length remains invariant when pasted into original JPEG photomicrographs taken at the same settings.
What that means is that you must make a gallery of standard Reference Bar images for each microscope magnification you use and for each zoom setting you use. You must carefully keep track of the magnification and zoom of any photomicrograph. With the Nikon, all image information is saved to a text file, so that part is easy for me. As it turns out, remembering to write down the magnification of each photomicrograph is not so easy. I carry a waterproof SOKKIA notebook, but I sometimes forget to record the magnification when I am in a hurry.
Finally, you must paste in Reference Bars before you crop, enlarge, or otherwise change the original photomicrographs. Saving PhotoImpressions files to JPEG combines all layers into one layer, so subsequent enlargements or other fiddling does not change the relative size of the Reference Bar and objects in the photomicrograph.
ORDERING STUFF is possible from the following web sites and catalogs:
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