depth of field

Regular readers of Micscape will know that Wim van Egmond and I have a particular interest in the desmids and naturally in drawing and photographing them. Personally I have some problems with their photography. I prefer examining living desmids, preserving them spoils the bright green colour even if a little copper acetate is added to the solution in order colour them. (The colour of living specimens is one way of easily distinguishing them from the diatoms which are an ochre colour.)

However no sooner do you try and draw or take a photo of a desmid in your nice fresh sample than the damn thing moves, sometimes by its own capability or by diatoms gliding along or the movement of micro-fauna, which of course will cause them to blur the photos or go out of focus. You can take the photo as the temporary mount is drying out, so that is there is not enough water for movement but not so dry the desmid is beginning to shrivel up. In this position the desmid will also be nearer the cover glass.

	Getting micro-organisms in focus using mouse-over images with different optical sections by Bill Ells & Wim van Egmond		Euastrum verrucosum wait for the second image to load and move your mouse over the image to switch focus

	Regular readers of Micscape will know that Wim van Egmond and I have a particular interest in the desmids and naturally in drawing and photographing them. Personally I have some problems with their photography. I prefer examining living desmids, preserving them spoils the bright green colour even if a little copper acetate is added to the solution in order colour them. (The colour of living specimens is one way of easily distinguishing them from the diatoms which are an ochre colour.) However no sooner do you try and draw or take a photo of a desmid in your nice fresh sample than the damn thing moves, sometimes by its own capability or by diatoms gliding along or the movement of micro-fauna, which of course will cause them to blur the photos or go out of focus. You can take the photo as the temporary mount is drying out, so that is there is not enough water for movement but not so dry the desmid is beginning to shrivel up. In this position the desmid will also be nearer the cover glass.


	Another problem is the depth of field or rather the lack of it in the light microscope. Desmids are three dimensional, something not always realised by beginners, and comparatively thick compared with say a botanical section of about 10 µm. Wim recently sent me two photomicrographs of a desmid. Genus Euastrum Species verrucosum. I have never taken such good photo's of this species, mainly because of its thickness (55 µm) and its many protuberances. On the second page Wim will give us details of his equipment and methods. Page 2 will show you a mouse-over Spirogyra! Page 3 shows some interesting features on Micrasterias papillifera! By pure coincidence our Australian friend Mike Dingley also wrote about the 3D aspect of a Euastrum species for this March issue of Micscape!