A convenient method of photomicroscopy

By Wan Yu, China

I am still interested in microscopic science while I am a data communication engineer working in Langfang, a city in the north of China, far away from my hometown. At the end of last year I bought an XSP-02 microscope which has three achromatic objectives (4X, 10X and 40X) and two Huygens eyepieces (10X and 16X). This kind of microscope is very basic - there is no condenser, the light reflected by a double-sided mirror (flat and concave) illuminates the sample - but a classic which is widely used in senior high schools for biological teaching and training.

There is a very convenient method for beginners to DIY a photomicroscopy system. You just need a digital camera, a tripod, and certainly a microscope is necessary. The fundamental of this method is the same as Paul James’ equipment that was published in the November 1999 edition of Micscape. In the photographic setup, the virtual image of the eyepiece is converted to a real image by the lens of the digicam and falls onto the sensor – instead of the retina. This method is so well-known that photographers always share their photos but omit the technical detail. As a beginner I tried a lot of methods to take a micrograph. The following is the best way that I have ever tried.

Section 1: Preparation and discussing

A compound microscope, a digicam and a tripod should be prepared before taking a micrograph. To avoid the shaking when you press down the shutter, a remote controller is recommended.

Microscope

The eyepoint of my Huygens eyepiece is too low (about 3mm) and the field of view is small, it is not fit for micrography. We should change it for a wild-field eyepiece, especially a WF10 eyepiece is recommended. Furthermore, the use of a condenser can improve the quality of images a lot.

Camera and lens

Both digicams and DSLRs that support macrophotography are fit for taking micrographs because of the image of the eyepiece is within the distance of distinct vision (250mm) from the eyepoint – the point we put our eyes to or camera lens to for observing. For a DSLR lens, the best choice is using a macro lens and the reverse of a standard lens such as 50mm/F1.8 can be an alternative – someone tried the experiment and the photos were amazing (See this webapge). For digicams, the Canon A640 is well-known. I used a Nikon Coolpix S8 with Zoom 5.8-17.4mm lens for imaging one month ago. When I adjusted the focal length of its lens to the maximum of 17.4mm, the images recorded could fully fill the sensor (Fig.2).

Fig.2: The micrograph taken with a Nikon Coolpix S8 Camera, a compact digicam design, showing some bacteria stained by methyl violet. (with 10X objective and WF10 eyepiece).

Otherwise, micrographs can be taken by simply putting the mobile phone camera over the eyepoint of the eyepiece. But some details are lost since images are too much compressed by the camera's software (Fig.3).

Fig.3: Cells of heart, a slice for biological teaching, was taken with a mobile phone camera (LG KT878).

In my photographic setup, I use a Nikon D90 digicam and a 35mm/F1.8 standard lens (I suppose that using a 50mm/1.8 lens may allow a full field of view to be recorded on the CMOS sensor). For some reason that I do not know exactly,the 18-105 zoom lens does not work as well as a standard lens in practice; there is more chromatic aberration or coma aberration (compare Fig.4 and Fig.10).

Section 2: Installation and operation

Install the digicam onto a tripod and move the lens over the eyepoint of eyepiece. Observe the image through viewfinder and adjust the objective to get the clearest view then take the photo. When you take the photo, remember to use your remote controller to reduce shaking.

Fig.4

Fig.5 shows another photomicroscopy system which consists of a XSP-35 microscope and a Nikon D90 camera, the lens used was a 35mm/F1.8 DX.

Fig.5

Sometimes the real image can not fully fill the CMOS sensor, so the photo should be cropped to an appropriate size using software (See Fig.6).

Fig.6

Section 3: Image Gallery

Fig.7: A fresh water diatom, this cropped photo was taken with the 40X achromatic objective and WF10 eyepiece, 18-105mm Zoom lens ( 92mm focus length was used).

Fig.8: The well-known green algae Spirogyra, 10X objective and WF10 eyepiece.

Fig.9: Vorticella campanula, 40X achromatic objective.

When I changed the D90’s lens for a 35mm standard lens, the quality of image improved a lot. The following two photos shows the cells of durian, stained by iodine, and were taken with a WF10 eyepiece.

Fig.10: 10X objective

Fig.11: The photo was taken with a 40X objective.

Comments to the author will be welcomed.

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