Photomicrography with a Canon 7D SLR

English: Canon EOS 7D with EF 28mm f/2.8 日本語: ...

English: Canon EOS 7D with EF 28mm f/2.8 日本語: キヤノン EOS 7D レンズ:EF 28mm F2.8 (Photo credit: Wikipedia)

“Necessity is the mother of invention (or actually discovery in this case)”

This blog is developed from a manuscript of a haematology book. No haematology book can be complete without photomicrographs. As I did not have access to a microscope camera I had to look for other ways to photograph peripheral blood and bone marrow slides. The first digital camera I had was the Nikon Coolpix 4500. The lens of this camera had a ring equal to that of a microscope eyepiece and the focusing mechanism, unlike most cameras was internal. These features gave me the confidence that if I hold the camera against the eyepiece of a microscope I will not be damaging either. It worked! I have since then used Canon IXUS 105, Canon 400D and Canon 7D for photomicrography. This post is about photomicrography by holding a camera close to the eyepiece of a microscope.

Nikon Coolpix 4500: Nikon Coolpix 4500 is a 4 megapixel camera that was the first camera I tried for photomicrography. It gave usable photographs but the images had many concentric rings. To overcome the “ring” problem one had to ensure that the area to be photographed was at the periphery, where the rings were absent/less prominent. The image below is that with megaloblastic anaemia where the rings were seen

 002

Photomicrograph of a the bone marrow of a patient with megaloblastic anaemia taken with Nikon Coolpix 4500 showing concentric rings

One could apply post processing to some of the photomicrographs to get images acceptable for displaying on a webpage. The same image with post processing is shown below.

Megaloblasts

Cameras Canon IXUS 105: Canon IXUS 105, a much later model, was free of concentric rings. It gave good photographs but gave six dots (I am not sure if this was an issue with the model or the piece I had). The images were large enough to be cropped and I have used these in the post morphology of myeloid precursors. All the images in this post are taken by holding a Canon IXUS against the eyepiece of a microscope.

Six Dots of Canon IXUS 105 001

The image taken with a Canon IXUS 105. The six dots are evident above and to the right (11 o’clock) of the myeloid cells.

Canon 400D with a 50mm f/1.8 II lens: The images of a digital SLR offers are of a better quality than compact cameras. The SLR also gives images that can be processed better. I had tied to use the 400D with the 18-55 kit lens, before using the Canon IXUS 105, but never succeeded. The photograph never filled the entire frame. Then the internet came to the rescue. The 400D set to manual focus took pictures. The 50mm f/1.8mm lens is an inexpensive lens of extremely good quality. I switched to a 50mm f/1.8 II lens. The 400D allows shooing in the RAW format allowing greater post-processing. The Low ISO of the 400D means shooting a slow sutter speeds (1/20-1/40 seconds) which resulted in blurring of images because of camera shake. The 400D does not have alive view mode. The Canon 7D overcomes these limitations.

Canon 7D with 50mm f/1.8 II lens: The Canon 7D allowed fast shutter speed and has a better image capturing device that has given the best images I have taken. The high ISO (unto 3200) allows shutter speeds of 1/100 and eliminates blurring because of camera shake. To take pictures by holding a digital camera close to the eyepiece of a microscope on has to

  1. Set the focus to manual
  2. Set the camera to aperture priority and set the aperture wide open
  3. I prefer setting the exposure to expose such that the histograms is snuggled to the right. This reduces the noise.
  4. Focus the images using the adjustment on the microscope. No focusing is done by the camera. Photographs are taken using one of the eyepieces of a binocular microscope. The two eyepieces may have different focus planes. A slide may appear to be in sharp focus when seen through both objectives but may still not be in sharp focus when through the eyepiece used for photography. Look and focus the slide though the eyepiece you intend to use for photography.
  5. Adjust the white balance. You may use auto white balance, custom white balance or adjust the white balance shift (add blue/green if the microscope lamp is too yellow). you can also adjust the temperature and tint on the image processing software after taking the picture.
  6. Sometimes the image has a bright spot (shown in the picture below). This has happen with the 400D and 7D. Images are framed with the 400D by looking through the viewfinder. The bright spot can not be seen on looking through the viewfinder. It can however be seen in the live view mode of the 7D. It is best to shoot using the live view mode. The spot can be eliminated by slightly tilting the camera. The problem of the bright spot has occurred with all brands of microscopes (local brands to Olympus). I have tried eliminate the spot by adjusting the condenser and changing the illumination but with little success. This has occurred only when seeing the slide under oil immersion objective (100X) never under 40X or 10X.

bright Spot Final

Why the 7D? Photomicrography does not use all the features of a 7D. A 600D or 650D would perform as well. SLR cameras by other manufacturers like Nikon or Sony should give the same results but my experience is limited to Canon SLRs. If you intend to use a camera for photomicrography you need to

  1. Preferably have an SLR – They have a superior image quality than compact cameras. Compact cameras can be used if an SLR is not available.
  2. Those using Canon SLRs may find the 50mm f/1.8 II lens most useful. Some believe this is the best value for money lens Canon has produced. It is incredibly sharp and incredibly inexpensive. ALWAYS USE A UV FILTER. The lens must never touch the eyepiece. I have found the performance better the the kit 18-55 lens.
  3. High ISO capabilities to allow high shutter speeds to eliminate blurring due to camera shake
  4. Live View gives a better view and helps in identifying and eliminating the bright spot.

I have used the 7D because I happen to purchase one for photography which is my hobby. What the 7D offers over a 600D or a 650D is never used in photomicrography. You may use any of the above mentioned cameras and get results.

ISO – The Exposure Triangle

ISO – The Exposure Triangle (Photo credit: abanakas)

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