#9 Thin Section Photomicrographs Using a Mobile Phone: Tips and Tricks

Like many of my colleagues, I have a lot of thin sections of many different rocks to look at. But sharing what you observe down the microscope is not as easy and convenient a process as it could, or indeed should be. When looking at sections, I make notes etc directly on my computer, and therefore I wanted the convenience of sitting at my computer rather than at a station in the microscope laboratory which is in a different part of the building.

Recently, the quality of the lenses and sensors on mobile phones has shot through the roof, and most modern smartphones now come with a pretty decent camera. Not to mention that on the same device you have the accessibility to many apps, including e-mail, via which you can share and send your images to other devices. Much easier than removing a memory card and inserting it into your laptop!

Hot To

Cover the other eyepiece to prevent entry of light from your surroundings. Then use both hands to offer the camera up to the eyepiece whilst sealing out as much light as you can.

1. The logistics of taking the photo with your camera.

Step 1
Locate the field of view you wish to photograph. Make sure that the image is in focus. You can of course take the image through either eyepiece, but I prefer using the one without the crosshairs. Make sure this individual eyepiece is in focus.

Step 2
Cover the other eyepiece to stop reflections. Light doesn’t only leave an eyepiece, it can also enter it. Light entering the open eyepiece will bounce around the optics and inevitably exit through the one that you want to take an image through causing nasty artefacts.

Step 3
If you are right handed, hold the phone in your right hand in portrait mode. It’s easier to handle this way, and the “take photo” is probably better accessed by your thumb/finger this way too. Using your left hand, shield the top and sides of the phone. This also allows you to stabilise and manoeuvre the phone into the desired position.

Step 4
Repositioning the camera takes a bit of practice but you’ll get the hang of it in no time. Firstly you want the lens vaguely in front of, and perpendicular to the image coming out of the eyepiece. You should see some sort of image appear on your screen. It will more than likely be overexposed and/or blurred. Once this image is central, using your left hand as a steady guide, adjust the spacing between your phone and the eyepiece. You are not focusing the image here, you are ensuring that the entire field of view is projected onto the camera lens equally and entirely. Too far away or too close and it will look like a small spotlight is illuminating part of the field of view, the rest of it is in darkness. As you move closer to the ideal distance, that spotlight will become large until “BAM!” suddenly the whole field of view is illuminated and you can take your picture once the camera has focused. This ideal distance is quite a narrow zone, so make sure you steady your hands and make gentle adjustments until the image is right.

The image shows what you expect to see at various distances from the eyepiece. You want to aim for full illumination which is in the middle of the range.

2. Some Common Issues
Dark crescents around the edge of the image – You are either too far away or too close to the eyepiece
Dark spots or areas inside otherwise well illuminated field of view – You phone is more than likely not perpendicular to the eyepiece, so adjust the attitude of the phone relative to the eyepiece.
Colour is off (too warm) – It’s likely the phone is reducing the exposure too much, so try reducing the diaphragm (or power of light) into the microscope. The former will increase the relief of the mineral boundaries making them more defined.
Camera won’t focus – Limitation of your camera phone and/or it’s camera software.

Reducing the diaphragm on the microscope gives better colour reproduction for some camera phones. It also increases the apparent relief of the minerals.

3. Things to do to increase quality
– Particularly when shooting in plain polarised or simple plain light, reducing the diaphragm aperture on the microscope will increase the image quality and colour reproduction.
– Make sure that you get a good light seal on both eyepieces.
– Make sure pin-sharp focus is achieved.
– Better microscopes = better images, better camera phones = better images.

4. Post-processing
If you want to really get the best quality image you can from your phone, I recommend that you take the following post-processing steps. I personally use photoshop, but most image editing packages will achieve the same results.

Step 1 – Adjust the levels. Using the histogram, move the left slider to either: A) to be under the peak of the blacks; or B) to exclude the black peak. Use whichever gives the best result for that image. Then adjust the righthand slider for whites to the left to achieve the desired brightness. You can also adjust the middle slider (contrast) to suit.

The levels for the image before they were adjusted.

Levels for the image after adjustment.

Comparison of the image before and after the levels were adjusted as described.

Step 2 – Apply Sharpening

This may or may not be necessary depending on your image. It’s always worth trying it to see. In photoshop, go to Filters > Sharpen > Unsharp Mask. I applied a strength of 46 % and a radius of 2.1 pixels. This will vary for each image. As a general rule I like to keep the strength slider higher than the radius slider to avoid black halos.

The unsharp mask in Photoshop is a very powerful tool.

It may not seem like your image needs sharpening, but after a unsharp mask is applied the results are stunning.

Step 3 (Optional)

If the colour balance is not completely right you can edit the colour balance manually. Go to Image > Adjustments > Colour Balance (or Cmd + B). This image, however, does not require it.

Final comparison of images. The only thing that has been done is a levels adjustment and sharpening applied.

5. Interconnectivity

Once great way of taking photomicrographs and keeping them together with any observations you may have is to use Evernote. Evernote is a great note taking application for your PC, Mac, Unix Machine, Mobile phone. iPad or tablet. Everything syncs wirelessly over the internet. I can write some notes on my computer about the slide I am looking at, and when I spot something interesting I can open up the Evernote app on my phone and take a photo which gets inserted into my notes. A few seconds later the photo automatically appears in the notes of my computer screen without the need for me to tell it to do anything! Truly a great tool for the geologist!

Evernote is a very useful tool for anyone who takes notes with any kind of media and/or the need to access the notes on a number of different devices.


3 thoughts on “#9 Thin Section Photomicrographs Using a Mobile Phone: Tips and Tricks

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