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The wonders of gravitational forces !!

April 15, 2013


I am Rob and I am doing a Guest Blog for Nikki while she is indisposed for a little while.

I am delighted to claim that it was me, who first introduced Nikki to photography a long time ago. She is my daughter and I am very proud of her and the progress she has made, such that I am now the pupil and she, the teacher. So it was not easy to think of a subject blog that is different to hers but still interesting, but here goes.

Think of a pendulum swinging back and forth. We see them every day even though we may not realise it. A child on a swing is a pendulum. A bird feeder swinging back and forth in the wind is a pendulum. Anything dangling on a string or rope can be a pendulum. You may not give them a second glance but they are quite amazing. Take the child on the swing, you give an initial push and the energy takes the swing upwards in an arc, but then the swing slows down as it reaches the top of the arc and gravity asserts itself  to make it fall back towards the earth, to the centre of its swing, its resting position. By the time it reaches the resting position however, the swing now has so much momentum it begins to swing upwards again but in the opposite direction, until gravity pulls it back to earth again. Eventually gravity wins out and the swing comes to the resting position, unless you keep pushing !! (and we’ve all been there !)

Of course a pendulum can swing in more than one direction at a time. It can swing east to west whilst simultaneously swinging north to south, the result is that the pendulum takes an elliptical path. The physics of this, is both fascinating & beautiful, because each elliptical path is slightly different from the previous one and the result can be captured photographically  revealing quite amazing patterns. In photography these are called physiograms, the tracing a swinging light.


All of these photographs were taken using a £13 Maglite torch with the front lens removed, suspended from the ceiling with string and some sort of weight on the torch to give it momentum and to stop it wobbling, I used my house keys!  The camera lies on the floor directly underneath the torch such, that the torch is shining directly onto the camera lens. The camera must be capable of either having a long shutter speed or the shutter being held open to give a time exposure (sometimes indicated by a ‘B’ mark on the shutter speed dial.) The room must be in complete darkness, so is more of an activity for the darker nights. With lights off and the torch on, we just need to get the torch swinging and then take the photograph. For most of these I used a shutter speed of 30 seconds, the maximum for my camera. The camera needs to be perfectly still for whole 30 seconds. I coloured them digitally in an editing program, but you can achieve the same effect by using the wrappers from Cadbury Roses chocolates over the torch-light. You may have to eat the chocolates in the course of your work !


These are my very first attempt, a consequence of my wife being out and little on TV ! The whole process took less than an hour to complete. There are physiograms available on the net much more complex and beautiful than mine and no doubt took a lot longer to make.


I hope you like these physiograms and have encouraged some of you out there, to have a go yourself.



I’ve been wanting to create these since I was 14 years old, having seen a one in my very first photography book (which I still possess today!). It’s taken me all this time to get motivated to doing it, hence why here are so many to now choose from. 🙂


This next one was created in the same way but the resulting image was ‘inverted’ (ie create a negative from the original image)within Photoshop.


I hope, my very first blog may have interested you a little and if you have got this far, thanks for reading, much appreciated. 🙂

4 Comments leave one →
  1. April 15, 2013 8:37 pm

    Well done on the blog Rob :o)

    • robmcdonald17 permalink
      April 16, 2013 6:01 pm

      Thanks Nicola for the support. Hope you are all well.

  2. Monika Rokicinska permalink
    April 23, 2013 7:35 pm

    Very interesting and helpful blog.
    Since i started my adventure with photography (and I’m just learning still) I was interested in capturing light tracks. So many fascinating things in it – light itself, movement captured as still image, unique and unpredictable patterns.
    Thank you so much for helpful tips – I will definitely try to do it myself 🙂

  3. robmcdonald17 permalink
    April 24, 2013 11:11 am

    Thank you Monika. Have a go at and good luck with it. Focussing can be tricky if camera on the floor, so I tried focussing from light source to the floor. 🙂

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