THE CAMERA OBSCURA IN THE SERVICE OF HISTORICAL REPRESENTATION

THE CAMERA OBSCURA IN THE SERVICE OF

  HISTORICAL REPRESENTATION

Photo1

I am one of many people who have a problem with their eyesight. Mine is not unique but also not very common. 

I have perfect vision in my right eye (my dominant eye) and a high degree of short sighted  vision  in the  left. 

The possibilities are  that this may have happened by accidentally  exposing my eyes to electroplated welding when I was 7 year old.

Now you may ask - what does this have to do with archery? Well, quite a lot but only personally to me.

When I shoot with my spectacles  I have no problem at any distance. When I shoot without my spectacles I am OK to about a 20 m distance, but after that I  have a problem calculating the distance accurately because the left eye loses optical sharpness and the image almost becomes two dimensional. 

I know that there are people who shoot perfectly with one eye, or even close an eye as if  shooting a rifle (?), but in my case this does not work and I do not like to lose any of my peripheral vision. I suppose if I had only the use of one eye all the time then maybe I would  have found a way of calculating the distance accurately.

What I see is demonstrated in the image below (photo 2). It is digitally presented but it is close to the reality!

                                Left eye                                                      Right eye

                                                   Photo 2

Previously I have taken  part in traditional archery festivals representing different historical eras, and spectacles were  a no-no for me. Please this is not a criticism of  other participants wearing spectacles and historical outfits, but it wasn’t right for me. So, all went well up to a maximum of 20 m, but for targets of 50m, 70m, and 90m, I was hoping for luck !

Moving on to Medieval times, spectacles (Photo 3)  were available and I have seen a  few players wearing them, quite comfortably tied on with leather or linen  and of course fitted with modern lenses. So from the distance they appear original and within the historical period. I tried them for a short period of time and it did not  work. 

Two basic reasons. Firstly they move around with sharp movements of the head, especially when I was wearing a helmet and taking part in 30 minute longbow archery demonstrations to the public.  There was  no time to put them back in place and secondly and far worse,  I was unable to wipe off the sweat that ran  on to them when  in full gear in hot weather.

                                                             Photo 3

Eye injuries are very common in all wars of any historical period. Many soldiers fought with the use of one eye only. An eye patch or cloth material was common not only for cometic reasons but also for further protection of injury.

So, this is where the camera obscura   and pinhole camera physics come in to the solution of my problem. Pinhole glasses  were known in the 16th century (Photo 4), but there is also historical evidence  of masks with very fine parallel horizontal slits that were used in Roman times - as yet I have been unable to confirm this and  anyone with a picture please let me know -  that had the same effect as pinhole glasses, i.e. correction of vision.

                                                                             Photo 4

                                 Photo 5 - Possibly post-medieval, look at Fig. 1

Here is a very basic explanation of how the pinhole camera works with the human eye.

http://www.invision2020.com/see-better-squint/

                               Photo 6

Also there is  plenty of information about camera obscura and pinhole camera and glasses on the net.

Using this knowledge I made a metal eyepatch, concave in the inside, to perfectly fit my eye socket (i.e. with no movement) , framed with soft leather for comfort and  I drilled approximately 80 holes, having destroyed 3 1mm drills in the process, very closely spaced together. Then - and this is very important - I  painted the metal with a non-reflective black paint inside and outside and through each hole in order to stop reflections that will blur my vision. (Photo 7).

                                                                     Photo 7

Whilst I have made a few pinhole cameras for my photographic art practices and have spent a lot of time calculating the correct size of the hole to relate to  the size and distance from where the image forms,  in my case I needed peripheral vision and not flat (as per camera) in order to be able to look sideways. This is why it is important that the metal of the eyepatch is concave in the inside and not flat. 

If someone wants to be absolutely perfectionist, the next time you have an eye test ask the optician to give you the distance from your optic nerve to the outer surface of your eye and then add the distance to the first hole in the centre of the eyepatch. If you know the distance it is easy to calculate the best possible diameter of the holes and of course another factor is the thickness of the metal. The thinner the better.

To give a small example : for about a 5cm distance between hole and image I need something like f 160 (f = aperture) i.e. 0.25 mm hole. 

So, I did not spend too much time with calculations and I have to say 1mm holes are rather large for the distance but I got back 80% of my vision with an acceptable loss of light (possibly 40% in my left eye - Photo 8) and a good three dimensional image depiction. 

Thanks to this marvellous organ called the brain and the light sensitive iris in the eye which  adjusts to the right amount of light, the system works. 

After some time and using the eyepatch through all  last summer’s longbow demonstrations, now, when the eyepatch is on, it feels like it is a part of me. The brain has learnt to look through the  same holes more or less and my accuracy in long distance shooting has improved!

Now you may ask- how about contact lenses! Very good idea but my eyes rejected them 10 years ago and as for laser surgery, not for me !

                               Left eye                                                                Right eye
                                                                      Photo 8

My first eyepatch is experimental and I  look forward to making another one in the future with finer holes and  metal. It works for me, (Photo 9 ) it looks original and somehow brings  to the attention of people a very common injury which is largely ignored by historical representations.

                                           Photo 9
                                                       

                                                                         

Acknowledgements 

Physics 20 Resources

http://www.spiritsd.ca/curr_content/physics20/light/pinholediagram.htm

Portsmouth Natural History Museum / Transformed into Camera Obscura for School Workshops

http://www.teamlocals.co.uk/portsmouth-natural-history-museum-transformed-into-camera-obscura-for-family-workshops-044

Glasses

http://wikipedia.unicefuganda.org/latest/A/Glasses.html

Museum of the History of Science / Italy

https://www.flickr.com/photos/jere7my/sets/72157622091191300/

©  GREX LUPORUM
Please do not reproduce without permission.