Photocraft was delighted to welcome, via Zoom, Stewart Robinson, Founder of "Lenses For Hire". Stewart presented an interesting talk that gave us a full understanding of why and how photographic lenses have developed over the (many) years, taking us far back in time to appreciate the full journey up to the present day.
Stewart opened by sharing with us how he came to start up the company. About to make his first-ever trip to the Arctic to photograph polar bears, he went into a branch of Jessops and asked the chap behind the counter if he could hire a lens. Getting a negative response and no real explanation as to why, he realised that this was an area where there must be demand, especially for the kind of trip he was about to make.
Yes, he had to spend a fair bit to buy in his first set of lenses and then set up the business but he has now sold it on to the employees and effectively works for them!
I'm not sure what our members studied at school but I can't remember anything that gave me such details in the way Stewart explained them.
We started with Euclid, back in around 300BC. He was more about geometry but determined the following:
1. That rectilinear rays proceeding from the eye diverge indefinitely; 2. That the figure contained by a set of visual rays is a cone of which the vertex is at the eye and the base at the surface of the objects seen; 3. That those things are seen upon which visual rays fall and those things are not seen upon which visual rays do not fall; 4. That things seen under a larger angle appear larger, those under a smaller angle appear smaller, and those under equal angles appear equal; 5. That things seen by higher visual rays appear higher, and things seen by lower visual rays appear lower; 6. That, similarly, things seen by rays further to the right appear further to the right, and things seen by rays further to the left appear further to the left;
7. That things seen under more angles are seen more clearly.
It became clear that there were many people interested in optics and lenses across the world. Some tried to develop their theories and one man became recognised more than most as making the next breakthrough. That was Ibin Haytham.
He understood that both light and colours were involved in how optics worked and so made further progress possible.
Over time there were many key figures, such as Johannes Kepler, Willebrod Snellius (it took many years for him to get fully recognised for his work in founding the mathematical law of refraction, now known as Snell's law, in 1621), Christian Huygens and Isaac Newton. Of course, all these people were doing their work in order to better understand vision and light.
Allow me to skip forward a while and enter the time of photography. By now, the main areas where efforts were being made was to overcome the various diffraction and aberrations that occur when using a lens. Much of this was being undertaken in what we know today as Eastern Europe.
Joseph Petzval developed a portrait lens with four elements:
This was used in conjunction with Voightlander cameras.
Stewart then told us about the huge amount of work being done by the Zeiss Company and three men who effectively can be said to have created much of the templates still in use today for manufacturing camera lenses.
These three were Paul Rudolph, Ernst Abbe and Otto Schott (the latter still very much a name in glass and used to make many filters) These three created many of the Zeiss lens structures still in use today and effectively copied by many other manufacturers.
Other factors were also now being worked on, such as coatings to better retain the light entering the lens
Throughout this time of development, we also saw the use of the zoom lens with various manufacturers looking to make their name by offering choices of wide and telephoto:
As each individual lens is added, so another is used to correct the distortion the first one causes, until the point where the light and colours meet is as close as possible to being the same.
The cost of lenses relates to both the amount and quality of the glass used. Stewart explained the sheer level of work that has been needed to make many of the top-end zoom lenses, hence the prohibitive prices!
Stewart is a Canon user and his own research shows him the vast array of lenses he can use with his camera. I am sure we are all familiar with the often long list of letters and numbers on our lens and thanks to Stewart, we now know that bit more about what they mean.
Thanks for staying with this and apologies if you feel there is something missing - I did not make any notes as I did not know it was my turn to do the blog!