I posted the previous thread while I was at work based on my memory of some research I did into lens design some years ago. Unfortunately, I missed a couple of steps out! Now I am at home, I have consulted the "bible" and can perhaps fill them in. A quick history of normal/wideangle lens design.
The first "photographic" lens was the made in 1839 by Woolaston. The big difference was that one surface was concave as opposed to the double convex design from the modified telescope/microscope lenses used previously. This gave a flatter field and reduced coma. Chevalier added a second double convex lens to this to produce the achromatic landscape lens. This was further developed by Grubb. The problem was that they were very slow in conjuction with the slow emulsions making portraits difficult. Petzval then used 2 disimiliar achromatic groups to produce a portrait lens. Much faster but soft in the middle with alot of aberation at the edges (quite liked in a portrait) This was about F3.7. From here the designs start to split. About 1860 the landscape lens was developed by using 2 symetrical pairs. The importance here is that the double pair allows for fast, well corrected but astigmatism was still a problem. By 1880, glass technology especially by Schott allowed this to be dealt with and Zeiss were producing such lenses as the Double Protar. However, these were becoming very complex and expensive.
Enter Cooke in 1893, He went back to the asymetric portrait lens and turned it into a triplet. This gave a compact relatively simple lens of up to F2.8. He was working for Taylor Hobson. In 1902 Zeiss pimched the desighn and called it the Tessar! So allow Taylor Hobson were later to copy the Barnack's, they were only getting their own back for previous history!
Now this is all very well for "normal" lenses. The trouble with the Tessar type lens is that it suffers from light fall off and it difficult to correct for the abberations caused by the assymetry. This gets far worse when you try to make a wide angle and about the fastest you cam make is F22. In it's normal length though it's derivatives are very good for collapsible lenses and folders.
Now the double symetrical pair is very different. Providing you have the space behind the lens, it is relatively easy to build a fast (f2) wide angle that is well corrected. The only big disadvantage is that they are bulky, typically having a very "waisted" apperance. The Super Angulon, Summicron and Summarons are all variations of this design. Most of the current Schneider LF lens are also of this pattern. The shape is what I was referring to in the J12 and the LF lens also show this. For this lens, the bulk is not a problem but you can't make them collapsible or easily into a folder. To make it smaller for collapsing, for a mirror box or for a folder with reasonable speed, you have to go to retrofocus designs and these came along later.
The bottom line is that it is not feasable to make a wide angle for a folder that has a reasonble speed, is well corrected and at a sensible cost. If you have the space for a fast double symmetrical pair, you can handhold it. I wouldn't like to handhold at F22 even with today's faster emulsions let alone with what was available 40 years ago.
Kim
