![hugo meyer aristoplane hugo meyer aristoplane](https://www.soperfectimages.co.uk/sy-photos/2022/01/12/11/small_ad5d96_Nikon_Nikkor_W_135mm_f5.6,_710278,1111.jpg)
I discovered that my optical mouse sometimes jumps and I insert letters in the wrong place, alongside the small keyboards on laptops that cause occasional double letters like nbominal They're faster and have less fall-off of illumination off-axis. VIIb (4/4 double Gauss), Protar V (5/2) and Perigraphe VIb (6/2 Dagor clone). Modern wide-angle lenses for large format have two very important advantages over the ancient anastigmats such as the W/A Aristostigmat and Cooke Ser. Georges Laloire has sent me undated data from Berthiot, probably published between the wars, that also claims 100° for f/14 Périgraphes. I have a SOM Berthiot brochure from, probably, the late 1940s that claims 100° for the 90/14 Périgraphe VIa and doesn’t mention convertibility in it SOM Berthiot’s convertible Dagor type is the Eurygraphe.
![hugo meyer aristoplane hugo meyer aristoplane](https://www.arsenal-photo.com/media/image/product/15879/lg/hugo-meyer-goerlitz-wide-angle-aristostigmat-63-16cm-clean-glass.jpg)
An undated SOM Berthiot catalog published between the wars (see ) says that f/14 Périgraphes cover 106°, illuminate 112°. The 1912 coverage estimates may be inflated. Recommended formats at f/25 are consistently between 100º and 110º without movements. It says that both are convertible, claims that the f/14s cover 115º and the f/6.8s cover 95º. Henri Gaud has posted a page from a 1912 Établissements Phillipe Tiranty catalogue - listing f/14 and f/6.8 Lacour-Berthiot Périgraphes. To some extent it depends on what's expected of a lens.