A lot has been written already on the Hermagis Eidoscope lenses and countless images are posted on line as any Google search will undoubtedly reveal.
This particular lens design was introduced already in 1903 by the French optical house "Hermagis". The soft focus effect is produced by excessive spherical aberration in a rectilinear design. As in most soft focus lenses, the effect is controlled by aperture changes. The lens has an achromat in front and one in the rear. Stopped down this lens is tack sharp as can be expected from a design perspective. Nice feature about this is the rear or front lens can be used as a stand alone and then this lens acts just like any other "landscape" design.
An image of my Hermagis Eidoscope #4 lens below, mounted on a Pentax 67 macro extension ring size #1. I need a second extension ring #3 to achieve a usable focus working distance with the Asahi Helicoid on a camera. A tidbit too long for focus at infinity but as explained earlier in my blog ,,, I can live without infinity focus ! Looking closely at the image below you'll observe the lens to be mounted on my Pentax 67-to-Linhof-Technika adapter so I can use my converted lenses on my view camera collection also.
This was actually the first soft focus lens I adopted on my Mamiya 645AFD MF camera and launched my foray in MF digital soft focus photography.
Nothing better to explain what the "look" of a lens is than showing a few images. Earlier this year in Spring I came across a bicycle rack in Germany that caught my eye and the following images are from that session. Again, digital capture, digital workflow.
This is a wonderful image and one can observe the smoothness in it and yet a very firm line. This is what soft focus is all about ... soft but firm ... not just out of focus ... not panty-hose or vaseline smeared on a filter although both of these diffusion generating tricks have their own merits ... there's a time and place for everything. The above image was taken at f6 aperture in the early morning hours under a covered sky.
About 6 months later I was in the same town and had the Kalosat 1A on my camera. I took a similar shot at f5.6 and the result below shows a very different signature. The digital work flow was the same as for the above image except I didn't sepia tone the image taken with the Kalosat 1A.
I'll refrain from debating what is "best" as the images are quite different The diffusion is obviously different as the optical design of both lenses cannot be compared.
The drawing of the Hermagis is more firm than the Kalosat in light of the small aperture difference. In the second image it is clearly Fall, the sky was really dark and contrast all around was lower. Not sure if the latter is related to the lens but a side by side test will have to decide on this later.