How to focus a soft focus lens

[djdister]

These instructions for the Verito from 1916 says to simply focus at whatever f stop is most pleasing for the effect...

[Mark Sawyer]

Here in ENGLISH are Heinrich Kuhn's instructions for using his Imagon invention: https://www.cameraeccentric.com/stat...s/imagon_2.pdf

Russ

It should be noted that the technique for focusing the Imagon with h/stops is very different than for other soft focus lenses with conventional f/stops. With the Imagon, you focus on the sharp image with the h/stops closed, then open the h/stops to add the glow of spherical aberration. With conventional f/stops (including when using the Imagon with a conventional diaphragm), just set the aperture for the desired degree of softness and "focus to taste". With a panchromatic emulsion, what-you-see-is-what-you-get.

[Bob Salomon]

It should be noted that the technique for focusing the Imagon with h/stops is very different than for other soft focus lenses with conventional f/stops. With the Imagon, you focus on the sharp image with the h/stops closed, then open the h/stops to add the glow of spherical aberration. With conventional f/stops (including when using the Imagon with a conventional diaphragm), just set the aperture for the desired degree of softness and "focus to taste". With a panchromatic emulsion, what-you-see-is-what-you-get.

No, there is a focus shift when you change H stops on the Imagon. You must focus it at the desired H stop.

[Mark Sawyer]

No, there is a focus shift when you change H stops on the Imagon. You must focus it at the desired H stop.

Not according to Kuhn, and his method makes sense if you want a sharp image with a soft overlay. Focus for the sharp image for the central aperture, then add the soft effect from the peripheral h/stop apertures. The out-of-focus shift IS the soft effect. If you focus with the h/stops open, they may compromise the sharp image from the central aperture, which throws the dominant image.

In practice, we do what we want.

From Kuhn, in the link Russ posted:

[Bob Salomon]

Not according to Kuhn, and his method makes sense if you want a sharp image with a soft overlay. Focus for the sharp image for the central aperture, then add the soft effect from the peripheral h/stop apertures. The out-of-focus shift IS the soft effect. If you focus with the h/stops open, they may compromise the sharp image from the central aperture, which throws the dominant image.

In practice, we do what we want.

From Kuhn, in the link Russ posted:

Why not quote Rodenstock’s instructions? Then you would avoid the focus shift.

[Mark Sawyer]

Why not quote Rodenstock’s instructions? Then you would avoid the focus shift.

Having the soft image from focus shift overlaid on the sharp image is the whole point of the Imagon.

To quote from the Rodenstock's instructions online at: https://www.cameraeccentric.com/stat...s/imagon_1.pdf

[xkaes]

That's exactly what Fuji says as well -- focus stopped down on the most important feature. Then open up to get the softness you want. I posted that six weeks ago.

Around and around we go.

[russyoung]

Having the soft image from focus shift overlaid on the sharp image is the whole point of the Imagon.

To quote from the Rodenstock's instructions online at: https://www.cameraeccentric.com/stat...s/imagon_1.pdf

Later instructions, written by Joseph Foldes for IMAGON also note to focus with the peripheral holes closed then open up: https://www.cameraeccentric.com/stat...s/imagon_1.pdf
russ

[Bob Salomon]

Later instructions, written by Joseph Foldes for IMAGON also note to focus with the peripheral holes closed then open up: https://www.cameraeccentric.com/stat...s/imagon_1.pdf
russ

Closing the holes will result in a focu# shift. Always focus an Imagon at your taking aperture.

[Mark Sawyer]

Okay, from the ground up...

Soft focus lenses work via spherical aberration, where the outside area of a spherical lens focuses on a different plane than the central area of the lens. Both the center and the periphery give sharp images, but on different focal planes. Together, this gives a focused (sharp) image overlaid with an out-of-focus (soft) image, thus both sharp and soft. The best effect comes from having the dominant image being sharp, with degrees of softness controlled by varying the aperture to change the ratio of outer-area light to center-area light.

In a conventional apertured soft lens, the outer area of the lens has a much larger area than the center of the lens. If you focus wide open, your image is dominated by light from the outer areas of the lens. As you close the aperture, you mask off the outside area, and the center area gives the dominant image. Thus, the dominant image moves from the outer area to the inner area, resulting in the focus shift for the dominant image. The majority of the light you focused on wide open isn't there any more after closing down.

The Imagon's H-stops work differently. With the disk in place, the image focus is always dominated by the large central opening, and only a small amount of light comes from the outer area. The main focus plane always comes from the big hole in the center, whether the little holes are open or closed. So you can focus a little easier on the sharp center-only image with the little holes closed, and when you open them, the softness is there but not overwhelmed by adding the whole massive area on the outside of the lens. And this eliminates the focus shift found in conventional apertured soft focus lenses.

It also gives a slightly different soft effect. If you like the traditional soft effect, just use the Imagon's traditional aperture, and focus after closing.

Hope this makes sense...