Using the S4 Soft Focus Attachment With the
Cooke S4/i 65mm and 75mm Prime Cine Lenses

The Cooke S4 Variable Soft Focus Attachment is designed for use on the 65mm and 75mm S4 cine prime lenses. Depending on the aperture used, a variable degree of softness can be applied to the image. The soft focus attachment fits directly on the 65mm S4 lens, and for this reason it is engraved as being for that lens. If you want to use it on the 75mm S4 lens you need to use the Cooke adapter ring which is engraved for use with the that lens.

Adjustment of the Soft Focus Effect

The soft focus attachment delivers a range of soft focus effects with the 65mm and 75mm S4 lenses as the aperture is varied. For the 65mm S4 prime lens the soft focus effect is greatest at T2, reducing to no special effect at T5.6. At apertures below that, the lens operates as a normal, sharp lens. The 75mm S4 lens provides the same effects, but when this lens is stopped down to T4 it is already fairly sharp.

In general, if you want a particular degree of softness you may need to use neutral density filters.

Comparison with Soft Focus Filters

The Cooke soft focus attachment works in a completely different way to nets or soft focus filters. Rather than bluntly scattering the light, it uses a higher order aberration effect to reduce sharpness at lower spatial frequencies in the image. It follows that the change in its effect with aperture is much more pronounced than with a soft focus filter or a net. Roughly speaking, a net or a softening filter has the same effect at all apertures; that is not quite the case, but certainly there is much less variation of softness with aperture when using nets and filters than with the Cooke Soft Focus Attachment.

The Origins of the Soft Focus Attachment

The origins of the Cooke Soft Focus Attachment are in Large Format Still Photography, with our Cooke PS945 Lens for large format photography: Cooke Optics Ltd. manufactures a highly acclaimed large-format stills lens for the 4x5” and 7x5” formats using this soft focus technology, which provides the same variable degree of softness.

At the request of the large format photographic community, this lens is based on the revered Pinkham & Smith portrait lenses of the early 20th century. Use of the Cooke PS945 lens by many professional large format photographers has, ironically, now revealed at least as many non-portrait applications for this lens as portrait applications. The ability of the lens to provide what is described as a “unique, and special luminosity” to the image with a range of lighting arrangements is especially valued.