Canon Asia has posted an interview article with the developers of the Canon EF 85mm f/1.4L IS USM. The developers initially thought it would be impossible to design such a lens and keep it under 1 kg in weight and have a compact design.
When the product planning department requested development of this lens, our development department was initially stumped by the high degree of difficulty in the design. When equipping large aperture lenses with image stabilisation, the arrangement of the focus and image stabilisation groups is an important factor for determining the size and weight of the lens. Lenses with a small f-number (large aperture) characteristically have large diameter glass. The image stabilisation group, which is a part of the optical system, needs to be able to move to compensate for camera shake, which naturally makes the group heavy. An actuating force is also required to drive the group, and this further adds to the lens' size and weight. Therefore, the development team’s first impression was that it would be almost impossible to develop the reasonably-sized, appealingly-priced 85mm f/1.4 lens with image stabilisation that the product planning department had requested. Read the full article
The Canon EF 85mm f/1.4L IS USM is available to rent at Lensrentals.com