articles/Fashion/hollywood-page4

Hollywood Headshots - part 4 of 1 2 3 4

by Tom Lee Published 01/12/2010

THE LENSES

The wide-aperture 85mm lens has always had a special place in the hearts of 35mm photographers. As such there have been a number of them offered over the years with apertures ranging from f1.2 to f2.0. The Nikkor RF 85mm f2.0 was released in 1948 (a glorious year, when your editor first saw the light of day!).

The reason is straight forward; this focal length (on a 35mm camera) produces a pleasing perspective in a portrait and so the 80 to 90mm 'slot' was bagged by the portrait designs. In order to create a pleasing background separation, wide apertures have been required. Nikon went to f1.2 in 1981 and Canon followed in 1989. Today, apart from a couple of lenses from 35mm to 50mm, very few lenses are offered with 1.4 or 1.2 maximum apertures. Such is the demand for the 85mm that it has always been a special case. The laws of optics also helped - it is possible to design an 85mm lens at a wide aperture with six or seven elements, and retain usable definition at f1.4.

First handling of a wide-aperture short telephoto is always a revelation, especially if you are coming up from a restricted aperture, general zoom (typically f4.5 maximum aperture) - the image is up to 16x brighter! The glass also looks impressive; there seems to be an enormous 'hole' down the middle of the lens. Although a wider aperture normally improves auto focus there can be a penalty for having to move large glass elements, the auto focus can be a little sluggish (but more than adequate for portrait work).

Sigma 85mm f1.4 EX DG HSM

The new Sigma 85mm f1.4 EX DG HSM is a sophisticated design using 11 elements in eight groups. It weighs in at 725g, has a minimum aperture of f16, a close-focus of 85cm (2.8ft) and is 86.4mm diameter by 87.6mm long (almost square then!). The engineering is the high standard we have come to expect from Sigma. A nice touch is the provision of a deeper lens hood extension for users with APS C-size chips - handy if you are the owner of both formats. It is available in Sigma, Sony, Nikon, Pentax and Canon fittings. It has one moulded glass element and one SLD element (special low dispersion). Focusing is via the rear elements to maintain low aberration and presumably to get around the need to shift a lot of glass about during focusing (as would happen if it were the simpler six element double Gauss design). The aperture has nine blades for more pleasing out-of-focus effects (the Bokeh).

It is an interesting side note to our Hollywood feature that the double Gauss lens design (eventually resulting in the Biotar, 1938 and the Sonnar) was created to accommodate the needs of Hollywood in the 1920s. The newer tungsten lighting was not as powerful, but was needed for the new sound movies because of the excessive noise of carbon arc lamps previously used. The response was to bring back out the double Gauss design, as apertures of f2.0 could be achieved with just six elements while still maintaining reasonable sharpness at the frame edges. Today, most wide-aperture lenses are derivatives of this original design although with Sigma's 11 elements, the connection is very difficult to make. The one thing that does remain though is the presence of the aperture diaphragm in the centre of the lens-train. This is normally required in the centre of the lens, to control coma aberrations, but restricts the minimum aperture to about f16 (so those bitching about this on the forums can desist right now!)

A Canon fit Sigma was used during Tom Lee's recent portrait seminar when the Canon-using delegates were cooing over the huge aperture in the rather low light (see Tom's feature on the previous pages). They also soon found out how narrow the depth of field is and how accurate the selection of focus point has to be. Fortunately the huge aperture makes focusing far easier.

Tom did manage to get us the front cover image for Imagemaker out of the shoot and special thanks go to our model Vivienne - good photographer, good lens, gorgeous model, it was difficult to miss!

Next up was the Nikon version which gave us the opportunity to carry out some technical tests and also for Tom to use the lens at a real wedding.

Focusing was very critical. Shooting at a resolution target, using assisted manual focus did not find the optimum focal point - the focus ready indicator was an unreliable witness. A series of shots from focus confirmation just on through to just off produced only one sharp image with varying amounts of defocus and chromatic aberration either side.

Using the focus point selected by the auto focus system then varying the aperture from f1.4 through to f5.6 showed improvements over the first two stops and then consistent performance. Resolution, contrast and chromatic fringing all improved when the lens was stopped down. The tests were carried out from off a tripod using mirror lock-up and electronic, radio release. The RAW images (from a Nikon D200) were then processed with typical detail settings of Amount 50; Radius 0.6 and Detail 80. Nothing in the tests revealed any issues and we confidently despatched the lens to a real wedding with Tom Lee.

Tom's wedding was quite a big bash between Raj and Dan, a delightful combination of Irish and Indian cultures, just the ticket to test lenses, even if it was frantic. Tom shot a little short of 800 images (we said it was a big bash) and so it was possible to do some analysis on his focal length use. Fiftyfour of his shots were between 70mm and 135mm focal length, 33 between 70mm and 90mm focal length and he managed to use the 85mm lens itself for 29 shots. They were a varied mix of portraits, close up detail and some of Raj arriving at the ceremony. Tom will undoubtedly work his magic on the final shots, but we have limited ourselves to minor corrections for exposure and a bit of sharpening. The narrow depth of field is exploited to concentrate the eye on the henna decoration of the bride's hand and the beautiful 'Kalira' attached to the bangles. Note also in the walking shot that an otherwise obtrusive background has been softened back very significantly by the aperture of f1.8.

One thing that the lens taught us is that the narrow zone of an image that are in focus are bitingly sharp and would often need a bit of softening work on skin to remain flattering!

• Hollywood Headshots page 1
  
• Hollywood Headshots page 2
  
• Hollywood Headshots page 3
  
• Hollywood Headshots page 4
  

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