Saturday, March 12, 2011

Portrait Theory: Lens Selection

After reading several articles in a row, like Ken Rockwell's March 2008 article, "Portrait Lenses", I found myself fearful that good information about classical photographic portrait technique technique is being drowned by voices high in search ranking but low on education and skill.  I belive that the classical foundations are critical to producing consistent, top caliber work.  It is easy to demonstrate that portrait masters like Irving PennYousef Karsh and Arnold Newman used the classical portrait techniques as the point of departure for their work.

What is the ideal classical portrait?  Like it or not, the ideal that challenges us all, even photographers, are paintings like Leonardo DaVinci's Mona Lisa.  I don't think it is a surprise that the most famous painting in the world is a portrait.  We are hard wired to recognize and appreciate every nuance of the human face.  Furthermore, we have the ability to detect even the slightest asymetry or distortion, ad adaptation that helps us choose healthy mates.  Classical portraiture, whether painting, sculpture or photography, aims at simultaneously capturing an accurate likeness and idealizing the sitter.  This balancing act is mastered by only a few artists in each generation, so it must be very difficult.  At least, there are rules of geometry that guide the way, which is the topic I plan to cover here in the next few posts.

So, the first order of business for a photographer is to choose a suitable portrait lens.  The rule of thumb criteria for this is well established and nothing like Rockwell's 15 foot theory.  Perspective is extremely important to making a pleasing portrait.  Perspective is determined by the camera to subject distance.  Most of use believe that the ideal camera to portrait subject distance to 5-7 feet and that the lens focal length should be twice normal focal length of the capture format, where the normal focal length is defined as the diagonal of the capture format.  For example, the full frame DSLR diagonal is 43mm.  Therefore, the ideal head and shoulders portrait focal length is 86mm.  It is therefore no surprise that Nikon, Canon, Zeiss and other lens makers offer several 85mm lenses that are tuned for portraiture.  Leitz is a bit of a maverick here.  First it set the standard normal focal length for the 24x36mm format to 50mm, a few millimeters longer than theoretcal.  Continuing the trend, 90mm is the Leica portrait standard, which it holds alone.

So, what does a classical portrait look like?  Simple, classical portrait of Ernest Hemmingway is the first Karsh I ever saw in person and the power of it is still impressive.  It was shot on 4x5 film using a 14" Kodak Ektar.  This is the image most of us have of Hemmingway.

What happens when a photographer deviates from the ideal?  Given a lens focal length that fills the frame with the head and shoulders, if the camera is too close, we get an unpleasant wide angle distortion, making th nose too large, forehead bulbous and ears recede.  Arnold Newman used just this technique as a deliberate hatchet job in his famous portrait of Alfried Krupp.  The classical foundation led him to choose the "wrong" lens to momentous effect.

So, keeping with the formual that 5-7 feet yeilds an ideal perspective, we have two common variants; full lenght and extreme close-up.  To accomplish a full length shot, a normal lens is in order.   For instance, the portrait below or Max Ernst and Dorthea Tanning by Irving Penn was made on 8x10 film using a Schneider 300mm.

Finally, the extreme close up, which can be very powerful, but seldom flattering.  Irving Penn used a normal 80mm lens on his Rolleiflex to shoot Truman Capote.  The wider than normal perspective slightly emphasizes Capote's hands and eyeglasses.

Whereas Arnold Newman used a Leica with a 135mm lens to capture Marilyn Monroe, achieving a voyeuristic mood.  We feel like we are intruding on a private moment.

Most readers of this blog shoot a DSLR, so the table below shows the focal length recommendation for the Nikon FX and DX formats.

(24mm X 36mm)
(23.7mm x 15.5mm)
“Voyeur” Effect 135mm 85mm
Full Frame Head 105mm 70mm
Classical Portrait 85mm 60mm
Medium 60mm 50mm
Full Length 50mm 35mm


benjamin gandhi-shepard said...

I guess that you need to know the rules before you can break them. Thanks for the lessons in classic technique. Keep 'em coming.

Preston Page said...

Exactly right, Ben, thank you. I think the classical approach contains the rich visual language that gives meaning and emotion to the "rules". Knowing what happens when they deliberately broken makes for more powerful and controlled expression.