Greetings, everyone. I have just registered, having come upon the site in the past week. Although I am not able to be actively photographing at present, I have for decades and look forward to dusting off my camera and D2 eventually.
The following is, I think self-explanatory, and I hope some may find it useful.
In the course of recently thinking through a return, after years, to making some large-format (4x5) portraits, but without the present ability to run film tests with the camera, I began looking up focal length, distance, and proportion information. The reason for my pursuit, was that I have but one lens for my 4x5, a 210mm, which is roughly equivalent to a 63mm on a 35 and a 110mm on my 645 medium-format camera. For a portrait of a single subject in these smaller formats, I would nearly always choose a lens at least 40-60% longer, unless photographing full standing figure in tight quarters. Since the planned portraits will often be ½- and ¾-length seated poses, I needed to get a better idea of how close I should consider getting to keep distortion within rather strict bounds, and how much cropping of the negative might be necessary at the distances required.
By distortion I mean the visible change in relative size of parts of the face or body as the camera moves closer to the subject. Since the 1960s especially, we have become used to constant distortion from TV news cameras and journalists up-close with very wide angle lenses. Most people today are barely even aware of it, though in my youth it was startling to most.
A web search for "portrait focal length comparison" provides numerous examples of facial distortion -- series of portraits of a subject showing frames with consistent head size taken with short to long focal length lenses (i.e., from extremely close to distant), and some others involving the figure, but I wanted a better measure of proportion for hands, knees, an extended foot, for the range of poses I had in mind. The portraits I intend are conceived with Classical painting and late-19th-, early 20th-Century studio photographic portraiture in mind. Ken Rockwell’s interesting dictum of a 15-foot minimum is not an option for me; I have neither the space nor the inclination to crop my 4x5 negative that severely, in addition to which, the degree of facial “flattening” and broadening at this distance may not suit all subjects well.
Not finding what I wanted, I set up a simple test. I cut two pieces of stiff card stock in half and folded each piece, producing four identically sized, self-standing cards. Then, I sat in a chair and roughly measured the following distances along an imaginary axis parallel to the floor, straight out in front of me: from the middle of my ear to the tip of my nose; from my nose to a comfortably extended hand, as on a chair arm or table; from my nose to my shoe tip on my crossing (upper) leg. The distances in inches are about 5.5, 15, and 30. I then placed the four cards those distances apart along the edge of a long table. Then, measuring from the nose card, I marked off 2-, 3-, 6-, and 9-foot distances and photographed the cards from each distance with a borrowed digital SLR. (See attachment for the ear and nose cards at 2 feet.)
Now, please note that my measurements were all approximate; that’s all they needed to be. Nonetheless, as the attached chart shows, the results are useful in helping to quantify the effects of perspective. I measured the relative sizes of the cards in the several images by using Photoshop’s ruler tool on the height, then derived the ratio of heights of the nose to the ear card, the hand to the nose card, and the toe to the nose card, at each distance.
The attached table shows the Photoshop ruler distances and, below in each row, their ratio (rounded off). Thus, for example, from about 2 feet away, the nose card is 1.25 times taller than the ear card—in practical terms, the front of the nose appears 25% larger than its actual size relationship to the ear, and somewhat larger in relationship to the eyes and facial planes, while the frontal planes of the face will also be disproportionately wider than receding ones. From 3 feet, the card is still about 14%larger than the ear, but from 6 feet, only 6%. However, from 6 feet, the hand card is still about 25% taller than the nose card, and even at 9 feet, the toe card is nearly 50% taller than the nose card; thus, my crossed leg would be noticeably disproportionate. Naturally, these all assume a frontal view; the ratios tend to diminish as the face and body turn towards profile, especially at 6 feet and more.
For my purposes, the results suggest that I may be able to photograph 6 feet from my subject’s face if I keep hands and elbows within a one-foot or so radius from the body and avoid straight-on poses that include knees. I will have to crop the negative but not extremely. At 8 feet, the drawing of the figure will improve and allow a bit more freedom. Using radical.org’s angle-of-view calculator, I see that at 8 feet, a vertically oriented film back will take in 5 feet, a bit more height than a typical full-length seated portrait.
Naturally, the gesture of the pose and other compositional—including tonal—factors may also affect the appearance of relative size, the perception of prominence. However, the exercise has been helpful in providing a more informed starting point.
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