BetterPhoto Q&A
Category: New Answers

Portrait standard distance from subject

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August 15, 2006

First a truism: Things close to the camera reproduce larger than things further away. Consider that distance (span) between ears and nose tip is only about a foot. If you are 4 feet away from the subject’s nose you are 5 feet from the ears. You shoot from this close position (prospective) and you will most likely get a poor likeness. What happens is; the subject already has an idea of there likeness based on a view (prospective) as seen from their make-up or shaving mirror. You must attempt to duplicate this prospective or more often than not you will be rebuked. What happens when you use too short a lens is you will always step in close to shoot. At close subject to camera distance, the nose is reproduced too large and the ears too small. The mismatch can be quite small but facial recognition is basted to tiny trait differences. In this case, minuscule reproduction errors matter a lot.

As a rule of thumb, you want a lens focal length that is longer than normal. Normal is a lens equal to the diagonal measure of the film or imaging chip. In the case of a 35mm film camera, the image formed at the film plane is 24mm x 36 mm. The diagonal measure is 43.3mm. Most consider the normal lens to be 50mm (rounded up from 43). This is too short for the make-up mirror prospective. Most consider 105mm to be the minimum focal length to use with a 35mm camera (Longer OK too). This works out to be approximately two and a half (2.5X ) greater than the digital measure. Using a 105mm or greater on a 35mm camera forces you to step back and in doing so, when you compose, you will automatically achieve the make-up mirror prospective.

Today, as we immerse ourselves into the digital world, we can’t yet abandon the standard 35mm format thinking because we have 80 years invested and it’s ingrained in us. Now let’s make the leap to your Nikon D50. Image sensor is 15.6mm x 23.7mm. Diagonal measure is 28.4mm. Multiply this diagonal by the magic factor of 2.5 and the answer is 71mm. We finally arrive at the focal length of choice for portraiture. Bottom line, use about 80mm which is slightly longer which is good. This focal length forces you to step back and compose and get the make-up mirror prospective.

In closing, there is no right and wrong in art. You are free to use any focal length. However, the rule I outlined has been proven to sell best if you are in the business.

Best of luck,

Alan Marcus
ammarcus@earthlink.net

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August 15, 2006

It comes down to what you see in your viewfinder and whether you want to change it by moving closer, further back, higher or lower, or changing angles to one side or another. This, btw, is why I don't like shooting portraits with a tripod even when using medium format.

Most photographers agree that for 35mm format, using a 105-135 focal length is good for portraits. For medium format, I like using a 150mm or a 250mm with a number 6 extension tube.
And for 4x5 view camera portraits, I like a 250 also.

Take it light.
Mark

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August 15, 2006

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August 15, 2006

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August 15, 2006

Sorry I tend to go overboard - can't help myself.

The concepts used to achieve a lifelike prospective with a camera, is more science than art. In art one can exercise poetic license. This license allows the photographer/artist to take liberties and deviate from convention to achieve some desired effect. As a rule, most successful portrait photographers achieve a lifelike prospective out of instinct. The rest of us poor saps must study the science and hope we can produce good repeatable results.

Actually achieving a lifelike prospective often makes or breaks the professional. You might not think it’s all that important but as I often state, minuscule distortions of facial proportion make the difference between “I love it” Vs “I don’t photograph well”.

Again the secret lies in duplicating the prospective as seen from the make-up mirror / shaving mirror. We talk about using one focal length Vs another but the real scoop is--

Viewing Distance:
Allow me to explain: When a displayed print is viewed from the “proper viewing distance”, the observer naturally sees an image that appears correct as to prospective. This magic distance is the same as was the camera-to-subject distance when the picture was taken. However this is only true for a contact print (a print the same size as the image on the film/chip). In the old days we used 8x10 and 5x7 and 4x5 films, contact prints were common. As films got better and negatives got tiny, the final print became an enlargement (always). Now you need to know that the amount of magnification plays the biggest part.

Consider that a 35mm camera is used to produce an 8x10 inch finished portrait. The negative is 24x36mm or 0.95 x 1.4 inches. To make an 8x10 from this tiny and nicely composed negative, the amount of enlargement (magnification) needed as about ten (10X). The standard lens for a 35mm camera is 50mm which is about two inches (2”). To derive the correct viewing distance for this print, we multiply the lens focal length times the magnification. Both values must be in the same unit. I will use inches. Thus 2 x 10 = 20. This guideline tells us that the proper print viewing distance is 20 inches. The same image taken using a 105mm (4 inch) lens; the math becomes 4 x 10 = 40”. The longer the lens the greater the viewing distance. Keep in mind that most portraits are framed and place on the mantel or desk or on the dresser etc. Thus the viewing distance is generally greater than reading distance which is usually 18 inches.

In the case of the Nikon D50, to make the same print will require a magnification of 14X (the chip is smaller) more enlargement is required.
Using the 80mm lens which is about 3 inches the math becomes: 3 x 14 = 42”. The print viewing distance now works out to 42 inches.

Sometime in the future you might treasure this tidbit. Maybe you will never need or want any of this. Anyway I made the presentation, use it or not.

Conclusion:
Using a 105 on a 35mm Vs a 80mm on the D50 delivers about the same prospective.
You guys can use any lens and any subject distance your hearts desire.
These are facts, as science gave me the insight to see them.

Alan Marcus
ammarcus@earthlink.net

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August 16, 2006

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August 17, 2006