07 January 2013

the science of portraits

Cameras do horrible things to people. Self-conciousness sets in, and with it uncontrollable rapid blinking and forced smiles. Even the most self-confident rapidly get that rabbit in the headlights look when faced with a huge unblinking glass eye. Ladies contort their heads into weird positions in a misguided attempt to hide real or imagined flaws or sagging.

For me portraits must be entirely natural. Unguarded and not posed.

This is why family portraits are a nightmare. Let's do the maths - it's all about probability. For an average picture with an average group of humans I'd estimate the input numbers as follows:

chance of an adult sitting properly without finger up nose: 99/100 = 0.99
chance of an adult having an acceptable expression: 4/10 = 0.4
chance of an adult having a great expression: 1/20 = 0.05

chance of a child sitting properly without their finger up their nose: 6/10 = 0.6
chance of a child having an acceptable expression: 5/10 = 0.5
chance of a child having a great expression: 2/10 = 0.2

For the purpose of the calculations that follow, it is important to note that having a great or acceptable expression and putting your finger up your nose or similar antics are NOT mutually exclusive, as demonstrated convincingly here by both Sadie and Zoë who manage to look beautific while respectively mining for gold and pretending to be an eel.

Single children

Contrary to popular wisdom, portraits of single children on their own, are therefore not too much of a challenge - probability of a great expression, natural, decently framed picture without orifice exploration is:

0.6 x 0.2 = 0.12 or 12%
i.e. 1 in every 8 or 9 photos is likely to be a great success

If you can even relate to kids a little, just set up your kit, shoot 8 to 9 photos and et voilà:

You want a picture of your son just before his milk teeth fall out and he looks all rabbit-like for the next five years? No problema señora:

Multiple children

Two kids together? Still do-able:

(0.6 x 0.5)2 = 0.0144 or 1.4%
i.e. 1 in every 69 photos is likely to be a great success

Three kids? We're starting to get into lower your expectations territory. Unless you want to shoot the 579 images that it would take to have at least one shot at them all looking great  over enough sessions for the kids to stay fresh, you'd better accept that at least two of them are going to look merely OK while the other one looks superb enough to make the mediocrity of the other two clearly noticeable:

(0.6 x 0.2) x (0.6 x 0.5)2 = 0.0108 or 1.1%
i.e. 1 in every 93 photos is likely to be a two-thirds OK with one-third great success

And best you bring your best reflexes and enough light for f11. You don't want to be a little out of focus for that one in 100 shot. Keeping them still is not an option.

Single adults / teenagers

Single person portraits of adults are already substantially more challenging. While it will probably be easy enough to get an acceptable photo unless the person is really camera-phobic...

0.99 x 0.4 = 0.396 or ~40%
i.e. one in every 2 to 3 pictures is likely to be OK

...getting a really natural and flattering picture can be a lot harder:

0.99 x 0.05 = 0.0495 or ~5%
i.e. one in every 20 properly exposed, lit and framed pictures might be pretty decent.

Teenagers can be more challenging still, although the standard deviation on that group is awfully high so I will omit probability calculations as largely meaningless for specific cases. I personally think morose is not actually that bad since it's at least natural and will likely make an authentic portrait, although not necessarily one parents would pay you for.


Hopefully I've already made my point and you know where this is going.

Let's say two grandparents, two parents and two kids. Want everyone looking their very best?:

(0.99 x 0.05)4 x(0.6 x 0.5)2= 0.000000054 or 0.0000054%
i.e. one in every 18,507 pictures is likely to be close to perfect.

I'm not really an 80/20 kind of person, but with these odds, I'll settle for OK, with a dash of lovely. Oh wait, one of the kids has run off and refuses to come back? Never mind, then it's time for alchemy. Just put grandpa with any available granddaughter:

Probability of success: 100%

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