I try to keep my impulses to correct other people's grammar and diction on a pretty tight leash, but there are two words in the photography world that I hear misused a LOT. And it bugs me.
Sorry, but I am about to vent.
"STROBE" - Arguably the best photo lighting blog on the 'net is the STROBIST blog. I'm not knocking anything about this blog. At all.
Except the name bugs me.
The Strobist has a built a great brand and appears to be living the dream of a monetized blog. It would be stupid of me to suggest or for the Strobist to ponder changing the name. But he's not talking about strobing.
"Strobe" is short for the word "stroboscope." This, by definition, means a series or short, bright flashes of light at intervals which can be used to record movement of an object, or to make a rotating object appear to be stationary, such as with an automotive timing light. There is a rather famous photo of a golf swing recorded with strobe, with the club seeming to make a sort of peacock fan around the golfer. In the 1970's, strobes were also used to illuminate the spastic gyrations of dancers wearing hideous clothing in places once referred to as "discoteques."
So, what the strobist writes about is "portable electronic flash photographic lighting." But, of course, "Portable Electronic Flash Photographic Lightingist" would be a crappy name for a blog, so forget it.
"PRIME" - In recent years, photo related internet discussion groups and forums have lit up with discussion of the pros and cons of fixed-focal length (non-zoom) lenses, which way to many people insist on calling "primes." There is such a thing as a "prime" lens, but most lenses people refer to as primes, aren't.
The prime focal length, as I can recall from Joseph Costa's Advanced Photojournalism class back at Ball State University, is the lens focal length which will closely reproduce a person's normal field of vision. That is, objects viewed through a prime focal length lens do not appear to be closer to the viewer or farther away. You can calculate the prime focal length for various film and digital sensor formats thusly:
Square root of ((width of sensor/film format squared) plus (height of sensor/film format squared))
Examples:
Prime focal length for 35mm film or FX (full-frame) digital sensors (24mm x 36mm):
(24*24) + (36*36) = 1872, square root of which is 43.27mm. Of course, 50mm is generally considered to be "close enough" to prime for this format.
Prime focal length for APS-C digital sensors, such as Canon 40D (22.2mm x 14.8mm):
(22.2*22.2) + (14.8*14.8) = 711.88, square root of which is 26.68mm. Sigma markets their 30mm ƒ/1.4 lens as a "prime" for this sensor size. Personally, I'd lean toward the Canon 28mm ƒ/1.8, since it would be usable on all EOS cameras.
So, a 50mm on a Canon 5D or Nikon D3/D700 would be considered a prime lens. The same lens on a Canon 40D or Nikon D300 would not be a prime, but a short telephoto. Likewise, a 28mm/30mm lens on a Canon 40D/Nikon D300 would be a prime, but on the Canon 5D or Nikon D3/D700 would be a wide angle.
A 300mm, although not a zoom, is also not a prime lens unless you happen to be using it on an 8"x10" view camera.
I can actually accept using "strobe" as a slang-ification when referring to single-pop flash lighting. I've been guilty myself of making reference to "strobing the IUPUI natatorium for a college swimming meet."
But I have to hold the line on "prime."
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