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Old October 3rd 05, 06:14 PM
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"BC" wrote in message
"Go ahead, outline "that evolutionary process" for me. I'd sure like to
how you get "fixed focal length" to evolve into "prime." What might the

intermediate steps look like, I wonder?"

Many of the earlier zoom lenses from the 1960's and 1970's comprised an
afocal zooming portion in the front, followed by a fixed focal length
lens group in the rear. That fixed focal length lens group was, and
still is, called a "prime lens".

That's interesting. If that FFL lens group would (or could if separated)
function independently as a stand-alone lens, then that seems like correct
usage. That is, you have what is essentially a prime lens with a zoom
attachment, even if they are built as a single unit.

I suspect that this may have led to
all fixed focal length lenses being called prime lenses.

For all I know you may be right, though I have always suspected the usage
came about through someone seeing "prime lens" correctly used, i.e. in
connection with some attachment such as a close-up lens or tele extender,
and the prime lens happening to be FFL, just assumed that was what "prime"
meant. But this is just speculation on my part.

As a side note, this early type of zoom lens automatically had a
constant f/# through zoom. However, it is not nearly as common a
design form as it used to be.

As I've pointed out to you earlier, respected manufacturers such as
Panavision do use the word "prime" to mean fixed focal length. The cat
is clearly out of the bag here, and we might as well get used to
"prime" and "fixed focal length" being synonyms.

I'm sorry I don't remember your earlier mention of this. (Was it recent?)
I've just Googled "panavision" and find you are correct, though as I've
mentioned previously other manufacturers (Schneider, Zeiss, Arri etc.) do
*not* use "prime" and "fixed focal length" synonymously, since they
catalogue "variable prime" lenses--lenses of variable focal length.
Panavision appears to be in the minority among lens makers as far as its
usage is concerned.

Incidentally, while looking I also found this, in connection with
Panavision's Camera 65 system: "This employed using 65 mm film in
conjunction with the APO Panatar lens, an integrated anamorphic lens (rather
than a prime lens with an anamorphoser mounted on it) set to a 1.25
expansion factor."

Now that clearly uses "prime lens" to distinguish the camera lens--whether
FFL or not--from the attachment used with it, which is correct usage. A link
in that sentence takes the reader to Wikipedia's definition for "prime
lens," which is the now popular and incorrect one. I think it's significant
that Wikipedia's definition of the term, though a popular one, does not
comport with their own use of the term in the Panavision article.

This sort of confusion could be avoided simply by not using "prime" to mean
fixed focal length, which no existing definition for "prime" can support in
the first place.