Speed of lens...?

[I @ M]

Look, the term arose in the Middle Ages

Wrong again!!!!!

Noah had to use an F/0.95 lens to document all the creatures embarking his ark cos his 25 asa film ( he after all was at the cutting edge of modern technology ) was too slow with the lack of daylight from the torrential rain. Even a tripod wouldn't work cause the elephants were rocking the boat to much.

[jjphoto]

I happen to agree that the origins of terms is important and useful but of course sources can some times conflict, as people always do.

I certainly don't particularly want to get involved in this debate but it's worth noting that shutters didn't even exist when faster lenses where being developed by the likes of Dallmeyer. Muybridge built electrical shutters for his famous work from the 1870's but before then people where still using caps on cameras to control exposures. A faster lens, such as the early Dallmeyer lenses, simply allowed a shorter (ie. a faster) exposure. Muybridges shutters where giving him around 1/1000th of sec exposures (on wet plates!).

How any of this is relevant to the original (OP's) question (which was answered long ago) is beyond me, but still interesting IMHO.

JJ

[ameerat42]

Wrong again!!!!!

Noah had to use an F/0.95 lens to document all the creatures embarking his ark cos his 25 asa film ( he after all was at the cutting edge of modern technology ) was too slow with the lack of daylight from the torrential rain. Even a tripod wouldn't work cause the elephants were rocking the boat to much.

Dang! Wrong again. m.

[arthurking83]

.....

I certainly don't particularly want to get involved in this debate but it's worth noting that shutters didn't even exist when faster lenses where being developed by the likes of Dallmeyer. Muybridge built electrical shutters for his famous work from the 1870's but before then people where still using caps on cameras to control exposures. A faster lens, such as the early Dallmeyer lenses, simply allowed a shorter (ie. a faster) exposure. Muybridges shutters where giving him around 1/1000th of sec exposures (on wet plates!).

.....

I don't think the type of shutter was relevant either. Just because it wasn't as shutter as we know it, a lens cap is still as good as any mechanical(or electronic) shutter will ever be as long as it does the job of exposing the sensing material for the correct amount of time.

What's even more amusing from later in photography history, but still some 100 years back, is a small excerpt from the Wiki link I posted...

For example, the 1911 Encyclopaedia Britannica states that "...[Lenses] are also sometimes classified according to their rapidity, as expressed by their effective apertures, into extra rapid, with apertures larger than f/6; rapid, with apertures from f/6 to f/8; slow, with apertures less than f/11."

I love it! f/5.8 was considered to be extra rapid and rapid was between f/6 and f/8 .. groovy!! So I now have a rapid mirror lens

I think this may be the origins of what's usually referred to as a fast lens.

With extra rapid up to f/5.8, the scale probably went something like this:

bloody rapid @ f/5.6 ; nausea inducing speed @ f/4 ; pretty damned quick @ f/3.5 ; oh! I missed that one @ f/2.8 ; freaking 'ell!! @ f/2.8 and finally ... fast @ f/1.8.

By the time they got past f/2.0 the fun in lens speed naming rights wore off and they all went to PMA for a local meetup ... and a drink or two.

[ameerat42]

Ultimately, all lenses work at the speed of light, c.
So there's nothing to worry about.

[arthurking83]

Ultimately, all lenses work at the speed of light, c.
......

Yes! but glass refracts the light into it various wavelengths!!
.... So which wavelength of light are you specifically referring too? .. the slower blue wavelength, normal visible green channel or the much more energetic red-IR channel.
Even this speed of light rate of work of the lens is open to conjecture.

If we take the equation n = c / v, you can clearly see that the lens is a bit of a bottle neck to the rapid rate of movement of the light itself, so the speed of the lens is not quite c proper, but something more accurately described as c/{v+n}

[fenderstrat1963]

@arthurking83 - is that why chromatic aberration occurs?

[William W]

Arthur –
The reason for my quoting the Manual of Photography was that it was the EARLIEST record I had at hand where the specific term “speed of the lens” was used and also defined.

As I mentioned there are many other texts which also use similar definitions and do not mention shutter speed.
Even the wiki extract you have quoted mentions the faster shutter speed being a result of the fast lens rather than a definition of it and that in and of itself that is significant IF we want to continue to look at the history of thet erm . . . as, if one reads my original post I was setting out an HISTORIC reference to explain how the term was coined and its (original) meaning.

I have no argument that the meaning of the term now, and in general parlance, refers to or makes people think of how the shutter speed of a fast lens will “be a faster shutter speed”.
I wrote –
“That said, there is obviously a direct relationship between the Speed of aLens, when that lens is put on a camera and a fast shutter speeds which can beused, because a fast lens is being used.
And that is easy to remember: but that relationship neither changes the historynor the Technical Term “Speed of the Lens” - which certainly stands apart fromany relationship to Shutter Speed.”

As previously mentioned some folk might not find the historical / research perspective interesting – but some also might.

The similarity with the word “gay” and how that word has changed meaning is a good example of how meanings of words change with time.

That’s it from me on this thread, however, I’m confused as to why the original info I posted would cause so much apparent concern: as it is quite clear to me that in that area of my original post, I was merely setting out the etymology of the phrase: “speed of a lens”.

WW

[ameerat42]

@arthurking83 - is that why chromatic aberration occurs?

Fenderstrat.
1. I am not Arthurking83.
2. So, not no. (That's yes.)
3. But AK has used some slightly incorrect terminology: "energetic". Though it applies to wavelengths of light (and e-m radiation), it is in fact quanta of shorter wavelength (blue-ish) rather than longer ones (IR etc) that are more energetic. So leaving the term aside for the moment, CA occurs because of what AK said about different wavelengths of light. The refraction is a function of their wavelength not their energy.

YOU SEE it in camera and other lenses because of the breakdown of the correction applied to the lens. Wide lenses are more prone and require many more elements to correct the effect of CA (and other As). This is because they bend the light a lot more - that is, through greater angles - than narrower lenses. The latter can be of simpler design.

Well, that's all.
(Not AK)

[fenderstrat1963]

Thank you for that (@ameerat42 <> arthurking83) && arthurking83 for the original information

[TOM]

F2 lens is twice as fast as a f2.8 lens, f1.4 is four times faster, f1 lens is eight times faster.