But wouldn't the design and the mount of the lens be the determining factor on how it will be used? If I manufacturer a lens that has a Pentax K mount, it's understood that it is intended/design for use on 35mm. If one chooses to use it on a different format, it would be up to that user to determine the new AoV based on the different format, much like is done now with the aforementioned 35mm equivalent.
I don't know if anybody ever answered this question; I apologize if I missed it here.
Focal length and aperture are a description of the product (a lens). Angle of view for the final image (as pointed out here) relates to camera size (or cropping). Cameras came in many sizes, and lenses could be used on most any of them, so the angle of view wasn't even known to the maker of the lens. This changed with cameras with dedicated lenses, but only for those cameras so still not a universal like focal length. With people regularly adapting lenses to different formats today, the situation is moving back toward what it was in the old full plate, half plate, etc days.
But wouldn't the design and the mount of the lens be the determining factor on how it will be used? If I manufacturer a lens that has a Pentax K mount, it's understood that it is intended/design for use on 35mm. If one chooses to use it on a different format, it would be up to that user to determine the new AoV based on the different format, much like is done now with the aforementioned 35mm equivalent.
But wouldn't the design and the mount of the lens be the determining factor on how it will be used? If I manufacturer a lens that has a Pentax K mount, it's understood that it is intended/design for use on 35mm.
The point has been driven home to me recently as I am looking to re-create Bill Brandt's signature wide-angle look. I've found that he used the Zeiss Protar f.18 8.5 cm. lens Serial No. 1355381
I've tried to find the equivalent angle of view for different formats and the corresponding lenses. But so far, I don't have a shopping list because the equivalents aren't up on a website somewhere for me to compare.
I recently saw an Angulon 90mm sell for a reasonable price here on APUG.
But I asked myself... Is 90mm wide enough? It's only 5mm "longer" so it might be. Except the Angulon is not the "Super" Angulon, so it would barely cover 4x5. And Bill Brandt was shooting "full plate" 6 1/2 x 8 1/2 inches... I shoot 4x5 inches.
Yes. When the convention began, it made complete sense, and designating by AoV made little sense.I think because long ago people used the same lens for different formats. The 210mm lens is always 210mm but the angle of view is quite different from 4x5 and 8x10 and many 210mm lens can be used for both 4x5 and 8x10.
Yes. When the convention began, it made complete sense, and designating by AoV made little sense.
(Wasn't sure where to put this, as we don't have a 'Lens' Section, but since 35mm is the general public's standard, I figured I'd put it here.)
Now that I'm shooting MF as well as 35mm (and APS-C), this question has really been bugging me.
I understand that the focal length of a lens is determined by the distance of the focal point to the film plane, whether it be label in mm, cm, or inches. But when you change formats, what an Xmm lens captures changes from format to format. In other words, a 50mm lens on a 35mm format camera will capture ~46° of the scene. But a 50mm lens on a 6x7 will capture ~81° of the scene. Same focal point to film plane distance, but a completely different image results.
Now it can be said that the general public knows what a 'XXmm' lens will give them as a final image, but that's only because it became the standard way back when. I know for a fact that people new to photography have a difficult time grasping the difference between what they will get as a final between a 24mm, 50mm, and 135mm. Many just don't have any idea what that means, and I'm sure back in the day it wasn't any difference. There is no (IMO) logical relationship between 50mm and 46°, that can be (relatively) immediately understood by a novice.
But if I say to someone who has a basic understanding of geometry that your eyes see ~200° of a scene, and that lens A gives you an image that represents 81° of that scene, I think they might have a better comprehension of what the end result will be. They can take their hands, hold them up to their face, and make blinders that give a 81° view of the scene, and get an idea of what they'll get in their image.
I personally try and convert a 'mm' lens into AOV lens, so I can 'see' what I'll get without having to try different lenses. In other words, I'll look at a scene, and say to myself I want approximately 55° of what I am seeing to be captured, and then grab the lens closest to that.
Labeling a lens as a 52° AOV would standardize the entire lens lineups across formats. No matter what format you're using, a lens with an AOV of 52° will give you 52° of the entire scene. So, in my case, my 24mm (35mm format) lens would be labeled as 81° AOV, as well as my 50mm MF lens (Mamiya RB67). But the way it is now, I have two lenses that are named the same, but give 'wildly' different results.
Discuss....
As a lens designer the related spec I pay attention to the most is horizontal and diagonal field of view (or corresponding image heights if more pertinent).
I can tell you the FOV's or AFOV's of all the lenses I've designed going back a decade or whatever my memory can handle but can only tell you the focal lengths of a very few (not that I couldn't calculate it. I remember the image plane sizes too).
My typical customer is intimately more familiar with what different fields of view values look like than photographers (who correlate a field of view more naturally to a focal length) . Most folks who use optics for observation-type purposes typically are (astronomers, sportsmen, war fighters, etc). Focal length values would confuse them. All approaches are valid as long as you don't put fingerprints on the optics.
You're comfortable with what you're familiar with.
[rant]Its understood by everyone but people who don't know very much.
Ignorant users of small format cameras are unaware of the basics and the history, make the common mistake of assuming that what little they know is all that's known and is universally true.[/rant]
And it continues to make complete sense in the present day.
Awesome!
So basically what I infer from your post is that essentially the rest of the world understands AoV/FoV, but only photographers understand and can relate to focal length. We're an odd bunch....
Initially, I wasn't suggesting anything, but I was curious as to why the system we know was settled on. At the time, lenses were designated with focal lengths in millimeters, centimeters, and inches. Why mm, and why not cm or inches? And with (at the time) there being 3 different designations (or more), why didn't they just abandon the FL, and not go with AoV. That has been answered earlier.
But now that I've been thinking about it, IMO, it would make more sense to use AoV (for the format the lens was intended to be used on), and it would be easier for a layman to have an understanding of what each lens will give them in their final image (as supported by the statement above).
But I'm happy to continue with the old (current) system, although I liken it to using cubits to determine fuel economy when all (standard) distance measurements are in miles or kilometers - 'My car gets 88,000 cubits per gallon!' (that's 25mpg if you're wondering.
Everything changes over time. Some will be accepting of a change, others will fight it tooth and nail. Such is life....
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