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How do apertures which seem too large to physically fit work?
Size of the entrance pupil vs size of the apertureHow do constant aperture zoom lenses work?Does the size of the front glass mean anything?How do different apertures affect photographs?Why aren't lenses designed with extra large apertures for autofocus beyond what's used for imaging?Who tells my camera which apertures my lens hasWhy do landscape photos with large apertures have dark corners?Which filters will fit Voigtlander 15mm?How can I use flash with large apertures?Why are large zoom ratio constant apertures lenses not generally available?Can too-tight lens hoods become accidental apertures?
A 400mm f4.0 lens is supposed to have a maximum aperture diameter of 10cm. Looking at such a lens they don't seem big enough to fit that kind of aperture including all the mechanics for control inside them. Do modern lenses have a way of focusing light into a smaller aperture to behave like a bigger one or are they really always the size that the formula (fstop = focal length / aperture diameter) suggests?
lens aperture lens-design physics
edited 2 hours ago
mattdm
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
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LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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add a comment |
A 400mm f4.0 lens is supposed to have a maximum aperture diameter of 10cm. Looking at such a lens they don't seem big enough to fit that kind of aperture including all the mechanics for control inside them. Do modern lenses have a way of focusing light into a smaller aperture to behave like a bigger one or are they really always the size that the formula (fstop = focal length / aperture diameter) suggests?
lens aperture lens-design physics
edited 2 hours ago
mattdm
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
A 400mm f4.0 lens is supposed to have a maximum aperture diameter of 10cm. Looking at such a lens they don't seem big enough to fit that kind of aperture including all the mechanics for control inside them. Do modern lenses have a way of focusing light into a smaller aperture to behave like a bigger one or are they really always the size that the formula (fstop = focal length / aperture diameter) suggests?
lens aperture lens-design physics
edited 2 hours ago
mattdm
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
A 400mm f4.0 lens is supposed to have a maximum aperture diameter of 10cm. Looking at such a lens they don't seem big enough to fit that kind of aperture including all the mechanics for control inside them. Do modern lenses have a way of focusing light into a smaller aperture to behave like a bigger one or are they really always the size that the formula (fstop = focal length / aperture diameter) suggests?
lens aperture lens-design physics
lens aperture lens-design physics
edited 2 hours ago
mattdm
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 2 hours ago
mattdm
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 2 hours ago
mattdm
122k40357653
edited 2 hours ago
mattdm
122k40357653
edited 2 hours ago
mattdm
122k40357653
122k40357653
asked 3 hours ago
LuLeBeLuLeBe
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 3 hours ago
LuLeBeLuLeBe
282
asked 3 hours ago
LuLeBeLuLeBe
282
282
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
LuLeBe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
Your observations of the lens leads you to both a correct, and incorrect, conclusion.
Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 cm.
Incorrect: the stated aperture size is not actually 10 cm in diameter. In reality, it is the the apparent size of the wide-open aperture (the iris), when viewed through the front of the lens, that is 10 cm in diameter.
For any lens, the aperture when viewed through the front of the lens is known as the entrance pupil. It is the entrance pupil that is 10 cm in diameter.
See also:
- Size of the entrance pupil vs size of the aperture
answered 1 hour ago
scottbbscottbb
20.5k75894
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
add a comment |
Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, image brightness will increases 4X. How do you think the optician compensated and maintained the exposure? The front group of lens elements acts as a magnifier. In other words, the diameter of the iris as seen by the outside world appears expand and contract with the zoom when in fact it is fixed as to diameter. It is the apparent diameter of the iris and not the actual diameter that determines the light gathering power of the lens. Note: most inexpensive zooms give up the ghost as the user zooms towards max magnification. A more costly zoom will likely maintain a constant exposure throughout the zoom.
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Your observations of the lens leads you to both a correct, and incorrect, conclusion.
Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 cm.
Incorrect: the stated aperture size is not actually 10 cm in diameter. In reality, it is the the apparent size of the wide-open aperture (the iris), when viewed through the front of the lens, that is 10 cm in diameter.
For any lens, the aperture when viewed through the front of the lens is known as the entrance pupil. It is the entrance pupil that is 10 cm in diameter.
See also:
- Size of the entrance pupil vs size of the aperture
answered 1 hour ago
scottbbscottbb
20.5k75894
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
add a comment |
Your observations of the lens leads you to both a correct, and incorrect, conclusion.
Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 cm.
Incorrect: the stated aperture size is not actually 10 cm in diameter. In reality, it is the the apparent size of the wide-open aperture (the iris), when viewed through the front of the lens, that is 10 cm in diameter.
For any lens, the aperture when viewed through the front of the lens is known as the entrance pupil. It is the entrance pupil that is 10 cm in diameter.
See also:
- Size of the entrance pupil vs size of the aperture
answered 1 hour ago
scottbbscottbb
20.5k75894
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
add a comment |
Your observations of the lens leads you to both a correct, and incorrect, conclusion.
Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 cm.
Incorrect: the stated aperture size is not actually 10 cm in diameter. In reality, it is the the apparent size of the wide-open aperture (the iris), when viewed through the front of the lens, that is 10 cm in diameter.
For any lens, the aperture when viewed through the front of the lens is known as the entrance pupil. It is the entrance pupil that is 10 cm in diameter.
See also:
- Size of the entrance pupil vs size of the aperture
answered 1 hour ago
scottbbscottbb
20.5k75894
Your observations of the lens leads you to both a correct, and incorrect, conclusion.
Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly should be. Only the front element is anywhere near 10 cm diameter. Where the iris mechanism is in the lens barrel, the diameter is substantially smaller than 10 cm.
Incorrect: the stated aperture size is not actually 10 cm in diameter. In reality, it is the the apparent size of the wide-open aperture (the iris), when viewed through the front of the lens, that is 10 cm in diameter.
For any lens, the aperture when viewed through the front of the lens is known as the entrance pupil. It is the entrance pupil that is 10 cm in diameter.
See also:
- Size of the entrance pupil vs size of the aperture
answered 1 hour ago
scottbbscottbb
20.5k75894
edited 1 hour ago
answered 1 hour ago
scottbbscottbb
20.5k75894
answered 1 hour ago
scottbbscottbb
20.5k75894
answered 1 hour ago
scottbbscottbb
20.5k75894
20.5k75894
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
add a comment |
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
1
1
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
That made it so clear, even better than the first answer. I think I understood it now, hopefully! Thank you very much!
– LuLeBe
1 hour ago
2
2
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
Or to flip the description around: the light that gets through the aperture formed a 10 cm disk where it met the objective lens. When you increase the f-stop you start intercepting some of that light.
– dmckee
43 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
@dmckee Absolutely, great way of stating it from the iris's viewpoint! =)
– scottbb
28 mins ago
add a comment |
Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, image brightness will increases 4X. How do you think the optician compensated and maintained the exposure? The front group of lens elements acts as a magnifier. In other words, the diameter of the iris as seen by the outside world appears expand and contract with the zoom when in fact it is fixed as to diameter. It is the apparent diameter of the iris and not the actual diameter that determines the light gathering power of the lens. Note: most inexpensive zooms give up the ghost as the user zooms towards max magnification. A more costly zoom will likely maintain a constant exposure throughout the zoom.
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
add a comment |
Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, image brightness will increases 4X. How do you think the optician compensated and maintained the exposure? The front group of lens elements acts as a magnifier. In other words, the diameter of the iris as seen by the outside world appears expand and contract with the zoom when in fact it is fixed as to diameter. It is the apparent diameter of the iris and not the actual diameter that determines the light gathering power of the lens. Note: most inexpensive zooms give up the ghost as the user zooms towards max magnification. A more costly zoom will likely maintain a constant exposure throughout the zoom.
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
add a comment |
Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, image brightness will increases 4X. How do you think the optician compensated and maintained the exposure? The front group of lens elements acts as a magnifier. In other words, the diameter of the iris as seen by the outside world appears expand and contract with the zoom when in fact it is fixed as to diameter. It is the apparent diameter of the iris and not the actual diameter that determines the light gathering power of the lens. Note: most inexpensive zooms give up the ghost as the user zooms towards max magnification. A more costly zoom will likely maintain a constant exposure throughout the zoom.
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
Lens designers have a few tricks up their sleeves. As an example, zoom lenses change focal lengths but the aperture diameter does not physically change with the zoom. This is an oddity because as the focal length changes, so does image brightness. In fact, if the focal length is doubled, image brightness falls off 4X. Conversely, if the focal length halves, image brightness will increases 4X. How do you think the optician compensated and maintained the exposure? The front group of lens elements acts as a magnifier. In other words, the diameter of the iris as seen by the outside world appears expand and contract with the zoom when in fact it is fixed as to diameter. It is the apparent diameter of the iris and not the actual diameter that determines the light gathering power of the lens. Note: most inexpensive zooms give up the ghost as the user zooms towards max magnification. A more costly zoom will likely maintain a constant exposure throughout the zoom.
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
answered 3 hours ago
Alan MarcusAlan Marcus
25.7k23060
25.7k23060
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
add a comment |
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
1
1
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
Right yes I know about constant aperture zoom lenses. I originally thought they'd have a larger aperture and just close it down when zoomed out. But that makes much more sense the way you explained it, thanks!
– LuLeBe
2 hours ago
add a comment |
LuLeBe is a new contributor. Be nice, and check out our Code of Conduct.
LuLeBe is a new contributor. Be nice, and check out our Code of Conduct.
LuLeBe is a new contributor. Be nice, and check out our Code of Conduct.
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