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Why don't lens mount adapters have the same effect as extension tubes?
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I use a Metabones adapter for Canon lenses on a Sony body. Why doesn't the lens adapter, which sets the lens further from the sensor, have the same effect as using extension tubes, allowing closer focus?
lens-adapter extension-tubes
edited 21 hours ago
xiota
4,76011043
asked 22 hours ago
Tim Hopper
1334
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Tim Hopper 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 |Â
up vote
6
down vote
favorite
I use a Metabones adapter for Canon lenses on a Sony body. Why doesn't the lens adapter, which sets the lens further from the sensor, have the same effect as using extension tubes, allowing closer focus?
lens-adapter extension-tubes
edited 21 hours ago
xiota
4,76011043
asked 22 hours ago
Tim Hopper
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
It should. What in the results differs?
– loonquawl
22 hours ago
1
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
2
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago
add a comment |Â
up vote
6
down vote
favorite
up vote
6
down vote
favorite
I use a Metabones adapter for Canon lenses on a Sony body. Why doesn't the lens adapter, which sets the lens further from the sensor, have the same effect as using extension tubes, allowing closer focus?
lens-adapter extension-tubes
edited 21 hours ago
xiota
4,76011043
asked 22 hours ago
Tim Hopper
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I use a Metabones adapter for Canon lenses on a Sony body. Why doesn't the lens adapter, which sets the lens further from the sensor, have the same effect as using extension tubes, allowing closer focus?
lens-adapter extension-tubes
lens-adapter extension-tubes
edited 21 hours ago
xiota
4,76011043
asked 22 hours ago
Tim Hopper
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 21 hours ago
xiota
4,76011043
asked 22 hours ago
Tim Hopper
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 21 hours ago
xiota
4,76011043
edited 21 hours ago
xiota
4,76011043
edited 21 hours ago
xiota
4,76011043
4,76011043
asked 22 hours ago
Tim Hopper
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 22 hours ago
Tim Hopper
1334
asked 22 hours ago
Tim Hopper
1334
1334
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Tim Hopper is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
It should. What in the results differs?
– loonquawl
22 hours ago
1
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
2
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago
add a comment |Â
It should. What in the results differs?
– loonquawl
22 hours ago
1
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
2
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago
It should. What in the results differs?
– loonquawl
22 hours ago
It should. What in the results differs?
– loonquawl
22 hours ago
1
1
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
2
2
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago
add a comment |Â
4 Answers
4
active
oldest
votes
up vote
22
down vote
accepted
Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens.
If you somehow bodged it horribly so that a Canon lens was mounted in the same place as the Sony lens, it would be focusing everything on a point 26mm behind the sensor and it would all be a bit of a disaster really. The EF to E lens mount adapter ensures that the Canon lens is mounted 44mm from the sensor so that the incoming light is focused in the correct place.
answered 22 hours ago
Philip Kendall
15.6k44780
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
add a comment |Â
up vote
4
down vote
Why don't lens mount adapters have the same effect as extension tubes?
They do. But whether it limits far-focus capability depends on one factor: the difference in distances from the image plane to the back of the lens mount flange between the two systems.
If the adapted lens's mount is deeper than the camera's mount, the adapter tube can make up the difference so that the lens sits exactly where it needs to in order to have full range of focus.
If the adapted lens's mount is shallower than the camera's mount, then the adapter is working exactly like an extension tube and will reduce far-focusing capabilities, if there's no glass element. If there is a glass element in the adapter, the adapter no longer acts like an extension tube, but is now acting like a teleconverter, where the lens has increased the apparently focal length (thereby also reducing the max. aperture) to regain focus-to-infinity.
See also: Can I use lens brand X on interchangeable lens camera brand Y?
answered 14 hours ago
inkista
39.5k557100
add a comment |Â
up vote
-1
down vote
The Metabone adapter is an optical accessory that mounts between the camera body and the camera lens. Such a mounting relocates the lens further forward. Such repositioning corresponds precisely like the action of extension rings or tubes in common use. However rings and tubes are void of lenses whereas the Metabone adapter contains lenses that modify the focal length of attached lens.
Supplemental optics similar to this device has been in use almost from the beginnings camera / lens design. We can mount such devices before or after the camera lens. These devices alter close focusing distance or they modify the lens, converting it to a telephoto or a wide-angle.
Many such supplemental lenses have been or are currently being marketed. The Metabone adapter revises the focal length of the attached lens, it shortens it about 70%. In other words, say a 50mm lens is combined with a Metabone adapter. The 50mm focal length is altered, it converts to become35mm. This action is analogous to add-on wide-angle converters commonly available. However, most such devices mount before the camera lens whereas the Metabone adapter mounts after the camera lens. Again, not a new idea.
How does the Metabone adapter realize a lens speed increase? The photographic industry uses the f-number system to specify the relative speed of a lens. The camera lens acts like a funnel in that it gathers light. The greater the working diameter of the lens (aperture) the brighter the projected image (speed of the lens). Entwined with aperture is focal length. Both are contributors as to how bright the projected image will be. Say the aperture diameter is untouched and the focal length doubled the projected image dims to 25% of its original brightness (2 f-stops). Conversely, if the focal length cut in half, the image brightens 2 f-stops.
The Math: 50mm lens 12.5mm aperture = f/4 --- 100mm lens 12.5mm aperture = f/8 --- 25mm 12.5mm aperture = f/2
Suppose you set your 50mm to f/8 achieved with a 6.25mm aperture. Now you mount a Metabone that shortens the focal length 70%. The revised focal length is35mm. The aperture remains unchanged at 6.25mm, the revised f-number is 35 ÷ 6.25 = 5.6 (written f.5.6). Simply stated, the Metabone shortened the focal length, this act increased the angle-of-view (more wide-angle), the image brightened as a result, the revised f-stop is f/5.6 = 1 f-stop speed gain.
The cleverness of the Metabone is, it shortens the focal length, this gives rise to a speed gain plus it adapts a lens designed for a larger format camera to operate on smaller format cameras mitigating the crop factor that would normally charge. Remarkable is the fact that back-focus distance (flange focus distance) of the lenses is corrected taken into account allowing lens interchangeability.
Also, Meabone is credited with suppressing some aberrations normally realized when a supplemental lens is added. (If all true, hats off to the optician
answered 21 hours ago
Alan Marcus
23.1k12453
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
add a comment |Â
up vote
-1
down vote
Extension tubes don't have any lens elements; they're completely hollow. Metabones adapters do have lens elements.
answered 18 hours ago
Frank
5987
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
add a comment |Â
4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
22
down vote
accepted
Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens.
If you somehow bodged it horribly so that a Canon lens was mounted in the same place as the Sony lens, it would be focusing everything on a point 26mm behind the sensor and it would all be a bit of a disaster really. The EF to E lens mount adapter ensures that the Canon lens is mounted 44mm from the sensor so that the incoming light is focused in the correct place.
answered 22 hours ago
Philip Kendall
15.6k44780
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
add a comment |Â
up vote
22
down vote
accepted
Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens.
If you somehow bodged it horribly so that a Canon lens was mounted in the same place as the Sony lens, it would be focusing everything on a point 26mm behind the sensor and it would all be a bit of a disaster really. The EF to E lens mount adapter ensures that the Canon lens is mounted 44mm from the sensor so that the incoming light is focused in the correct place.
answered 22 hours ago
Philip Kendall
15.6k44780
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
add a comment |Â
up vote
22
down vote
accepted
up vote
22
down vote
accepted
Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens.
If you somehow bodged it horribly so that a Canon lens was mounted in the same place as the Sony lens, it would be focusing everything on a point 26mm behind the sensor and it would all be a bit of a disaster really. The EF to E lens mount adapter ensures that the Canon lens is mounted 44mm from the sensor so that the incoming light is focused in the correct place.
answered 22 hours ago
Philip Kendall
15.6k44780
Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens.
If you somehow bodged it horribly so that a Canon lens was mounted in the same place as the Sony lens, it would be focusing everything on a point 26mm behind the sensor and it would all be a bit of a disaster really. The EF to E lens mount adapter ensures that the Canon lens is mounted 44mm from the sensor so that the incoming light is focused in the correct place.
answered 22 hours ago
Philip Kendall
15.6k44780
answered 22 hours ago
Philip Kendall
15.6k44780
answered 22 hours ago
Philip Kendall
15.6k44780
answered 22 hours ago
Philip Kendall
15.6k44780
15.6k44780
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
add a comment |Â
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
Very helpful. That makes sense!
– Tim Hopper
21 hours ago
add a comment |Â
up vote
4
down vote
Why don't lens mount adapters have the same effect as extension tubes?
They do. But whether it limits far-focus capability depends on one factor: the difference in distances from the image plane to the back of the lens mount flange between the two systems.
If the adapted lens's mount is deeper than the camera's mount, the adapter tube can make up the difference so that the lens sits exactly where it needs to in order to have full range of focus.
If the adapted lens's mount is shallower than the camera's mount, then the adapter is working exactly like an extension tube and will reduce far-focusing capabilities, if there's no glass element. If there is a glass element in the adapter, the adapter no longer acts like an extension tube, but is now acting like a teleconverter, where the lens has increased the apparently focal length (thereby also reducing the max. aperture) to regain focus-to-infinity.
See also: Can I use lens brand X on interchangeable lens camera brand Y?
answered 14 hours ago
inkista
39.5k557100
add a comment |Â
up vote
4
down vote
Why don't lens mount adapters have the same effect as extension tubes?
They do. But whether it limits far-focus capability depends on one factor: the difference in distances from the image plane to the back of the lens mount flange between the two systems.
If the adapted lens's mount is deeper than the camera's mount, the adapter tube can make up the difference so that the lens sits exactly where it needs to in order to have full range of focus.
If the adapted lens's mount is shallower than the camera's mount, then the adapter is working exactly like an extension tube and will reduce far-focusing capabilities, if there's no glass element. If there is a glass element in the adapter, the adapter no longer acts like an extension tube, but is now acting like a teleconverter, where the lens has increased the apparently focal length (thereby also reducing the max. aperture) to regain focus-to-infinity.
See also: Can I use lens brand X on interchangeable lens camera brand Y?
answered 14 hours ago
inkista
39.5k557100
add a comment |Â
up vote
4
down vote
up vote
4
down vote
Why don't lens mount adapters have the same effect as extension tubes?
They do. But whether it limits far-focus capability depends on one factor: the difference in distances from the image plane to the back of the lens mount flange between the two systems.
If the adapted lens's mount is deeper than the camera's mount, the adapter tube can make up the difference so that the lens sits exactly where it needs to in order to have full range of focus.
If the adapted lens's mount is shallower than the camera's mount, then the adapter is working exactly like an extension tube and will reduce far-focusing capabilities, if there's no glass element. If there is a glass element in the adapter, the adapter no longer acts like an extension tube, but is now acting like a teleconverter, where the lens has increased the apparently focal length (thereby also reducing the max. aperture) to regain focus-to-infinity.
See also: Can I use lens brand X on interchangeable lens camera brand Y?
answered 14 hours ago
inkista
39.5k557100
Why don't lens mount adapters have the same effect as extension tubes?
They do. But whether it limits far-focus capability depends on one factor: the difference in distances from the image plane to the back of the lens mount flange between the two systems.
If the adapted lens's mount is deeper than the camera's mount, the adapter tube can make up the difference so that the lens sits exactly where it needs to in order to have full range of focus.
If the adapted lens's mount is shallower than the camera's mount, then the adapter is working exactly like an extension tube and will reduce far-focusing capabilities, if there's no glass element. If there is a glass element in the adapter, the adapter no longer acts like an extension tube, but is now acting like a teleconverter, where the lens has increased the apparently focal length (thereby also reducing the max. aperture) to regain focus-to-infinity.
See also: Can I use lens brand X on interchangeable lens camera brand Y?
answered 14 hours ago
inkista
39.5k557100
answered 14 hours ago
inkista
39.5k557100
answered 14 hours ago
inkista
39.5k557100
answered 14 hours ago
inkista
39.5k557100
39.5k557100
add a comment |Â
add a comment |Â
up vote
-1
down vote
The Metabone adapter is an optical accessory that mounts between the camera body and the camera lens. Such a mounting relocates the lens further forward. Such repositioning corresponds precisely like the action of extension rings or tubes in common use. However rings and tubes are void of lenses whereas the Metabone adapter contains lenses that modify the focal length of attached lens.
Supplemental optics similar to this device has been in use almost from the beginnings camera / lens design. We can mount such devices before or after the camera lens. These devices alter close focusing distance or they modify the lens, converting it to a telephoto or a wide-angle.
Many such supplemental lenses have been or are currently being marketed. The Metabone adapter revises the focal length of the attached lens, it shortens it about 70%. In other words, say a 50mm lens is combined with a Metabone adapter. The 50mm focal length is altered, it converts to become35mm. This action is analogous to add-on wide-angle converters commonly available. However, most such devices mount before the camera lens whereas the Metabone adapter mounts after the camera lens. Again, not a new idea.
How does the Metabone adapter realize a lens speed increase? The photographic industry uses the f-number system to specify the relative speed of a lens. The camera lens acts like a funnel in that it gathers light. The greater the working diameter of the lens (aperture) the brighter the projected image (speed of the lens). Entwined with aperture is focal length. Both are contributors as to how bright the projected image will be. Say the aperture diameter is untouched and the focal length doubled the projected image dims to 25% of its original brightness (2 f-stops). Conversely, if the focal length cut in half, the image brightens 2 f-stops.
The Math: 50mm lens 12.5mm aperture = f/4 --- 100mm lens 12.5mm aperture = f/8 --- 25mm 12.5mm aperture = f/2
Suppose you set your 50mm to f/8 achieved with a 6.25mm aperture. Now you mount a Metabone that shortens the focal length 70%. The revised focal length is35mm. The aperture remains unchanged at 6.25mm, the revised f-number is 35 ÷ 6.25 = 5.6 (written f.5.6). Simply stated, the Metabone shortened the focal length, this act increased the angle-of-view (more wide-angle), the image brightened as a result, the revised f-stop is f/5.6 = 1 f-stop speed gain.
The cleverness of the Metabone is, it shortens the focal length, this gives rise to a speed gain plus it adapts a lens designed for a larger format camera to operate on smaller format cameras mitigating the crop factor that would normally charge. Remarkable is the fact that back-focus distance (flange focus distance) of the lenses is corrected taken into account allowing lens interchangeability.
Also, Meabone is credited with suppressing some aberrations normally realized when a supplemental lens is added. (If all true, hats off to the optician
answered 21 hours ago
Alan Marcus
23.1k12453
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
add a comment |Â
up vote
-1
down vote
The Metabone adapter is an optical accessory that mounts between the camera body and the camera lens. Such a mounting relocates the lens further forward. Such repositioning corresponds precisely like the action of extension rings or tubes in common use. However rings and tubes are void of lenses whereas the Metabone adapter contains lenses that modify the focal length of attached lens.
Supplemental optics similar to this device has been in use almost from the beginnings camera / lens design. We can mount such devices before or after the camera lens. These devices alter close focusing distance or they modify the lens, converting it to a telephoto or a wide-angle.
Many such supplemental lenses have been or are currently being marketed. The Metabone adapter revises the focal length of the attached lens, it shortens it about 70%. In other words, say a 50mm lens is combined with a Metabone adapter. The 50mm focal length is altered, it converts to become35mm. This action is analogous to add-on wide-angle converters commonly available. However, most such devices mount before the camera lens whereas the Metabone adapter mounts after the camera lens. Again, not a new idea.
How does the Metabone adapter realize a lens speed increase? The photographic industry uses the f-number system to specify the relative speed of a lens. The camera lens acts like a funnel in that it gathers light. The greater the working diameter of the lens (aperture) the brighter the projected image (speed of the lens). Entwined with aperture is focal length. Both are contributors as to how bright the projected image will be. Say the aperture diameter is untouched and the focal length doubled the projected image dims to 25% of its original brightness (2 f-stops). Conversely, if the focal length cut in half, the image brightens 2 f-stops.
The Math: 50mm lens 12.5mm aperture = f/4 --- 100mm lens 12.5mm aperture = f/8 --- 25mm 12.5mm aperture = f/2
Suppose you set your 50mm to f/8 achieved with a 6.25mm aperture. Now you mount a Metabone that shortens the focal length 70%. The revised focal length is35mm. The aperture remains unchanged at 6.25mm, the revised f-number is 35 ÷ 6.25 = 5.6 (written f.5.6). Simply stated, the Metabone shortened the focal length, this act increased the angle-of-view (more wide-angle), the image brightened as a result, the revised f-stop is f/5.6 = 1 f-stop speed gain.
The cleverness of the Metabone is, it shortens the focal length, this gives rise to a speed gain plus it adapts a lens designed for a larger format camera to operate on smaller format cameras mitigating the crop factor that would normally charge. Remarkable is the fact that back-focus distance (flange focus distance) of the lenses is corrected taken into account allowing lens interchangeability.
Also, Meabone is credited with suppressing some aberrations normally realized when a supplemental lens is added. (If all true, hats off to the optician
answered 21 hours ago
Alan Marcus
23.1k12453
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
add a comment |Â
up vote
-1
down vote
up vote
-1
down vote
The Metabone adapter is an optical accessory that mounts between the camera body and the camera lens. Such a mounting relocates the lens further forward. Such repositioning corresponds precisely like the action of extension rings or tubes in common use. However rings and tubes are void of lenses whereas the Metabone adapter contains lenses that modify the focal length of attached lens.
Supplemental optics similar to this device has been in use almost from the beginnings camera / lens design. We can mount such devices before or after the camera lens. These devices alter close focusing distance or they modify the lens, converting it to a telephoto or a wide-angle.
Many such supplemental lenses have been or are currently being marketed. The Metabone adapter revises the focal length of the attached lens, it shortens it about 70%. In other words, say a 50mm lens is combined with a Metabone adapter. The 50mm focal length is altered, it converts to become35mm. This action is analogous to add-on wide-angle converters commonly available. However, most such devices mount before the camera lens whereas the Metabone adapter mounts after the camera lens. Again, not a new idea.
How does the Metabone adapter realize a lens speed increase? The photographic industry uses the f-number system to specify the relative speed of a lens. The camera lens acts like a funnel in that it gathers light. The greater the working diameter of the lens (aperture) the brighter the projected image (speed of the lens). Entwined with aperture is focal length. Both are contributors as to how bright the projected image will be. Say the aperture diameter is untouched and the focal length doubled the projected image dims to 25% of its original brightness (2 f-stops). Conversely, if the focal length cut in half, the image brightens 2 f-stops.
The Math: 50mm lens 12.5mm aperture = f/4 --- 100mm lens 12.5mm aperture = f/8 --- 25mm 12.5mm aperture = f/2
Suppose you set your 50mm to f/8 achieved with a 6.25mm aperture. Now you mount a Metabone that shortens the focal length 70%. The revised focal length is35mm. The aperture remains unchanged at 6.25mm, the revised f-number is 35 ÷ 6.25 = 5.6 (written f.5.6). Simply stated, the Metabone shortened the focal length, this act increased the angle-of-view (more wide-angle), the image brightened as a result, the revised f-stop is f/5.6 = 1 f-stop speed gain.
The cleverness of the Metabone is, it shortens the focal length, this gives rise to a speed gain plus it adapts a lens designed for a larger format camera to operate on smaller format cameras mitigating the crop factor that would normally charge. Remarkable is the fact that back-focus distance (flange focus distance) of the lenses is corrected taken into account allowing lens interchangeability.
Also, Meabone is credited with suppressing some aberrations normally realized when a supplemental lens is added. (If all true, hats off to the optician
answered 21 hours ago
Alan Marcus
23.1k12453
The Metabone adapter is an optical accessory that mounts between the camera body and the camera lens. Such a mounting relocates the lens further forward. Such repositioning corresponds precisely like the action of extension rings or tubes in common use. However rings and tubes are void of lenses whereas the Metabone adapter contains lenses that modify the focal length of attached lens.
Supplemental optics similar to this device has been in use almost from the beginnings camera / lens design. We can mount such devices before or after the camera lens. These devices alter close focusing distance or they modify the lens, converting it to a telephoto or a wide-angle.
Many such supplemental lenses have been or are currently being marketed. The Metabone adapter revises the focal length of the attached lens, it shortens it about 70%. In other words, say a 50mm lens is combined with a Metabone adapter. The 50mm focal length is altered, it converts to become35mm. This action is analogous to add-on wide-angle converters commonly available. However, most such devices mount before the camera lens whereas the Metabone adapter mounts after the camera lens. Again, not a new idea.
How does the Metabone adapter realize a lens speed increase? The photographic industry uses the f-number system to specify the relative speed of a lens. The camera lens acts like a funnel in that it gathers light. The greater the working diameter of the lens (aperture) the brighter the projected image (speed of the lens). Entwined with aperture is focal length. Both are contributors as to how bright the projected image will be. Say the aperture diameter is untouched and the focal length doubled the projected image dims to 25% of its original brightness (2 f-stops). Conversely, if the focal length cut in half, the image brightens 2 f-stops.
The Math: 50mm lens 12.5mm aperture = f/4 --- 100mm lens 12.5mm aperture = f/8 --- 25mm 12.5mm aperture = f/2
Suppose you set your 50mm to f/8 achieved with a 6.25mm aperture. Now you mount a Metabone that shortens the focal length 70%. The revised focal length is35mm. The aperture remains unchanged at 6.25mm, the revised f-number is 35 ÷ 6.25 = 5.6 (written f.5.6). Simply stated, the Metabone shortened the focal length, this act increased the angle-of-view (more wide-angle), the image brightened as a result, the revised f-stop is f/5.6 = 1 f-stop speed gain.
The cleverness of the Metabone is, it shortens the focal length, this gives rise to a speed gain plus it adapts a lens designed for a larger format camera to operate on smaller format cameras mitigating the crop factor that would normally charge. Remarkable is the fact that back-focus distance (flange focus distance) of the lenses is corrected taken into account allowing lens interchangeability.
Also, Meabone is credited with suppressing some aberrations normally realized when a supplemental lens is added. (If all true, hats off to the optician
answered 21 hours ago
Alan Marcus
23.1k12453
answered 21 hours ago
Alan Marcus
23.1k12453
answered 21 hours ago
Alan Marcus
23.1k12453
answered 21 hours ago
Alan Marcus
23.1k12453
23.1k12453
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
add a comment |Â
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
1
1
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
You're confusing the Metabones adapter (glassless) with the Speedbooster (glass). The question is about the adapter.
– Philip Kendall
14 hours ago
add a comment |Â
up vote
-1
down vote
Extension tubes don't have any lens elements; they're completely hollow. Metabones adapters do have lens elements.
answered 18 hours ago
Frank
5987
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
add a comment |Â
up vote
-1
down vote
Extension tubes don't have any lens elements; they're completely hollow. Metabones adapters do have lens elements.
answered 18 hours ago
Frank
5987
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
add a comment |Â
up vote
-1
down vote
up vote
-1
down vote
Extension tubes don't have any lens elements; they're completely hollow. Metabones adapters do have lens elements.
answered 18 hours ago
Frank
5987
Extension tubes don't have any lens elements; they're completely hollow. Metabones adapters do have lens elements.
answered 18 hours ago
Frank
5987
answered 18 hours ago
Frank
5987
answered 18 hours ago
Frank
5987
answered 18 hours ago
Frank
5987
5987
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
add a comment |Â
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
2
2
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
The Speedbooster does, but not the T Smart Adapter
– Tim Hopper
17 hours ago
add a comment |Â
Tim Hopper is a new contributor. Be nice, and check out our Code of Conduct.
Tim Hopper is a new contributor. Be nice, and check out our Code of Conduct.
Tim Hopper is a new contributor. Be nice, and check out our Code of Conduct.
Tim Hopper is a new contributor. Be nice, and check out our Code of Conduct.
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It should. What in the results differs?
– loonquawl
22 hours ago
1
If by "lens adapter" you mean what is essentially an extension tube with optical elements in it, then they don't do the same thing because of what the optical elements add to the total lens equation.
– twalberg
22 hours ago
2
@twalberg No, something like this - a glassless adapter. The Metabones ones are optically the same, just add some clever electronics for autofocus, aperture control, IS etc.
– Philip Kendall
22 hours ago
If it allows for closer focus, then you won't be able to focus to infinity. Most people prefer being able to focus to infinity so adapters are designed like that. However, there are adapters that has adjustable length to allow both close and infinity focus.
– user3528438
18 hours ago