When will these people get it? Telephotos CAN shrink

"RichA" wrote in message
...
Telephotos of specific speeds cannot be shrunk like wide angle lenses
and normal primes just because a sensor is smaller.

A 300mm f2.8 needs a lens at least 110mm across and it needs multiple
elements because aspherics are not used on large elements yet.
Whether the sensor is 4/3rds or FF, the lens is going to be that big.

http://forums.dpreview.com/forums/re...ssage=40554613


Can't be shrunk!?! Oh yes they can and have been. Both the Minolta Vectis
/ RD 3000 and the Minolta and Pentax 110's had telephoto lenses and they
were smaller for the same magnification. Whilst the overall size needs to
be larger than short focal length / prime lenses (to fulfil the sensor size
X the magnification / f ratio) they do NOT need to be as large as on a full
frame 35mm lens.

http://en.wikipedia.org/wiki/Minolta_110_Zoom_SLR
http://en.wikipedia.org/wiki/File:Pe..._70mm_lens.jpg ~= 140mm
for 35mm body

conversely even a basic lens on a larger format (e.g. 6X7) is humungous

http://en.wikipedia.org/wiki/File:Te..._300_63_ft.jpg

it is only f6.3 and even at this size needs the tripod to support the lens
rather than the camera.

"R. Mark Clayton" wrote in
:


"RichA" wrote in message
.
..
Telephotos of specific speeds cannot be shrunk like wide angle lenses
and normal primes just because a sensor is smaller.

A 300mm f2.8 needs a lens at least 110mm across and it needs multiple
elements because aspherics are not used on large elements yet.
Whether the sensor is 4/3rds or FF, the lens is going to be that
big.

http://forums.dpreview.com/forums/re...ssage=40554613


Can't be shrunk!?! Oh yes they can and have been. Both the Minolta
Vectis / RD 3000 and the Minolta and Pentax 110's had telephoto lenses
and they were smaller for the same magnification. Whilst the overall
size needs to be larger than short focal length / prime lenses (to
fulfil the sensor size X the magnification / f ratio) they do NOT
need to be as large as on a full frame 35mm lens.

http://en.wikipedia.org/wiki/Minolta_110_Zoom_SLR
http://en.wikipedia.org/wiki/File:Pe..._70mm_lens.jpg ~=
140mm for 35mm body

conversely even a basic lens on a larger format (e.g. 6X7) is
humungous

http://en.wikipedia.org/wiki/File:Te..._300_63_ft.jpg

it is only f6.3 and even at this size needs the tripod to support the
lens rather than the camera.



Equivalency has nothing repeat, nothing to do with the physics of lenses.
A 300mm lens in order to have an f-ratio of f2.8 NEEDS a front element or
"clear aperture" of at least 110mm.

Rich wrote:




Equivalency has nothing repeat, nothing to do with the physics of lenses.

And everything to do with how we use lenses.

BugBear

"Rich" wrote in message
...
"R. Mark Clayton" wrote in
:


"RichA" wrote in message
.
..
Telephotos of specific speeds cannot be shrunk like wide angle lenses
and normal primes just because a sensor is smaller.

A 300mm f2.8 needs a lens at least 110mm across and it needs multiple
elements because aspherics are not used on large elements yet.
Whether the sensor is 4/3rds or FF, the lens is going to be that
big.

http://forums.dpreview.com/forums/re...ssage=40554613


Can't be shrunk!?! Oh yes they can and have been. Both the Minolta
Vectis / RD 3000 and the Minolta and Pentax 110's had telephoto lenses
and they were smaller for the same magnification. Whilst the overall
size needs to be larger than short focal length / prime lenses (to
fulfil the sensor size X the magnification / f ratio) they do NOT
need to be as large as on a full frame 35mm lens.

http://en.wikipedia.org/wiki/Minolta_110_Zoom_SLR
http://en.wikipedia.org/wiki/File:Pe..._70mm_lens.jpg ~=
140mm for 35mm body

conversely even a basic lens on a larger format (e.g. 6X7) is
humungous

http://en.wikipedia.org/wiki/File:Te..._300_63_ft.jpg

it is only f6.3 and even at this size needs the tripod to support the
lens rather than the camera.



Equivalency has nothing repeat, nothing to do with the physics of lenses.
A 300mm lens in order to have an f-ratio of f2.8 NEEDS a front element or
"clear aperture" of at least 110mm.

Yes yes, if it is literally the same focal length then it will be the same
size, however the point is that to get the same MAGNIFICATION on a smaller
format you only need a smaller lens. Look at all those D lenses that will
only fill an APS-C sensor. They are lighter and smaller, but if you use
them in full frame then the area outside the sensor area has aberrations at
best or nothing at all.

See http://en.wikipedia.org/wiki/Lenses_...d_DSLR_cameras

"R. Mark Clayton" wrote in message
...
Yes yes, if it is literally the same focal length then it will be the same
size, however the point is that to get the same MAGNIFICATION on a smaller
format you only need a smaller lens. Look at all those D lenses that will
only fill an APS-C sensor. They are lighter and smaller, but if you use
them in full frame then the area outside the sensor area has aberrations
at best or nothing at all.

Which of course ignores the fact that you can simply crop a FF camera image
(same *actual* focal length lens) to achieve results similar to the smaller
sensor image. So a 100mm lens on a FF camera with 2:1 crop, is exactly the
same as a 100mm lens on a 4/3 camera. Except the FF camera gives you the
choice of 100mm field of view, 200mm field of view, or anything in between,
with similar levels of performance to the 200mm equiv. only 4/3 camera.
The argument by proponents of smaller sensor camera's that their lenses are
smaller is simply "smoke and mirrors" or we'd all be using phone camera's
with "telephoto" lenses :-)

Trevor.

"Trevor" wrote in message
...

"R. Mark Clayton" wrote in message
...
Yes yes, if it is literally the same focal length then it will be the
same size, however the point is that to get the same MAGNIFICATION on a
smaller format you only need a smaller lens. Look at all those D lenses
that will only fill an APS-C sensor. They are lighter and smaller, but
if you use them in full frame then the area outside the sensor area has
aberrations at best or nothing at all.

Which of course ignores the fact that you can simply crop a FF camera
image (same *actual* focal length lens) to achieve results similar to the
smaller sensor image. So a 100mm lens on a FF camera with 2:1 crop, is
exactly the same as a 100mm lens on a 4/3 camera. Except the FF camera
gives you the choice of 100mm field of view, 200mm field of view, or
anything in between, with similar levels of performance to the 200mm
equiv. only 4/3 camera.
The argument by proponents of smaller sensor camera's that their lenses
are smaller is simply "smoke and mirrors" or we'd all be using phone
camera's with "telephoto" lenses :-)

Trevor.



That depends - 35mm cameras were limited by the grain size and sensitivity
of the films loaded in them. Indeed when David Bailley started using 35mm
SLR's professionally ~fifty years ago, he was criticised because the images
would be too grainy to print at full page size.

With digital sensors the same resolution can be extract from a smaller image
(within the laws of physics obviously), so the camera can be smaller and
still capture the subject at the same magnification / field of view.

Obviously less light will enter a smaller lens so for low light work you
might still want a bigger lens and bigger sensor, however with cameras now
boasting thousands of ASA (against a typically few hundred for film) this
will seldom be an issue.

"RichA" wrote in message
...
On Feb 13, 6:14 am, bugbear wrote:
Rich wrote:

Equivalency has nothing repeat, nothing to do with the physics of
lenses.

And everything to do with how we use lenses.

BugBear

Yes, a 200mm lens on an 16 megapixel m4/3 camera provides as much
pixel coverage per given object area (linearly) as a 300mm lens on a
36mp FF, more or less. So a Panasonic G3 and a 200mm lens would match
the resolution (sensor differences aside) of a Nikon D800 with a 300mm
lens for a specific object. A 200mm f2.8 lens is considerably smaller
than a 300mm f2.8 lens with the same speed. But it's NOT a 300mm lens
and there are the usual arguments about f2.8 not being worth as much
on a small sensor as a large, so noise control isn't comparable.
In fact, a 200mm lens at f2.0 is almost as heavy as a 300mm f2.8 lens,
it's just shorter. Even then, you won't be able to match the FF
quality with a m4/3rds camera, not with only 1 stop of lens speed
advantage.

If it has the same number of pixels it will. You might have to compensate
for the lower light gathering by increasing the exposure time!

In article , R. Mark Clayton
wrote:

Yes, a 200mm lens on an 16 megapixel m4/3 camera provides as much
pixel coverage per given object area (linearly) as a 300mm lens on a
36mp FF, more or less.

4/3rds has a 2x crop factor, so a 200mm lens is equivalent to 400mm on
full frame.

"nospam" wrote in message
...
In article , R. Mark Clayton
wrote:

Yes, a 200mm lens on an 16 megapixel m4/3 camera provides as much
pixel coverage per given object area (linearly) as a 300mm lens on a
36mp FF, more or less.

4/3rds has a 2x crop factor, so a 200mm lens is equivalent to 400mm on
full frame.

Sorry picked this up from the previous poster and was looking at the number
of pixels.

What annoys me is having glass for 35mm full frame, but getting a smaller
image on "D" rated cameras unless I pay ££££ for one with a full frame
sensor (as opposed to £££) - ten times as much for approx twice the area is
a rip off.

"R. Mark Clayton" writes:

"nospam" wrote in message
...
In article , R. Mark Clayton
wrote:

Yes, a 200mm lens on an 16 megapixel m4/3 camera provides as much
pixel coverage per given object area (linearly) as a 300mm lens on a
36mp FF, more or less.

4/3rds has a 2x crop factor, so a 200mm lens is equivalent to 400mm on
full frame.

Sorry picked this up from the previous poster and was looking at the number
of pixels.

What annoys me is having glass for 35mm full frame, but getting a smaller
image on "D" rated cameras unless I pay ££££ for one with a full frame
sensor (as opposed to £££) - ten times as much for approx twice the area is
a rip off.

Not sure what you mean by "D" rated. In the Nikon line, for example,
the D700 isn't even twice the price of the D300s, and that's where the
jump from APS-C to full-frame takes place (they're reasonably similar
otherwise).

And the full-frame sensor costs a LOT more than the APS-C one;
semiconductor yields go down drastically as size increases.
--
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Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
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