Why are rangefinder lenses so much smaller than the SLR counterparts?
Mike Nielsen
can't a 50mm Summilux-R be designed to be as small as a 50mm
Summilux-M?
Joe
diaphram.
Joe
bc1...@my-deja.com
Mike Nielsen <mnie...@carolina.rr.com> wrote:
> The subject line really says it all, but, for example, why
> can't a 50mm Summilux-R be designed to be as small as a 50mm
> Summilux-M?
>
>
(distance from rear lens element to film plane) because there is no
reflex mirror. This is particularly true of wide angle lenses, which
for SLRs must be designed as bulky reversed telephotos. Although I
don't have the Summilux formula, it is generally true that normal (50mm)
lenses benefit from a relaxed working distance requirement.
-Brian
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Anthony
news:37DF1CE8...@carolina.rr.com...
> The subject line really says it all, but, for
> example, why can't a 50mm Summilux-R be designed
> to be as small as a 50mm Summilux-M?
I believe it is related to the smaller distance to the film plane in
rangefinders. The smaller this distance, the less light you need for a
given lens speed to project onto the film--so you can get away with smaller
lenses. My digital camera has a f/3.5 lens, and yet the lens is barely the
size of a dime in diameter. 'Course, the image is very tiny, and extremely
close to the lens.
-- Anthony
Wilfred Kazoks
the physical diameter of the aperture. A 35mm focal length lens with a 10mm
maximum aperture diameter will be an F3.5 lens.
With your digital camera you said the image is very close to the lens
therfore it must have a small focal length. Suppose it was a 14mm lens and
the maximum aperture was 4mm across, it too would be an f3.5 lens.
14mm/4mm=f3.5
Regards Wilfred
Anthony wrote in message ...
Chuck Ross
<mxsm...@hotmail.com> wrote:
> Wilfred Kazoks <wilfre...@alphalink.com.au> wrote in message
> news:37df...@news.alphalink.com.au...
>
> > No this is not correct. The f number of a lens relates
> > the focal length to the physical diameter of the aperture.
> > A 35mm focal length lens with a 10mm maximum aperture
> > diameter will be an F3.5 lens.
>
> I'm aware of this.
>
> > With your digital camera you said the image is very
> > close to the lens therfore it must have a small focal
> > length.
>
> No, I said (in effect) that the lens could be small in diameter because it
> is so close to the image plane in the camera. I had previously read that
> this was the reason why rangefinder lenses could be smaller for a given
> speed than SLR lenses, even for the same film format.
>
> So, why _are_ Leica rangefinder lenses of a given speed smaller in diameter
> than the average SLR lens of the same speed? They all seem pretty tiny
> compared to SLR lenses of comparable focal lengths and speeds.
>
> -- Anthony
A special lens construction is required for the lens to allow the
mirror to flip up in an SLR, so the lens has to clear that area. RF
lenses don't need to do that, thus they can be of a smaller design.
Or something like that....
--
http://www.enteract.com/~ckross/
Digital and Film-Based Photography
remove "MYPANTS" to reply
Anthony
Jim Williams
diameter
>than the average SLR lens of the same speed? They all seem pretty tiny
>compared to SLR lenses of comparable focal lengths and speeds.
Mostly because they don't need an auto-diaphragm mechanism or coupling
linkages for a full-aperture metering system. These parts have to be housed
in the lens barrel outside the light path, so to make room for them the
barrel has to be made bigger.
Actually, though, some SLR lenses (such as modest-speed normals) probably
are fatter than they need to be -- take one apart and you'll see there's
quite a bit of extra space inside. I suppose the manufacturers make them a
larger diameter either so that various lenses will use the same size
filter... because a tiny lens on a big, bulky camera would look silly...
because big lenses look cooler and "more professional"... or probably a
combination of all these.
SpooRL
>A special lens construction is required for the lens to allow the
>mirror to flip up in an SLR, so the lens has to clear that area. RF
>lenses don't need to do that, thus they can be of a smaller design.
The light travels farther to reach the film, so more light-collecting power (in
diameter of glass elements) is required with SLRs than with RFs to transmit a
given amount of light to the film. Same thing as when you add extension tubes.
You lose light.
Spoo