sensor to flange distance

In article <hs6tj.11109$J41.4364@newssvr14.news.prodigy.net>, Paul
Furman <paul- RemoveThis @-edgehill.net> wrote:

> Would it be worthwhile to design a new APS DSLR with a smaller
> sensor-to-flange distance? There are problems with oblique angles on
> sensors so maybe it's a dumb idea but maybe a way to have smaller or
> cheaper lenses?

olympus 4/3 has the shortest flange distance, but the lenses (and the
cameras) aren't much smaller or cheaper. also, the oblique angle bit
is mostly olympus marketing and not as big of an issue as it's made out
to be.

> AFAIK everyone uses the old full frame distance, right? They could just
> design the lens to stick into the body further assuming the mirror is
> already smaller & there is more room. The only problem there is if you
> put that on a full frame body the mirror would get smashed.

canon ef-s protrudes back a little further, so canon made a minor
change to the mount to prevent putting ef-s lenses on a standard ef
mount.

> It *ought* to be possible to lock up the mirror with the new live view
> DSLRs but I'll bet they don't have that function, they should though,
> there's some old fisheyes which need this snd very few old film bodies
> can mount it safely. Plus there's rangefinder lenses that could be used.

there are two problems. the first is that it is restricted to full
frame dslrs. on crop sensor dslrs (except for some of the early ones),
the mirror box is smaller, therefore preventing the old lenses from
even fitting when the mirror is up.

the second issue is you need to be sure that the mirror doesn't flap
back down, or if it does, it won't harm either the lens or the camera.
with live view, you'd need a mode that doesn't drop the mirror prior to
taking a photo.
 >> Stay informed about: sensor to flange distance 

nospam wrote:
> Furman <paul-.TakeThisOut@-edgehill.net> wrote:
>
>> AFAIK everyone uses the old full frame distance, right?
>
> canon ef-s protrudes back a little further, so canon made a minor
> change to the mount to prevent putting ef-s lenses on a standard ef
> mount.

Ah, OK thanks all. Are other brands the same?

>> It *ought* to be possible to lock up the mirror with the new live view
>
> the mirror box is smaller, therefore preventing the old lenses from
> even fitting when the mirror is up.

That could be bigger easily. I'm also wondering about rangefinder lenses
on a full frame DSLR.

> the second issue is you need to be sure that the mirror doesn't flap
> back down, or if it does, it won't harm either the lens or the camera.

I understand the mirror needs electricity to hold it open so a use a
clip in the mirror box to hold it. Could you put rangefinder lenses
inside that? I'm guessing the mirror box needs to be bigger yet, maybe
even the mirror retracted further to the side, or would it work?
 >> Stay informed about: sensor to flange distance 

In article <jV9tj.586$pl4.9@newssvr22.news.prodigy.net>, Paul Furman
<paul- RemoveThis @-edgehill.net> wrote:

> >> AFAIK everyone uses the old full frame distance, right?
> >
> > canon ef-s protrudes back a little further, so canon made a minor
> > change to the mount to prevent putting ef-s lenses on a standard ef
> > mount.
>
> Ah, OK thanks all. Are other brands the same?

nope, only canon did that. with nikon (and i'm pretty sure with pentax
and sony), you can mix and match lenses. interestingly, third party
canon ef-s lenses have the standard ef mount and will fit on canon full
frame cameras, probably because they're designed to use the normal
flange distance for the nikon, pentax and sony mounts.

> I understand the mirror needs electricity to hold it open so a use a
> clip in the mirror box to hold it. Could you put rangefinder lenses
> inside that? I'm guessing the mirror box needs to be bigger yet, maybe
> even the mirror retracted further to the side, or would it work?

i'm not entirely sure clipping the mirror up is a good idea, but i've
never tried it. let us know how it works out.
 >> Stay informed about: sensor to flange distance 

"Paul Furman" <paul-.TakeThisOut@-edgehill.net> wrote in message
news:hs6tj.11109$J41.4364@newssvr14.news.prodigy.net...
> Would it be worthwhile to design a new APS DSLR with a smaller
> sensor-to-flange distance? There are problems with oblique angles on
> sensors so maybe it's a dumb idea but maybe a way to have smaller or
> cheaper lenses?
>
> AFAIK everyone uses the old full frame distance, right? They could just
> design the lens to stick into the body further assuming the mirror is
> already smaller & there is more room.

Congratulations! You've reinvented the wheel. Or in this case, the EF-S lens
mount.

Funny that Canon is the one to have done this, since they're already the
ones with the shortest flange to film distance. (Which, by the way, is 44mm
or so. Which means that oblique angles really aren't a problem, even on FF.)

David J. Littleboy
Tokyo, Japan
 >> Stay informed about: sensor to flange distance 

nospam wrote:
> In article <jV9tj.586$pl4.9@newssvr22.news.prodigy.net>, Paul Furman
> <paul-.TakeThisOut@-edgehill.net> wrote:
>
>>>> AFAIK everyone uses the old full frame distance, right?
>>> canon ef-s protrudes back a little further, so canon made a minor
>>> change to the mount to prevent putting ef-s lenses on a standard ef
>>> mount.
>> Ah, OK thanks all. Are other brands the same?
>
> nope, only canon did that. with nikon (and i'm pretty sure with pentax
> and sony),
Yep, Pentax & Sony, in addition to Nikon use the same mount.
Nikon's D3 allows you to use DX (ie smaller image circle)
lenses even though it is a full-frame camera - it simply
crops to the smaller area. I have quite successfully used a
Pentax 18-55 DA lens on a film camera - it vignettes badly
at 18mm, but by 24mm you have full frame coverage.

Because of the longer flange distance, by necessity the
lenses are retro-focus designs and hence the light is
hitting the sensor at an angle fairly close to
perpendicular, which is optimal for digital sensors.
 >> Stay informed about: sensor to flange distance