WHY won't Nikon meter with old lenses?

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I've got a friend interested in getting a DSLR, and he's waffling between the
Canon 350, Nikon D70, or Pentax *ist-DS. He's a lot like me... interested in
tinkering with different lenses on the cheap. I've been playing with some old
screwmount lenses on my *ist-DS and find it a lot of fun to see what I can do for very
little money on glass. I know a fair bit about the K-mount and M42 Pentax stuff, but
not much about the other two brands.

In particular, Nikon lenses from way be to antiquity alegedly can be mounted
to the newest DSLR's. I've heard of pre-AI lenses needing a modification to prevent
damage, but it looks like something that can be done cheaply by people who've done it,
or carefully by oneself. My question is on the metering. Is it a purely marketing
reason why they disallowed even stop-down metering on the D70 et al? I can see if
there's a mechanical linkage missing to stop down an older otherwise autoaperture
lens, but if it still uses the same mechanical connection it's extremely
short-sighted. At least the Pentax has a stopdown-meter-release mode to use non-A
glass.

Just wondering if there's an actual technical limitation or if it's just
marketing "genius."

-Cory

--

*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
 
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papenfussDIESPAM@juneauDOTmeDOTvt.edu wrote:
> I've got a friend interested in getting a DSLR, and he's waffling between the
> Canon 350, Nikon D70, or Pentax *ist-DS. He's a lot like me... interested in
> tinkering with different lenses on the cheap. I've been playing with some old
> screwmount lenses on my *ist-DS and find it a lot of fun to see what I can do for very
> little money on glass. I know a fair bit about the K-mount and M42 Pentax stuff, but
> not much about the other two brands.
>
> In particular, Nikon lenses from way be to antiquity alegedly can be mounted
> to the newest DSLR's. I've heard of pre-AI lenses needing a modification to prevent
> damage, but it looks like something that can be done cheaply by people who've done it,
> or carefully by oneself. My question is on the metering. Is it a purely marketing
> reason why they disallowed even stop-down metering on the D70 et al? I can see if
> there's a mechanical linkage missing to stop down an older otherwise autoaperture
> lens, but if it still uses the same mechanical connection it's extremely
> short-sighted. At least the Pentax has a stopdown-meter-release mode to use non-A
> glass.
>
> Just wondering if there's an actual technical limitation or if it's just
> marketing "genius."
>
> -Cory


Are you sure it doesn't meter or just that it can't set aperture. I'd
think you could put it in manual & see the +- slider thingy in the
viewfinder.


--
Paul Furman
http://www.edgehill.net/1
san francisco native plants
 
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Paul Furman <paul-@-edgehill.net> writes:
> Are you sure it doesn't meter or just that it can't set aperture. I'd
> think you could put it in manual & see the +- slider thingy in the
> viewfinder.

It's not just that it can't SET the aperture, it also can't READ the
aperture. It has no way to know if you've stopped the lens down. The
camera has no mechanical coupling to the aperture ring, so turning the
ring sends no information to the camera.

Maybe they could have programmed it to support stop-down metering, or
maybe that would have confused people.

A reasonable fix might be to jazz up the histogram function, so it
could tell you the whole scene was overexposed by 0.7 stops or
whatever, and you'd make an adjustment. It would also be nice to be
able to get histograms or exposure analysis on selected parts of the
image using the directional pushbuttons.
 

Jim

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<papenfussDIESPAM@juneauDOTmeDOTvt.edu> wrote in message
news:d5agji$669$1@solaris.cc.vt.edu...
>
> Just wondering if there's an actual technical limitation or if it's just
> marketing "genius."
>
Money. Getting the pre-AI or AI-S lenses to work requires lots and lots and
lots of mechanical parts which make the cameras more expensive. By the way,
pre-AI lenses can't be mounted on the N series film cameras, so the loss of
usefulness of pre-AI lenses is nothing new.
As for the AI-S lenses, they work quite well on my F3.
Jim
 
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<papenfussDIESPAM@juneauDOTmeDOTvt.edu> wrote in message
news:d5agji$669$1@solaris.cc.vt.edu...

> Just wondering if there's an actual technical limitation or if it's just
> marketing "genius."
>
> -Cory

I'm sort of in the same situation... with an expanding collection of older
lenses.
I think the restriction has <allegedly> something to do with the matrix
metering taking distance info into account when deciding what subject
category to go for.

In reality I guess it's misplaced marketing genius - as a result, I mainly
use Canon.

--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm
 
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Paul Furman <paul-@-edgehill.net> wrote:
: > Just wondering if there's an actual technical limitation or if it's just
: > marketing "genius."
: >
: > -Cory

I was kidding on the "genius" part, BTW. Probably typical situation of
engineering and marketing not getting along.


: Are you sure it doesn't meter or just that it can't set aperture. I'd
: think you could put it in manual & see the +- slider thingy in the
: viewfinder.

All I know is what I've read online. Basically, there's the possibility of
physical damage in some cases, but supposedly any pre-AI lens won't meter. I can't
comprehend the alphabet soup of the lens/body standards for Nikon, which certainly
doesn't help. If I owned one, I might be more interested.

I can understand the lack of mechanical coupling for cost reasons, but I'm
still wondering why it can't be operated stop-down. Matrix metering doesn't have to
work, and open-aperture metering doesn't need to work necessarily. Does the body lack
the physical linkage to stop down the aperture? If not, I see no reason (other than
marketing) to have the feature not work.... at least in some degraded mode.

-Cory


*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
 
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> : Are you sure it doesn't meter or just that it can't set aperture. I'd
> : think you could put it in manual & see the +- slider thingy in the
> : viewfinder.

No, you can put it in manual, but you will not see any exposure settings
whatsoever. Just shutter speed, and in some cases focus lock.

> All I know is what I've read online. Basically, there's the possibility
> of
> physical damage in some cases, but supposedly any pre-AI lens won't meter.
> I can't
> comprehend the alphabet soup of the lens/body standards for Nikon, which
> certainly
> doesn't help. If I owned one, I might be more interested.

AI lenses will not meter, and pre AI lenses must be converted to AI or they
will ruin the camera. Has to do with the aperture ring interfering with the
lens mount.
>
> I can understand the lack of mechanical coupling for cost reasons, but I'm
> still wondering why it can't be operated stop-down. Matrix metering
> doesn't have to
> work, and open-aperture metering doesn't need to work necessarily. Does
> the body lack
> the physical linkage to stop down the aperture? If not, I see no reason
> (other than
> marketing) to have the feature not work.... at least in some degraded
> mode.
>
> -Cory

All the components in the D70 link to the lens via contacts connected to a
chip in the lens. Some lenses can be converted to accept a chip and will
meter in the camera. There's like one guy who does it, and he's very picky
about which lenses he will convert.
 

frederick

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Paul Rubin wrote:

> Paul Furman <paul-@-edgehill.net> writes:
>
>>Are you sure it doesn't meter or just that it can't set aperture. I'd
>>think you could put it in manual & see the +- slider thingy in the
>>viewfinder.
>
>
> It's not just that it can't SET the aperture, it also can't READ the
> aperture. It has no way to know if you've stopped the lens down. The
> camera has no mechanical coupling to the aperture ring, so turning the
> ring sends no information to the camera.
>
http://home.carolina.rr.com/headshots/Nikonhome.htm
Some MF lenses can be modified.
Many wouldn't be worth modifying anyway, as AF versions with the same
glass are available second hand cheaply, not all Nikon glass is good, as
a general rule new zoom lenses are in a class above old ones, and in
some cases asian collectors will buy your old MF nikkor glass at good
prices in the belief that they they are investing in collectables.
 
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Paul Rubin <http://phr.cx@nospam.invalid> wrote:
: Paul Furman <paul-@-edgehill.net> writes:
: > Are you sure it doesn't meter or just that it can't set aperture. I'd
: > think you could put it in manual & see the +- slider thingy in the
: > viewfinder.

: It's not just that it can't SET the aperture, it also can't READ the
: aperture. It has no way to know if you've stopped the lens down. The
: camera has no mechanical coupling to the aperture ring, so turning the
: ring sends no information to the camera.

: Maybe they could have programmed it to support stop-down metering, or
: maybe that would have confused people.

That's what I'm thinking... it's what the Pentax does. Without knowing a few
things about the lens (min/max aperture, current aperture), the more advanced features
(auto-aperture, matrix metering, etc) cannot be done. That doesn't inherently mean
that the meter should not function. The meter needs to see how much light is coming
in the lens... that's all! Whether or not you set an aperture or have the body
determine what aperture to use, the meter should still work.... at least wide-open
metering (as you peer through the viewfinder).

Now, it gets more complicated if you or the camera want to stop it down. I'm
not familar with the mount... is there a physical lever that actuates the aperture
from the camera, or is it *all* done electronically?

I'm taking a look at this:
http://www.mir.com.my/rb/photography/hardwares/nikonfmount/ais_lars.htm

From that picture, the only important feature required for stop-down-metering
would appear be the stop-down lever. If you set the ring on the lens to what you
want, the camera moves the lever, takes a meter reading, and programs accordingly.
What am I missing?


*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
 
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papenfussDIESPAM@juneauDOTmeDOTvt.edu wrote:

> Paul Rubin <http://phr.cx@nospam.invalid> wrote:
>
> : Maybe they could have programmed it to support stop-down metering, or
> : maybe that would have confused people.
>
> That's what I'm thinking... it's what the Pentax does. Without knowing a few
> things about the lens (min/max aperture, current aperture), the more advanced features
> (auto-aperture, matrix metering, etc) cannot be done. That doesn't inherently mean
> that the meter should not function. The meter needs to see how much light is coming
> in the lens... that's all! Whether or not you set an aperture or have the body
> determine what aperture to use, the meter should still work.... at least wide-open
> metering (as you peer through the viewfinder).
>
> Now, it gets more complicated if you or the camera want to stop it down. I'm
> not familar with the mount... is there a physical lever that actuates the aperture
> from the camera, or is it *all* done electronically?
>
> I'm taking a look at this:
> http://www.mir.com.my/rb/photography/hardwares/nikonfmount/ais_lars.htm
>
> From that picture, the only important feature required for stop-down-metering
> would appear be the stop-down lever. If you set the ring on the lens to what you
> want, the camera moves the lever, takes a meter reading, and programs accordingly.
> What am I missing?

The D70 does have an manual button for DOF preview. Of course with an
old lens that wouldn't do anything. It does seem fairly simple though to
program a mode to meter actual light rather than calculating from wide
open metering. This feature would enable all sorts of interesting
arrangements. Even forget about auto metering shutter speed & just allow
viewing the meter reading to shoot manual would be nice.

--
Paul Furman
http://www.edgehill.net/1
san francisco native plants
 
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: The D70 does have an manual button for DOF preview. Of course with an
: old lens that wouldn't do anything. It does seem fairly simple though to
: program a mode to meter actual light rather than calculating from wide
: open metering. This feature would enable all sorts of interesting
: arrangements. Even forget about auto metering shutter speed & just allow
: viewing the meter reading to shoot manual would be nice.

Exactly... it's what the Pentax does on old lenses where it doesn't know what
wide-open is. Hit a button to have it:
- Stop down to what the aperture ring is set to
- Set the shutter speed to the metered amount (via spot or center-weighted)
- Release aperture, but hold setting as the current 'M' value

The whole thing takes about 1/4 sec. I'm not clear from any
pictures/descriptions of how the D70 mount works why that cannot be done.

-Cory

*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
 
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papenfussDIESPAM@juneauDOTmeDOTvt.edu wrote:

> : The D70 does have an manual button for DOF preview. Of course with an
> : old lens that wouldn't do anything. It does seem fairly simple though to
> : program a mode to meter actual light rather than calculating from wide
> : open metering. This feature would enable all sorts of interesting
> : arrangements. Even forget about auto metering shutter speed & just allow
> : viewing the meter reading to shoot manual would be nice.
>
> Exactly... it's what the Pentax does on old lenses where it doesn't know what
> wide-open is. Hit a button to have it:
> - Stop down to what the aperture ring is set to


For a manual aperture lens, I assume you would have a dark viewfinder?



> - Set the shutter speed to the metered amount (via spot or center-weighted)
> - Release aperture, but hold setting as the current 'M' value
>
> The whole thing takes about 1/4 sec. I'm not clear from any
> pictures/descriptions of how the D70 mount works why that cannot be done.


The lens has a little lever facing the mount, spring loaded to open up.


--
Paul Furman
http://www.edgehill.net/1
san francisco native plants
 
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Paul Furman <paul-@-edgehill.net> wrote:
: > Exactly... it's what the Pentax does on old lenses where it doesn't know what
: > wide-open is. Hit a button to have it:
: > - Stop down to what the aperture ring is set to

: For a manual aperture lens, I assume you would have a dark viewfinder?

During the automatic stop/meter/set, yes the viewfinder is dark. Also, if
you're using an even *older* (M42 screwmount) lens, the physical linkage does not
actuate the aperture. Fortunately, those lenses have an A/M knob/ring/lever to
manually stop them down. Then you can compose wide open, manually stop, have it
meter, and fire. It's tedious, but at least it works.

: > The whole thing takes about 1/4 sec. I'm not clear from any
: > pictures/descriptions of how the D70 mount works why that cannot be done.

: The lens has a little lever facing the mount, spring loaded to open up.

Sounds like it works the same. Unless moving the ring on the aperture does
not limit the *actual* motion of the iris when the camera body moves the lever, it
should be possible to work the same way.

-Cory

*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
 
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