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Infinity on Nikkor lenses?

 
 
B.A.S.
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      05-06-2004
I've got a pretty significant case of backfocus (very evident in all
photos, even at smaller apertures with wide depth of field) with my new
D70 and 24-85 ED G.

I'm going to head to the dealer on Friday to try and determine if its
the body or the lens.

One oddity I've noticed is the focus setting when the lens is set all
the way to infinity. When set all the way up against the infinity stop,
the lens reads out with the far edge of the infinity symbol lined up
with the focus mark. Every other SLR lens I've owned over the last 30
years has lined up with the *center* of the infinity, 'figure 8' mark.

Does every Nikkor lens work this way (this is my first Nikkor), or is
this lens defective?
 
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B.A.S.
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      05-06-2004
B.A.S. wrote:

> I've got a pretty significant case of backfocus (very evident in all
> photos, even at smaller apertures with wide depth of field) with my new
> D70 and 24-85 ED G.
>
> I'm going to head to the dealer on Friday to try and determine if its
> the body or the lens.
>
> One oddity I've noticed is the focus setting when the lens is set all
> the way to infinity. When set all the way up against the infinity stop,
> the lens reads out with the far edge of the infinity symbol lined up
> with the focus mark. Every other SLR lens I've owned over the last 30
> years has lined up with the *center* of the infinity, 'figure 8' mark.
>
> Does every Nikkor lens work this way (this is my first Nikkor), or is
> this lens defective?


Here's a link to a pic of the lens set at infinity:

http://home.nc.rr.com/thesimms/DSCN3121.JPG

To Infinity and Beyond!
 
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Mxsmanic
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      05-06-2004
B.A.S. writes:

> Does every Nikkor lens work this way (this is my first Nikkor), or is
> this lens defective?


A fair number of Nikkors will focus past infinity, mainly to allow for
thermally-induced changes in infinity focus under differing
environmental conditions.

--
Transpose hotmail and mxsmanic in my e-mail address to reach me directly.
 
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Roger Halstead
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      05-06-2004
On Thu, 06 May 2004 02:30:28 GMT, "B.A.S."
<(E-Mail Removed)> wrote:

>I've got a pretty significant case of backfocus (very evident in all
>photos, even at smaller apertures with wide depth of field) with my new
>D70 and 24-85 ED G.


I've been a photographer since the 50s and I never heard the term
"back focus" until recently on this group. What the devil is back
focus? I'm guessing it has to do with infinity, but why call it back
focus.

Many Nikon lenses used to have dual markings for regular film and IR
film. So with them there were to infinities.

>
>I'm going to head to the dealer on Friday to try and determine if its
>the body or the lens.
>
>One oddity I've noticed is the focus setting when the lens is set all
>the way to infinity. When set all the way up against the infinity stop,
>the lens reads out with the far edge of the infinity symbol lined up
>with the focus mark. Every other SLR lens I've owned over the last 30
>years has lined up with the *center* of the infinity, 'figure 8' mark.


It's a broad mark and I can't remember having a lens that focused
properly against the stop. Then again I don't pay much attention to
that sort of thing. That's the nice part about SLRs, you focus for a
sharp image and not to any distance setting on the lens. The only
thing I've ever used those for was to set the flash.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

>
>Does every Nikkor lens work this way (this is my first Nikkor), or is
>this lens defective?


 
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Philip Homburg
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      05-06-2004
In article <(E-Mail Removed)>,
Roger Halstead <(E-Mail Removed)> wrote:
>On Thu, 06 May 2004 02:30:28 GMT, "B.A.S."
><(E-Mail Removed)> wrote:
>
>>I've got a pretty significant case of backfocus (very evident in all
>>photos, even at smaller apertures with wide depth of field) with my new
>>D70 and 24-85 ED G.

>
>I've been a photographer since the 50s and I never heard the term
>"back focus" until recently on this group. What the devil is back
>focus? I'm guessing it has to do with infinity, but why call it back
>focus.


Back focus is important for video. If you have a zoom lens, it is very
important that the lens stays in-focus when zooming. (For still picture
photography it is nice, but not required).

So, what you do is you vary the distance between the lens and the body
until you find the right back-focus distance.

I have no idea what that has to do with still picture photography. Focusing
problems are caused by a screen/AF-sensor that is out of alignment compared
to the sensor/film plane.

If a lens is too far from the body, focusing at infinity might be impossible,
but that is not what people are complaining about.


--
Everyone I've met who had any experience with the phenomenon have confirmed my
opinion that if a Ph.D. in computer science knows anything at all about
computers, it's probably pretty much an accident. -- J.D. Baldwin, in asr
 
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B.A.S.
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      05-06-2004
Roger Halstead wrote:
>
> I've been a photographer since the 50s and I never heard the term
> "back focus" until recently on this group. What the devil is back
> focus? I'm guessing it has to do with infinity, but why call it back
> focus.
>


The term has apparently been coined by camera users to describe the
problem where the camera's AF system says an image is in focus when in
fact the in-focus area is a bit (or in my case, a lot) 'in back of' the
subject supposedly focused upon. With my D70 if I take an outdoor pic of
someone standing 25 feet away, at 85mm and wide open with my 24-85 ED G
3.5-4.5, with their face in the AF sensor area, their face will be out
of focus, and the grass a foot or two behind them will be in focus. This
is with the camera in single area AF-S mode, and the central AF sensor
locked on. Happens every time.

It's far enough out of whack that stopping down to say f8 in the same
situation still doesn't give you a really sharp result. If I move the
focus a tick closer manually in either case after the camera has
focused, I get tack sharp results, so I'm sure it's just a calibration
thing. Most likely it's the body, but I need to try some other lenses to
make sure.

I'm inclined to hold off sending it in to Nikon for a few weeks (I'm
past the store return date), until I see posts from others with the
problem indicating whether Nikon was able to fix theirs.

If at least some users manage to get theirs fixed, I will send the
camera in, and then if there's still a problem, sell my camera body and
lens and move on to another brand. I have this option as I've just
started to build my AF DSLR kit, and it's not too late to change
directions.

Most of my previous experience has been with Contax/Zeiss MF 35mm, and I
have to say I'm not too impressed at first blush with Nikon build
quality. But Nikon components sure weigh a lot less, and cost a lot less
(at least the mid-grade bodies and lenses I've begun buying into), both
of which is OK with me. I really don't expect the same 'hewed from
stone' look and feel I got with Zeiss lenses. Bottom line is, if the
performance is acceptable, I can live with the consumer-grade build
quality.

Overall I like the D70, and have gotten used to the two-ring zoom on the
24-85. If the rig could just focus properly, I'd be eager to buy several
more Nikkor lenses and stick with this kit for a good long while...

B.A.S.

P.S. Before I get slammed for whining and daring to complain in the face
of those who haven't experienced this problem, let me assure you it is
real, at least with my body/lens. I can supply pics to anyone interested
in viewing them. I have 30+ years of experience in the field, with
everything from large format (Linhoff, Calumet) to medium format
(Pentax, Mamiya, Yashica, Bronica) to 35mm (Konica, Pentax, Yashica,
Contax).
 
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Chris Berry
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      05-06-2004

"B.A.S." <(E-Mail Removed)> wrote in message
news:Zkpmc.15420$(E-Mail Removed) m...
>
> P.S. Before I get slammed for whining and daring to complain in the face
> of those who haven't experienced this problem, let me assure you it is
> real, at least with my body/lens. I can supply pics to anyone interested
> in viewing them. I have 30+ years of experience in the field, with
> everything from large format (Linhoff, Calumet) to medium format
> (Pentax, Mamiya, Yashica, Bronica) to 35mm (Konica, Pentax, Yashica,
> Contax).


OK... so you know what you're on about...
The only thing I can think of with my very limited experience is that the AF
sensor isn't the same optical distance from the lens as the film plane.
Definitely a case for sending it back though.
You didn't mention if it was the viewfinder or the actual "prints" that are
out of focus - or what model body you're using.
My Experience with Nikon's digital products is that they just don't
compete - no matter how good the lenses are.
BTW, your problem seems to have nothing to do with the mounting distance
between the lens and the "film plane" - just an af sensor and film plane
discrepancy.
The again it could be software...
I don't think it's the lens either b/c the af sensing is through the lens.
cb


 
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David J Taylor
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      05-06-2004
Some long focal length lenses can focus past the infinity setting to allow
for changes in the focal length or the lens mechanics with temperature.

Cheers,
David


 
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B.A.S.
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Posts: n/a
 
      05-06-2004
Chris Berry wrote:
> "B.A.S." <(E-Mail Removed)> wrote in message
> news:Zkpmc.15420$(E-Mail Removed) m...
>
>>P.S. Before I get slammed for whining and daring to complain in the face
>>of those who haven't experienced this problem, let me assure you it is
>>real, at least with my body/lens. I can supply pics to anyone interested
>>in viewing them. I have 30+ years of experience in the field, with
>>everything from large format (Linhoff, Calumet) to medium format
>>(Pentax, Mamiya, Yashica, Bronica) to 35mm (Konica, Pentax, Yashica,
>>Contax).

>
>
> OK... so you know what you're on about...
> The only thing I can think of with my very limited experience is that the AF
> sensor isn't the same optical distance from the lens as the film plane.
> Definitely a case for sending it back though.
> You didn't mention if it was the viewfinder or the actual "prints" that are
> out of focus - or what model body you're using.


It's a D70. The digital image upon close inspection on-screen or printed
is out of focus. I find the viewfinder image so small and dim, and
lacking manual focus aids like microprism or split-image, that I'm
unable to tell whether or not it's in focus through the viewfinder. Hey,
that's why I moved to AF in the first place - between my eyes and early
onset arthritis, manual focus was becoming hit or miss, even with the
great viewfinders on my Contax's.

> My Experience with Nikon's digital products is that they just don't
> compete - no matter how good the lenses are.
> BTW, your problem seems to have nothing to do with the mounting distance
> between the lens and the "film plane" - just an af sensor and film plane
> discrepancy.


I suspect you're right, though it may just be a calibration thing
(either physical or firmware).

> The again it could be software...
> I don't think it's the lens either b/c the af sensing is through the lens.
> cb
>
>


I too suspect it's not the lens...

B.A.S.
 
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B.A.S.
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      05-06-2004
David J Taylor wrote:

> Some long focal length lenses can focus past the infinity setting to allow
> for changes in the focal length or the lens mechanics with temperature.
>
> Cheers,
> David
>
>


Thanks David and mxsmanic - I'm coming to the conclusion that the 'past
infinity' issue is a non-issue with this lens.

B.A.S.
 
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