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Nikon 28mm f/2.8 D mis-focusing?

 
 
Karl Winkler
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      02-26-2007
I went ahead and got a 28mm f/2.8 D lens for my D200 as to have a
"standard" prime lens. It seems to work properly but for the fact that
it appears to focus slightly behind where it is supposed to. When the
subject is very close (say, 1 foot away) it seems plenty sharp. But in
the "normal" focal distances, say 4 feet to 20 feet), it seems to do
this mis-focusing thing and the intended focal plane is soft. I've
tried several different apertures, so I don't think it's just the
softness associated with being wide open.

Has anyone else experienced this? Is there a way to adjust the lens to
counter this?

-Karl

 
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Toby
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      02-26-2007

"Karl Winkler" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
>I went ahead and got a 28mm f/2.8 D lens for my D200 as to have a
> "standard" prime lens. It seems to work properly but for the fact that
> it appears to focus slightly behind where it is supposed to. When the
> subject is very close (say, 1 foot away) it seems plenty sharp. But in
> the "normal" focal distances, say 4 feet to 20 feet), it seems to do
> this mis-focusing thing and the intended focal plane is soft. I've
> tried several different apertures, so I don't think it's just the
> softness associated with being wide open.
>
> Has anyone else experienced this? Is there a way to adjust the lens to
> counter this?
>
> -Karl


AFAIK the lens can't misfocus, as it is the camera that does the
autofocusing. Do you have the same issue with any other lenses? Try manual
focusing using the "green spot" rangefinder in the viewfinder which lights
when correct focus is achieved and see what results you get.

Toby


 
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Karl Winkler
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      02-26-2007
On Feb 25, 8:58 pm, "Toby" <(E-Mail Removed)> wrote:
> "Karl Winkler" <(E-Mail Removed)> wrote in message
>
> news:(E-Mail Removed) ups.com...
>
> >I went ahead and got a 28mm f/2.8 D lens for my D200 as to have a
> > "standard" prime lens. It seems to work properly but for the fact that
> > it appears to focus slightly behind where it is supposed to. When the
> > subject is very close (say, 1 foot away) it seems plenty sharp. But in
> > the "normal" focal distances, say 4 feet to 20 feet), it seems to do
> > this mis-focusing thing and the intended focal plane is soft. I've
> > tried several different apertures, so I don't think it's just the
> > softness associated with being wide open.

>
> > Has anyone else experienced this? Is there a way to adjust the lens to
> > counter this?

>
> > -Karl

>
> AFAIK the lens can't misfocus, as it is the camera that does the
> autofocusing. Do you have the same issue with any other lenses? Try manual
> focusing using the "green spot" rangefinder in the viewfinder which lights
> when correct focus is achieved and see what results you get.
>
> Toby


Toby,

Makes sense. I don't have this problem with any other lenses (I have
the 17-55 and 70-200 zooms, and I started out with the 18-70 kit lens
- all are sharp as can be). I'll give the rangefinder thing a try as
you suggest. I wonder if it's just not a sharp sample of this lens?

-Karl

 
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Toby
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      02-27-2007
snip

> Makes sense. I don't have this problem with any other lenses (I have
> the 17-55 and 70-200 zooms, and I started out with the 18-70 kit lens
> - all are sharp as can be). I'll give the rangefinder thing a try as
> you suggest. I wonder if it's just not a sharp sample of this lens?
>
> -Karl


You need to find out if the lens has problems with curvature of field. Is
the center sharp when the corners are sharp, or do the corners and center
come into focus at different distances? Try a few different shots (manually
focused at slightly different distances on a tripod) of a brick wall or
something flat with some good detail, and see if everything is in focus at
the same distance setting. Then let the camera autofocus and see if the
autofocused image is as sharp as the best manually focused image. It should
be.

Toby


 
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darkroommike
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      03-02-2007
Umm, on a Nikon digital body you aren't using the corners of
the image, so it will be harder to spot than on film--try
another sample of the lens if you can borrow one, shoot
both, side by side at the questionable focusing distances
both AF and MF, heck borrow an AI or AIs if nothing else.
darkroommike

Toby wrote:
> snip
>
>> Makes sense. I don't have this problem with any other lenses (I have
>> the 17-55 and 70-200 zooms, and I started out with the 18-70 kit lens
>> - all are sharp as can be). I'll give the rangefinder thing a try as
>> you suggest. I wonder if it's just not a sharp sample of this lens?
>>
>> -Karl

>
> You need to find out if the lens has problems with curvature of field. Is
> the center sharp when the corners are sharp, or do the corners and center
> come into focus at different distances? Try a few different shots (manually
> focused at slightly different distances on a tripod) of a brick wall or
> something flat with some good detail, and see if everything is in focus at
> the same distance setting. Then let the camera autofocus and see if the
> autofocused image is as sharp as the best manually focused image. It should
> be.
>
> Toby
>
>

 
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