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dioptric correction of poor focus

 
 
Poldie
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      06-21-2008
Just wondering if it is possible to accidentally correct, using the
dioptric correction on the viewfinder, a poorly focused shot. (Not
that this correction would end up on the picture, of course.)
Perhaps, though, some people with eyesight quality a, wearing glasses/
contact lenses b and using camera lens c could take a manually
focussed shot and be disappointed when they get home.
 
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N
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      06-21-2008
"Poldie" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Just wondering if it is possible to accidentally correct, using the
> dioptric correction on the viewfinder, a poorly focused shot. (Not
> that this correction would end up on the picture, of course.)
> Perhaps, though, some people with eyesight quality a, wearing glasses/
> contact lenses b and using camera lens c could take a manually
> focussed shot and be disappointed when they get home.


Undoubtedly and one reason why I don't use manual focus.

 
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David J Taylor
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      06-21-2008
Poldie wrote:
> Just wondering if it is possible to accidentally correct, using the
> dioptric correction on the viewfinder, a poorly focused shot. (Not
> that this correction would end up on the picture, of course.)
> Perhaps, though, some people with eyesight quality a, wearing glasses/
> contact lenses b and using camera lens c could take a manually
> focussed shot and be disappointed when they get home.


Yes, this can happen with some viewfinders. Try to ensure that the
graticule is in focus, so that your eyes are focussing at the correct
viewing distance.

Cheers,
David


 
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N
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      06-21-2008
"David J Taylor"
<(E-Mail Removed)-this-bit.nor-this-bit.co.uk> wrote in
message news:3e57k.13181$(E-Mail Removed) m...
> Poldie wrote:
>> Just wondering if it is possible to accidentally correct, using the
>> dioptric correction on the viewfinder, a poorly focused shot. (Not
>> that this correction would end up on the picture, of course.)
>> Perhaps, though, some people with eyesight quality a, wearing glasses/
>> contact lenses b and using camera lens c could take a manually
>> focussed shot and be disappointed when they get home.

>
> Yes, this can happen with some viewfinders. Try to ensure that the
> graticule is in focus, so that your eyes are focussing at the correct
> viewing distance.
>
> Cheers,
> David
>



David, what vision quality do you have?

 
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David J Taylor
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      06-21-2008
N wrote:
> "David J Taylor"
> <(E-Mail Removed)-this-bit.nor-this-bit.co.uk> wrote in
> message news:3e57k.13181$(E-Mail Removed) m...
>> Poldie wrote:
>>> Just wondering if it is possible to accidentally correct, using the
>>> dioptric correction on the viewfinder, a poorly focused shot. (Not
>>> that this correction would end up on the picture, of course.)
>>> Perhaps, though, some people with eyesight quality a, wearing
>>> glasses/ contact lenses b and using camera lens c could take a
>>> manually focussed shot and be disappointed when they get home.

>>
>> Yes, this can happen with some viewfinders. Try to ensure that the
>> graticule is in focus, so that your eyes are focussing at the correct
>> viewing distance.
>>
>> Cheers,
>> David
>>

>
>
> David, what vision quality do you have?


I wear both distance and reading glasses. When outdoors, I have the
diopter correction set to zero (viewfinder at infinity).

David


 
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Paul Furman
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      06-21-2008
Poldie wrote:
> Just wondering if it is possible to accidentally correct, using the
> dioptric correction on the viewfinder, a poorly focused shot. (Not
> that this correction would end up on the picture, of course.)
> Perhaps, though, some people with eyesight quality a, wearing glasses/
> contact lenses b and using camera lens c could take a manually
> focussed shot and be disappointed when they get home.


No, that only helps you get best focus on the screen where the image is
rear projected like a movie screen. It's not a direct optical path. You
do see a partial view through a direct optical path because the screen
is translucent but your eye has much more DOF so a little diopter
adjustment won't matter significantly. The screen appears to be about 2
or 3 feet away so it's like being under a black cloth looking at the
ground glass of a large format camera. The diopter adjustment on an SLR
is like putting reading glasses on under the black cloth.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
 
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dj_nme
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      06-21-2008
N wrote:
> "Poldie" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Just wondering if it is possible to accidentally correct, using the
>> dioptric correction on the viewfinder, a poorly focused shot. (Not
>> that this correction would end up on the picture, of course.)
>> Perhaps, though, some people with eyesight quality a, wearing glasses/
>> contact lenses b and using camera lens c could take a manually
>> focussed shot and be disappointed when they get home.

>
> Undoubtedly and one reason why I don't use manual focus.


The real answer to N's question is no.
The dioptre adjustment on a (D)SLR camera's viewfinder only adjusts the
focus of the viewfinder eyepiece onto the viewfinder screen.
It will actually help in determining if the camera has focused onto what
you wanted it to and is not a hindrance (quite the opposite).
 
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N
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      06-22-2008
"David J Taylor"
<(E-Mail Removed)-this-bit.nor-this-bit.co.uk> wrote in
message news:7B77k.13273$(E-Mail Removed) m...
>N wrote:
>> "David J Taylor"
>> <(E-Mail Removed)-this-bit.nor-this-bit.co.uk> wrote in
>> message news:3e57k.13181$(E-Mail Removed) m...
>>> Poldie wrote:
>>>> Just wondering if it is possible to accidentally correct, using the
>>>> dioptric correction on the viewfinder, a poorly focused shot. (Not
>>>> that this correction would end up on the picture, of course.)
>>>> Perhaps, though, some people with eyesight quality a, wearing
>>>> glasses/ contact lenses b and using camera lens c could take a
>>>> manually focussed shot and be disappointed when they get home.
>>>
>>> Yes, this can happen with some viewfinders. Try to ensure that the
>>> graticule is in focus, so that your eyes are focussing at the correct
>>> viewing distance.
>>>
>>> Cheers,
>>> David
>>>

>>
>>
>> David, what vision quality do you have?

>
> I wear both distance and reading glasses. When outdoors, I have the
> diopter correction set to zero (viewfinder at infinity).
>
> David
>


Interesting. I have bifocals, but my general correction is about +10 and I
have a few other problems as well. I don't remove my glasses when using the
viewfinder and therefore have to work to see the edges of the composition.
I rely completely on the camera's AF system. Manual focus for me would be
worse than hit and miss. I just can't focus correctly on things that are
close.



 
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N
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      06-22-2008
"David J. Littleboy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ...
>
> "N" <(E-Mail Removed)> wrote:
>>
>> Interesting. I have bifocals, but my general correction is about +10 and
>> I have a few other problems as well. I don't remove my glasses when
>> using the viewfinder and therefore have to work to see the edges of the
>> composition.

>
> Try looking through the viewfinder of a Nikon F100 or Canon 1-series dSLR
> next time you are in a larger camera store. You should find them much
> better than the more affordable models. Sigh. (Presumably the current
> Nikon pro dSLRs have nice viewfinders as well, but I've not checked.)
>
>> I rely completely on the camera's AF system. Manual focus for me would
>> be worse than hit and miss. I just can't focus correctly on things that
>> are close.

>
> It depends on the focusing screen. The Maxwell (replacement) screen in my
> Rolleiflex TLR works great for manual focus, but I tried to focus a stock
> Hasselblad in a camera store the other day and couldn't focus at all.
>
> The screens in most current SLRs are designed for brightness, not ease of
> manual focus. Some current dSLRs have interchangeable screens and an
> optional manual focus optimized screen. But even with a good screen,
> magnification such as that provided by the Canon angle finder C (or the
> flip-up magnifier in the Rollei TLR) helps.
>
> David J. Littleboy
> Tokyo, Japan
>
>


I use a D80 and recently bought the Nikon angle finder for it. Of course,
there are many times when the angle finder is just not practicable and times
when it is. However, it has it's own focus adjustment and I wondered how,
having a diopter adjustment for the camera viewfinder, and a focus
adjustment on the angle finder, would one know when the subject itself was
actually in focus.

As you suggested it may be just a matter of getting focus on the graticule,
but for me that is still difficult, not impossible, but a bit hit and miss.

 
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N
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      06-22-2008
"David J. Littleboy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ...
>
> "N" <(E-Mail Removed)> wrote:
>> "David J. Littleboy" <(E-Mail Removed)> wrote:
>>>
>>> The screens in most current SLRs are designed for brightness, not ease
>>> of manual focus. Some current dSLRs have interchangeable screens and an
>>> optional manual focus optimized screen. But even with a good screen,
>>> magnification such as that provided by the Canon angle finder C (or the
>>> flip-up magnifier in the Rollei TLR) helps.

>>
>> I use a D80 and recently bought the Nikon angle finder for it. Of
>> course, there are many times when the angle finder is just not
>> practicable and times when it is. However, it has it's own focus
>> adjustment and I wondered how, having a diopter adjustment for the camera
>> viewfinder, and a focus adjustment on the angle finder, would one know
>> when the subject itself was actually in focus.

>
> It's easy: if the image appears in focus it is in focus. Otherwise, you
> don't know.
>
> But it's the same with or without the angle finder: you adjust the diopter
> adjustment(s) so that the markings on the screen are in focus. I'd suggest
> setting the camera diopter adjustment to the middle of its range when
> using the angle finder.
>
>> As you suggested it may be just a matter of getting focus on the
>> graticule, but for me that is still difficult, not impossible, but a bit
>> hit and miss.

>
> Try to find the illumination/lens focus conditions under which it's
> easiest to see the markings on the screen. I find that it's easy with a
> mostly white PC screen roughly in focus, harder when the screen is way out
> of focus, harder with a dark background. (I have the grid screen for the
> 5D, which is designed to be bright. The easy to manually focus with f/2.8
> lenses screen for the 5D doesn't have grid lines, and I do a lot of
> architecture/landscape with a 24mm f/3.5 lens.)
>
> David J. Littleboy
> Tokyo, Japan
>
>


Thanks David, that all makes sense and I'll use that idea of the PC screen.

 
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