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Viewfinders!

 
 
Steffen Kluge
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      07-24-2006
tomm42 wrote:
> The Canon uses a prism and the Nikon uses mirrors, makes a big
> difference, the Canon probably has some magnification too. The D70
> should be compared to the Rebel XT, also has a mirror based prism, and
> the 30D compares to the Nikon D200. I bought the D200 cause I couldn't
> stand the D70 viewfinder.


Wrong. The D70 uses a pentaprism. The only Nikon DSLR using viewfinder
mirrors is the D50.

Cheers
Steffen.
 
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Steffen Kluge
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      07-24-2006
Steffen Kluge wrote:
> tomm42 wrote:
>> The Canon uses a prism and the Nikon uses mirrors, makes a big
>> difference, the Canon probably has some magnification too. The D70
>> should be compared to the Rebel XT, also has a mirror based prism, and
>> the 30D compares to the Nikon D200. I bought the D200 cause I couldn't
>> stand the D70 viewfinder.

>
> Wrong. The D70 uses a pentaprism. The only Nikon DSLR using viewfinder
> mirrors is the D50.


Wrong again! I guess I deserve this for relying on information on the
'net (dpreview in this case)... Ah, well.

To clarify, both the D70 and D70s viewfinders use penta-dach-mirrors
which perfectly explains why they are so dim.

Cheers
Steffen.
 
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Neil Harrington
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      07-24-2006

"Steffen Kluge" <(E-Mail Removed)> wrote in message
news:OUZwg.10292$(E-Mail Removed)...
[ . . . ]
>
> To clarify, both the D70 and D70s viewfinders use penta-dach-mirrors which
> perfectly explains why they are so dim.


I don't find the roof-mirror viewfinder systems to be "so dim," either in
the D70s, the Maxxum 5D, or a couple of my Maxxum 35s that use that
arrangement. With the same or similar lenses the mirror systems look just
about as bright to me as glass pentaprisms. The early "penta mirror" systems
I understand were noticeably dimmer, but I never had one of those.

You want to see *dim* you should look in the Maxxum 700si. That has a solid
glass pentaprism, but it also has an LCD overlay on the focusing screen that
is the reason for its dimness.

Neil


 
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Bill
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      07-24-2006
Neil Harrington wrote:

>> To clarify, both the D70 and D70s viewfinders use penta-dach-mirrors which
>> perfectly explains why they are so dim.


For anyone who is curious, the "penta-dach-mirror" is merely a mirror
inside the top of the viewfinder chamber and not a prism. The word
"dach" is German for roof.

Why Nikon chose German wording is beyond me though...

>I don't find the roof-mirror viewfinder systems to be "so dim," either in
>the D70s, the Maxxum 5D, or a couple of my Maxxum 35s that use that
>arrangement. With the same or similar lenses the mirror systems look just
>about as bright to me as glass pentaprisms.


I think a lot of people are abusing the term. The viewfinder appears dim
because there is less viewable area and total amount of light that hits
your retina is less. The light transmission is about the same as a
prism.

When I first used a DSLR I too thought it was dim. But when I took a
piece of cardboard and made a FOV crop for my film body eyepiece, and
compared them side-by-side, I found they were the same.

Besides, you get used to it. The only time I find it a problem is in
very dim light using a slow lense.
 
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Neil Harrington
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      07-24-2006

"Bill" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed).. .
> Neil Harrington wrote:
>
>>> To clarify, both the D70 and D70s viewfinders use penta-dach-mirrors
>>> which
>>> perfectly explains why they are so dim.

>
> For anyone who is curious, the "penta-dach-mirror" is merely a mirror
> inside the top of the viewfinder chamber and not a prism. The word
> "dach" is German for roof.
>
> Why Nikon chose German wording is beyond me though...
>
>>I don't find the roof-mirror viewfinder systems to be "so dim," either in
>>the D70s, the Maxxum 5D, or a couple of my Maxxum 35s that use that
>>arrangement. With the same or similar lenses the mirror systems look just
>>about as bright to me as glass pentaprisms.

>
> I think a lot of people are abusing the term. The viewfinder appears dim
> because there is less viewable area and total amount of light that hits
> your retina is less. The light transmission is about the same as a
> prism.
>
> When I first used a DSLR I too thought it was dim. But when I took a
> piece of cardboard and made a FOV crop for my film body eyepiece, and
> compared them side-by-side, I found they were the same.


That's interesting. I never tried anything like that, but with my 35s I have
compared identical and/or similar lenses on the Maxxum 5 (which has the roof
mirror system) and Maxxum 600si (solid glass pentaprism), and could never
see any significant difference in brightness between them.

>
> Besides, you get used to it. The only time I find it a problem is in
> very dim light using a slow lense.


I was somewhat surprised with my first digital SLR by the smaller viewfinder
image. I never expected that -- of course I knew the film-plane image would
be smaller, but I expected the viewfinder system to increase magnification
to compensate for it. I guess there must be some reason why they couldn't do
that. But as you say, you get used to it.

Neil


 
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Steffen Kluge
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      07-25-2006
Bill wrote:
>>> To clarify, both the D70 and D70s viewfinders use penta-dach-mirrors which
>>> perfectly explains why they are so dim.

>
> For anyone who is curious, the "penta-dach-mirror" is merely a mirror
> inside the top of the viewfinder chamber and not a prism. The word
> "dach" is German for roof.


It's an arrangement of mirrors, otherwise you wouldn't get an upright
side correct image in the viewfinder. As far as I can twist my mind
around it you'll still need three reflections on mirror surfaces, just
like you need three total reflections on a pentaprism's glass-air
boundaries. Metallic reflections are far more lossy than total
reflections. Anyone who ever swapped their mirror diagonal for an
expensive prism diagonal in their telescope knows that.

> Why Nikon chose German wording is beyond me though...


Well, after all they started out as the Nippon version of Zeiss Ikon

>> I don't find the roof-mirror viewfinder systems to be "so dim," either in
>> the D70s, the Maxxum 5D, or a couple of my Maxxum 35s that use that
>> arrangement. With the same or similar lenses the mirror systems look just
>> about as bright to me as glass pentaprisms.


Cropping doesn't affect the surface illumination, only the size of the
illuminated area. The total mount of light coming out of a 100% 35mm
viewfinder is larger than that coming out of a 100% DSLR viewfinder, but
it is spread over a larger matte area.

> I think a lot of people are abusing the term. The viewfinder appears dim
> because there is less viewable area and total amount of light that hits
> your retina is less. The light transmission is about the same as a
> prism.


No, prisms have better transmission than mirrors, as long as their
non-reflecting sides are properly coated.

> When I first used a DSLR I too thought it was dim. But when I took a
> piece of cardboard and made a FOV crop for my film body eyepiece, and
> compared them side-by-side, I found they were the same.


The D2H finder is brighter than the FE2 finder, and substantially
brighter than the D70 finder. Prism vs mirror is only part of the story,
I suppose. The matte screens will be different, too.

Cheers
Steffen.


 
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