«

Roger N. Clark (change username to rnclark) wrote:

>
> Why do DSLR's still use mirrors?

Simple. If it didn't have a mirror (or surface that acts like a mirror)
it wouldn't be a single lens REFLEX. The term reflex means it has a
mirror in the viewfinding train. This is true film OR digital.

Note that a "twin lens reflex" also generally has a 45 degree folding
mirror also.

Don Stauffer wrote:
> Roger N. Clark (change username to rnclark) wrote:
>
>>
>> Why do DSLR's still use mirrors?
>
> Simple. If it didn't have a mirror (or surface that acts like a mirror)
> it wouldn't be a single lens REFLEX. The term reflex means it has a
> mirror in the viewfinding train. This is true film OR digital.
>
> Note that a "twin lens reflex" also generally has a 45 degree folding
> mirror also.

The TLR (twin lens reflex) cameras which I've used or examined seem to
have a fixed mirror in the viewfinder.
It doesn't have to move out of the way, as does in a SLR camera.
They may have a folding hood for the focus screen or an interchangeable
viewfinder prism eyepiece or a peep-sight "sports finder" as accessories.

dj_nme wrote:
> Don Stauffer wrote:
>> Roger N. Clark (change username to rnclark) wrote:
>>
>>>
>>> Why do DSLR's still use mirrors?
>>
>> Simple. If it didn't have a mirror (or surface that acts like a
>> mirror) it wouldn't be a single lens REFLEX. The term reflex means it
>> has a mirror in the viewfinding train. This is true film OR digital.
>>
>> Note that a "twin lens reflex" also generally has a 45 degree folding
>> mirror also.
>
> The TLR (twin lens reflex) cameras which I've used or examined seem to
> have a fixed mirror in the viewfinder.
> It doesn't have to move out of the way, as does in a SLR camera.
> They may have a folding hood for the focus screen or an interchangeable
> viewfinder prism eyepiece or a peep-sight "sports finder" as accessories.

Yes indeed. That lens does not need to move, since it does not block
the film/image chip area. The TLR preceded the SLR. The SLR mfgs had
to come up with a reliable way to have the mirror flip up, and then
return exactly to the same place it left (staying in alignment). And,
at a price people could afford.

Paul Furman wrote:
> dj_nme wrote:
>> Don Stauffer wrote:
>>> Roger N. Clark (change username to rnclark) wrote:
>>>
>>>>
>>>> Why do DSLR's still use mirrors?
>>>
>>> Simple. If it didn't have a mirror (or surface that acts like a
>>> mirror) it wouldn't be a single lens REFLEX. The term reflex means
>>> it has a mirror in the viewfinding train. This is true film OR digital.
>>>
>>> Note that a "twin lens reflex" also generally has a 45 degree folding
>>> mirror also.
>>
>> The TLR (twin lens reflex) cameras which I've used or examined seem to
>> have a fixed mirror in the viewfinder.
>> It doesn't have to move out of the way, as does in a SLR camera.
>> They may have a folding hood for the focus screen or an
>> interchangeable viewfinder prism eyepiece or a peep-sight "sports
>> finder" as accessories.
>
> Ah, that's what those are all about, thanks. Presumably they could use
> cheaper optics in the viewfinder lens, or is it simply a duplicate lens?

Keep in mind that TLR cameras almost exclusively use medium format
roll-film.
The really cheap end of the TLR camera market (EG: Kodak Duaflex) have a
fixed non-focusing lens and a reflex viewfinder, sort of a "pretend" TLR
camera.
The serious-amateur/low-end-pro TLR cameras with a fixed lens (EG:
Yashica Mat) tend to have a slightly faster viewfinder lens (EG: f1:3.2
lens/f1:2.8 viewfinder) to exaggerate out of focus blur and make
focusing easier.
The top end of the market have interchangeable lenses and viewfinders,
some even have accessory eye-level pentaprism finders and co-existed in
the studio with medium-format SLR camera up until digital killed off
most pro use of film.