What is a "twin-lens reflex camera (TLR)"

[ericmark]

I started to read the Ansel Adams books on line.
http://manualesdecine.files.wordpress.com/2012/05/the-camera-ansel-adams-series-no-1.pdf
http://manualesdecine.files.wordpress.com/2012/05/the-negative-ansel-adams-series-no-2.pdf
http://manualesdecine.files.wordpress.com/2012/05/the-print-ansel-adams-series-no-3.pdf
In the first one he makes reference to Twin-lens reflex camera and I realised I also called them twin lens reflex cameras. However reflex refers to moving the mirror it's a reflex action as the mirror swings out of the way with a SLR before taking the photo. However with the so called "Twin-lens reflex camera" the mirror seems to be static there is it seems no reflex action. So how did it get the name? I am guessing at one time the mirror did move but when and with what camera?

 

[saladdays]

This should answer your questions: http://en.wikipedia.org/wiki/Twin-lens_reflex_camera

Don't forget to thank me!

 

[JohnD]

reflex refers to the reflections method, which is used for the viewfinder.

Not the fact that in an SLR, thr mirror moves.

 

[ericmark]

It would seem the first dictionary I looked at referred to reflex as movement but when I looked in a larger one as said reflex refers to use of the mirror.

The Oxford Dictionary had a number of definitions including:-

3 - archaic (of light) reflected.
bent or turned backwards.

Origin:
early 16th century (as a noun denoting reflection): from Latin reflexus 'a bending back', from reflectere 'bend back' (see reflect).

As far as the SLR camera goes I was surprised to find originally more to set focus than as a view finder the Corfield Periflex had a periscope affair to focus with which did not capture the whole scene.

I had expected to find the twin lens reflex camera was originally made different not the single lens reflex.

As to the wikipedia site which I had linked to in my original post it did say the mirror was the reason for the word reflex but one does have to be careful as there are errors with wikipedia. Look up DOS for example and it says it stands for "Disk Operating System" clearly an error as many early computers did not have any disks read for example an old Amiga instruction book and it refers to "Device Operating System". The IBM mainframe operating system in the 1960s which it says first used the word DOS had spools of tape and punch cards. Hence why I did not trust the explanation of the T in a TLR camera.

The Wikipedia site under disadvantages lists "The design of the leaf shutter limits almost all TLRs to a maximum shutter speed between 1/100th and 1/500th of a second." what it fails to point out is with a SLR shutter the fully open time is around 1/200 second or less (The maximum speed at which you can use a standard flash gun) Rotary focal-plane shutter according to Wikipedia were only used in the Olympus Pen which went up to 1/500 second and when you follow the link it says how it is a 4/3rds camera which are not SLR's anyway as they have no mirror which was there huge advantage as the lens could be placed closer to the receptor making the lens very much smaller for same performance.

The opening lines when Wikipedia describes a SLR as using the single lens as a view finder, and completely misses cameras like Corfield Periflex even though it has a page on that camera.

I like Wikipedia but one does need to be careful.

 

[JohnD]

with a SLR shutter the fully open time is around 1/200 second or less

an SLR (or other camera, such as some Leicas) with a cloth blind shutter can have as long an exposure time as you desire.