I stand corrected. The question came up the other day (in the discussion of the new A99II) as to what "reflex" means in camera terms. I always thought it meant a mirror that moved out of the way—that is, that flipped up out of the light path of the lens. Several readers disagreed.
They're right and I'm wrong. I contacted our friend Todd Gustavson, Curator of the Technology Collection at George Eastman Museum in Rochester (you've met Todd before). He says it's simple: "If it uses a mirror for image preview, composing, and or focusing, it’s a reflex camera." It doesn't matter how many lenses are involved or whether the mirror moves or stays put.
So, technically, Sony's "SLTs" (SLT stands for single lens translucent) are still SLRs. Furthermore—how cool is this—the first camera, the Giroux daguerreotype camera, used a mirror for focusing, so it's a reflex camera too.
Todd is one of the pre-eminent experts on cameras in the world, the author of many books including the must-have Camera: A History of Photography from Daguerreotype to Digital. He shoots with a Nikon Dƒ himself.
Mike
(Thanks to Todd)
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TLR
Posted by: Mark Walker | Wednesday, 21 September 2016 at 04:16 PM
Interesting, I agree with the mirror rather than movement, but that rather wide definition means that a Leica or other rangefinder is also a reflex camera by virtue of it's focus mechanism.
Mike
Posted by: Mike Shimwell | Wednesday, 21 September 2016 at 04:32 PM
I think there is a danger of overthinking this, a reflex camera is one that is called a reflex camera. Your definition above of "If it uses a mirror for image preview, composing ..." would mean the Box Brownie is a reflex camera since it uses a mirror in the viewfinder to preview and compose.
Posted by: Richard Parkin | Wednesday, 21 September 2016 at 05:06 PM
And of course TLRs like the Rolleiflex, where the mirror is fixed.
Posted by: Fazal Majid | Wednesday, 21 September 2016 at 05:07 PM
TLRs are, by name and by common usage, "reflex" cameras, so that makes sense.
(So, also, "reflex" doesn't mean you view through the taking lens in all cases.)
Posted by: David Dyer-Bennet | Wednesday, 21 September 2016 at 05:30 PM
Remember the "TLR"? The Twin-Lens Reflex? Of Rolleiflex fame? That bad boy was THE professional camera of it's time. It used mirrors that did not flip up, either. BTW, both Ricoh and Yashica also made TLRs, and the Yashicaflex was the camera that MANY students developed their skills on in college photography courses. I'm sure you remember this, Mike! ;-)
Posted by: Stephen Scharf | Wednesday, 21 September 2016 at 05:37 PM
Yes, as in twin lens reflex. The mirror has it.
Posted by: Carl Weese | Wednesday, 21 September 2016 at 05:45 PM
Well since we're stuck with the term "full frame" (aren't ALL current digital cameras using the full sensor and therefore by definition full frame?) then it's up to us as to whether the term reflex has evolved to mean a moving mirror rather than any mirror.
Language evolves, whether we like it or not.
Gordon
Posted by: Gordon Cahill | Wednesday, 21 September 2016 at 05:54 PM
Hi Mike,
I found this definition of a reflex camera on the web, but I am not sure of the source: -
reflex camera
noun
a camera with a ground-glass focusing screen on which the image is formed by a combination of lens and mirror, enabling the scene to be correctly composed and focused.
And from Wikipedia: -
A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system (hence "reflex", from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured. With Twin lens reflex and rangefinder cameras the viewed image could be significantly different from the final image. When the shutter button is pressed on a mechanical SLR the mirror flips out of the light path, allowing light to pass through to the light receptor, allowing the image to be captured.
Posted by: Arthur | Wednesday, 21 September 2016 at 06:17 PM
I can't speak to the camera book linked here, but I was disappointed that his "500 cameras" book did not contain 1 APS camera.
Posted by: KeithB | Wednesday, 21 September 2016 at 06:48 PM
My burning question is, how many angels, holding mirrors, can stand on the head of a pin?
BTW my Enormous Full Frame 4x5 is much bigger than your pathetic little 35mm full frame. 8-)
Posted by: c.d.embrey | Wednesday, 21 September 2016 at 08:06 PM
In fact reflex cameras are older than photography:
https://aehistory.wordpress.com/1700/01/01/1700-camera-obscura-in-drawing-process/artist-using-camera-obscura/
But in modern times we should confine mirrors to bathrooms only.
Posted by: s.wolters | Thursday, 22 September 2016 at 01:23 AM
So is my 5x7 Stereo Graflex a SLR or a TLR?
Two lenses, one mirror, one ground glass, and one shutter, but both lenses are taking lenses as well as viewing lenses. It could be two SLRs but for the single shutter , mirror and ground glass.
Posted by: hugh crawford | Thursday, 22 September 2016 at 04:17 AM
I would add "... or beamsplitter" to the "mirror" reference. I would consider any camera with a prism beamsplitter, like many cinema cameras, to be "reflex" cameras.
Posted by: dwig | Thursday, 22 September 2016 at 10:39 AM
Sony's SLT cameras do not use the reflected image for preview, just for autofocus. The SLTs use an electronic viewfinder driven from the main sensor.
Posted by: Jack | Thursday, 22 September 2016 at 10:47 AM
> "If it uses a mirror for image preview, composing, and or focusing,
> it’s a reflex camera."
That very ecumenical definition also encompasses cameras with focusing aids relying on a moving mirror to determine the "distance" to the subject — i.e. to find the "range" of said subject...
Posted by: Nicholas | Friday, 23 September 2016 at 04:36 PM