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What is an SLR?

David Pogue
Tech Critic
Yahoo Tech

Dear Pogue:

In your Yahoo Tech column, you referred to Sony mirrorless cameras as SLRs. The NEX and A7 cameras are not SLR cameras! It’s misleading to call them that.

—Adelino

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Hi, Adelino…

Well, technically, SLR stands for “single-lens reflex,” which describes the light path in traditional pro cameras. The light comes into the lens, hits an angled mirror, shoots up into a prism apparatus, and then gets bounced into your eye, which you’ve pressed against the viewfinder. That’s what “SLR” technically means.

Mirrorless cameras like the Sony NEX models work differently. To save space, they eliminate the mirrors and prisms: The light comes in through the lens and strikes the sensor directly. When you look into the viewfinder, you don’t see the light beamed in from the lens; you see a tiny screen showing the preview of the scene. 

Unfortunately, the world hasn’t settled on a name for these mirrorless, interchangeable-lens cameras. I’ve heard them called MILCs (mirrorless interchangeable-lens cameras), DSLMs (digital single-lens mirrorless), CSCs (compact system cameras), MSCs (mirrorless system cameras), DILS (digital interchangeable-lens system), ILCs (interchangeable-lens compacts) and even EVILs (electronic viewfinder with interchangeable lens).

Those names all have one thing in common: If I used any of them, my readers wouldn’t know what I meant (I try to write for a general audience).

Most people have heard of an SLR, though. And I’d guess that most people think it refers to a camera with interchangeable lenses, big sensors, and excellent photo quality — not necessarily a camera with a certain light path.

Interchangeable lenses, big sensors and excellent photo quality: Those are all characteristics of the models I described in my column. And  that’s why I referred to them as SLRs (while also explaining that they’re mirrorless).

Even so, my use of the term seems to have riled up plenty of sticklers. So next time I’ll either introduce and explain a term like ILC (that’s what  Popular Photography uses) — or I’ll avoid abbreviations altogether.

—DP