When it comes to travel, landscape, and seascape photography, I always try to keep at least one long focal length lens in my bag for photographing subjects to which I either cannot get closer or—in the case of a Siberian tiger guarding her cubs—to which I have no business getting closer.
Photographs Ó Allan Weitz 2020
The definition of a long telephoto lens depends on whom you ask, not to mention what format camera they are using. For some, a 105mm lens is long. For others, it’s anything beyond 200mm or 300mm. For me, 300mm has always been the gateway lens for serious telephotos, and unless you choose a lens with a maximum aperture of f/5.6 or f/6.3, telephotos can start getting pricey—especially the ones with maximum apertures of f/2.8 or wider.
Are there longer lens options available that won’t require you to go from three meals a day down to two for the next six months? The answer is yes, and they’re called mirror lenses.
What Is a Mirror Lens?
In a nutshell, a mirror lens is a compact telescope. Conventional, or refractive, camera lenses use formulated clusters of glass elements to gather light and transmit the focused image to the camera sensor (or film surface). Mirror lenses contain a series of angled circular mirrors that gather the light and, rather than transmit a focused image directly to the camera sensor (or film plane), reflect the incoming light back and forth, each time reflecting a narrower portion of the image until a highly magnified portion of the original image reaches the camera’s imaging sensor.
Also known as catadioptric lenses, or “cats,” some mirror lenses contain glass elements clustered together with no air between the elements. These are called “solid cats” and are shorter though notably heavier than their mirrored counterparts. The advantage of solid cats is that, unlike mirror optical systems, in which the mirrors can sometimes be jarred out of alignment, the glass elements in solid cats are cemented together into a single solid unit, making them far more resistant to misalignment due to impact or heavy vibrations.
All of the accompanying photographs were taken with Nikon F3s, Nikon FM2s, and a 500mm f/5 Reflex-NIKKOR on Kodachrome 64 slide film. The resulting images were scanned using my Franken-Scanner outfitted with a Sony a7R III and a 55mm f/2.8 Micro-NIKKOR Ai-S macro lens.
The Pros of Mirror Lenses
Let’s keep it simple—they are lightweight, they are small, and they are affordable. The most expensive telephoto lens currently sold at B&H (the Sony FE 600mm f/4 GM OSS) costs $12,995. The most expensive mirror lens sold at B&H (the Rokinon Reflex 300mm f/6.3 ED UMC CS) costs $299. The 600mm Sony is 17.68" long and weighs 6.7 lb. The 300mm Rokinon is 2.9" long and weighs 11.2 ounces. The 500mm mirror lenses aren’t much larger (about 4.7" or less) and they typically weigh less than 1.5 lb.
Part of the reason mirror lenses are less costly is that glass lens elements require far more production time and expensive equipment to produce, compared to cutting circles into flat sheets of mirrored glass. A big advantage of mirror lenses is that, due to their design, image files produced by mirror lenses are free from chromatic and off-axis aberrations, which are common with traditional refractive telephoto lenses.
The Cons of Mirror Lenses
When it comes to mirror lenses, the cons come with a one-two punch. The first punch is that they have a single fixed aperture. The sucker-punch is that mirror lenses are slow. How slow? Well, f/6.3 is considered fast, and most are f/8. Nikon made a super-fast 500mm f/5 Reflex-NIKKOR back in the early ’70s, and if you can find a clean used one—bully for you—snag it before I do! Nikon also used to produce a 1000mm f/11 Reflex-NIKKOR, which was a bear of a lens to shoot with, even when mounted on a tripod.
I should also warn you, mirror lenses tend to be about a half-stop slower than advertised and they vignette slightly toward the corners, but—IMHO—the vignetting invariably works in favor of the pictures these lenses capture.
The only other so-called downside of mirror lenses is an aesthetic issue having to do with donuts. Not the kind you dip in coffee, but the hollow circular twirls of light formed by out-of-focus specular highlights in the foreground and background of photographs taken with mirror lenses. These donuts are common to photographs taken with mirror lenses, which has to do with the way the light travels into and around the mirror system inside the lens barrel. Depending on one’s tastes, some find these circular highlights to be disturbing, but these are subjective qualifiers. From my experience the donuts usually work fine, sometimes they don’t, and in many cases they aren’t even an issue—they don’t exist.
Who Makes Mirror Lenses?
Back in the day, every camera manufacturer produced at least one mirror lens, usually in the 500mm range. These days there are only five manufacturers of mirror lenses, and three of these are one-and-the-same lens sold under different labels. Though most manufacturers have focused their R&D budgets on conventional telephoto lenses, the recently introduced Tokina SZX 400mm f/8 Reflex MF lens is available for most popular lens mounts, including T-mounts. What makes this lens so cool—aside from the fact it’s small enough to fit it in your coat pocket and costs less than $300, is that it can focus down to 45.3" (a 0.4x magnification ratio!), which is amazingly close for a 400mm lens.
Other manufacturers of mirror lenses include Bower, which produces a 500mm f/6.3 mirror lens in dedicated mounts, as well as a T-mount version for most major brands. Opteka produces a 500mm f/6.3 and a slightly slower 500mm f/8 mirror lens in a choice of lens mounts.
If you prefer a shorter focal length, Rokinon’s Reflex 300mm f/6.3 ED UMC CS is available in a wide choice of lens mounts, as is its kissing cousin—the Samyang Reflex 300mm f/6.3 ED UMCV CS mirror lens.
Though I’ve managed to capture some truly impressive photographs with mirror lenses under extremely challenging shooting conditions, I’ll be the first to tell you mirror lenses are not as sharp as their conventional telephoto counterparts. Are they sharp? Yes, they are, but they come in a close second to their faster counterparts containing glass elements. With that in mind, one of the most advanced pieces of combined technologies ever created by human beings is the Hubble Telescope, which happens to be a mirror lens. It’s a big one, but it’s a mirror lens, nonetheless.
Do you have any experience with mirror lenses? If so, what do you think of them, and—more importantly—what are your thoughts on donuts? Let us know in the Comments section, below.