It might be obvious from my some of my photos that I'm a sucker for shallow depth of field. I like to shoot close, tight portraits that utilize large apertures to separate subject from surroundings. I discovered this love when using a Mamiya 645 Pro with an 80mm f/1.9 setup, and subsequently a Pentax 6x7 with the standard 105mm f/2.4.
Somebody unfamiliar with medium format photography might not think that an aperture of f/1.9 is very wide. After all, 35mm and digital-full frame cameras are often equipped with lenses that have maximum apertures of f/1.8, f/1.4 and even f/1.2. Ultrafast lenses like Leica's f/0.95 Noctilux are still available and increasing in popularity (albeit for price tags of up to $10,000).
Simply put, the larger the film or sensor, the smaller the aperture required to create depth of field equivalent to a fast lens on smaller formats. A wide aperture lens would be large, heavy and difficult to focus. Medium format cameras are already quite cumbersome, so there's not much incentive to push them further. This concept applies to large format, too - It's uncommon to find a modern lens with an aperture faster than f/4.5 or so.
Arguably a major reason to shoot large format (4x5 film or larger) is for the exponential increase in quality and the potential for enlargements. A 35mm negative might print at 8x10, but would begin to show grain and loss of resolution beyond that. Medium format negatives, being more than twice the size of 35mm, can easily print beyond 20x24. Large format negatives could produce wall-sized prints with little loss in resolution. Note that all of this is dependent on viewing distances and scanning techniques, but the point remains that large format images can store a lot of information.
Large format photographers routinely shoot at small apertures - sometimes down to f/64 or smaller - to maximize depth of field and capitalize on the potential for deep and detailed prints. To shoot wide open can render the majority of the negative soft and out-of-focus, negating all benefits that I've just mentioned. And yet, there are a number of photographers aiming to do just that. Depth of field is a tool to lead the eye to points of interest, to isolate subjects and to interpret the world in a way that the human eye doesn't routinely see.
This is where high-speed aerial lenses come in to the picture. In past times of war, military organizations around the world were utilizing gigantic aerial cameras for surveillance purposes. In America, Kodak was producing cameras equipped with the 7" (178mm) Aero Ektar, which had a maximum aperture of f/2.5. In the Britain, there was an 8" (203mm) f/2.9 Dallmeyer Pentac. Both lenses cover up to 5x7 and produce a depth of field roughly equivalent to that of an f/0.7 lens in 35mm format. It's not just the size of the aperture that makes these lenses interesting, but also the very unique and painterly quality created by the out-of-focus areas of the image (the "bokeh"). There are also 6", 12", and 13.5" Aero Ektars that are also interesting.
Aerial lenses must first be salvaged from cameras for which film is no longer in production, then modified to fit more usable equipment. Unlike other large-format camera lenses, they are not equipped with shutters, which adds another challenge. The best and most common option is to attach them to a camera with a focal plane shutter. One such example, the Graflex Speed Graphic, is a vintage press camera that comes equipped with a shutter within the camera body that can fire up to 1/1000 of a second. The combination is truly an impressive sight to behold.
My first foray into large format photography was, of course, using one of these aerial speed lenses. I was able to acquire a mint condition Aero Ektar locally and source a Speed Graphic as well. Custom lens boards are hard to come by, as the only makers have recently stopped fabricating them. Unfortunately, these days it's up to the photographer to devise a system to secure the lens to the camera of choice. Mines came with the long tubular board you see pictured, but I eventually upgraded to a JoLo board, which centers the lens' weight more properly on the front standard.
Ultimately, I sold the the first Speed Graphic and Aero Ektar to finance other projects. I've since owned a few of them and I've shot dozens of exposures with the combination. I've sold them all, but I always seem to regret that and carefully watch for the opportunity to own another of these beauties.
I have recently acquired an 8-inch (203mm) Dallmeyer Pentac, which is sometimes considered the "poor man's" alternative to the Aero Ektar. The Aero, which was always made by Kodak, is razor sharp at most apertures. The Pentac, by comparison, are available in both Dallmeyer and unbranded versions. There's sometimes questionable build quality, a reputation for softness and glow wide open. My specific lens might or might not be a clone, so it's a real gamble. But for less than 1/2 the price of the Ektar, it's worth the risk and will surely give great results for portraiture,
Bokeh is the name of the game, but as mentioned this isn't purely the result of a large aperture. Part of the "character" of the out-of-focus areas can be attributed to the fact that these aerial lenses have more than twice as many aperture blades as common lenses. This means that the aperture is rounder. Consider this: an aperture made of just 6 blades will show out-of-focus highlights as hexagonal shapes. The Pentac has 20 aperture blades that produce bokeh highlights that are almost perfectly round! This is considered "smoother" and more desirable by many photographers.
Although still quite large, the Pentac is definitely shorter and more subtle than the Aero Ektar. It should also be more manageable and easier to attach to a camera. I've sold all my 4x5 equipment, but hope to acquire a suitable replacement within the next two months. Out of necessity, this will probably be another Speed Graphic, whose built-in-shutter will make it easy to use this lens. Aside from sheet film, I should also be able to use the Speed Graphic for both polaroids and tintypes.
I'm very excited to begin testing this lens and hope to show that they're every bit as capable as their more expensive cousins. Stay tuned!
Update; Since this was originally written, I've also owned a 125mm f2 Schneider Xenon, 200mm f/3.5 Konishiroku Hexar, 178mm f/2.5 Buhl projection lens, and many others. There are tons of fast lenses that you can get for medium and large format that will give you similar looks - but in my opinion, the Aero Ektar is still king!
If you're interested in owning one of these lenses, I'd highly recommend considering John Minnicks' Aero Liberator cameras. John pairs the Aero Ektar with Graflex D and Super D SLRs. They're works of art that allow you to make some incredible images!