Silverbased

Projects and ponderings for film photographers

Archive for the ‘Photo Zeitgeist’


Sawing Expensive Glass In Half

A tip of the hat to friend Katrin for forwarding a great link to Wired’s gadget blog, with a look at some optics exhibits at the Deutsches Technikmuseum Berlin.

The museum shows several camera lenses cut open—one of which appears to be a Leica Tri-Elmar-M:

Leica Tri-Elmar-M, Bisected

I realize this museum is in Berlin, and thus wants to showcase Germany’s well-regarded optics industry. Still, it’s a bit heart-stopping to note that this particular Leica lens is now out of production, and was hardly an inexpensive item—one currently for sale on eBay has a “Buy It Now” price of USD $3,350!

This is an unusual lens for M-mount rangefinder cameras, that can be switched to 28, 35, or 50mm focal lengths. Note that it is not exactly a zoom lens, as only those three discrete focal lengths are available. (This makes sense on a rangefinder camera, where the viewfinder also switches between several discrete choices of frame lines.)

It’s actually rather impressive that the lens achieves this (and has a good reputation for sharpness to boot) with so few lens elements (8 elements in 6 groups).

If you were interested in my past post about simple camera-lens design, check out the link. The complexity that goes into sophisticated camera lenses can be pretty impressive.

Voigtländer Bessa-R: 21st-Century Vintage

It may be stretching a point to review the Voigtländer Bessa-R as a “vintage camera”: This model was only discontinued a few years ago, and several of its younger siblings are still in active production.

Yet for a classic rangefinder lover, the appearance of this new camera in 2000 was like throwing raw meat in front of a hungry beast: The “R” of the model designation might as well stand for Retro Rangefinder Revival.

For years I have happily bought and enjoyed used equipment; but the Bessa-R and its matching lenses actually caused me to open my wallet and plunk down serious cash on new-in-box photo gear for the first time in decades.

Bessa R versus Rebel DSLR

Think Different: Bessa-R versus Canon Rebel DSLR. With the digital’s crop factor, both lenses give equivalent coverage, speed

Despite the umlaut-festooned name, the current Voigtländer lineup comes from Japan’s Cosina. This is a company which has been quietly cranking out cameras for many decades—but with only a tiny fraction sold under their own name.

Over the past 30 years, Cosina ironed out a standardized kit of parts—including shutter, film transport and meter electronics—to build a basic, no-frills SLR. And this “platform” (as the auto industry would call it) was quickly adaptable to different lens mounts and camera styles. So, many entry-level cameras for other brands were really manufactured by Cosina, like the Nikon FM10, the Canon T60, Olympus OM2000, or any of the Vivitar SLRs.

The rest of Cosina’s business is making optical glass and lens components—and interestingly, building computer LCD projectors (again, all sold under other brand names). Anyway, they’ve developed quite a lot of expertise at being the low-cost supplier of optics and opto-mechanical products without compromising quality—for example, making aspherical lens surfaces cheaply.

But the president of the company, Hirofumi Kobayashi (the son of Cosina’s founder) is also a camera nut, and in particular, a lover of vintage German rangefinders. So eventually he had the brainwave, “Let’s launch a ‘prestige’ brand to show people what we can really do.”

After some wrangling, Cosina worked out the licensing to use the trademarks from the long-defunct Voigtländer company of Germany (although Cosina still doesn’t own the name outright). This licensing arrangement is why the cameras are still weirdly marked “Voigtländer Germany” on the top and “Made in Japan” on the bottom.

Cosina’s first bombshell product was an ultrawide, rectilinear 15mm f/4.5 lens of excellent quality (including an accessory wide-angle viewfinder that was impressive by itself). This was something even Leica & Zeiss hadn’t attempted before; and even if they had, it would certainly have cost thousands of dollars. But Cosina priced it at under $400.

The original camera body offered to match the 15, the Bessa L, was an oddball with no viewfinder of its own (scale focusing being fine, given wide-angles’ enormous depth of field). The L was a rather quick-and-dirty adaptation of Cosina’s standard SLR camera platform—but notable for its idiosyncratic revival of Leica’s pre-WWII 39mm threaded lens mount. (LTM or M39 for short.)
Bessa-R, 21mm Color-Skopar and Finder

Voigtlander Bessa R; at left, the tiny 21mm wide-angle with accessory viewfinder

Cosina’s next body was the Bessa R, their first rangefinder model. This also shocked people, by offering an outstandingly crisp and bright viewfinder that was arguably clearer than that of many “classic” models from Leica, Contax, Canon & Nikon. The R’s film door and top and bottom panels were made of plastic, which caused some rangefinder purists to bristle, but this did allow for a lighter weight body.

And Cosina kept introducing more and more interesting, top-quality lenses. One strength of lenses for rangefinders is that without an SLR’s flipping mirror in the way, a lens can recess more deeply into the body and be made much more compact.

Compact Voigtländer Ultron 35mm f/1.7

This Voigtländer Ultron 35mm f/1.7 can be much smaller than an equivalent lens for SLRs

Also, because slow lens speed does not reduce viewfinder brightness, rangefinders let you opt for even svelter, moderate-aperture lenses if you prefer that. For an interchangeable-lens travel kit, a Bessa R plus a few lenses saves ounces even compared to the far-from-chubby Olympus OM system equivalents that I own.

I bought and adore Cosina’s laughably-tiny 21mm f/4.0 wideangle (which needs an auxiliary viewfinder, natch). A lens this wide is not something you need every day; but it’s so compact that it’s painless to carry it along for the moments you do:

Sample from 21mm Color-Skopar

Compared to the elitist pricing of the Leica M series, Cosina simply rewrote the cost/performance equation for rangefinder lenses. They are not always cheap relative to SLR equivalents, but the build quality is always solid and nicely finished. The silky feel of the half-stop aperture detents on my 35mm f/1.7 is quite lovely.

A variety of companies besides Leica have made 39mm thread-mount lenses over the years, particularly Canon (in their 1950s, pre-SLR days). These all turn up on eBay from time to time, including some cheap, idiosyncratic Russian optics originally made for the Zorki and Fed rangefinder cameras. The quality control with these is quite erratic, but you can get lucky and find an excellent one.

Vintage Russian Jupiter-8 Normal Lens

Ratty-looking but surprisingly sharp 1961 Jupiter-8 lens, 50mm f/2.0. Standard equipment on many vintage Zorki Russian rangefinders

After the Bessa R, Cosina followed up with the R2 model. This was essentially the same camera, but with metal panels all around, plus a change to a different lens mount: Leica’s “modern” (post-1954!) M-series bayonet. (There’s an adapter which allows you to mount 39mm Leica thread-mount lenses on an M bayonet body, with no loss of function.)

The R and R2 bodies can be ID’d at a distance by their top plate, which slopes away diagonally from the viewfinder windows. All subsequent Bessa models have a step-down top panel design instead, and all continue the M bayonet mount and metal construction. The current bodies weigh about 10% more than my old plasticky R.

The bayonet attachment is obviously a lot less fumblesome than the thread mount for changing lenses quickly. (Threading lenses onto an M39 body goes easier if you rack their focus out to the closest distance, thus retracting the rangefinder coupling.) And the throat of the M bayonet is a little larger, allowing for wider-aperture designs.

So, while the original Voigtländer lens lineup used screw mounts, the trend is for the recent Cosina introductions to be M bayonet only. (Note that you can’t go backwards and mount those on an R screwmount body.) Cosina’s new M bayonet 35mm f/1.4 looks very nifty—even lighter and more compact than my f/1.7 threaded version. But the later lens releases have been accompanied by price increases, making them less of a bargain compared with the original series.

Cosina’s good work also caught the attention of Zeiss: Today there is a new Zeiss Ikon rangefinder line, manufactured by Cosina (in fact, just a re-engineered version of the Bessa series). This is intended as a showcase for Zeiss’s top-end lens designs. All but two of the lenses are assembled by Cosina, however.

Why Rangefinder?

But to take a step back for a moment… There’s a more general philosophical question, about what rangefinder cameras are good for.

Unlike an SLR, rangefinders allow you to maintain “eye contact” with your subject right through the moment of exposure. Also, the area visible outside the framelines can help you anticipate where unpredictably-moving subjects are headed next. So rangefinders have long been a favorite for people photos and street shooting.

People Pictures with the Ultron 35I find that my Bessa is the camera I grab for group events, where I expect to take shots of people wandering around interacting with each other.

Compared to the shallow depth of field of an SLR groundglass, the RF viewfinder sharply renders all of the potentially distracting clutter within the frame. You might find this makes you more conscious of when you need to move around to get a clearer viewpoint.

On the minus side, rangefinders aren’t the best choice for exact, tight framing. Most rangefinders stop focusing at about 3 feet from the camera. Different brands have more or less accurate framelines, but you generally get a bit more coverage on the film than what the viewfinder showed. That’s fine if you don’t mind “casual” framing, or plan to crop anyway—but I’m a no-cropping purist, and this aspect sometimes bugs me.

An RF viewfinder does not change its angle of view when you switch lenses; with the Bessas you need to flip a lever to switch in different-sized framelines matching each focal length. But this means that for a particular viewfinder, there is only one frame size that makes the maximum use of the visible area.

Switch to a wider lens choice, and you’ll need an auxiliary viewfinder (slid into the camera’s hot shoe). Go to longer focal lengths, and you’ll be framing your subject in successively smaller rectangles within the middle of the image. Thus, on my Bessa R the 35mm frame is great to use; but the one for a 90mm lens is really somewhat marginal.

You get used to all this quickly enough—but it’s not quite the seamless experience of swapping lenses on an SLR. And manufacturing an interchangeable lens mount with rangefinder coupling adds a lot to the complexity and cost of the camera.

So if you always plan on using just one focal length, you might consider that there have been many delightful fixed-lens rangefinders made over the years—often quite a bit more compact than the Bessa line, and with leaf shutters bordering on the inaudible. I have long pined to own a 1970s Yashica Electro GX—nice and compact, with a fixed 40mm f/1.7 lens and aperture-priority auto. But they’re maddeningly difficult to find in North America, although apparently less so in Japan.

Anyway, today’s current Bessa lineup has become rather confusing, with autoexposure and manual versions of three different viewfinder variations. Two remarkable new models are the R4A and R4M—unfortunately the most expensive ones—whose viewfinder shows the view of wide-angle lenses up to 21mm without a need for auxiliary viewfinders.

All the Voigtländer “A” models offer both manual metering and aperture-priority autoexposure—although their electronic shutters mean they’re dead without batteries. I have not personally touched any of the auto versions, but the description/diagram of the viewfinder display makes it sound slightly distracting to me.

The Bessa bodies offer the cheapest entry point today into a modern rangefinder system. But as their prices have crept north of $500, I’m becoming less enthusiastic about their value-for-dollar (My own closeout Bessa R was just $250). Ultimately, they are all still derived from the same old econo-SLR platform, so they share a few quirks and flaws:

• Because they’re based on a retooled full-sized chassis, their height and width is really no smaller than a typical film SLR. It’s only in their front-to-back body+lens depth where they have a significant advantage.

• The metal, vertically-traveling shutter provides for a nice 1/2000 sec. top speed, and flash sync at 1/125th. But it is not nearly as quiet as the iconic, cloth-shutter Leica shlurp. Instead, a Bessa makes a pretty sharp “clack.” (Actually, if you want stealth, any leaf-shutter camera is the best alternative.)

Lightweight Lenses Make Bessa Hang Cockeyed• The strap lugs on the R are on the front of the body—unmoved from their original SLR position.

However, given the lack of a mirror box, and the smaller RF lenses, the balance is completely different: With lighter lenses, the camera hangs at an angle, digging its hot-shoe into your ribs. (The lug position doesn’t appear to have changed with the current lineup.)

• With the subjects I shoot, I definitely hit the RF close-focus limit more frequently than I’d like.

• A black Bessa R is finished in black paint over white plastic for its top panel—which makes its inevitable “brassing” look particularly tacky. (Would it have been so hard to mold that part using solid black resin?)

• Most worrying, the film transport derived from their old platform just doesn’t quite have the reliability that you’d expect in a $500 camera. About once every second or third roll, my R has a brief frame-spacing hiccup (though this appears to be getting better, not worse, with wear). And I’ve heard a number of stories of people experiencing total jam-ups. On the other hand, I’ve also heard of people “fixing” the problem by sharply thwacking their Bessa against the heel of their hand (if you try this, I’m not responsible).

Now against all of that, I must end by mentioning the positives: A Bessa is just about the handsomest camera around (especially in black). The viewfinder is simply a delight. (A DSLR-using acquaintance once literally gasped when she looked through it—this fueled at least two full months’ worth of smugness on my part.) And the wonderful Ultron 35/1.7 is on my short list of lenses to grab whilst running from my burning home.

Plus, a camera that flies so completely in the face of today’s camera mainstream is a proud, defiant badge of eccentricity—one I am happy to wear.

Aperture: Digital’s Dirty Little Secret

You don’t need me to repeat the litany of complaints about compact digital cameras. Autofocus lag. Poor viewfinders. Image noise in low light. Mike Johnston half-jokingly concluded that the entire class shares so many inherent flaws that you shouldn’t even waste your time comparison-shopping between brands.

Recently I’ve posted my own grumbles about digitals’ lithium batteries, and their excessive depth-of-field. But I’d like to take a moment to discuss another subtle failing of digital point-and-shoots, one I rarely see mentioned: Aperture range.

Usually, the range of available apertures on a compact digital is a scant 2 or 3 f/stops. I’m serious: Go check out the “aperture range” listed in some typical specs …I’ll wait for you to come back.

Now, trading off aperture versus shutter speed—to control motion blur and depth of field—is a cornerstone of creative photography. So how could digital camera manufacturers permit such a crippling flaw?

How F/numbers Are Defined

Remember that f/ numbers are defined as the ratio of the lens focal length to the aperture’s diameter.* So as you change to longer focal lengths, the size of an “f/8-sized” hole must grow larger too. But teeny digital sensor chips demand ultra-short focal lengths; on a digi compact, f/8 could mean an opening only 1 millimeter across.

A hole that tiny almost starts behaving like a pinhole. And as any pinhole photographer will tell you, if your hole’s too tiny, you run into a problem: the limits of diffraction.

Diffraction: The Optical Wild Card

Optical calculations generally assume that light rays follow mathematically straight lines, until they’re bent by some air-glass surface.

But it’s not that simple. Because of its wave nature, light grazing the edge of an obstacle can veer off-course. These light waves diffracting in random directions can reduce the sharpness and contrast of an image.

Diffraction Blur

As the aperture stop of a lens becomes smaller, an increasing proportion of the light grazes the edge of the iris opening—rather than passing unaffected through the middle.

Rather than focusing to a single point, this stray light forms a fuzzy bulls-eye pattern instead.

How all this affects image sharpness gets into some choppy waters, technically. With digital cameras, the diameter of those bulls-eyes can can even grow larger than the spacing between sensor pixels. You might have paid for an 8 megapixel camera—but if each point of light is smeared over several pixels, you might effectively get only 2! (For a more technical discussion of these complications, I recommend this helpful page.)

Note that zoom lenses add another wrinkle: An opening of a given diameter equates to different f/stops, depending on what focal length the lens is zoomed to.

The diameter of the lens elements determines the widest possible aperture; but the corresponding f/number changes as you zoom (this is the reason zooms list a range like 2.8–4.0 as their maximum aperture). And if the smallest-possible iris diameter remains constant, this equates to dimmer f/stops (higher f/numbers) as you zoom towards the telephoto end of the range.

Anyway, the upshot of all this is simple: There is some limit to the smallest f/stop which can be used, before diffraction damages sharpness too severely. And tiny image formats suffer the worst from this effect.

A digital point-and-shoot’s lens might stop down to only f/5.6 at the wide-angle setting; and f/8 at the telephoto end. (Contrast that with with lenses for 35mm cameras, which can close down 2 to 3 stops further.)

What about opening wider?

This explains why compact digitals must limit their smallest f/stop. But could we extend the f/stop range to wider apertures? This would also help with our image noise and depth-of-field headaches too.

But the problem here is not optical; rather, it’s a function of what today’s camera marketplace demands.

You can’t increase a lens’s maximum f/stop without adding to its diameter, weight, and cost. And with compact size being a highly-desired camera feature, that’s a tough sell today. Thus, it’s rare to see maximum apertures greater than f/2.8 (and remember, that only applies at the wide end of the zoom range). Compare this to 35mm film compacts of the 1970s, where affordable models often sported excellent, faster-than-f/2.0 lenses.

Actually, the tiny sensor of a digital compact would permit the design of an ultra-fast lens—let’s say f/1.4—that would be smaller and cheaper than its 35mm equivalent. But the snag is, it would not be a zoom. Zoom lens design has made enormous strides in the past decades; but we still can’t avoid a speed penalty of a couple of f/stops, compared to the best single-focal-length designs.

And zoom range is a major tick mark on today’s camera-shopping checklist. With a few notable exceptions, camera makers consider it commercial suicide to offer a zoomless camera (aside from their cheapest and tiniest models).

F/2.8 at Different Focal Lengths

Both lenses open to f/2.8—the difference is in their focal length. Smaller image formats allow more compact lenses of the same speed.

Between a rock and a hard place

So lens design for small-sensor cameras is hemmed in at both ends. The smallest f/stop is limited by diffraction. The widest is limited by market demand for zooms—but compact and inexpensive ones. Thus the range of available apertures only covers 2 or 3 stops—seriously limiting creative exposure choices. (With primes for 35mm, the range can be 7 or 8 stops instead.)

As new digital models are introduced, some oft-heard complaints—like autofocus lag and poor viewfinders—are gradually being addressed. Other problems like image noise in dim light might be tamed eventually, using better sensors or savvier image-processing.

But any lens is still bound by the laws of optics. No amount of technological whiz-bangery can change that. Compact cameras imply tiny sensor sizes; tiny images imply short focal lengths.

And with those limitations, using aperture in the way a creative photographer demands becomes impossible.

*Note: This explanation of f/numbers ignores a few optical complications, which do not affect the main point here.