Pentax Auto 110: World's Most Versatile Camera

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(Please Note: This was written back in the late 1980s, and I haven't changed the text to bring it up to the 21st century. I'll be adding some illustrations as I find the photos...)

It's not my usual practice to get worked up enough to
write a story about a camera that's younger than I am, that
has electronic controls, & that I don't know how to fix if it
breaks. Throw in a plastic body, program shutter and the fact
that the manufacturer is still In business....gee, I
shouldn't even own one! But in the case of the Pentax Auto
110 I've made an exception, because this camera has
characteristics that make it truly unique, and give it
capabilities beyond other 110 or even larger cameras.

The Pentax Auto 110 was the world's first and only
subminiature SLR system. It wasn't the first subminiature SLR
- that honor goes to the Narciss, a Russian 16mm SLR that debuted
in the early 1960's, before the 110 cartridge was introduced by
Yellow Box Inc. It wasn't even the first 110 SLR - that was
Minolta's 110 Zoom, an aperture-priority autoexposure model
of the mid-70's, following the horizontal arrangement of the
Kodak Pocket Instamatics and fitted with a decidedly
unpocketable, non-interchangeable f/4.5 zoom lens, and
metering through a sort of miniature telephone dial on the
front panel next to the lens. What the Auto 110 was, though,
far outweighed its lack of chronological priority. It was
introduced in 1978 as a system, the most thorough the 110
format would ever see: its modest but pocketable 24mm f/2.8
lens was interchangeable with an 18mm wide angle or a 50mm
telephoto, both with the same f/2.8 speed; a 70mm tele and a
20-40 f/2.8 wide-to-tele zoom would follow, as well as a 1.7X
teleconverter. In addition to optics, the Auto 110 was
designed to accept a power winder, and its lack of a standard
hot shoe (there wasn't room) was made up for by the provision
of a proportionately teeny weenie dedicated flash that
coupled mechanically with the body to set the camera at f/2.8
and 1/30 sec. All this was available, if desired, in a
miniature aluminum attache that looked like a cross between a
Halliburton case and a makeup kit.

A system that fits in the palm of your hand: the Auto 110 with its 50mm tele lens mounted, 18mm wide angle, 24mm normal lens and nickel-sized 1.7x teleconverter in front.

The Auto 110 focused to 14" (10" with the wide angle),
without resorting to an internal swing-away closeup lens as
the Minolta had done. Also unlike the Minolta, its TTL
metering (a first for a 110 camera) allowed for filters
without compensation, and a variety were offered in each of
the tiny sizes. Auxiliary closeup lenses were also provided
for those for whom 14" wasn't close enough.

The Auto 110 was equipped with an electronically
controlled, program automatic behind-the-lens leaf shutter
and an instant-return mirror. More modest tasks than this had
sent a number of previous attempts, even with a roomy 35mm
body shell to put it all into, to early and unmarked graves.
But it was a unique combination, and one which Asahi
engineers deftly used to their advantage. Whereas in 35mm
SLRs a leaf shutter between the lens and the mirror becomes a
nightmare of complexity and the need to cross-couple it with
a removable lens diaphragm would most likely have sent it far
beyond any hope of redemption, the combination in the Auto
110 resulted in an extraordinarily simple design, made all
the simpler by its autoexposure control requirements. The
110's automatic diaphragm and leaf shutter system contains
neither a diaphragm nor a leaf shutter as we generally think
oŁ them; the entire system consists of two V-shaped blades
which form a square opening between them, similar to the
diaphragm (but not the shutter) of any number of 70's-era
35mm compact viewfinder cameras. Having closed at the
beginning of the mirror-raising sequence, these are
instructed to travel in an opening direction for a given
period of time (determined by the light intensity), at the
end of which they close again. If the "given period of time"
is less than, say, 1/60 sec., the blades will begin closing
without ever having reached their fully open (f/2.8)
position; hence, for speeds from 1/30 to the max. of 1/750,
both the duration and distance of travel vary together for an
effect which Canon (at just about the time the Auto 110 was
being introduced) endowed with the pretentious title of
"Program Operation". When done in this way, there's really
nothing to long as you don't have to know just what
aperture and shutter speed you got for any given exposure. So
the logical final touch is to just let the built-in meter
handle everything on its own in automatic-only operation,
with no indication of what it's doing other than a yellow
light that comes on at all speeds allowing full aperture
(1/30 sec. or longer).

The other trick in a leaf-shutter SLR is the need for
a light seal to protect the film when the shutter is open for
viewing. In the Auto 110, this task is handled very elegantly
by the instant-return mirror itself, which seals against a
flange in front of the film plane when in the down position.

Many of the mechanical arrangements which make the
Auto 110 work could not be scaled up to 35mm size; they work
only in the 110 size, for several reasons: first, while the
Auto 110 is unquestionably the smallest SLR ever successfully
marketed and among the smallest ever built, it is quite bulky
in proportion to its film size, compared to larger format
cameras of conventional design. If doubled in size to bring
it up to a 35mm full frame, it would be 7 3/4" long, 4 1/4"
high and 2 1/2" thick without lens, and using it would feel
sort of like holding a sixpack in front of your face.
Secondly, the mechanisms themselves are quite massive. In 110
size the blade shutter, mirror and light baffle work very
quietly, but doubling their dimensions would increase their
weight by 800% for every moving part, while in order to
maintain the shutter speed range these massive parts would
have to move twice as fast. The result would hardly be likely
to meet wide acceptance. Another limitation imposed on the
Auto 110 by its mechanical layout comes in the area of lens
design. You may have noticed that all Auto 110 lenses have
the same maximum aperture, from the normal lens (for which
f/2.8 may be a tad slow) to the zoom (for which it's quite
fast). This is because the diaphragm is built into the body
and must work with all lenses. Another problem associated
with this arrangement is that the diaphragm is located
behind, rather than within, the lens. This has a decided
effect on the optical design of the lens, especially in the
longer focal lengths. The front element of the 50mm tele, for
instance, measures 30mm across - - much larger than one would
find on a 50mm f/2.8 normal lens for a 35mm camera. This is
necessary to allow rays of light to reach the corners of the
frame through the rear-mounted diaphragm. But it's more than
just a matter of size: enlarging the front element of an
f/2.8 Tessar wouldn't get you anything but extra glass. The
design of the lens has to be changed so that the rays of
light will converge near the rear of the lens rather than
near the center as is usually the case. Further, the point of
convergence should be about the same for all focal lengths. A
lesson in how to qo about this had been given in the 1950's,
with the interchangeable-front-cell lenses of the Retina and
Contaflex cameras; the ancestor of these, in turn, had been
the supplementary wide angle and tele attachments which went
on the Contaflex I and II and the Rollei TLRs. Despite
obvious differences, the basic problem, keeping the diaphragm
in the same place, exists in all of these, and the basic
optical approach is similar. Essentially, the rear portion of
the wide angle and tele lenses resembles the normal lens. The
front portion comprises a Galilean telescope with some degree
of magnifying (in the tele) or reducing (in the wide angle)
power. As in any Galilean optic the field of view becomes a
function of the objective diameter; hence the increase in
size as the lens varies in either direction from the normal
24mm. Even the zoom can utilize this approach, with a moving
element in the forward section changing it from a magnifying
to a reducing optic as it moves. Again, this succeeds only
because of the small format: on a 35mm camera a 100mm f/2.8
tele with a front element nearly 2 1/2" in diameter would
surely be found unacceptable, as indeed it was in the
Contaflex series and the Canon EX.

The question of optical attributes which are a
function of this particular format size brings us to one of
the Auto 110's most intriguing and significant features, and
one which seems to have escaped the notice of the camera's
own designers. The Auto 110's 24mm normal lens, particularly
in combination with the camera's reflex viewing and
through-the-lens autoexposure systems, is about as near an
approximation of a human eye as you're ever likely to (or
would ever care to) find in a photographic camera. It
approximates both the focal length and the maximum aperture
of the human eye, and its field of view corresponds to that
typically provided in the eyepiece of optical instruments
such as binoculars and microscopes. The net result of this is
that the Auto 110 can photograph through the eyepiece of such
instruments far more satisfactorily than any other camera
ever made. Even the diameter of Its filter thread, at 25.5mm,
allows the lens to nest snugly over a standard 23mm
microscope eyepiece for a quick but steady shot. Proper
exposure is nicely taken care of by the TTL meter, and the
camera's small size and light weight don't jeopardize the
steadiness of the instrument.

One of the most fascinating ways to use an Auto 110 is to perch it on each of the eyepieces of a stereo microscope, as shown here. The camera's through-lens focusing and autoexposure systems give fool-proof results; an example is shown below.

Another happy coincidence
relates to lens speed. During the 1950's it was a fairly
common trick to provide an otherwise limited SLR (such as a
Contaflex, or an Exa) with long-telephoto capability by
attaching a monocular to the front of the lens. The major
problem was always that the diameter of the monocular
objective was small relative to the resulting focal length oŁ
the lens. Typically, binoculars and monoculars tend to be
designed to provide a 5mm diameter exit pupil: the most
common of these are 7x35, 8x40 and 10x50mm styles. These,
when attached to a 50mm lens, provide an effective focal
length of 350, 400 and 500mm, but in all cases the maximum
effective aperture is f/10. That's pretty slow, and it shows
in the dim viewfinder as well as the long shutter speeds,
both of which one would just as soon do without when handling
a supertelephoto lens.

Mount the same device on the 24mm lens of the Auto
110, however, and it's a different story. The view through
the finder looks much the same, but it's brighter - the 7x35
becomes a 168mm f/4.8, just 1 1/2 stops slower than the
normal f/2.8 and over 2 stops faster than it could provide on
a 35mm camera. That translates into shutter speeds over 4
times faster, which in turn means sharper pictures. Again the
TTL meter compensates nicely for the 1 1/2 stop reduction in
speed, but in this case there is a catch (albeit one that can
be lived with): with a hand held monocular, unlike a
telescope or microscope, there's a pretty good chance of
encountering enough light to make the lens begin to stop
down. At these higher exposure values the camera will tend to
overexpose slightly, since the meter doesn't know that the
light it's reading is all coming through the central 5mm (the
exit pupil) of the 8 1/2 mm (lens aperture) that it thinks
it's looking at. So if it sees enough light to require a
reduction of, say, one f/stop to 6mm diameter, it only winds
up closing off part of the unused edge area and allows the
whole 5mm beam through unaffected. The result: a 1-stop
overexposure, well within the capacity of most 110 films.

One thing to watch for when selecting a monocular for
this purpose is its angular coverage. The 24mm lens on the
Auto 110 covers about 48 degrees across its 21.5mm diagonal;
in order to prevent vignetting, the eyepiece of the monocular
must cover at least as much. This means a 7x monocular must
cover 48/7 or about 7 degrees minimum; an 8x, 6 degrees. Most
modern glasses meet this requirement easily, but some older
ones don't. Mine, a 7x dating from the early 50's, covers 6.5
degrees; vignetting is not visible with it at large
apertures, but begins as the lens stops down in bright light.
It is also important to get the camera lens as tight into the
eyepiece as possible, just as it is with your eye.

Other unique applications come to mind: it can be used
to photograph the viewfinder display of another camera,
through the eyepiece...... its light weight and low vibration
level permit use with lightweight telescopes and instruments
that could not support a larger camera, as well as those
whose eyepieces cannot be removed...... It can even be used to
measure the field of view of an instrument, by photographing
through the eyepiece and measuring the diameter of the image
on the negative. And finally, the apparent distance of a
viewfinder or instrument display can be accurately measured
by bringing the display to focus in the Auto 110 viewfinder,
and then simply reading the distance off the footage scale on
the lens.

As price trends have indicated since the model was
discontinued a couple of years ago, the Auto 110 is a classic
design which is destined to be (indeed, which already is) a
sought after collectors' item. More even than that, however,
it is a uniquely practical machine, as useful as it is
adorable, and one which, despite Pentax's gallant efforts to
exhaust all possibilities, still has considerable room for
future expansion at the hands of an adventurous amateur


Auto 110 camera
Auto 110 Super camera
18mm wide angle lens
18mm Pan-focus w.a. lens
24mm normal lens
50mm telephoto lens
70mm telephoto lens
20mm - 40mm zoom lens
1.7x tele converter (by Soligor)
Dedicated flash units
Power winder
Close-up lens sets
Filter sets
Various component and system cases

Images Taken with the Auto 110:

This one is hardly a fair example: it was taken with a 3 diopter closeup lens AND a 1.7x Soligor teleconverter on the normal lens, at a distance of less than 12 inches from the moving subject. Still, it's an example of a photo that could never have been taken with any other pocketable camera.

Here's another one I'd like to see you take with your 35mm AF point&shoot: a herd of aphids on a stem, taken by placing the Auto 110 first on one, then the other eyepiece of an American Optical stereomicroscope... it's as easy as click, wind, click (aphids don't move very fast; they all register okay, though one was wiggling his little derriere in the left frame and blurred a little). To see this in 3 dimensions, print it out and place it in an antique stereoptican viewer (the right-hand image should be about 3 1/2 inches wide for proper spacing). Each of these bugs is about half the size of a small ant.

A more conventional image, this one shows the resolution of the 18mm wide angle lens in Lindsay's hair and the upholstery texture, in spite of the grain in the ISO400 film.
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