Pentax LX

35mm MF film SLR camera


Production details
Announced:June 1980
System: Pentax K (1975)
Imaging plane
Maximum format:35mm full frame
Mount and Flange focal distance:Pentax K [45.5mm]
Imaging plane:36 × 24mm film
Model:Electronically controlled
Speeds:125 - 1/2000 + B
Exposure metering:Through-the-lens (TTL)
Exposure modes:Aperture-priority Auto
Physical characteristics

Manufacturer description #1


The heart of the Pentax LX 35mm SLR is its Integrated Direct Metering (IDM) system. Incorporating a new-generation Silicon Photo Diode situated at the base of the mirror box, this system performs integrated light metering functions for both automatic and TTL flash exposures directly off the film plane and provides center-weighted readings for manual exposures as well. The result is superb exposure accuracy under the most challenging lighting conditions. Moreover, with the integrated system, viewfinder indication and automation are available with all viewfinders without special couplings, thus permitting greater compactness and overall balance, and eliminating the need for exposure compensation no matter which viewfinder or focusing screen is used.


The LX's unique titanium electro-mechanical shutter delivers electronically controlled stepless speeds from an ultra-fast 1/2000th second all the way down to 125 seconds in the automatic mode, and offers a full range of manual speeds from 1/2000th to 4 seconds. Moreover, its special design permits use of all dial settings from 1/2000th second to "X" without batteries in virtually all temperatures.


The LX system includes a wide array of interchangeable viewfinders and nine different focusing screens to meet the challenge of almost any photographic situation. The unique FB-1 System Finder features optional eyepieces while the standard FA-1 Finder provides built-in diopter correction and hotshoe sync, including contacts for TTL Auto electronic flash. There's also a handle-mount TTL flash unit that synchronizes via the "X" terminal on the camera body. Hundreds of other precision accessories makes that LX one of the most complete professional-use SLR systems ever.


Never before has a professional system camera been so small, so Iightweight yet so rugged. Weighing a mere 803 grams (28 ounces) with standard FA-1 viewfinder and 50mm f/1.4 lens, the Pentax LX opens up a whole new dimension in precision 35mm SLR photography.

Designed to meet the most demanding requirements of the photographer in the studio or on the go, the LX is specially constructed. Its highly durable body allows it to take even the toughest assignments, from capturing climbers atop a freezing mountain to close-ups in the scorching sands of the desert. Special sealings and gaskets have been used in all key parts of the camera body and interchangeable finders for added resistance to moisture and dust. Even the film advance mechanism uses sealed ball bearings to provide smooth, trouble-free film transport under the most adverse conditions.

The LX has also achieved a new level in human engineering design with all the controls positioned for maximum ease of operation and convenience. Moreover, because the exposure measurement system is in the body, the need for special finder couplings and bulky accessories has been eliminated, thereby providing superb balance and handling ease with both eye-level and waist-level viewfinders.


No matter how suddenly or subtly the lighting may change, the superbly accurate Integrated Direct Metering (IDM) system of the Pentax LX measures light reflected directly off the film plane to ensure precise automatic exposure measurement even as the image is being captured on film. From the simplicity and ease of automatic flash photography with Pentax TTL Electronic FIash Units to the precision of IDM measured exposures in photomicrography, macrophotography or astrophotography, from the instant response and depth of field control provided by LX aperture-preferred automatic operation to the convenience and accuracy of high speed remote controlled automatic exposures with motor drive, the Pentax LX gives you the freedom and flexibility to concentrate completely on the infinite images of the photographic challenge while the camera does the work.

The IDM System

As you activate the LX metering system by pressing Iightly on the shutter release, Iight transmitted through the unique dual-system instant return mirror reflects off a secondary mirror into an ultrasensitive Silicon Photo Diode (SPD). The SPD cell transmits the information to the LX "brain" which computes the approximate shutter speed and displays it in the full information display while you focus and compose your image in the large, exceptionally bright viewfinder. As you release the shutter, the mirror system swings up and out of the way allowing the light to strike either the specially designed fixed pattern on the first shutter curtain (at higher speeds) or the film itself (at mid-range and slower speeds). This light reflects directly into the SPD cell, providing the LX "brain" with the information it needs to compute the precise speed required for an accurate exposure from the camera's continuously variable range of an ultra-fast 1/2000th second all the way down to 125 seconds (at f/1.2 in normal temperatures and humidity). Because the SPD measurement cell is seated in the body beneath the mirror, no exposure compensation is required with accessory viewfinders or focusing screens, and no blind is required for long time exposures or remote-control photography.

Added Precision in Difficult Lighting

You're always in complete control with auto exposures even in difficult lighting, thanks to the LX exposure compensation dial. Whether it's a special effect or just compensation for strong back-or front lighting, the exposure compensation dial lets you override the automatic exposure setting by a full ±2 EV in 1/3 increments for precise control. A special warning in the viewfinder lets you know you're off the "1X" normal exposure setting.


When the hectic pace slows and your photographic sixth sense tells you manual exposure control will add something special to the final image, the Pentax LX delivers. Simply activate the meter with a Iight touch of the shutter release and the exclusive dual system mirror transmits significantly more light to the ultra-sensitive SPD for metering accuracy. The LX "brain" will display its center-weighted reading in the viewfinder while you just align the pointer by changing shutter speed or aperture. Quick. Easy. Accurate. And you're in control.


Whether you've elected full automatic exposure control or manual, exposure information and a great deal more is always at hand in the full information LX viewfinder.

  • Aperture Window displays f/stop set on camera lens (not visible with FE-1 and FF-1 Finder models)
  • Red Flag Exposure compensation warning
  • Blue Flag indicates position of Shutter Dial
  • Red LED indicates over-exposure
  • A indicates automatic exposure selected
  • Shutter Speed Scale represents indexed range of shutter speeds from 4 to 1/2000th second.
  • Green LED's glow to indicate meter selection of hand holdable speeds from 1/2000th to 1/30th second.
  • "X" Electronic flash synchronization. Red LED glows to indicate automatic flash sync and flash ready with Pentax dedicated flash units, flickers as an auto flash exposure check with TTL integrated units.
  • Yellow LED's glow to indicate meter selection of speeds slower than 1/15th second as reminder to open lens, use tripod or flash.
  • "LT, B" In manual, indicates "S" shutter setting; Red LED glows to indicate long time exposure in automatic.


Titanium Electro-Mechanical Shutter

In designing the LX, Pentax engineering craftsmen opted for a horizontally-run metal focal plane shutter to aid in keeping internal vibration at an absolute minimum. Titanium was selected as the material for the shutter curtains because of its greater durability and resistance to temperature extremes. For you, the photographer, this means reliability, accuracy and dependability even under the most difficult shooting situations.

Stepless Speeds in Auto

When you set it for automatic exposure operation, the LX delivers electronically-controlled shutter accuracy from a stepless range of speeds between an ultra-fast 1/2000th second all the way down to 125 seconds. You get the precise speed required for a proper exposure, even if its 1/895th second! Failsafe Manual Speeds - In manual, the LX provides a full range of shutter speeds from 4 full seconds to 1/2000th second. Not only that, because of its electromechanical shutter design, you can use all speeds from 1/2000th second to "X" even if the camera batteries fail! You get battery-less flexibility unparalled in any other 35mm system SLR.


The Pentax LX System lets you select just the right viewfinder to meet your specific photographic requirements. Viewfinders can be interchanged quickly and easily in seconds for incredible composition and focusing versatility. Each Finder provides special gaskets along the base for added resistance to dust and moisture. And because the LX Integrated Direct Metering System measures Iight in the body, auto- mation is always available and no exposure compensation is required regardless of the viewfinder used.


When it comes to focusing versatility, the Pentax LX delivers with nine different focusing screen models available to meet the needs of almost any type of photographic assignment from the fast action of sports to the demanding world of astrophotography. Each screen is specially treated with a newly created Pentax coating which enhances light transmission and ensures the brightest possible viewfinder image. Interchangeable Focusing Screens can be changed quickly and easily through the mirror housing of the camera. Each screen comes packed with a special pincer-type tool which lets you release the screen frame, interchange the screen and return the frame to its original position while never touching the screen surface.


When used with the versatile new Pentax AF-280T or powerful AF-400T Automatic Electronic Flash units, the Pentax LX provides you with a new dimension in operating ease and electronic flash exposure versatility. Because they fully integrate with the camera's IDM light measurement system, the electronic "brain" of the LX reads both ambient lighting and electronic flash at the film plane to control the flash output for a proper exposure of any subject in the flash unit's range, regardless of the f/stop set on the lens! No more exposure compensation when using flash with filters, close-up accessories or special tele/wide flash adapters! No more bothersome calculations to determine the best exposure setting for bounce flash or reflected lighting! Just precise automatic flash exposures, and a whole lot more!


Whether you're involved in the world of sports or capturing the hectic pace of a political campaign, you'll enjoy the versatility and compact styling of the Motor Drive LX. With this precision unit you can select from single frame operation or take sequential photographs at speeds up to 5 frames per second in "High" or as slow as 0.5 frames per second in "Low." Even film rewind has been automated, allowing you to rewind a full 36-exposure film cassette at the touch of a button in less than 8 seconds! Of course, the Motor Drive LX is fully synchronized with the Pentax LX at all shutter speeds (except "B") and provides an LED end of film warning/battery check. The Motor Drive LX mounts quickly and easily to the base of the camera via the tripod socket. The shutter can be triggered by the camera Shutter Release Button, the release on the optional Battery Grip M or by remote control with the optional Remote Control Accessories.

As power, you have the options to meet your particular needs. For maximum portability and convenience, there's the Battery Grip M which carries 12 penlight batteries. For the ultimate in compactness, choose the Ni-Cad Battery Pack M with its optional 6-hour Charger Pack M. Or for the laboratory or studio, take advantage of standard AC current with the Power Pack M. The LX Motor Drive System also includes a 250 Exposure Bulk Film Back which interchanges quickly and easily with the standard back on the camera to give you flexibility on the sports field or in the science lab.


Powered by only four 1.5-volt AA penlight batteries, the Winder LX can record the action at speeds up to 2 frames per second while retaining full synchronization with all shutter speeds (except "B"). For added convenience, the Winder LX also provides single frame capability with automatic film advance plus a special auto rewind feature that lets you rewind a full 36-exposure cassette in about 15 seconds. Attaching quickly to the tripod socket on the camera base, special gaskets enhance resistance to moisture and dust for added durability. Other features include an LED which flashes when the film stops automatically at the end of the cassette, and optional remote control capability.

Manufacturer description #2

TYPE: 35mm full-frame single lens reflex camera, with IDM off-the-film plane aperture-preferred automatic or full manual exposure measurement, TTL integrated flash control with Pentax "T"-type flash units.

LENS MOUNT: Pentax Bayonet Mount with fully automatic diaphragm coupling.

SHUTTER: Electro-mechanical horizontally-run titanium focal plane shutter; manual speeds mechanically controlled from 1/2000th second to "X" (1/75th second) and electronically controlled from 1/60th second to 4 seconds; mechanical speeds and "B" operational without batteries; automatic exposures electronically controlled in stepless range from 1/2000th second down to 125 seconds; shutter lock provided; shutter dial locks at "automatic" with push-button release; built-in curtain blind for use with Watch Data LX.

FLASH CONTROL: TTL measurement of ambient and electronic flash lighting directly off film plane with "T"-type Pentax flash models providing auto flash synch at "X" and visible ready light/exposure check in viewfinder when flash reaches full charge; automatic flash synch and visible viewfinder ready light with other Pentax dedicated flash models.

FLASH SYNCHRONIZATION: FP terminal and X terminal, plus contacts for TTL integrated automatic flash control at camera front; FA-1 standard Finder features built-in X-synch hotshoe with TTL contacts.

SELF-TIMER/PREVIEW: Multi-Function Lever provides 4 to 12 second delay manufaly activated self-timer, depth of field preview and mirror-lock capability.

EXPOSURE MEASUREMENT: Open aperture, center-weighted, through-the-Iens light metering for both automatic and manual modes. Integrated Direct Metering (IDM) system measures light at the film plane via Silicon Photo Diode (SPD): high speed measurements for automatic operation are made off fixed pattern on front shutter curtain, slow speed measurements off curtain and film automatic electronic flash/ambient light measurement with TTL "T"-type flash models. Manual exposure range from EV 1 to EV 19 (ASA 100, f/1.4); stepless automatic exposure range extends to EV -6.5 - EV 20 (125 second at f/1.2 to 1/2000th second at f/22 at ASA 100 under normal temperatures and humidity). Meter activated by light pressure on shutter release with automatic shut off after 25 seconds. ASA film speed range: ASA 6 - 3200.

EXPOSURE COMPENSATION: Up to ±2 EV automatic exposure compensation in automatic mode by dial control; dial indexed at 1/4X, 1/2X, 1X, 2X and 4X with click stops at 1/3 EV positions; red flag appears in viewfinder to indicate dial is off "1X" normal exposure position; dial lock provided at "1X" with push button release.

VIEWFINDER: Standard FA-1 Interchangeable Eye-Level Pentaprism Finder features silver-coating and shows 98% vertical, 95% horizontal of picture area plus full data viewfinder display; built-in diopter correction by adjustment screw. Finder removable by release lever.

VIEWFINDER DISPLAY: Tri-color display for TTL measured shutter speeds with green LEDs indicating hand-holdable speeds from 1/2000th second to 1/30th second, yellow LEDs as slow speed warning from 1/15th second to 4 seconds, and red LEDs to indicate overexposure or long time and X synch ready light with TTL and dedicated flash units; blue flag indicates automatic at "A" and manually selected shutter speeds; aperture visible in standard FA-1 finder model.

FOCUSING SCREEN: SC-21 standard with center split-image spot surrounded by microprism collar on ground glass field; fully interchangeable with 8 other focusing screen models through the lens mount.

FILM TRANSPORT: Pentax Magic Needle Loading System. Single-stroke, rapid wind lever with 120° throw and 25° standoff angle; built-in shutter cocked indicator. Accepts Winder LX and Motor Drive LX for automatic film advance and automatic rewind capability.

EXPOSURE COUNTER: Additive two-way exposure counter moves from loading indicator to "36" with color-coded indexes at "0", "20", "24" and "36"; operates in reverse to indicate precise film location for rewind or tracking of multiple exposures.

FILM REWIND: Crank type: Film Rewind Button doubles as multiple exposure button to disengage film advance mechanism. Automatic rewind with Winder LX and Motor Drive LX.

POWER SOURCE: Two 1.5-volt alkaline or silver oxide mini-batteries power all electronic systems in both automatic and manual modes; LED flickers in viewfinder to indicate low battery condition; mirror locks when batteries fail.

MIRROR: Large back-swing type, instant-return mirror to virtually eliminate image cutoff with most lenses; lock provision.

BACK COVER: Standard camera back with spring catch, built-in film memo holder. Back is fully interchangeable with Dial Data LX, Watch Data LX and LX Bulk Film Magazine.

OTHER FEATURES: Optional hand grips, special gaskets to minimize entry of dust and moisture, rubber fittings at base for stability on flat surfaces, interchangeable strap fasteners, Tripod Spacer Ring for use with very compact or large diameter lenses, neck strap with shoulder pad.

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35mm full frame

43.27 24 36
  • Dimensions: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm
  • Area: 864mm2

Travellers' choice


Among autofocus lenses designed for 35mm full-frame mirrorless cameras only. Speed of standard and telephoto lenses is taken into account.

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Image stabilizer

A technology used for reducing or even eliminating the effects of camera shake. Gyro sensors inside the lens detect camera shake and pass the data to a microcomputer. Then an image stabilization group of elements controlled by the microcomputer moves inside the lens and compensates camera shake in order to keep the image static on the imaging sensor or film.

The technology allows to increase the shutter speed by several stops and shoot handheld in such lighting conditions and at such focal lengths where without image stabilizer you have to use tripod, decrease the shutter speed and/or increase the ISO setting which can lead to blurry and noisy images.

Original name

Lens name as indicated on the lens barrel (usually on the front ring). With lenses from film era, may vary slightly from batch to batch.


Format refers to the shape and size of film or image sensor.

35mm is the common name of the 36x24mm film format or image sensor format. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43mm. The name originates with the total width of the 135 film which was the primary medium of the format prior to the invention of the full frame digital SLR. Historically the 35mm format was sometimes called small format to distinguish it from the medium and large formats.

APS-C is an image sensor format approximately equivalent in size to the film negatives of 25.1x16.7mm with an aspect ratio of 3:2.

Medium format is a film format or image sensor format larger than 36x24mm (35mm) but smaller than 4x5in (large format).

Angle of view

Angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

As the focal length changes, the angle of view also changes. The shorter the focal length (eg 18mm), the wider the angle of view. Conversely, the longer the focal length (eg 55mm), the smaller the angle of view.

A camera's angle of view depends not only on the lens, but also on the sensor. Imaging sensors are sometimes smaller than 35mm film frame, and this causes the lens to have a narrower angle of view than with 35mm film, by a certain factor for each sensor (called the crop factor).

This website does not use the angles of view provided by lens manufacturers, but calculates them automatically by the following formula: 114.6 * arctan (21.622 / CF * FL),


CF – crop-factor of a sensor,
FL – focal length of a lens.


A lens mount is an interface — mechanical and often also electrical — between a camera body and a lens.

A lens mount may be a screw-threaded type, a bayonet-type, or a breech-lock type. Modern camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body, unlike screw-threaded mounts.

Lens mounts of competing manufacturers (Canon, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance can also be different.

The flange focal distance (FFD) is the distance from the mechanical rear end surface of the lens mount to the focal plane.

Lens construction

Lens construction – a specific arrangement of elements and groups that make up the optical design, including type and size of elements, type of used materials etc.

Element - an individual piece of glass which makes up one component of a photographic lens. Photographic lenses are nearly always built up of multiple such elements.

Group – a cemented together pieces of glass which form a single unit or an individual piece of glass. The advantage is that there is no glass-air surfaces between cemented together pieces of glass, which reduces reflections.

Focal length

The focal length is the factor that determines the size of the image reproduced on the focal plane, picture angle which covers the area of the subject to be photographed, depth of field, etc.


The largest opening or stop at which a lens can be used is referred to as the speed of the lens. The larger the maximum aperture is, the faster the lens is considered to be. Lenses that offer a large maximum aperture are commonly referred to as fast lenses, and lenses with smaller maximum aperture are regarded as slow.

In low-light situations, having a wider maximum aperture means that you can shoot at a faster shutter speed or work at a lower ISO, or both.

Closest focusing distance

The minimum distance from the focal plane (film or sensor) to the subject where the lens is still able to focus.

Closest working distance

The distance from the front edge of the lens to the subject at the maximum magnification.

Magnification ratio

Determines how large the subject will appear in the final image. For example, a magnification ratio of 1:1 means that the image of the subject formed on the film or sensor will be the same size as the subject in real life. For this reason, a 1:1 ratio is often called "life-size".

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Electronic manual focus override is performed in the following way: half-press the shutter button, wait until the camera has finished the autofocusing and then focus manually without releasing the shutter button using the focusing ring.

Electromagnetic diaphragm control system

Provides highly accurate diaphragm control and stable auto exposure performance during continuous shooting.

Manual diaphragm

The diaphragm must be stopped down manually by rotating the detent aperture ring.

Preset diaphragm

The lens has two rings, one is for pre-setting, while the other is for normal diaphragm adjustment. The first ring must be set at the desired aperture, the second ring then should be fully opened for focusing, and turned back for stop down to the pre-set value.

Semi-automatic diaphragm

The lens features spring mechanism in the diaphragm, triggered by the shutter release, which stops down the diaphragm to the pre-set value. The spring needs to be reset manually after each exposure to re-open diaphragm to its maximum value.

Automatic diaphragm

The camera automatically closes the diaphragm down during the shutter operation. On completion of the exposure, the diaphragm re-opens to its maximum value.

Fixed diaphragm

The aperture setting is fixed at F/ on this lens, and cannot be adjusted.

Number of blades

As a general rule, the more blades that are used to create the aperture opening in the lens, the rounder the out-of-focus highlights will be.

Some lenses are designed with curved diaphragm blades, so the roundness of the aperture comes not from the number of blades, but from their shape. However, the fewer blades the diaphragm has, the more difficult it is to form a circle, regardless of rounded edges.

At maximum aperture, the opening will be circular regardless of the number of blades.


Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

Maximum diameter x Length

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

For lenses with collapsible design, the length is indicated for the working (retracted) state.

Weather sealing

A rubber material which is inserted in between each externally exposed part (manual focus and zoom rings, buttons, switch panels etc.) to ensure it is properly sealed against dust and moisture.

Lenses that accept front mounted filters typically do not have gaskets behind the filter mount. It is recommended to use a filter for complete weather resistance when desired.

Fluorine coating

Helps keep lenses clean by reducing the possibility of dust and dirt adhering to the lens and by facilitating cleaning should the need arise. Applied to the outer surface of the front and/or rear lens elements over multi-coatings.


Lens filters are accessories that can protect lenses from dirt and damage, enhance colors, minimize glare and reflections, and add creative effects to images.

Lens hood

A lens hood or lens shade is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare. Flare occurs when stray light strikes the front element of a lens and then bounces around within the lens. This stray light often comes from very bright light sources, such as the sun, bright studio lights, or a bright white background.

The geometry of the lens hood can vary from a plain cylindrical or conical section to a more complex shape, sometimes called a petal, tulip, or flower hood. This allows the lens hood to block stray light with the higher portions of the lens hood, while allowing more light into the corners of the image through the lowered portions of the hood.

Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. In addition, lens hoods can offer some degree of physical protection for the lens due to the hood extending farther than the lens itself.


Teleconverters increase the effective focal length of lenses. They also usually maintain the closest focusing distance of lenses, thus increasing the magnification significantly. A lens combined with a teleconverter is normally smaller, lighter and cheaper than a "direct" telephoto lens of the same focal length and speed.

Teleconverters are a convenient way of enhancing telephoto capability, but it comes at a cost − reduced maximum aperture. Also, since teleconverters magnify every detail in the image, they logically also magnify residual aberrations of the lens.

Lens caps

Scratched lens surfaces can spoil the definition and contrast of even the finest lenses. Lens covers are the best and most inexpensive protection available against dust, moisture and abrasion. Safeguard lens elements - both front and rear - whenever the lens is not in use.