Pentax LX


The Pentax LX is a professional 35mm single-lens reflex camera produced by Pentax in Japan. It was introduced in 1980 to commemorate the 60th anniversary of Asahi Optical Co., and was produced until 2001. It is the top-of-the-line professional, or "system", camera in the Pentax manual focus range, with manual and aperture priority automatic exposure modes and an advanced light metering system. The LX uses the K mount, which is the Pentax proprietary bayonet lens mount, and has a large body of accessories. The camera has several unique or uncommon features, and compared with contemporary professional camera bodies from rival manufacturers, like the Canon New F-1 or Nikon F3, the LX body is smaller and lighter, weighing in at with its standard FA-1 finder.
Due to the peculiar font used for the Pentax LX logo, the model is sometimes misspelled as 'ILX'.

Construction and features

The LX is constructed of a solid metal alloy cast frame and metal covering plates, intended to be more durable than entry-level and mid-range cameras. Underneath the satin black finish is black chrome, meant to avoid a brassy look on the underlying metal as the surface finish wore through from use. All buttons and dials are fully weather and dust sealed, the LX being the first camera to have this feature, even among professional-grade contemporaries. This weather sealing made it suitable for photography in mechanically-difficult coastal environments with salt in the air.
The camera has an uncommon frame counter, being able to keep track of the frame number in either direction, whether advancing or rewinding the film. This feature aids in taking "random-access" multiple exposures anywhere along the film strip, as the counter only advances when the film does. The camera's self-timer lever is multi-functional, allowing for mirror lock-up and depth of field preview. The film take-up spool is of the "Magic-Needles" type, as found on the Pentax M Series cameras, which simplified loading. Both the viewfinder and focusing screen are interchangeable to suit the task at hand, with a large choice of [|alternatives] available.
These features made the LX highly sought-after among professionals both during and after production, with prices on e-commerce sites like eBay in the range of $200 to $400.

Shutter and metering

The shutter and light metering systems of the LX were considered very sophisticated, as much or more than any other camera of its time. The horizontally-running titanium shutter curtains are mechanically operated at all shutter speeds faster than, and including, the second flash sync speed, and electronically for all speeds slower than it. Because the upper range is entirely mechanical, all speeds within are available without batteries in the camera. The film speed dial can be set from 6 to 3200 ASA, and co-axially is an exposure compensation dial, operating with a range of ±2 EV in EV steps. The front shutter curtain has a special reflective white dot pattern, visible when the shutter is cocked, which assists in the light metering process.
The LX metering system is branded Integrated Direct Metering, which is a dynamic aperture-priority, center-weighted metering system which measures light off-the-film-plane, through the lens. In operation, it is essentially a "refined" version of the Olympus OM-2's metering system. Pre-release exposure information is obtained from light passing through a semi-silvered area of the reflex mirror and then reflected down by a small secondary mirror to a silicon metering cell in the base of the camera—in contrast to the OM-2's need for a second cell in the viewfinder for the same task. Once the shutter is released, the light reflected off the first shutter curtain and the film itself continues to be measured by the same photocell as the exposure takes place, continuously adjusting the exposure time to match the varying light level of the subject. A shutter speed prediction is then calculated and given to the user through a vertical row of LEDs visible in the viewfinder, seen as an advance of the display row in the ME Super from 1979.
In the automatic mode, the speed indicated is only an approximation of the actual speed the camera will use, which is completely variable, a feature broadly distinct to professional auto-exposure cameras. The mode's exposure metering ranges from -6.5 EV to +20 EV. Shutter speeds in the automatic mode range from second to 125 seconds, making the camera excellent for available light photography. In contrast, the 8-second maximum of both the Nikon F3 and Canon New F-1's automatic modes make the exceptionally long exposure time only achievable with bulb photography.
In the manual mode, the predicted shutter speed is still displayed in the viewfinder as a recommendation, allowing the user to choose the speed indicated, or any other speed, by turning the shutter speed dial to align a translucent blue flag along the LED row. The blue flag, together with the aperture f-stop window, meant that manual exposure settings are still visible in the viewfinder without batteries, unlike the LCD screens seen in the F3. Shutter speeds on the dial are fixed between second and 4 seconds. The manual exposure metering has a range from +1 EV to +19 EV.
Like the Nikon F3 and the Canon New F-1, the viewfinders do not play a role in the metering process, since the metering is done entirely within the body of the camera. The Pentax LX functions fully with any of the interchangeable viewfinders, or even without one. Unlike either, however, as the exposure information is actually displayed on the camera body itself, the electrical contacts on the viewfinders are not necessary for showing exposure, and are instead only present in some for the hot shoe on the top. The system also removes any necessity for a viewfinder window blind, which would be necessary in other SLRs to prevent light from coming in the eyepiece and adversely affecting the exposure.
TTL flash control is also available using Pentax and certain third-party dedicated units in the hot shoe, which are controlled by the camera taking measurements from the IDM during the exposure. The TTL capabilities are extended to dedicated external flash units via a special lead which connects to the conventional PC socket and additional contacts adjacent to it. The hot shoe and PC socket can also be used with non-dedicated flash units.

Interchangeable accessories

A number of professional accessories were made available for the LX, in addition to the conventional hot shoe flashes, including interchangeable viewfinders and focusing screens, a specialized winder and motor drive, a few detachable camera backs, and other miscellaneous accessories.

Viewfinders

The LX has six interchangeable viewfinders, some of which show the lens aperture f-stop via a small window within them. The available viewfinders are:
  • The standard FA-1 eye-level pentaprism finder, which has a hot shoe and built-in adjustable diopter correction from 0 to 1.5 for users with corrective lenses. The aperture f-stop is visible at the top of the finder window.
  • The FA-1W eye-level pentaprism finder; the same as the FA-1, but with a diopter correction range of 1 to 3.
  • The FA-2 eye-level pentaprism finder intended to be compact and lightweight; the same as the FA-1, but without the hot shoe or the f-stop window.
  • The FE-1 waist-level "Magni-Finder" intended for close-up photography or situations where magnification is needed for accurate focusing. The f-stop is not visible through the viewfinder, and it has no hot shoe.
  • The FF-1 waist-level finder can fold to be almost flat when not in use. There is no hot shoe, and the aperture f-stop is not visible.
  • The FB-1 system finder base, which is used with any of three separate bayonet-mounted eyepieces:
  • * The FC-1 action eyepiece, which can rotate 180° to provide either an eye-level view with a high eyepoint or a waist-level view.
  • * The FD-1 "Magni-Eyepiece" which magnifies the view through the lens at a 45° viewing angle. The eyepiece features a diopter correction range of -4.5 to +3.5.
  • * The FD-2 standard eyepiece, which has a 45° viewing angle, ideal for microscopy. Aperture f-stop is not visible in the viewfinder.
To switch viewfinders, a small lever is pushed to release the current one, allowing it to be removed and replaced with another. The task of changing can be performed with one hand. Both the LX and the Canon New F-1 use a more secure rail system to attach viewfinders, as opposed to the Nikon F3's dual latch system.

Focusing screens

The LX has a total of 17 focusing screens that are specially coated to appear brighter than the screens in other cameras. The 9 focusing screens designed for the earlier Pentax MX system can also be used in the LX, as they have the same dimensions, though are not as bright. To switch focusing screens, a small "pincette", supplied with each new screen, is used to remove the current one from the focusing screen frame through the lens mount, and then to insert the new screen in its place.
The original 9 screens include:
  • The standard SC-21 ground-glass focusing screen with a split-image and microprism collar center.
  • SA-21, a simplified version of the SC-21 with only the microprism center.
  • SA-23, similar to the SA-21, but modified to aid in focusing high-speed lenses.
  • SB-21, a simplified version of the SC-21 without the microprism collar.
  • SD-21 all-matte focusing screen with crosshairs in the center, intended for astrophotography and macrophotography.
  • SD-11, similar to the SD-21 but with a clear background.
  • SE-20 all-matte focusing screen intended for use with macro and telephoto lenses.
  • SG-20, similar to the SE-20 but with an etched 6mm grid pattern intended for aligning architectural subjects or multiple exposure composition.
  • SI-20, similar to the SE-20 but with an engraved axial scale intended for determining subject size in microscope and bellows photography.
Five screens were added in the late model, most of which were variations of previous screens redesigned for long telephoto lenses:
  • SA-26, similar to the SA-23, but designed for lenses with focal lengths greater than 300mm.
  • SA-32 all-microprism field screen with finer microprism center.
  • SA-37, similar to the SA-32, but intended for use with telephoto lenses or close-up photography.
  • SC-26, similar to the SC-21, but designed for lenses with focal lengths greater than 300mm.
  • SE-25, similar to the SE-20, but designed for lenses with focal lengths greater than 300mm.
Three additional focusing screens were added for the limited release of the [|LX 2000], which were about
EV brighter than original LX screens:
  • SC-69, the same as the late-model SC-26.
  • SE-60 plain all-matte field screen designed for use with mirror lenses and Pentax "Star" lenses.
  • SG-60 all-matte field screen with a grid, designed for use with mirror lenses and Pentax "Star" lenses.