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. (hence the Roman numerals LX), 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 570 grams (1.26 pounds) with its standard FA-1 finder.

Due to the peculiar font used for the Pentax LX logo, the model is sometimes misspelled as 'ILX'.

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.

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 1⁄75 second flash sync ('X') 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 (used to correct exposure metering in unevenly-lit environments), operating with a range of ±2 EV in 1⁄3 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 (IDM), 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 1⁄2000 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.