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Leica 1.4x and 2x teleconverters

Leica produced two apochromatically corrected tele-converters for its R-series lenses, the APO-Extender-R 1.4x and the APO-Extender-R 2x. Like any tele-converter, they enlarge the central part of an image to increase the focal length of the primary lens, while reducing the intensity of light on the imaging receptor. The APO-Extender-R 1.4x increases the focal length by 40% and leads to a one-stop loss in lens speed (a lens set to f/2.8 will become a f/4), and the APO-Extender-R 2x doubles the focal length and results in two aperture stops in lens speed loss (a lens set to f/2.8 will become a f/5.6).

Tele-converters offer a convenient, light-weight, and low-cost means of extending telephoto reach. However, in addition to darkening the image in the viewfinder, which makes focusing more difficult, they reduce sharpness and contrast in the image and might introduce chromatic aberration and flare. The degradation of image quality will generally increase with the magnification of the tele-converter, such that a 2x converter will deteriorate the outcome more than a 1.4x one. The extent to which the degradation from tele-converter use is visible in final prints depends on the quality of both the tele-converter and the primary lens. Leica's APO-Extenders are highly corrected and - in combination with the excellent R-lenses - deliver very good imaging performance that does not show the marked decline in sharpness observable with tele-converters of some other brands. Yet, some quality loss is to be expected.

Both APO-Extenders maintain the fully automatic iris diaphragm of the lens with which they are coupled. Also, the closest focusing distance of the primary lens remains unchanged, so that the maximum magnification ratio of the lens is increased. Both tele-converters are highly corrected for aberrations and optimized to work with Leica's APO-lenses, notably its APO-Telyt line of long tele primes. Up until the end of the R-system in 2009, the APO-Extenders were sold with front and rear caps, as well as a soft leather case. The adjacent table summarizes the core specifications of the tele-converters. A non-APO version of the 2x converter that had been in Leica's product catalog since 1981 has the same optical formula and physical measures as the APO-Extender-R 2x, but the non-APO version was not corrected for chromatic aberrations to the same extent as the APO-Extender and is clearly inferior with respect to imaging quality, in particular in combination with lenses longer than 250mm.

Specifications of Leica tele-converters
 APO-Extender 1.4xAPO-Extender 2x (ROM)Extender 2x (non-APO)
Order number112491126911236
Production period1986-20091992-20091981-1988
Aperture range2.8 - 222.8 - 222.8 - 22
Magnification1.4x2x2x
Elements/groups5/47/57/5
Length36mm (1.4")35mm (1.4")35mm (1.4")
Maximum diameter62mm (2.4")70mm (2.8")70mm (2.8")
Weight220g (7.7oz)270g (9.5oz)270g (9.5oz)
Leica price (€, 2008)1,6501,950-
Ebay price (€)250-500400-80040-80
Current ebay offerscheckcheckcheck

The 1,4x APO-Extender-R was originally intended for specific lenses within the R-system, notably the APO-Telyt 280mm f2.8 lens, and early version of the tele-converter bear a respective designation on the converter-body. It has a strongly protruding front element and can, thus, only be mounted on lenses whose rear elements are far enough recessed within the lens body. The APO-Extender 2x does not have a corresponding limitation in compatibility and can be physically mounted onto all of Leica's telephoto lenses. Yet, Leica states that the APO-Extender 2x is designed for lens units with a maximum aperture of 1:2 or smaller. Indeed, when used with a fast lens, such as the Leica Summilux-R 50 mm f/1.4, there is no increase in light compared to using a lens with a 1:2 aperture number. This means an exposure compensation of -1EV should be applied when shooting wide-open, or that the lens should be stopped down to at least f/2.

Lens compatibility
Leica lensAPO-Extender 1.4xAPO-Extender 2xExtender (non-APO) 2x
50mm f/2-100mm f/4100mm f/4
60mm f/2.8-120mm f/5.6120mm f/5.6
90mm f/2-180mm f/4180mm f/4
90mm f/2 APO-180mm f/4 APO180mm f/4
90mm f/2.8-180mm f/5.6180mm f/5.6
135mm f/2.8 APO-270mm f/5.6 APO270mm f/5.6
180mm f/2 APO250mm f/2.8 APO360mm f/4 APO360mm f/4
180mm f/2.8 APO250mm f/4 APO360mm f/5.6 APO360mm f/5.6
180mm f/2.8250mm f/4360mm f/5.6360mm f/5.6
180mm f/3.4 APO-360mm f/6.8 APO360mm f/6.8
250mm f/4-500mm f/8500mm f/8
280mm f/2.8 APO400mm f/4 APO560mm f/5.6 APO560mm f/5.6
280mm f/4 APO400mm f/5.6 APO560mm f/8 APO560mm f/8
350mm f/4.8-700mm f/9.6700mm f/9.6
400mm f/2.8 APO560mm f/4 APO800mm f/5.6 APO800mm f/5.6
400mm f/4 APO560mm f/5.6 APO800mm f/8 APO800mm f/8
500mm f/8-1000mm f/161000mm f/16
560mm f/4 APO800mm f/5.6 APO1100mm f/8 APO1100mm f/8
560mm f/5.6 APO800mm f/8 APO1100mm f/11 APO1100mm f/11
800mm f/5.6 APO1100mm f/8 APO1600mm f/11 APO1600mm f/11
800mm f/6.31100mm f/8.81600mm f/12.61600mm f/12.6
35-70mm f/3.5-70-140mm f/770-140mm f/7
35-70mm f/4-70-140mm f/870-140mm f/8
70-180mm f/2.8 APO-140-360mm f/5.6 APO140-360mm f/5.6
80-200mm f/4-160-400mm f/8160-400mm f/8
105-280mm f/4.2150-400mm f/5.9210-560mm f/8.4210-560mm f/8.4
Source: summilux.net.

In addition to lens compatibility, the Leica user also has to be aware of camera-compatibility, as the R-bayonet has undergone several changes over time. The APO-Extender-R 2x is available in both non-ROM (order no. 11262) and ROM (11269) versions, while only a non-ROM version of the 1.4x exists (perhaps because the ROM chip could not be fitted alongside the protruding elements of the converter). Moreover, there are some compatibility issues with Leicaflex cameras, which are detailed in the textbox below.

Leica APO-Extender FAQ

Can the APO-Extender-R 1.4x be used with the Leicaflex cameras?

Mounting the 1.4x Extender on a Leicaflex requires a slight modification of the flange. When the modified extender is on the Leicaflexes, the auto-diaphragm is functional, but metering is stop-down only, not at full aperture.

Can the APO-Extender-R 2x be used with Leicaflex cameras?

No, the ROM version will not fit, because the chip interferes with the Leicaflex mount. Moreover, the non-ROM 2x APO extender has an R-only flange and will not fit any of the Leicaflexes, as the rear of the extender gets into the way of a light baffle at the top of the Leicaflex and SL mirror box. However, the extender's mount can be modified to work on the SL2.

Does the non-APO Extender-R 2x for Leicaflex offer auto-diaphragm?

No, the Extender-R (Leica order number 11237) that is dedicated for use with Leicaflex cameras only offers stop-down metering.

What advantages does the ROM-version of the APO-Extender 2x offer?

The ROM chip on the tele-converter makes it possible to transmit certain lens-specific information to the Leica R8 or R9 cameras. However, the strip of electrical contacts on the Extender-R does not have any benefit if used with a non-ROM lens or with a camera other than the R8 or R9.

For which Leica lenses is the loss of image quality particularly noticeable when an Extender is attached?

Lenses that provide a low-contrast rendering wide open, such as the Summicron 90mm f/2, tend to show a strong degradation of image quality in combination with a tele-converter.

How many copies of the APO-Extenders were produced and sold?

Leica assigned about 3,250 serial numbers to the 1.4x and about 37,000 to the 2x [leica-wiki].

Further Reading

The APO-Extenders are genuine complements for Leica's apochromatically corrected tele-lenses when used on Leica reflex cameras. Moreover, they can be combined with an R-lens and the Leica Ocular-R to form a telescope. In this case, they enhance the reach of the primary lens similar to their effect in photography.