Review of Kenko Mirror Lens 400mm F8

Staff Blog

Review of Kenko Mirror Lens 400mm F8

Aug 30, 2015
By Marina Stepanenko, Vido
This kind of lenses has its origin in astronomic telescopes and in 1970-th was very popular due to its compact construction and low price. This time as a object of review we take modern representative of catadioptric (or mirror) system lens - Kenko Mirror Lens 400mm F8. Lets take a close look.1.jpg

If we look inside Kenko Mirror Lens 400mm F8 we may find system of mirrors that helps radically to reduce the size of the lens comparing with classic optical lens: 400mm F8 from Kenko weights approximately 500g, while other 400mm analog with classic optical system will be not less than 1.5 kg and have corresponding size.

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Simple optical construction gives another advantage - low chromatic aberrations. Chromatic aberrations usually appear in tele lenses. To minimize these aberrations venders use lenses made of low dispersion glass, that as a result bumps the costs and the price of the product. Kenko Mirror lens 400mm F8 is compact and lightweight, but the price for these 2 important and attractive features is F8 that is cannot be changed. Light volume can be controlled by 67mm size neutral density filters, ISO or shutter speed. Focusing is realized only in manual mode and that is the standard for mirror lens except discontinued Sony SAL 500 f8 Mirror. Kenko Mirror lens 400mm F8 that adopts T-mount mounting standard can be used with almost every camera using T-mount adapter. In our case lens was tested on Micro Four Thirds mount camera with crop-factor 2x, so the lens had focus length equivalent to 800mm lens on full frame.

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With T-mount for Micro Four Thirds

Ergonomics

Lens has a big wide focusing ring with ridged rubber finish. The rotation of focusing ring is smooth with good resistance and this is very important because due to long focal length focusing is very severe and easy to miss.

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The rotation of focusing ring is about 270 degrees that allows to focus from 115cm getting 1:2.5 magnification scale. Kenko Mirror Lens 400mm F8 may be used as macro lens, but the range of utilization can be limited. Lens body is made from metal and presented in 3 color variations: Black, Titanium and White.

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Example of shot. 3 m distance to the object.

What is the limits of challenge with Kenko Mirror Lens 400mm F8
400mm focal length is great, but 800mm is greater. We shot 2 cuts from one point using usual DSLR lens and Kenko Mirror Lens 400mm F8.
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Usual DSLR lens (effective focal length 85mm)

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Kenko Mirror Lens 400mm F8 (effective focal length 800mm)
Super tele lenses allow in amazing way to compress perspective and make photos unusual.

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Pair of shots at night to check lens magnification.

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Usual DSLR lens (effective focal length 85mm)

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Kenko Mirror Lens 400mm F8 (effective focal length 800mm)

Shooting of heavenly bodies

Kenko Mirror Lens 400mm F8 is interesting from point of shooting the Moon and the Sun (for shooting the Sun very strong dimming effect ND filters must be used). But as for the Moon - no problem - in case of high shutter speed the resolution of details is impressive. Be aware, due to rotation of Earth the Moon can disappear out of the frame.

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In Movie mode with exclusive Micro Four Thirds system cameras function Extended Tele Converter the Moon shifting is more noticeable. At this point equivalent focal length of the lens is 1600mm and vibration feels even when someone walks around the tripod.

Impressions

As a low budget version of super tele lens Kenko Mirror Lens 400mm F8 might be very attractive product. Compact size, lightweight, affordable price for sure are the sales points. The possibility to use lens with any camera mount system and minimum aberrations are features to be highly evaluated. Among points to be improved can be fixed aperture and low shutter speed that is not enough for shooting on hands. To shoot on hands shutter speed must be 1/400 1/800c. In general I would like to recommend Kenko Mirror Lens 400mm F8 to photographers who are looking for super tele lens or some who needs light and compact super tele lenses for traveling.