800mm f/8 RF

With thanks to Roy Niswanger for his images and feedback on the 800mm f/8 RF


In addition to the more common 500mm and 250mm catadioptric telephoto lenses Minolta also produced lenses of 800mm and 1600mm focal length. These huge lenses are guaranteed to get attention!


Some of the rarest (and most expensive) lenses produced for the Minolta manual focus system were the 800mm f/8 RF and 1600mm f/11 RF lenses. The 800mm was first introduced in 1972, and was originally marked as "80cm". It initially came with 2x, 4x, and 8x ND filters, as well as red, orange and yellow filters, which were attached at the rear of the lens. The lens had a black body, and a weight of 1.8 kg. In October 1973 the lens was updated in line with a rebadging of Minolta's lens line, and became the 800mm f/8 RF Rokkor-X. At this time the filters provided with the lens were reduced to a 4x ND, plus red,orange and yellow.

The lens remained essentially unchanged until June 1981, when it underwent a significant design change. The external case was redesigned with an integrated handle, and the colour went from black to white (as shown in the image above). The lens became slightly heavier, at 1.96kg, and the wide focusing ring was replaced by a thinner ring with a metal stop to enable easier focusing. The lens remained in this form until production ceased.

Unlike normal telephoto lenses, the 800mm uses a catadioptric design to enable the 800mm focal length to be achieved in a smaller package. These lenses are often called 'mirror lenses' because they use mirrors as well as optical elements in their construction, as shown below:

A basic mirror lens design, showing the manner in which the optical path is bent.

Mirror lenses are very common on ebay, and can be quite inexpensive. A quick search reveals Vivitar and Rokinon 800mm mirror lenses for under $200 for various camera bodies. At this price they are quite inexpensive, and a fraction of the price that the Minolta 800mm f/8 RF was when new. So why would the Minolta lens be so much more? Well first of all, like with all things, you get what you pay for. Many of the mirror lenses available on the market and advertised as f/8 have a theoretical aperture of f/8, but a light transmission value that is actually lower than this figure. Additionally, they often exhibit significant light falloff towards the edges, and are generally less than satisfactory optically.

The Minolta lens is in a different class altogether. With a significantly larger design it is a true f/8 lens, with minor light falloff and very good optical performance. Of course, an 800mm lens provides enormous magnification, as shown below.

Austin, Texas skyline from 2.2 miles, seen with a 40mm lens, approximating the natural viewpoint of the human eye.
Minolta 800mm f/8 RF, converted to Canon EOS mount, at 800mm on a full-frame Canon 5D body. Note the lack of pincushion distortion often seen in telephoto lenses.

While cheaper and lighter than a traditional design telephoto lens, the mirror design does have two disadvantages. Firstly, the aperture is fixed at f/8. Given that it cannot be changed, there is no capacity to stop down the lens for greater depth of field if desired (albeit the shooting of large telephotos at longer shutter speeds is problematic in any event). Secondly, the mirror lens design results in the centre of the lens being obscured by the second mirror (as can be seen in the lens design diagram). This can result in out of focus specular highlights forming distinct circles on the image in some circumstances.

If you look at the photo above you can see the 500mm f/8 RF at its best. The location has been chosen to minimise the detail in the background, resulting in an image that is very similar to one achieved with a traditional design lens. The image is sharp and while contrast is slightly lower than one might expect from a modern telephoto lens from one of the major manufacturers, it is still good. Additionally, it is very difficult to handhold a Canon 800mm supertelephoto, while with the Minolta 800mm f/8 RF it is quite possible!

Minolta 800mm f/8 RF on Canon 5D, handheld at approximately 25 yards (full-frame, uncropped).

In this second handheld image the lens has been mounted on a Canon 50D, for an effective focal length of 1280mm. The image shows some blur, but this is attributable to the shutter speed of 1/800s as opposed to any shortcoming in the lens.

Minolta 800mm f/8 RF on Canon 50D, handheld for a focal length of 1280mm, 1/800s f/8 (full-frame, uncropped).

I mentioned previously that the lens design can result in out of focus highlights showing a distinct "ring" shape, resulting in bokeh which can be distracting. The image below shows an example of the out of focus rendition of the lens, and while it isn't too bad, the results can be more noticeable than this if the separation between subject and background is reduced, or if the background includes more specular highlights.

Image showing the less than perfect out-of-focus rendition (or "bokeh") of the lens, which is inherent in the catadioptric design.

The Minolta 800mm f/8 RF was a very expensive lens when available new, and due to rarity, collector demand, and the ease of conversion to the popular canon EOS lens mount I would expect that it will continue to attract a premium. A price in excess of $1000 for a good condition later model (white body) lens would be expected.

The lens comes with a sturdy case, as befits a super-telephoto of this price.

There's no question when you see the lens in the case that you are dealing with an expensive and precise piece of optical equipment!

As was mentioned previously, the lens reviewed in this article has been converted (in a non-destructive manner) to take the Canon EOS lens mount. While this is normally difficult with Minolta lenses (due to the aperture mechanics and the shorter mount to film-plane distance) in this case it is easy as the lens is a fixed aperture. Additionally, given that catadioptric lenses are actually designed to focus past infinity, the problems associated with ensuring exact infinity focus are avoided. Catadioptric lenses are designed this way because in changing temperatures the mirrors can actually fractionally contract or expand, which can minutely affect the focusing. The design also means that these lenses do not suffer from the chromatic abberation that often affects longer telephoto lenses.

The Minolta 800mm f/8 RF mounted on a Canon 5D Mark II. Canon 17-40mm f/4 EF L provided for size reference.

Until you see just how small the Minolta 800mm f/8 RF is when mounted on a camera it is difficult to understand just how different it is to a lens with a traditional design. At 1.96kg and only 16.5 cm in length it is a midget compared to say the Canon 800mm f/5.6 which while only one stop faster, weighs 4.5kg and is 46cm in length. This does mean that for surveillance work, or even for travel where a long lens was required it would be a great choice.

Canon 5D Mark II with Minolta 800mm f/8 RF plus Tokina RMC 2x teleconverter for an effective focal length of 1600mm (uncropped full frame)

It is easy for some photographers to dismiss the mirror lenses manufactured by Minolta as unacceptable due to the bokeh issue discussed above. However this conclusion can be premature. The 800mm f/8 is capable of taking great photos, the photographer simply has to use it in circumstances where the disadvantages inherent in its space and weight saving design are minimised.

That said, when compared to a quality telephoto lens of traditional design, the 800mm RF f/8 falls short. A modern telephoto will generally show higher contrast and sharpness, and many feature additional benefits such as image stabilisation etc. that improve their useability in lower light. That said, these options are heavy, bulky, and considerably more expensive than the Minolta. Overall, if you require a long lens that is hand-holdable, you can't go past the 800mm f/8 RF.

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