Tamron 55BB (500mm f8 catadioptric)

I pulled out a catadioptric lens I haven’t used for an age tonight. It is a Tamron 500mm SP mirror lens, with a fixed aperture of f8. These lenses carry the SP label, and were made up until about 2005. The point of this post is to show you how good this lens actually is. Most people turn up their noses at cats, as (probably quite rightly) they are regarded as soft, of low contrast, and generally inferior as a breed. However, the Tamron 55BB is of a different class. As I just can’t afford the wonga for a fast 500 mm L lens from Canon, this one will do me instead, and here’s why. The 55BB has silver mirror coatings, not the usual aluminium, and the coatings are on the back surface of the glass elements – Tamron used the glass carrying the coatings as a  corrective optical element. This is known as a “Mangin” mirror design. Just about everyone else uses front surface mirrors, with less optical correction resulting.

The first picture is a shot of the Telstra telecommunications tower on Black Mountain, Canberra, shot from my balcony tonight on a Canon 5D body. The tower is about 3 kilometers away as the crow files, and tonight the air was cool and clear:

Tamron 55BB Cat - Image 1

Looks pretty bland, yes? So, lets cut to the chase and now look at a cropped portion of this image:

Tamron 55BB blog 2

This level of the tower contains a revolving restaurant. Lo and behold, look in the central left window of the restaurant, and you can actually clearly see a person standing up. The Alto restaurant revolves once every 85 minutes, and given this image’s metadata says it was an 8 second exposure, it revolved 0.565 degrees during the exposure – if it had been static, it would be pin sharp! I am seriously impressed – not too bad at 3km distance.

Furthermore, this crop is only about 1% of the area of the original image, showing just what a milestone camera the Canon 5D is, especially in low light. The red dot on the first image isn’t a hot pixel – it is a warning light towards the top of the tower.

So, the wrap up – The Tamron 55BB 500mm f8 is no slouch – plenty of contrast, sharp and capable of making good images.

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