Tamron 500mm f/8 SP macro (Adaptall-to-Nikon) Review / Test Report
Lens Reviews - Nikon / Nikkor (APS-C)

Lens kindly provided for testing purposes by Dr. Thomas Rubach!

Introduction

The Tamron 500mm f/8 SP BBAR MC macro is the first mirror lens that found its way to the testing lab. Mirror lenses are rather strange beings. They combine both heaven and hell ... heaven because they offer an extreme reach, compact size & low weight and all that for an affordable price tag - hell because they have no variable aperture, (usually) no AF, they're slow and their bokeh (out-of-focus blur) looks very odd. That's enough to give users a serious headache and consequently they're not overly popular these days. In fact the Sony AF 500mm f/8 is the only mirror lens from a primary manufacturer that is still in production (and it is the only AF mirror lens out there). Naturally you can still find lots of mirror lenses on the used market like the "Russian ton" (MC Rubinar 1000 f/10), the Tokina 500mm f/8 RC and this Tamron 500mm f/8 BBAR.

As mentioned mirror lenses are extremely compact relative to their long focal length. This is achieved by "folding" the optical path using two mirrors - here's a simplified schema of a mirror lens:

From a photographic point of view this approach has advantages and disadvantage. As you may notice there aren't many glass elements involved here. Consequently mirror lenses do not suffer from a significant amount of chromatic aberrations (color shadows at the image borders). On the downside the mirrors eat quite a bit of contrast which is why many mirror lenses have a reputation to produce dull images. The secondary mirror sitting in the middle of the light path causes two more effects - it reduces the amount of light that can enter the lens (which costs about one f-stop) and it "punches a hole" into the aperture shape which is responsible for the dreaded donut-like effect on out-of-focus highlights (see the bokeh chapter).

The build quality of the Tamron is very good. The lens is mostly made of metal and the very broad, rubberized focus ring operates very smooth and very well damped. The Tamron 500mm f/8 has an "adaptall" mount - this is a proprietary mount system by Tamron. Using dedicated adapters you can mount these adaptall lenses to virtually any system out there. However, typical for such adapter solutions there's no electronic coupling. This is not a big deal when it comes to the Nikon Ai-S adapter because the lens simply behaves like a manual focus Nikkor lens and the Tamron has no aperture mechanism nor AF anyway so there isn't too much to set anyway. Used on the Nikon D200 the focus confirmation in the viewfinder remains active giving you a bit of a focus guidance. The D200 had quite some troubles to provide a proper white balance with this lens (probably another side-effect of the mirror design) so you better set the WB manually.

Specifications
Equiv. focal length750 mm (full format equivalent)
Equiv. aperturef/12 (full format equivalent, in terms of depth-of-field)
Optical construction7 elements in 4 groups
Number of aperture blades-
min. focus distance1.7 m (max. magnification ratio 1:3)
Dimensions84 x 92 mm
Weight595 g
Filter size82 mm (non-rotating)
Hood-
Other featuresAdaptall II system (generic mount)




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