Tamron SP AF 180mm f/3.5 XR Di LD IF Macro lens
by Paul Fisher

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MECHANICAL PERFORMANCE

The mechanical performance of a lens is just as important as the optical performance.  If the lens feels bad in the hand, or loose & rickety, it will not inspire confidence. If the focus is slack or too slow, shots will be out of focus, or missed altogether. Here, the Tamron 180mm macro is both exceptionally good, and also about average.
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Tamron SP AF 180mm F/3.5 XR Di LD [IF] Macro 1:1 Lens on a Nikon D100

The manual focus on this lens is a delight! It is beautifully smooth and well damped, and the very large focus ring makes handling a pleasure. The focusing ring has a sliding clutch to enable almost instant change from manual to autofocus, just by sliding the ring up or down the lens barrel by a couple of millimeters. There is a firm click stop on the clutch so you won't find yourself accidentally changing modes.

I've had some discussions about the autofocus with the dealer who lent me the review sample, and he obtained a response, direct from Tamron. Tamron comments were basically that researched the product requirements with professional  photographers prior to design. The feedback they had from serious photographers was that AF is rarely used in very close-up photography as time is generally spent focusing manually quite exactly, considering depth of field requirements, hyperfocal distance, etc. They therefore concentrated on optical and build quality and were able to produce an excellent lens at an affordable price. Tamron just received a 4 star rating from German Photo magazine for this product.

This is a specialized lens and not really designed for general purpose fast point and shoot work, fast AF is not important for this type of user. There are many other Tamron lenses designed for this other purpose.   

The focus throw on this lens is very long, 270 degrees from 1:1 to infinity. The majority of this is within the close-up range, allowing very precise focusing close-up. A further effect is that the autofocus is extremely accurate and locks on well, provided the light is adequate. I would like to see a focus range limit switch on the lens, so that if it fails to lock AF focus and starts hunting, the wait is minimized.
  

I found that I used this lens as a manual 99% of the time, just slipping into AF occasionally to "touch up" focus. In this mode of operation, the AF is quite adequate. The focus ring goes into free-wheel during autofocus, which is a great convenience.	..
The Tamron 180 is an internal focusing design, which means that the lens does not "grow" when focusing closer, and the front element does not rotate. These are important issues when shooting at very close quarters, and when using filters.
The tripod collar is a well-designed, removable gadget. The collar grips the lens barrel tightly, allows easy rotation between portrait and landscape positions, and can be removed and replaced in seconds. I think the mounting foot is a little too far forward, so that a camera such as the D100 or heavier is not quite balanced. However this is a very minor gripe. Other reviews have criticized the collar as not being sufficiently rigid. However, I found that it quite solid, fitting the tripod mounting plate well, and gripping the lens barrel snugly. The filter effect control (FEC) works extremely well, and provides the ideal solution when using graduate or polarizing filters with the lens hood in place. It may be important to mention that this lens transmits -and the camera shows- the effective aperture while at the highest magnification, which is not the case with all macro lenses. .