Advice about lenses

Started Mar 21, 2012 | Discussions thread
Steve Balcombe
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Re: Advice about lenses
In reply to KentG, Mar 27, 2012

KentG wrote:

I also suggest the Tamron 60/2 as an option. The wide maximum aperture means it has a narrower DOF at the wide setting,

This is the one (and for me, only) strength of this lens, making it an interesting option for those who like narrow DoF portraits but don't want to buy a lens specifically for that purpose. However it is still some way short of the 85/1.8 in its background-blurring capability, and the very cheap 50/1.8 is roughly equal.

F2 being the cropped equivalent of F2.8 whereas an F2.8 lens is equal to F4.

This is an over-generalisation which needs some explanation. Equivalent focal length is a very familiar concept nowadays - a 60 mm lens on a crop camera has the same field of view as a 60 x 1.6 = 96 mm lens on full frame. However to get the same depth of field and background blur you must also increase the f-stop on the crop camera in the same proportion. So a 60 mm f/2 lens on crop is equivalent to a 96 mm f/3.2 on full frame. (We can call that 100 mm f/2.8, that's near enough for most purposes.) What you can't do, though, is cherry-pick the numbers you want to make your point - f/2 on crop is equivalent to f/3.2 on full frame only if you also increase the focal length in the same proportion.

the Tamron is not as sharp as the Canon 60 until around F4 but is suffers from much less vignetting at the wide end (its actually a FF lens).

The Tamron 60 mm macro is NOT a full frame lens. It is a Di II lens - Tamron's name for a reduced image circle lens for crop cameras.

The vignetting on the Canon is quite strong at f/2.8, I agree - but it is easily corrected if you want to. Many people won't bother for portraits.

The Canon has to be set about F4 to equal the Tamron at F2. The Tamron has a little more CA but not a great amount.

This is the other side of the coin - and your language is very biased towards the Tamron, Kent. The Canon in fact has exceptionally low CA.

The one unique feature of the Tamron is it is an internal focusing lens, unlike most macros so the barrel does not extend in macro mode.

It is NOT a unique feature - the Canon is also internal focusing.

While the working distance from the sensor is the same non-extending barrel means that is stays farther away from the subject so in the case of living creatures it disturbs them less.

Neither of these lenses is a great choice for living subjects, but the working distance is approximately the same so they are equally good/bad.

Tamron is a little noiser focusing because it uses a micro-motor instead of USM and has no limiter switch but does allow full time manual override like a Canon.

Yep, but again your language is biased. The Canon 60 mm is a very fast-focusing lens, and I don't just mean by the (often poor) standards of macro lenses. The Ring USM is a real strength of this lens.

Neither has a limiter switch, by the way (just to show I'm not being biased... :-))

Otherwise I would suggest locating an older Tamron 90/2.8 macro, which is a very sharp lens and can be had for less money than $400 if you check around.

The Tamron 90 has a poor AF system, an extending barrel, and a working distance which is no better than the 60's we are discussing. It is a very poor choice, especially considering the Canon 60 mm macro is only $429 at B&H. It is also too long for the majority of portrait use on a crop camera.

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