Sigma 70mm f/2.8 EX DG Macro PAF - Objetivo para Pentax (distancia focal fija 70mm, apertura f/2.8 f stop), negro
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Descripción del producto
Color del producto: Negro
Componente para: SLR
Distancia más cercana de enfoque: 0,25m
Diámetro: 7,6 cm
Estructura de lente (elementos/grupos): 10/9
Longitud: 9,5 cm
Número de hojas de diafragma: 9
Productos compatibles: Pentax
Tamaño de filtro: 6,2 cm
Tipo de lente: Macro
Ángulo de visión diagonal (max): 43,3°
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In a nutshell, this lens is fantastic. It is very sharp corner-to-corner on my Nikon D300. It is sharp wide open at f/2.8 and stays sharp up until about f/11, where it starts to soften just a bit. Lens construction is very sturdy and typical of the top-end sigma primes. Autofocus speed is adequate but not as fast as the best Nikon lenses. It also makes a little more noise when focusing. Manual focusing is excellent with a very smooth and precise feel. I really like this lens and it may be one of the sharpest prime lenses on the market. I highly recommend it.
At this price, it is a great lens to have in your bag.
And HUNK it is. Heavy, big. Be prepared for this. Use a can of peas to get the idea. This isn't a complaint; on my Pentax K10D, it balances well and is a pleasure to hold. But it will start weighing you down after time around the neck.
My negative comments: The lens hood should be sized tighter so that it stays in place when reversed and you place it in a bag. The Sigma 'EX' crinkle finish is fine but not my favorite. The supplied case is bigger than it needs to be and yet doesn't provide much padding.
My most used lens. I didn't know that 70mm on an APS-C sensor (105mm equivalence for 35mm) would be such a nice focal length but it has become my new 'standard' lens.
Focus is slow compared to AF-S lenses, but only because there's such a huge focal range. This lens does seem hunt a lot on my D90, even in bright light. It'll often have to run the focus across the entire range to get a lock, and that's a pain. However, flipping the focus limiter switch solves it and makes it focus just as fast as my other non AF-S lenses. So that's ok. And for macro shots I'd usually be focusing manually anyway, so it's not a big deal. But it's just not quite as quick as my AF-S lenses.
I also don't like the fact that the lens cap won't snap on when the sunshade is screwed on. Makes it a bit of a pain when you're out and about and want to cap the lens, as you've got to unscrew the shade (and put it somewhere - it doesn't reverse) to put the cap on. A pain compared to Nikkor shades that allow the cap while they're installed, even while reversed.
But there is one major negative that none of the other reviews have touched upon. And it's nearly a deal-breaker for me. This is NOT a true f2.8 fixed lens. It is from 10ft to infinity, but below that the max aperture grows as the subject distance decreases. At 1:1 magnification, 3-4 inches away, maximum aperture is f4.8. This is not really what I had in mind when I bought this lens, and I may return it because it's not going to work as well as I had hoped. I bought an f2.8 lens expecting a constant aperture. I was wrong. I actually think it's a bit of deceptive advertising on the part of Sigma. Since it's primary purpose is to be a Macro lens, they should be clear that it's an f2.8 lens only at decidedly non-macro focal ranges. This is really an f4.8 Macro lens, which isn't so great. So just be advised before you purchase this lens.
Apparently, a variable aperture at decreasing macro distances is common to many macro lenses, including Nikon's own 60mm f2.8 and 105mm f2.8 macro lenses. So I can't pick on Sigma too much for this. I'm new to the world of dedicated macro lenses, and I didn't know this 'feature' was just the way these lenses worked. Taking this into consideration, the 70mm Sigma is perhaps more deserving of four (4) stars, rather than three. I'd edit my star rating but I can't.
This also makes me reevaluate my comments about potentially returning this Sigma. I was strongly considering returning the Sigma and picking up the 60mm f2.8 Nikkor Macro instead. I had assumed that the Nikkors would be truly constant f2.8 lenses. I would have been wrong! Since the Nikkor's do this variable aperture thing too, I'm thinking I'll just keep the Sigma - as other than this aperture thing, it's a great lens. Lesson learned! :-)
The detail in macro-closeups is truly remarkable!