Sigma 17-70mm F2.8-4 Contemporary DC Macro OS HSM Lens for Pentax

Excelente lente, el motor de enfoque es practicamente inaudible, si bien no es un lente macro puro funciona a la perfección en su menor distancia, captura detalles increibles. Muy luminoso

Update 1 (May 7 2013): I ended up returning my D7100 because I didn't really need to upgrade just yet. So now I'm using it on my trusty D90. The lens is still as sharp as ever. Autofocus is still fast. Having OS is a dream indoors. Since my D90 doesn't have spectacular ISO range before noise shows up, it's nice knowing I can go down to 1/40 or 1/30 and the image comes out tack sharp.I also ended up getting another one of these for a friend and his copy is just as sharp.If you're on a crop sensor, don't hesitate into looking at this lens. For 500 bucks, it's a steal. I don't know how Sigma can put such sharp glass, but they've done it.Quick comparison of this lens against the Nikon 17-55mm f/2.8G ED-IF AF-S DX Nikkor Zoom LensBuild: The 17-55 is a tank. Weather proofed, but also very heavy. On the other hand, this Sigma 17-70 contemporary is plastic, but also lighter and more compact. When I had the 17-55, I felt the weight on my arms and neck, but with this 17-70, I don't feel much of it.Focus: The 17-55 is slightly faster. In a side by side comparison, there's not much to say except sometimes the Sigma will hesitate for about 1/4 a second, but the focus is always spot on afterwards.Zoom Ring: The 17-55 is stiff as all hell when you go toward the wide end (~17-20) and the long end (~45-55). This is quite common with the 17-55. The 17-70 however is buttery smooth throughout the zoom range.Sharpness: 17-70 beats the 17-55 hands down. Wide open, I had serious issues with the edges being soft and the corner soft. Even with the Nikon at f/4 throughout the range compared to the sigma 17-70 at f/4, the entire frame is sharper than the 17-55.Bokeh: From what I can see, the 17-70 is creamier. Since bokeh is subjective, people may disagree with me, but I like the smooth transition of the 17-70 more than I do the 17-55.If you're looking into a 17-55, don't get it unless- You want a tank- You want a giant lens with an even bigger lens hood.- You need the constant f/2.8- You need weather proofing.Otherwise, if you want- Lightweight lens for walkaround- Sharp sharp sharp sharp sharp- Optical Stabilization- Don't need a constant f/2.8- Want some decent macroLook into getting the Sigma 17-70.----------ORIGINAL REVIEW FOLLOWS----------I bought my copy of this lens from Adorama since it wasn't Prime available here, but I thought I'd fill people in here.This lens is sharp, sharp, sharp. My copy is pretty good, only requiring a -1 to be sharp, but even at 0 it was still very sharp.I'm using this on a D7100 and it resolves just fine. The edges and corners wide open aren't mushy, but rather sharp enough to tell details of what's there. Mind you, it's not 14-24 corner sharpness, but it fares much better than my previous Nikon 17-55 f/2.8, which had bad blur outside of the center.The minor issue I'm referring to is the preview scrolling bug. Basically, when you use this lens, go into playback, and then zoom, if you try to move the zoom cursor, it won't scroll if you hold it down. You have to press it manually to have it scroll.This small error is fixed by going into live view, then pressing the playback button. Now if you zoom, you should be able to scroll again by holding the directional pad. This has apparently been an error before with the Sigma lenses. Hopefully, the new dock will be able to address this issue in a firmware update. That or Nikon applies a firmware update to the D7100, but I doubt that happening any time soon.Otherwise, I'm pretty surprised at how this 500 dollar lens has superb sharpness and rendition of colors. I haven't had to do any exposure adjustment, the lens was sharp out of the box, and unlike the other reviewer who had mush sides on his copies, mine doesn't seem to exhibit the same issue on my D7100.The best part about this lens is that in the future, when Sigma releases the dock, the software with it actually allows micro focus adjustment at 4 different focal lengths (17, 35, 50, and 70) and also at 4 different focal distances, for a total of 16 different fine tune adjustments!I will continue to update this as I use it more and more, but from the tests I've done at each focal length, it's easy to say that this lens definitely is worth the money paid. If you're on a DX and want a sharp walkaround lens, look no further than this lens.

I've had this lens for about 2 months. I have a Canon Rebel XT with the older 18-55 II non IS lens. It was nearly impossible to get good pictures of my kids unless we were outside in good light. Now, that's not as much of a problem. The wider aperture allows much more light to hit the sensor giving me more keepers. The macro abilities are much better as well. With the 70mm zoom and the close focus distance, I can get great pictures of flowers and such. It's not close enough for shots of insects, but bees and dragonflies will work, if they sit still long enough. Before the 18-55 was a limiting factor in my pictures, now the Rebel is. With the older 8 megapixel sensor, it is easy to get sharp pictures right down to the pixel level. The ability to use faster shutter speeds and the addition of the OS on this lens helps. If you have the newer 18-55 is II lens, I don't know how much of an upgrade this is. But for someone like me that is still living in the dark ages of dslr photography (and will be for a while) this is a worthy upgrade. I'm not getting great vibrant colors with it, but I never did with my 18-55 either. I don't know it it's the camera, lens or just me.Pros:Feels durable/solidOS works well. Took a hand held one second shot while braced. Couldn't blow the picture up, but works for sharing.Zoom and focus rings work smooth.Image quality is great. I've had a lot of positive comments about the pictures I've taken with it.Front element does not turn during focus. Great for polerizers and gradient filters.Much improved auto focus ability over 18-55Wider aperture allows for a brighter viewfinder. Better for composing shots in lower light.Cons:Much heaver then the non IS version of the 18-55. Not sure about the newer ones.Focus ring is right next to the zoom ring, and turns during auto focus. I had to adjust how I hold my camera.No full time focus. I have to switch to manual to adjust focus.AF/Manual focus switch is a little hard to move, could be a good thing, and I may get used to it.Lens cap doesn't snap on tightly, I have to snap it on, then screw it tight.The cons are a bit more nit picky then anything really. For anyone with an older 18-55 looking for an upgrade, this is a great choice. I can't compare this to the 18-55 IS II lens however. There are plenty of reviews comparing to other lenses. For the money, this seems like a good bet.