[darkeeboy]

I have been thinking about upgrading my kit lens (18-105vr) on my D90 for something better. Ive heard good things about the Sigma 18-50 F2.8, as well as the Tamron 17-50 2.8. Is it worth the upgrade? I'll be losing some tele-range, but have the 70-300vr to fill in the gap. Is the lens much sharper, thereby worth the investment?

[jonnypb]

have a search on here for the tamron 17-50 2.8 as it's a highly regarded lens. it's the one i'd got for if i were you

[jomike]

Originally Posted by darkeeboy

I have been thinking about upgrading my kit lens (18-105vr) on my D90 for something better. Ive heard good things about the Sigma 18-50 F2.8, as well as the Tamron 17-50 2.8. Is it worth the upgrade? I'll be losing some tele-range, but have the 70-300vr to fill in the gap. Is the lens much sharper, thereby worth the investment?

Is your 18-105VR not sharp? I find mine to be very sharp and most reviews seem to comment on the lens' sharpness, so if your only reason for upgrading is for more sharpness you might be disappointed. My Tamron 90mm macro is sharper than the 18-105VR, but I have to pixel peep to see the difference.

If you are shooting indoor sport in low light or small kids indoors the extra speed of the lenses you mention would count. For more sharpness, go for a prime, the Nikon 50mm f/1.4 springs to mind or the new 35mm f/1.8.

[darkeeboy]

I suppose the kit is sharp, but I also have a 50mm f1.8 and the shots are perfect, but get frustrated with the fixed zoom, so am trying to replicate those shots with a zoom... hence the thought of a f2.8 zoom.

[jomike]

A prime lens will always be sharper than a zoom, and just because a lens has a wider aperture does not necessarily make it sharper.

Kit lenses have a reputation, but Nikon's kit lenses, although not always built to a high standard, have always performed well and the 18-105VR is one of the better ones.

If you are photographing moving subjects in low light without flash (the VR on the 18-105 cancels out its slowness to a degree on stationary subjects), the Tamron 17-50 is probably your best bet. (the Sigma is only f/2.8 at 18mm and stops down as you zoom IIRC), but don't expect a huge jump in sharpness if any.

[dazza74]

If your looking to acheive something similar to what your getting with the 50 1.8 I don't think investing in something like the tamron 17-50 2.8 is such a bad thing, I replaced my Nikon 18-70mm DX lens with one and have never regretted it, having the 2.8 is nice and it's a good range 17-50. One I've taken at 2.8 with it at 44mm :

[darkeeboy]

looks great, I suppose its the greater DOF that Im looking for in the kit lens.

[jomike]

Originally Posted by darkeeboy

looks great, I suppose its the greater DOF that Im looking for in the kit lens.

I think you mean less DOF

Depth Of Field is the area of an image that is in focus. One of the factors that influences DOF is the aperture, a wider aperture (smaller f number) will give you a smaller area of the image in focus with more of the blurred background (the quality of which is called bokeh) which is, I suspect, the effect you are after.

The Tamron 17-50, with its wider aperture, will be better at this than the kit lens.

[darkeeboy]

thats it, forgot the word "control"...after DOF ;-)