[Elliot]

I sold off all my Pentax equipment (save a M200 lens) very recently and missed Pentax almost immediately. So I just purchased a K-S2 and 18-135 kit. I like the lighter camera, and think it will work well. I now need to rebuild my favorite lenses.

To keep costs down, I ordered a 55-300 lens for the telephoto (just $266 new), but then saw the Sigma 18-300 Contemporary lens, and wondered if anyone could offer a comparison. I wish the 55-300 had a DC drive, but appreciate its quality for an inexpensive lens, WR, and quick shift focus. Does anyone have experience with both, as I would rather carry around one lens for most purposes than two?

[boriscleto]

There are tradeoffs with a superzoom like the Sigma. It is F6.3 at the long end, vs F5.8. It is not WR. I haven't seen many sample shots from the Sigma, but those I have seen wouldn't make me want the lens over a Pentax kit. In fact, I wish I still had my 55-300 for time I don't want to lug around the lil'Bigma.

[UncleVanya]

All that I have seen would make me buy the two pentax lenses over the sigma

[Elliot]

It sounds like the two Pentax route is going to be the way to go. I will keep an eye out for the 70 f/2.4 next, as I really like that lens. I sold a really nice used copy.

Now, to the Rosewood Crawfish Festival!

[C_Jones]

I have had a Pentax 55-300 and had a Sigma 18-300. The Sigma takes nice images at all lengths and so did my 55-300. The Sigmva has the wide angle advantage and had a silent focus. The 55-300 AF was not silent. That was one of the things I wanted was silent AF. Part of the Sigma lens outer barrel moves sometimes when the AF is utilized, whereas the Pentax does not. The Sigma also does not have WR. I ended up returning the Sigma due to its outer barrel movement during AF, but other than that it is a really nice lens that provides a large range, nice images and silent AF. I now have the Pentax 16-85 and Sigma 150-500 DG OS.

[interested_observer]

There is a rule of thumb about focal length ranges for zooms. The 4x rule (it's really a suggestion as opposed to a hard fast rule) - the ratio of the lower end to the upper end. So 300/18 = ~16 (a zoom factor of 16x - which is a real stretch) The reason for the 4x figure is that for most lenses, the optical design is reasonable, with few compromises. Going for wider focal length ranges, the compromises tend to creep in to the design, and image quality suffers.

Wide angle lenses tend to go with a factor of 2x. Look at the wide angle lenses that do really well, 8-16, 10-20, 12-24, 14-24, 15-30, etc.

Now, there are always exceptions. Sigma's Big Ma is 50-500 (so 10x). On this lens, things just aligned and worked out for Sigma. There is also the DA 18-135 (7.5x), that I think that has worked out very well.

For the superzooms - which are nice single lens solutions, which reduces the need for lens changes, you are trading optical compromises for convince.

[jddwoods]

I just bought a DA 55 - 300 HD WR 6 months ago. Its one big drawback is noisy autofocus. As long as you don't get the DA-L version, you can mitigate some of the noise by using quick shift to prefocus and let the screwdrive autofocus complete the fine focus. The noise is not too bad this way. I was considering the Sigma to get the quieter autofocus but went with the Pentax for its significant advantages: Weather resistance, faster aperture, better build quality, and lower cost. Since I have some limiteds I do not need the wide angle capability. As to which lens is sharper I cannot tell you since I have no experience with the Sigma but the Pentax is surprisingly sharp for zoom in good lighting and relatively compact with no zoom creep.