Originally posted by WhimsicalV I need one that will go relatively wide (at least 18mm) and zoom in relatively far (at least 100 preferable). I am willing to sacrifice the zoom in the case of the ones that have the f/4 because low light shooting is common for me.
Every lens involves a compromise. You have to choose how much priority you give to low cost, light weight, bulk, fast aperture, range of focal lengths, general image quality, sharpness in the corners, weather-resistance, flare resistance, autofocus, and a host of other things.
As I understand it, you are saying that you would like something covering 18mm or wider to 100mm or longer, but you would be willing to compromise on the telephoto reach in favour of a faster aperture. Seems to me that if low light photography without flash is a priority, it probably means one of the f2.8 zooms, like the DA*16-50, Tamron 17-50 or Sigma 17-50, because f4 won't be fast enough (at least without raising the ISO too much). You might also want the f2.8 for subject separation. If you need more reach, you might also need to get a longer f2.8 zoom, like the DA*50-135, or one of the 70-200 f2.8 lenses, as a companion to the xx-50.