Originally posted by VE2CJW Has anyone ever compared the Pentax 55-300 to a Sigma 120-400mm? Since the Sigma is a lot more expensive, is it much better than the Pentax as to sharpness? Sharpness is what I am looking for but I simply can't buy a Pentax DA* lens, too expensive for an old retired geek like myself. I could get a Sigma 120-400mm lens for around $800. used around here and also a Sigma 150-500 for the same price. Of course, I would prefer having a 150-500mm lens but it has to be shrarper than my Pentax 55 to 300mm lens.
Can't comment on the 120-400mm but did have a 150-500mm and was never real impressed. Up close and filling the frame usually was decent, but anything far away was a crap shoot. Honestly I would look for a FA or a F* 300mm lens for around the price of the 150-500 and crop.