Originally uploaded by jstevewhite
So I broke down and bought a Sigma 50-500 zoom lens, known in many circles as "Bigma" because it's a four pound monster of a lens with a vicious zoom and a cult following.
So far it seems the cult following is warranted. I've spent quite a few hours on pixel-peeper.com looking at images from long lenses like this, and the Bigma is head-and-shoulders above other third party offerings, from Sigma and from other vendors. Of course, Pentax doesn't make a lens in this range. The 60-250 f4 is a sweet piece of glass, but not long enough. I have the Tamron 180mm f2.5 and matched 1.4x TC that gets me a ~250mm f4 that's the equal of any zoom, and a 2x TC that makes it a 360mm f5, and still at least comparable to the zoom quality.
I shot fifty or sixty images in as many minutes, of inconsequential stuff like bike horns and swingset swivels, foxtails in the sunlight, and dead leaves. I saw lens shake in many images - 500mm is a LONG lens to stabilize regardless of the system - so I tripodded up, although the image accompanying this post is handheld. Critical focus is important, as the depth of field is very low, even at f11+.
I think this is not a low-light lens for anything that's not stationary. It's a sunlight lens - in the light haze today, I still had to shoot at ISO 800+ to get truly sharp images. No matter - I can't wait to shoot pix of the moon with this lens. It even has an aperture ring, so I can use the non-A teleconverter I have to make it a 1000mm f13 super telephoto! Combining ISO 1600 with some image stacking should net some really detailed images of the craters.
I think I'm going to return the Sigma 1.4x TC, however. It says it's for this lens, but if the zoom is at 50mm, the front element of the TC will impact the rear element of the lens. Not good, IMO. I'll pick up the Pentax 1.7x "Magic TC" instead. It has an autofocus motor inside it and adjusts focus by moving TC elements. This means that even manual focus lenses "snap in" to focus automatically when you get them close.
I can't wait to get out into some real woods and see what kinda bird/animal shots I can come up with using Bigma, though!