Summary: It's not a great lens but for a great 1000mm lens you have to pay $12,000. For the price it's great. Construction is fine, not too heavy, it's completely manual in operation and the optical quality although a little milky it's a lot better than what I expected for the price. I use a lens like this 5% of the time so I'm not going to spend a lot of money on it. I am completely satisfied and actually surprised as it is better than what I expected.
Summary: The lens by itself is quit sharp actually, although you need to work hard to get the manual lens to focus right. It's quite frustrating though to focus with the double zoom adapter and it doesn't give great results, so you really need to struggle to have a focus.
Summary: This lens is awesome! It of course, needs a tripod to function properly, but this is as expected with a mirror 500mm lens. I have taken and continue to take, absolutely awesome photos of the moon and landscape with this lens. It could not be obtained better even at 400 dollars, I'm sure.
Summary: The lens itself is amazing is Ooms out really really really really far and it looks awesome the only thing is you probably want to take your photos into light room or Photoshop and up the contrast and saturation the colors with this Lens are pretty weak so you'd want to turn them up in editing mode
Summary: I bought this lens to put on my backup camera (dslr). I now sit on the back porch and can take pics of the wildlife from a bench. I put a monopod on the camera because it is cumbersome but with a 2X converter it is great for long shots.
Summary: Fun to play with. Take some getting used to since this is old school manual all the way. Stick on a strong tripod with remote shutter release and be patient with focusing. This will take some time (and luck) to get just right. No electronics in this. Set camera on manual and no lens modes. On a Lumix G5 and using the extender this will reach out to 2000mm. This is in no way a $20,000 lens and has the expected visual quirks.
Summary: I just got this lens last week, for the money, or even at twice the cost you could not find a better 500mm lens (1000MM W/2x adapter). Very good quality mechanically. I'm using it on a Canon EOS T3, and the photos are very sharp with good color and almost zero chromatic aberration, even when using the 2x adapter at a 1000 MM.
Summary: I have had this lens for a couple of days now and I like it a lot. Very smooth operation and build quality at a great price. If you use this in low light conditions you will need a tripod. The lens has no auto-focus or image stabilization, of course at this price I can't image anyone would expect it to. On a sunny day with a quick exposer you can ditch the tripod if you are quick at adjusting your focus.
Summary: I purchased this lens mainly for birding. It's built very well and I love the fast 6.3 focal ratio. The color and contrast is excellent. I've also used it for astrophotography with good results; very similar to an APO lens. It can be hand-held but you need a fast ISO and shutter speed. The depth of field is razor thin so it's going to be difficult to snap moving targets that are coming or going away from you while keeping them in focus.