I just want to emphasize how ridiculous this is. We are resolving wires that are 1/4” in diameter from a 1/4 mile distance. This photo has a bit of JPEGging going on, but in the original I could read a hand-written tag on one of the white boxes.
The first question this brings up is why does anyone need a zoom like this? Bird watching? Airplanes taking off? Checking the gas price at a service station from 3 miles away?
This is where I want to talk about usability. This lens has incredible resolving power, but only under the most ideal conditions! Let’s look at what it takes to get the above image:
To get the wires in focus above, I had to digitally zoom in at 12X using the LCD screen of my camera and manually focus. The autofocus wasn’t accurate enough, and continually missed focus. The focal plan is comparatively small at these lengths.
The tripod I was using was very steady, and I could see shaking from the slightest wind - or even my dog walking within 10ft of the tripod.
The camera had to be on a timer of at least 5 seconds to dampen after hitting the shutter button. One could also use a hand held shutter remote.
The shutter speed has to be fast enough to cut out blur of even the most minor shakes.
The day cannot be too hot (clouds help) because at long distances the effects of hot air rising is enough to completely blur your image.
The next problem I ran into was the changing focal planes at different focal lengths. If you dial in focus perfectly at 500mm then move it to 600mm you will have to re-focus.
Finally, regarding the Sigma MC-11 adapter I would give an overall rating of 8/10. This is a Sigma adapter mounting a Canon lens onto a Sony body. I cannot expect that it will be perfect. At the shorter telephoto end you will get responsive autofocus that works well. Towards the farther end you can’t expect the same. You will need to manually focus it close to the right focal plane, then let the lens take it from there. Without cropping, the focus was pretty good. But once you zoom in and pixel peep you’ll notice that the autofocus never hit spot on. It will always need manual focusing while doing a digital zoom.
If you need absolute resolution power and have a sturdy tripod available then you can take some incredible shots. Just don’t expect to be able to catch that cardinal before it flies away.