This is primarily directed to members that shoot with long fixed lenses.

Yesterday I was out shooting with the 7DII, 600 f4 plus 1.4TC.
(I have just posted a couple of shots under the post title of "Leucistic Sika Deer").
The shots were at approx. Half a mile. Sky overcast. Temperature approx. 12 Degrees Celcius.
I suspect I need to micro adjust this setup but I can't see that it would result in much better images.
My question is:- Is it realistic or not, to expect sharp images at this distance?
Thanks in anticipation.

I would say you have a couple of things working against you. First, and foremost, the distance. That is quite a small subject at that distance. Next, the TC can introduce additional optical issues. It not only multiplies your focal length by 1.4, it also magnifies any optical aberrations by 1.4, as well. I'm not familiar with your camera enough to know if it is an FX or DX format. However, once we get to the projected image size, the number of and size of each photosite on the sensor is going to be a part of the issue as well. I hope this answers some of your questions.
--Bob

I am not entirely sure of the distance... but the image below was done with Canon 500mm IS lens fitted with both Canon 2X II and 1.4X II teleconverters (1400mm effective focal length...image EXIF is incorrect), on an older, 6MP APS-C camera (so no micro adjustment possible and equivalent to 2240mm on full frame). Everything was mounted a stable tripod and in-lens image stabilization was engaged (its the self-cancelling type, on this lens). I don't recall using mirror lockup, but probably not since 1/160 shutter speed isn't prone to mirror slap. Largely un-cropped here, image was done at ISO 200 and was shot RAW. A bit of sharpening plus some boost of contrast and color saturation were needed in post processing:



Image is more an experiment with the stacked teleconverters than a serious shot. It's okay in small size and at Internet resolutions, but not very printable much larger than 5x7".

The problem with super long telephoto work at great distances is that atmospheric conditions come into play... and you can't do much about them. Above was shot shortly after a rain shower when the air was clearer than usual. It was also lightly overcast, with some late afternoon sun peeking through on the right. Cool, too... so there weren't any heat mirage effects. Little or no wind, either. Even a light breeze can have an effect at such distances. I don't recall if I put a sandbag on top of the lens/camera rig... I do that sometimes when using very long telephotos, to help absorb vibrations.

High density sensors such as 7DII are probably more susceptible to camera shake blur, than older low resolution models such as was used above. Canon issued a white paper about this, around the time they introduced the original, 18MP 7D. They recommended a step or two higher shutter speeds to offset the increased possibility of shake blur.... It's probably even more of a consideration with 20MP 7DII and 70D, the various 24MP APS-C models... even the 5Ds models, whose sensors have virtually the same density as 7DII's.

After looking I don't think it bad when you take everything into account. Everyone has pointed out the obvious reasons that it is not a wall hanger but it is a record of what you saw. Think, if that was a shot of "Big Foot" I don't think anyone would complain. I took some shots of wolves working a bison herd from a distance of over 1/2 mile just to record how they did it. I had wind, dust and heat to deal with and there was no way I could shorten the distance between me and the subjects. There is one other thing you could try and that is live view with a cable release and if that isn't any better then you need to move in closer or wait for after a rain and no wind.

On anything other than a cold clear morning the heat waves would kill any kind of shot you took. As a land surveyor we often had to take measurements of 1/2 mile (1/4 section - 40 chains) or 1 mile ( 1 section - 80 chains) to break down section lines. We went out at the crack of dawn to get the shots before the sun came all the way up and caused the churning of the atmosphere. Now we use GPS equipment that doesn't care about optics or atmospheric bending of light and it gets much better results. So the bottom line is, if you want any kind of usable results you need those rare cold clear mornings before the sun has a chance to warm the lower atmosphere.