Yes, anyone who shoots over water where air and water temperature differ will know exactly what you mean.I think the term "heat haze" is a bit misleading. The actual problem with thermal distortion is temperature gradients. I live on the Oregon coast were it rarely gets hot, but all summer we have temperature inversion (i.e. increasing temperature with increasing altitude). That condition also causes eddy currents of warm and cool air to form lenticular structures in the air. On a casual glance, the air looks perfectly clear, but if you throw an 800mm lens into the mix, the subject will be very distorted. Video really shows up the problem as the subject will wiggle and squirm like a worm, when actually not moving at all. I normally don't save the distorted images, but the below example will give the idea. The first image was shot at 400mm with an R7 and a Tamron 18-400 and the second with an SL2 and an EF800mm f/5.6L with 2x TC. The lenses are in no way comparable, but you can see the the lens is not the limiting factor in the first image. The power wires are wiggly and even the pole is not entirely straight. You can also see the areas of fuzziness, particularly on the dangling arc suppressors. That was a bad air day, but I have seen many worse. The second image shows just how clear the image can be on a good day with a good lens, whereas in the first case, a better lens would have only served to show up the wiggles and fuzz to greater extent. The distortion problem is worst when the air is still and the sun is shining. If there is a breeze blowing, it tends to break up the lenslets that form in the air and clears the image, at least to a degree. For reference, the power pole is about a mile away about 800 ft higher than the camera in an area of often heavy thermal inversion.
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) and all detrimental to long distance photography. Hot below is the more documented situation, but there are also mirages over ice in polar regions and where I am, the worst examples occur during inversion conditions (i.e. cold over the ocean and warmer with increasing altitude). The best conditions for shooting whale migration (later this week, BTW) are cloudy days (which are in the forecast, so maybe a few good shots). I find the air to typically be good right after a rain so long as fog doesn't develop because the rain tends to even out the air temperature.
