Q: One more item of interest that you may be able to comment on is multi-coating. I note that some of the more recently produced lenses are multi-coated. Theoretically, these lenses should be better but is there enough of an actual difference to seek them out over the more readily available single coated lenses? Any comment?

A: Multi-coating can make a big difference in a very small number of circumstances.  If you shoot against the light or into the sun a lot, you should go for multi-coating, if it is available for the lens that interests you.  But for most pictures taken by most people, multi-coating won't make any noticeable difference to their images.

In fact, very few shots are taken into the light.  The best shots often have the light source to one side – maybe at 45 degrees to the subject – and up quite a bit, as the sun is throughout the day, which gives some modelling and shape to the objects or people photographed.

If the sun is within the image, you are unlikely to get a good picture, and may of course damage your eye or the shutter (the sun shining through a powerful lens can burn a hole in a shutter if the mirror is up).  If the sun is just outside the image area, but shining on the lens, contrast will be reduced, and multi-coating might help, but a good lens shade or hood will help more.

Multi-coating may be more important with wide-angle lenses, which generally are of a much more complex optical design, with a larger number of elements than standard or telephoto lenses.  However, my single-coated 65mm Flektogon produces images that are not distinguishable from my multi-coated 50mm Flektogon.  I shot with a single-coated 50mm Flektogon for years before getting the multi-coated version, and didn't notice the difference for the type of pictures that I take.

So if there are two lenses, one multi-coated and one single-coated at very similar prices and in similar condition, I suppose one would go for the multi-coated version, which will at least be the newer of the two.  But in most cases a significant price differential is not justified.