Focus Question

I photograph a lot of old buildings. (use 18-200 AF Nikon lens) I zoom right out to get the whole building then let the camera autofocus, but when I hold focus and zoom right in, it is out of focus. So I hold focus, then zoom out again. I took the camera and lens for service, but they said it was normal. Doesn't sound normal to me - any ideas?

I think the problem might be that you are holding the focus when you zoom in. Try zooming out, let it autofocus and shoot, then zoom in, let it autofocus and shoot. This should solve your problem as the focus point is different between zoomed out and zoomed in.

Sounds like it could be an af-s vs af-c issue. With af-s the camera will focus once when the shutter is half pressed and with af-c continuously. So if you half press with af-c and zoom in it should refocus as you zoom.

Back Button Focus will give you a hybrid of these two systems.

This sounds normal to me. The reason why is if you've ever done any type of AF tuning on a zoom lens, most times you will get a different value at the telephoto end of the zoom vs. the wide end. Maybe it won't be a huge difference, but it's normal to obtain different values.

If you decide to try AF tuning, my suggestion is to perform it closer to the telephoto end rather than the wider end. That's because your depth of field is shallower on the telephoto end where being in focus is more critical.

Here's a Nikon article explaining the process:

https://www.nikonimgsupport.com/eu/BV_article?articleNo=000006300&configured=1&lang=en_GB

Even though zoom lenses are usually considered "parfocal", it is perfectly normal to have a bit of a focus shift with a change in focal length.

Thanks everyone for that - I was not aware that focus shift whilst zooming was normal. I'm a retired pro wedding photographer (40+ years) and I'm still learning new things. Now I spend my time travelling in the bush, shooting landscapes and old bridges.