beginner here. Would you use manual focus in this situation?
To answer the direct question: if I were using a lens and body combination which didn't support autofocus, then I'd use manual focus as that's the only option.
However, note that:
- Using an FX lens on a DX body doesn't affect whether it can autofocus or not.
- There aren't many modern lenses which don't support autofocus full stop - the only Nikon lenses are the PC (tilt-shift) lenses, although there are a wider range of manual focus third party lenses.
- Lenses designated AF (as opposed to AF-S or AF-P) do not have an autofocus motor in the body but can still autofocus on a body with an autofocus motor built in (anything other than the the D3xxx or D5xxx series).
- Lenses designated AF-S or AF-P can autofocus on any body, even those without an autofocus motor built in.
Yes, it is possible to use a Nikon lens without an autofocus motor in the lens with a Nikon body without an autofocus motor in the body. In fact, prior to the later half of the 1980s that is the way every Nikon SLR and lens was used.
Of course, since the combination will not be able to autofocus, you'll need to focus the lens manually.
Some caveats to consider when using manual focus with digital cameras designed to be primarily used with autofocus:
- Viewfinders. Back in the pre-autofocus era the viewfinders of even the most inexpensive SLR bodies were larger and brighter than the viewfinders of most DSLRS. Following the advent of AF, all but some of the most expensive professional bodies tend to have smaller and dimmer viewfinders.
- Focusing aids. Camera's in the pre-autofocus era have some or all of a variety of focusing aids to help the photographer manually focus the lens. These are rarely, if ever, included in modern cameras intended to be used with autofocus.
- Focusing mechanisms. Most older manual focus lenses have focus rings with a much longer 'throw'. To move the focus point of the lens the same amount requires a larger movement of the focusing ring. This allowed more precise manual focus than with most of our modern AF lenses that have a shorter 'throw' so that even the tiniest of movements moves the focus point a greater distance.
- Expectations. Nailing focus when using a 35mm SLR in the pre-autofocus days was usually not as critical as it now is. Viewing sizes for prints from 35mm film rarely exceeded 8x10 inches. The vast majority of 35mm negatives were never printed larger than 4x6 inches. That's a far cry from the current environment in which we look critically at 50MP images zoomed in to 100% on large monitors. Even a 24MP image file viewed at 100% on a 23-24" HD (1920x1080) monitor is like looking at a piece of a 60x40 inch print! For larger intended viewing sizes, particularly in a professional environment, medium and large format photography was the norm.
Some of the greatest photos of the first half of the 20th century were taken with cameras that not only had no autofocus, but had no through the lens viewfinder either! Focusing was done by careful calculation or measurement of the subject distance and using a focusing scale on the lens, along with selecting an aperture that would give enough depth of field to compensate for any focusing errors. Framing was done based on the photographer's experience and knowledge of the angle of view provided for the particular lens and film size being used.