What are the benefits of (expensive brand new) manual focus lenses? Why did you, for example, buy a manual focus Carl Zeiss 85/1.4 rather than an auto-focus Nikon 85/1.4? I'm not concerned with these two lenses in particular. I'm curious about the reasons for buying expensive brand new manual focus lenses in general.
While you can obviously manual focus with an autofocus lens, manual focus lenses are catered towards manual focus users. Some possibilities:
- Longer focus throw (Autofocus lenses typically have short focus throws in order to focus faster.)
- More distance markings or depth of field markings (DoF markings are particularly useful)
- Wider focus ring
- Better feel, such as smoother or more dampened and resistant focus ring.
- Higher quality grip
- Lower weight since there is no AF motor
- No chance of AF motor failing (which could lock up the focus ring on certain lenses)
In addition, it could have been bought for its optical quality, bokeh, size, weight, build, prestige of Zeiss, and other qualities not intrinsic to simply being a manual focus lens.
Because auto-focus doesn't work for what you do, or simply because you don't use it. Then you can get a better quality lens for the same money.
Auto-focus works fine when some part of the image is exactly in focus, but if you for example want to put the focus between two objects so that they end up at the front and back edge of the DOF, auto-focus is useless.
Easy to get one or three batteries sharp with autofocus, but not two:
Simply because usually* you would want to spend as much money as possible on the actual glass.
Usually* you would want the fastest lens, with the best glass. In this case you would lose the auto focus because:
a. the awesome glass you want doesn't come in AF
b. the same awesome lens with AF is just too expensive.
Not all lenses are made equal, you just can't judge a lens solely by it's specifications.
*I say "usually because obviously different people have different priorities.
Don't forget that not all DSLR cameras are easy to use with manual focusing. Semi-professional cameras have dimmer viewfinder making the manual focusing process almost impossible, because you can't be sure you've focused right.