dslr - How can I make it easier to focus with my manual f/1.4 lens without making it worse for slower lenses?

I have a Canon 17-40mm f/4 and a Samyang 35mm f/1.4 lens, and a Canon 6D.

The problem is that when I'm trying to focus at f/1.4, the DOF in viewfinder is much wider than on the photo so it's much harder to get the right focus. I thought about buying a focusing screen, but the problem with that is that it darkens the viewfinder a lot with the Canon f/4 lens.

This post has been marked as a duplicate, however, in those posts there is no other solution than Live View. I would like to know how others solve this issue.

Please, what are your solutions besides focusing in Live View? (It's not the most practical or battery saving method.)

Answer

Sounds to me like you've never actually used a different focus screen on your 6D, and you're obsessing about something you've read online.

Just get the super-precision matte screen (Eg-S).

I've adapted manual focus lenses to both my 5DMkII and 50D--both of which have the same interchangeable focus screen feature your 6D does. Swapping the focus screen is relatively quick and painless, as there's a small latched door--unlike the dRebel models, where the screen isn't meant to be changed.

With my 50D, I used a split-circle focus screen (Katzeye) with my manual focus lenses, like my OM-mount 50mm f/1.2. But because the prism collar (NOT the entire screen) blacked out with f/5.6 lenses, whenever I went birding with my 50D and the 400mm f/5.6L USM, I'd swap the screen back to the default matte screen that came with the camera.

However, being lazy (and cheap), when I got the 5DMkII, I decided not to go with another Katzeye, but got the Canon Eg-S "super precision matte" focus screen instead. It works fine at accurately depicting the DoF for f/1.2 wide open, and, while it's slightly darker than the default screen, it still works just fine when I use my 400/5.6 or 24-105 f/4L IS USM. The custom function setting for the focus screen is merely to help adjust the metering. Once I swapped in the Eg-S, I never swapped it out.

To my surprise, the accuracy of manual focus with the super precision matte screen is equivalent to using the split circle screen. Something I would not have expected from my 20+ years shooting a film SLR with a split-circle screen.