On focusing screens

Joined
Mar 23, 2020
Messages
16
I have been a manual focus shooter for a good while now (Leica M being my primary system) and I have a Nikon Df on the side. It sees quite little action, for whatever reason.

I don't have many lenses for Df, but I have two screw-drive AF lenses and one pre-Ai lens for it. The pre-Ai 135mm f/2.8 is most definitely the most fun one to shoot! Seems like I need to have some mild and friendly challenge for the shoot to be engaging and fun.

I like the focus dot but I don't like how it's pretty inaccurate with shorter focal lengths (20mm f/1.8 and 55mm f/3.5). The dot is perfect or at least good enough with the 135/2.8. My Df might have a mild issue with the AF module perhaps? Secondly of course the dot is there in the corner so my shooting is not the most fluent it could be.

So we arrive at the question of focusing screens.

I'm looking at these traditional split prism ones like type E, Ec-B in particular, and K3.

There's a lot of information and misinformation on the internet about focusing screens on DSLRs. I assume some bad experiences are because of poor fitting.

There's often talk about lens speeds and whatnot when talking about retrofitted screens. Talking about either Ec-B or K3 screens, what should I expect when using...

* ultrafast primes (f/1.2-1.4)
* fast primes (f/1.8-2.8)
* slow zooms (f/3.5-5.6)

I understand that AF and the DRF dot and metering shouldn't be affected at all from having a new screen installed.

If I am convinced this could breathe new life to my Df usage I'd send my camera for AF calibration and they'd fit the screen before calibrations so that it should be installed tiptop?

And finally, this might sound funny, any thoughts about fitting a split prism focusing screen on another Nikon body such as D750 or D810 instead of Df?
 
Joined
Sep 20, 2009
Messages
17,278
I'm probably not the best person to answer this since I'm not really technical.
I can just share some experiences.

I worked for decades with a Pentax SP500 and the focus screen was a center with micro-prisms, a ring around the center with a different size of micro-prisms and the rest was a matte screen.
This is the best focussing screen I ever used. Almost exclusively with a f/1.4 lens though.
Better than split-image types and better than the rangefinder system. For instance, when you need to focus on some kind of repeating pattern with a rangefinder, it can be difficult to see if you have aligned the parts of the same "cel" of the pattern or not. No such issue here.
No black out either

I had a split focus screen installed on my D700, made by Katz-eye - not in business any more.
I had to adjust this one with a screw that was present in the D700 to fine tune the focussing screen. This is why I'm pretty sure there is no relation between the AF and the focus screen: I had to use the AF to fine tune the focussing screen.
I have no idea if this adjustment system is still present in later digital models. Much easier and more flexible than using shims.
After it was fine tuned, it worked very well.

I have a standard K3 focussing screen in my Fm3A.
I doesn't black out with slower lenses but f/4 is the slowest lens I have.
I read modified K3 screens fo Df are available so, that's what I would look for.
I have no experience with E or Ec-B screens.
 
Joined
Mar 23, 2020
Messages
16
What exactly is this "screen blackout" that I see often talked about? Is there a point in light levels where the microprisms just don't work anymore?

I can ask about the correction screws from the repair if I decide to go for it.
 
Joined
Sep 20, 2009
Messages
17,278
When the widest aperture lets in too little light, the split prims becomes black and therefore of no use anymore.
The K3 from the FM3a is supposed to not have that behaviour.
 
Joined
Jul 8, 2019
Messages
829
Location
SF Bay Area, California, USA
Check the specs.
From what I just saw, the Ec-B screen does not have a split image rangefinder. It is a matt screen.
And the K3 screen does not have autofocus indicators.

Most split image rangefinders and micro grid screens will black out with f/5.6 lenses. And as you get close to f/5.6, you have to center your eye, to prevent a black out. It is not a sudden black out, but a gradual one, as there is less light.
For the film F SLRs, I think Nikon had a split image screen model that would work with slower lenses. I think the prism angle was angled for the slower lenses. But I don't know how well they worked for faster lenses.

I think the AF on a dSLR is done by an AF sensor on the bottom of the mirror box, not in the prism. So the AF should not be affected by the screen change.
BUT, the metering might. IF it is in the prism.

This question makes me wonder WHY they dumbed down the screen on a dSLR, so that it was not as easy to manual focus a lens.
I had thought it was for the AF, but then knowing that the AF module is on the bottom of the mirror box, AF is not the reason.

In the screen of a dSLR, the focus point indicator and grid are as sharp as the focused image. So they must be on the focus plane, which is the screen. If you change the screen, will you lose these? If you cannot see/select the AF point, you don't have AF. Something to research.
The Ec-B has the AF points and I presume can be wired into your Df, but it does not look like the K3 screen has them.

My own screen preference was/is the P/Apollo screen, which I have in my F2.
I first used a microgrid screen and LIKED it better than a split image screen. But then I put the Nikon P screen in. The P screen is similar to the Pentax SP500 screen, with the exception that the split image prisms are at 45 degrees, and there is a cross-hair to help me keep the horizon level. With the angled split image prisms, I don't have to tilt the camera to use the split image rangefinder on a horizontal object. I gradually got to like the combination.
 
Joined
Mar 23, 2020
Messages
16
If you cannot see/select the AF point, you don't have AF. Something to research.
On Nikon Df I only ever use the central focusing point. It's the way that works very well with Leica M and I reckon it should be good enough for lower-resolution Nikon. Df's 3D tracking is not very accurate so I won't miss it either. In this sense it doesn't matter if I lose the grid.

I didn't realize Ec-B was something Nikon also made. Over at focusingscreen.com and elsewhere on the internets people only ever refer to the Canon-made Ec-B that has a split view and it fits Nikon.
 

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