5D2, focusing screens and f/4

I like the concept of focusing screens. With the standard EG-A screen, I simply can't do manual focus through the viewfinder. I would change it, except I don't want to do camera surgery every time I mount my 70-200 f/4. How bad do AF operation and viewfinder brightness really become with one of those screens on f/4 or slower lenses?

Its not a problem, well you notice it in low light.
I noticed it in dim bars and night clubs on my 24-105, but I presume you would using your 70-200 in good light?

Get it, love it.

That's the idea, but I assume one day I'll want to take that one long shot, eat the f/4 and push the ISO. Does the custom screen (KatzEye or Canon) hurt the AF or just dim the viewfinder?
Edit: also, do you feel the impact on metering?

Are you suggesting an "s" screen ie Eg-S?
There is a loss of 1/2 stop at f 2.8, 1 stop at f4 and 1 1/3 stop at f 5.6
It sounds as if you have AF lenses, why are you angsting over MF for all situations? For MF under dim conditions you can always use Live View set to exposure simulation. Tripod users always find that magnified Live View is the best MF approach.

I dunno, sometimes it just seems like it'd be more convenient to be able to use manual focus handheld and reliably rather than plop down a tripod. Plus, I realised that sometimes in very low light, what's keeping from from taking a shot isn't so much the low-light capabilities of my camera (high ISOs, wide glass) but the dodgy AF. I could get a usable shot, except I can't focus properly.

I mean, I've started playing around with my dad's old full-manual camera. It comes with a rangefinder that works not unlike a manual focus screen, and frankly I quite like how that feels. I don't want to give up on AF but sometimes, when it fails, I wouldn't mind a backup solution that doesn't require a 2-3 minute set-up time.

armis wrote in post #14062287
That's the idea, but I assume one day I'll want to take that one long shot, eat the f/4 and push the ISO. Does the custom screen (KatzEye or Canon) hurt the AF or just dim the viewfinder?
Edit: also, do you feel the impact on metering?

I honestly couldn't say I noticed any impact on AF, but saying that I did swap the F/4 for a 1.4 Prime in the end because of the dark viewfinder in low light... i was doing more and more events that I just got fed up.

I used the EG-S not Katzeye, i can't comment on those, you have nothing to lose apart from the cost £25 $30?, if you place you EG-A in the box and keep it clean there's no reason you can't re-use it, I actually replace mine when they get stubborn spots on I've never successfully cleaned one and Im on about my 3rd EG-S in 2 years..

Why not use AF assist from a EX speedlight to help out with the focussing in darker shoots?

The Katzeye and similar screens are more customizable with features. Instead of a screen that loses brightness like the Canon super high precision EG-S, which enhances depth of field rendering with fast lenses to aid manual focus, you could choose to have the third party screen made with a split image and/or microdiaprism focus assist feature. The split image type are most useful with shorter focal lengths and the microdiaprism work best with telephotos.

One downside to the third party screens, Spot Metering is no longer usable. The other metering modes are fine... Only Spot is effected. The split finder and/or microdiaprism cover it almost entirely.

Oh, and the third party screens are a whole lot more expensive than the Canon.

Cleaning those optical plastic screens isn't easy. Best way is to just flood clean them, first with something like Windex (non-ammonia formula), then with distilled water and possibly dilute isopropyl alcohol (70% "rubbing" alcohol is dilute enough) to prevent water spots. Don't wipe, touch or rub them with anything, or they will be damaged and unusable.

armis wrote in post #14062287
Does the custom screen (KatzEye or Canon) hurt the AF or just dim the viewfinder?

Custom screens don't affect AF. Light for AF goes through the reflex mirror and is reflected by another mirror to the AF sensors in the base of the mirror box. The focusing screen isn't in that path.

3rd party screens also darken like the eg-s screens (everything other than the center focusing aids). The split prism and micro prism also darken, but they darken a little weird. Normally it's only half of it that darkens...so you have 1 black half-circle for the split, and a checkboard (a mix of bright and black) for the microprism collar. The outside area also darkens...I think it may be similar to the eg-s screen (not sure how accurate the DOF rendering is though. You may be able to adjust your eye to get it to back to normal, but it's harder to do that the slower the lens and darker the room is.

@ f/4 you may be annoyed because the partial blackout makes it kind of a distraction, and a little hard to see things in the center of the frame unless you're in good light.

The microprism collar is really useful though (and more accurate than the rest of the screen) when you have good light and/or are using fast lenses.

I think next time, I would probably go for the eg-s type screen (and also a camera that allows interchangable focusing screens) just so that there are no "distractions" in the center of my screen.

Oh, also, katzeye and focusingscreen.com don't offer the K-3 type focusing screen for the 5D or 5DmkII. There may be others that offer that specific type though. focusingscreen.com offers focusings screens that are similar to the ones you can get in the 1D series (microprism circle and cross split circles (no microprism collars though)).

Ok so just to make sure I have this right: screens don't interfere with AF at all, screw up spot metering (for 3rd party stuff, not the actual EG-S?) but don't affect the others at all, and of course do wonky stuff to the viewfinder in low light. Do I have a clear understanding of things?

The EG-S doesn't affect spot metering...or any of the metering modes, as long as you change the menu option in your camera.

They don't really do anything wonky in low light though...I may have said something wrong that confused you. Hopefully I can clarify things (without making a mess of it).

The microprisms and split prism only darkens weird (dark bright checkerboard microprism and darkened half split prism) at slower apertures. The slower it is, the more pronounced the effect. And even then, you may be able to reposition your eye so that the effect is minimalized. You can't do that for the rest of the screen (or the eg-s screen) to make it look brighter though.

In low light, it's dark overall, but the microprism and split prism don't darken "weird." Oh, just to clarify, it's not like the precision screen is darker than the stock screen in low light...it's just dark. The precision screen only darkens when using slower apertures.

If you're getting the EG-S screen, you don't need to worry about anything concerning the microprisms, split prism and weird affects slower apertures have on them. Just know that using the EG-S screen with lenses with maximum apertures slower than f/2.8 will cause the viewfinder to appear darker compared to the stock focusing screen.

But, even though it gets "darker", it's really not that bad. I can still see well enough to take a picture manually focusing at ISO 12800 1/25s f/4 (old manual focus lens, so it's stopped down to f/4)...so I don't think you'll have a problem simply looking through the viewfinder at f/4.

I use a 135mm f/3.5 and my 15-85mm @ 85 (f/5.6) in normal light and I don't have any trouble seeing through the viewfinder. Again, because of the slower aperture of these lenses, the microprism collar in particular becomes a little hard to see through, but the rest of the screen (which again, I think, is similar to the eg-s) is perfectly fine.