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In theory this question applies to other brands beside Canon, but I'm going by the Canon experience here. Namely:

Why would I want to change a functional focusing screen with another one? And what is a 'super-precision' focusing screen? It's a silly name; it's not like we have imprecision by default. What are we getting, here, and losing (other than cash) by swapping the screens?

I have a recent body (6D), and I read about different focusing screen options (if I recall, three options from the settings). I never hear about these things in reviews, etc. All I know is that the focusing screen is interchangeable.

Do I care? If so, why?

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4 Answers 4

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Actually, the default screen is imprecise. With the advent of autofocus, modern viewfinder screens are designed to be bright even with slow lenses, at the cost of not really showing the difference in focus at fast apertures.

With the "imprecise" screen, it's hard to see the exact, "critical" focus needed for fast lenses. But autofocus doesn't care, so if you're using that, you still get accurate focus and have the advantage of a brighter screen for composition.

This isn't magic or anything; screens designed for manual focus show the difference better because they diffuse the light more, which also means that the brightness is reduced — and so the viewfinder seems dimmer. Since slow kit lenses are the norm, rather than yesteryear's 50mm f/1.4, and since the vast majority of users depend on autofocus, the default has changed.

But a camera with interchangeable screens lets you choose what you want even if your use is different from the modern majority.

Alternate screens may also feature focusing aids like split prisms or microprism regions. And, some have different patterns of grid lines for composition.

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  • \$\begingroup\$ +1 - I ran into this issue myself when trying to use LiveView to do macro photography of some insects. My manual focus shots looked sharp in LiveView but always ended up just a hair out of focus whereas the auto-focus nailed it every time. It was puzzling until I realized the problem was my reliance on the rear panel, not my eyes! \$\endgroup\$
    – Drew
    Feb 17, 2013 at 1:12
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    \$\begingroup\$ @AndrewHeath: I find that hard to believe. The LiveView image is exactly what the sensor is seeing, so if that image is in focus, your final image will be, too (unless the camera or the subject is moving, of course). \$\endgroup\$
    – Tim Pietzcker
    Feb 17, 2013 at 6:53
  • \$\begingroup\$ Another point to make is that with extremely fast lenses, problems with front- or backfocusing become more apparent, and without a special focus screen you wouldn't notice that when relying on autofocus. I noticed that sometimes with my 50mm f/1.2 and 85mm f/1.2, the image in the viewfinder looked in focus, the final image wasn't (for example the autofocus had locked on the nose instead of the eyes, and there was no way to tell with the standard focusing screen). \$\endgroup\$
    – Tim Pietzcker
    Feb 17, 2013 at 6:56
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    \$\begingroup\$ Focusing with an LCD screen is a different issue, but Andrew is right in that it can have similar problems due to resolution. Most newer cameras work around this by allowing one to zoom in (often significantly) to focus and with features like "focus peaking", which effectively show you the contrast-detection visually. \$\endgroup\$
    – mattdm
    Feb 17, 2013 at 13:30
  • \$\begingroup\$ @Tim: The LiveView image is not exactly what the sensor is seeing. The sensor has a 20.2MP resolution. The screen on the back only has 1MP resolution. There is a lot of interpolating going on between the two. \$\endgroup\$
    – Michael C
    Feb 18, 2013 at 1:55
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I extremely recommend the grid focusing screen. EG-D I think it is.

I cannot live without a grid focusing screen. http://www.bhphotovideo.com/c/product/590409-REG/Canon_3356B001_Eg_D_Precision_Matte_Focusing.html

Having those lines in my view finder means I can arrange people in a shot better and I can also line up lines in the architecture, etc, and I can also figure out if I'm horizontal or perspective skewed somehow.

I don't care about AF improving focusing screens.

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  • \$\begingroup\$ I was definitely missing the grid lines! Yes, this is a very good point. My 6D doesn't have 'em other than in live view, the 450 did. \$\endgroup\$
    – Emmel
    Feb 17, 2013 at 11:44
  • \$\begingroup\$ Just pay a few more dollars and buy the focus screen for the 6d. That's what I did! In fact, the 6d grid focus screen is the same as the 5d2's one. \$\endgroup\$
    – Peter pete
    Feb 17, 2013 at 12:23
  • \$\begingroup\$ Done. Got it today and it rocks. It'll reduce my need to use the camera borders as my guidelines and have to inevitably fix tilt in Lightroom later. \$\endgroup\$
    – Emmel
    Feb 19, 2013 at 18:43
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You don't care if you're using Auto Focus lenses.

The other options are matte focusing screens to make manual focusing easier.

Why don't DSLRs come equipped with “classic” focusing screens (split prism, etc)?

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  • \$\begingroup\$ I just ordered a new focus screen for my Canon 50D. I have always hated the standard screen, its impossible for me to use to manually focus. I much prefer manual focus. I followed the links in this posing and found a Taiwan firm that still offers a nice split prism for the 50D. Great news. \$\endgroup\$
    – Pat Farrell
    Feb 17, 2013 at 16:09
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Another thing you could do, if you're having trouble focussing is to use Magic lantern (if supported by your camera) and do it's 'Focus peaking' thingo on Live view.

It'll draw red or green dots on the screen to indicate where exactly the focus is.

I love it! I can't wait till it gets released for the 6d one day. Currently I use it on my old 50d.

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