I'm stepping into the abyss of custom Taiwanese focusing screens

Kit Lens Jockey

Nov 12, 2016
My 5D4 spends a lot of its time with f1.4 and faster lenses on it. When I had a 6D, I was always curious about how different focusing screens would work on it. Moving up to the 5D line pretty much killed that idea, until I realized that it is still physically possible to change the screen in them, and focusingscreen.com sells custom replacements to fit them.

Granted I do not do a lot of manual focusing, but its always bugged me that I can't see what kind of DOF I'm going to get through the viewfinder with fast lenses. Granted this is a gamble, but I'm going to give it a shot. I'll try to remember to report back how a precision focusing screen works in a 5D4. Hopefully the metering isn't thrown too far off.


When you have to shoot shoot don't talk
Sep 4, 2013
If you have not bought one yet look up: https://www.focusingscreen.com
They have a lot of options, good guides to replacing the original focus screen with the new one and send you tools with the new screen. I found the original recommendation about them at the Zeiss site.
On my 7D (original model) the focus screen is not defined as "user replaceable" but it took only a few minutes.
Best of luck 8)

Kit Lens Jockey

Nov 12, 2016
Yep, that's where I find it. At first I thought they might be gouging me on an original Canon part, but from what I've read, the screens to fit a 5D4 are actually different.

Like I said, I really just want an accurate view through the finder with fast lenses. Things look a lot different at 1.2 than they do at 2.8.

Mt Spokane Photography

I post too Much on Here!!
Mar 25, 2011
As I understand it, they purchase 1 series focus screens and cut them down to fit various models, so you usually get a Canon screen but one that is not made for your model.

If you are getting a screen with split prism, the center prism is likely too large for a crop camera sensor and will not be optimal. A type S should be fine.

$100 for a screen that cost $10 before milling it down is very lucrative.


Feb 15, 2015
AFAIK, focusingscreen.com is the last remaining source. All others do not make Canon fitting ones any more or have folded outright (Katzeneye, Beatie, Intenscreen etc.). FSC is easy to deal with. 1D screens cost around $35, so for custom work a $100 charge is fine with me. If you are adventurous, you can also get a 1D or 5D2 screen and shave it down with a razor blade yourself. Did that for my prototype 5DsR screen before it was available from FSC.


May 11, 2014
21.1144° S, 55.5325° E
Once upon the time we were discussing this and I learned that the 5D3 is not showing the f/1.4 image on your focusing screen but one stopped down to f/2.8.
Be sure to have a magnetic screwdriver when you start the job.
Also, check the new screen meticulously for scratches before you start the installation.
If not, you have made the scratches in case you received a faulty screen.

Kit Lens Jockey

Nov 12, 2016
Finally got the screen yesterday. It takes them a few days to make it, then obviously the shipping from Taiwan. So, it was about two weeks total from when I ordered it to when it showed up.

My first impressions are very good. I put the screen on and mounted my 50mm 1.2L to it, and what's seen in the viewfinder looks very similar to the actual photos taken at f1.2.

I did some experimenting using the DOF preview button on the camera, and my initial impressions lead me to believe that it changes the maximum aperture you can see through the viewfinder to about f1.4. And by that, I mean that if I look through the viewfinder and stop the lens down, I see pretty much no difference between f1.2 and f1.4, but then as I go to f1.6 and everything beyond, the viewfinder gets darker, and the out of focus areas get sharper. This is contrasted with the original screen that wouldn't show any difference until about f2.8.

As far as metering goes, I'm able to get a good impression of how far this gets thrown off, because I have another 5D4 with the original screen still installed. If I mount my 50 1.2L to both of them, set the shutter speed and aperture the same, point each camera at the same scene, it seems like the metering on the camera with the modified screen is around 1/3 stop off from the camera with the original screen. The camera with the original screen wanted to use ISO 500, whereas with the same settings pointed at the same scene, the camera with the new screen wanted to use ISO 640. What did surprise me is that when I ran the same test with my 11-24, which is an f4 lens, the two cameras still seemed to be only 1/3 stop off from each other. The viewfinder really is not that dark, even with an f4 lens.

As far as the quality of the screen itself, I'm very impressed. It does not look like it was crudely trimmed down from a larger screen. The screen itself comes in the original Canon packaging, with some printed stickers on it to indicate that it's actually made for a 5D IV. I felt a little cheated when I realized that all they're doing is cutting down larger Canon screens, but it's really good work. I don't think I have the tools or the skill to do whatever they do to make these screens. It's pretty much indistinguishable from the factory screen.

I'll try to remember to update this with more impressions once I use the camera with the new screen, but I'm pretty happy so far. It's actually really cool to sit there with an f1.2 lens and manually focus back and forth and watch everything in the foreground and background of the scene go from sharp to way out of focus right there in the viewfinder. It's really nice to be able to see what your photo will actually look like with a fast lens right in the viewfinder.

Kit Lens Jockey

Nov 12, 2016
Ok, something incredibly weird is going on with the camera's metering with this new focusing screen, and I don't understand it at all.

I wanted to do some solid testing to determine what adjustments I should really be making to my standard metering in light of the fact that I have this new screen in there that the camera doesn't know about, and I know that's throwing off the metering. I decided to mount up lenses of various maximum apertures, and do a side by side comparison, on a tripod, of my 5D4 with the modified focusing screen, and with the other 5D4 I've got that has not been modified. What I did is shoot the exact same indoor scene with auto ISO and the same shutter speed and aperture, and checked to see what I had to adjust the exposure compensation by to get the modified camera to match the auto ISO that the un-modified camera was choosing.

I expected that regardless of the lens, I'd have to set the exposure compensation to underexpose the image a little bit since the camera's metering is reading the light through a focusing screen that generally makes things darker in the viewfinder. Here's what I found, based on the lens...

50mm f1.2L - Modified camera requires -1/3 stop exposure compensation to match the unmodified camera

24-70mm f2.8L II - Modified camera requires -2/3 stop exposure compensation to match the unmodified camera

11-24mm f4L - Modified camera requires +1/3 stop exposure compensation to match the unmodified camera

Canon 2x Extender III with 70-200mm f2.8L (basically an f5.6 lens) - Modified camera requires +1/3 stop exposure compensation to match the unmodified camera

I'm so perplexed as to why the exposure compensation needed to get a "proper" exposure changes like this as I go to using darker lenses. It makes sense that the f1.2 and f2.8 would need a little negative compensation since the modified screen makes the viewfinder darker, and therefore the camera would normally be over-compensating and over-brightening the photo. But why on earth does the metering then go the other way when I mount darker lenses to it? The viewfinder is even darker with those lenses, and yet the exposure compensation must now be set to positive to get the proper exposure?? Makes no sense to me. Clearly I don't fully understand what's happening in regard to the relationship between the focusing screen and metering in the camera.