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03-13-2018, 06:34 AM   #1
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Focusing Screens, Again

Yep, This again.

I have been looking through the forums and have come across a wealth of information about what the focusing screen replacements effect, however most seem to be sticking with the K3 or S-type screens.

Has anyone tried the Ec-L with Grid focusing screen from focusingscreens.com? How well does it work?

Should I expect the same negative effects of the S-type on metering and P-TTL use when using the Ec-L with Grid type?

It also sounds like there may be a work around for the metering by simply not utilizing spot metering Is this correct or am I misinterpreting the others experiences?

03-13-2018, 09:10 AM - 1 Like   #2
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I haven't used the Ec-L or the S-type specifically, but I have used a number of K3 screens and other screens with a split-prism in the center, like the Ec-L, and I have followed the various threads over the years. Basically, putting anything between the lens and meter other than the screen that the meter was designed for, is going to have some effect on metering.

The Ec-L will have metering issues similar to the K3 or F6 screens. This is because the split prism in the center will partially "black out" in some lighting conditions, and the meter will have a big black blob in the middle of the screen, throwing off the reading in unpredictable ways. The impact may vary depending on the size of the split-prism, the lens, lighting conditions, and the metering mode, but it will happen - it's just the nature of split-prism screens. Split-prisms affect spot metering in particular, as it is looking right at the center of the screen where the blackout will occur..

The S-type screens have a "microlens" surface across the entire screen, which may also affect metering in some conditions, but the effect tends to be more consistent than a screen with a split-prism. If I recall correctly, they tend to darken the overall view slightly. In this case, spot metering doesn't really make a difference.
03-13-2018, 09:53 AM   #3
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QuoteOriginally posted by W.j.christy Quote
It also sounds like there may be a work around for the metering by simply not utilizing spot metering Is this correct or am I misinterpreting the others experiences?
You are correct, though how much depends on camera model and lens mounted. Katz Eye tested their screen (similar to the Nikon K3) on the Pentax K-7 and found metering to be equivalent to the stock screen in matrix and center-weighted modes. Spot metering, however, showed moderate positive bias (required -0.6 EV compensation) for f/2.8 metering aperture and -1.5 and -2.5 EV for f/4 and f/5.6 respectively. (Katz Eye courtesy of the WayBack Machine) It is reasonable to expect similar behavior from other screens having focusing aides at center of field. Their results are somewhat surprising since the Katz Eye (as with the Nikon K3) is very resistant to prism black-out down to almost f/8.

I have a Katz Eye screen and almost never use spot metering because of this behavior. That has not been a huge loss since spot metering is a specialized tool and of limited usefulness unless one is specifically intending to place exposure to a specific value within the frame. FWIW, the incompatibility of center-focus aides and spotmetering is a long-standing issue and explains in part why spotmetering has traditionally been a rare feature on SLR cameras. I will also add that I confirmed meter accuracy with the Katz Eye in other than spot mode on both the K10D and K-3 before putting the screen into regular service.

I did not test P-TTL and can only report that I get generally good results with P-TTL flash in both evaluative and center-weighted modes.


Steve

Last edited by stevebrot; 03-13-2018 at 10:05 AM.
03-13-2018, 11:25 AM - 2 Likes   #4
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I tried and own many focusing screens. In my opinion:

Ec-L is not the best screen for fast lenses. Cross type is a little over done and the focusing area is busy with these lines and is a little distractive. AND, a big issue is, the rest part of the screen does not help focusing. You are limited to put objectives in the middle.

Katz Eye screen has same issue: limited to using the center part.

I will recommend Ec-S or Ee-S, which uses entire screen for focusing. You can put objective in the corner and still focus accurately.

My favorite is Ec-B. It ha single horizontal split image in the center, and the rest part of the screen is also precision matte. I don't have any problem focusing with this screen even using the corners. And it is quite bright. brighter than Ee-S screen. SO basically it combines the split image and precision matte.

both affect metering, so we have to live with it anyway.

03-13-2018, 07:09 PM   #5
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QuoteOriginally posted by grahame Quote
Ec-L is not the best screen for fast lenses. Cross type is a little over done and the focusing area is busy with these lines and is a little distractive.
Agreed. I've never understood the attraction of this form of split. Ditto for the double split type.

QuoteOriginally posted by grahame Quote
Katz Eye screen has same issue: limited to using the center part.
I am not sure what you mean. The matte field on the Katz Eye and Nikon K3*, while not as sensitive to display of out-of-focus at wide apertures as the S-type screens, is equivalent to that used on the Ec-B (Canon's general-purpose split-image)**. I use the matte field of my Katz Eye all the time for off-axis manual focus.


Steve

* The K3 screen was the standard screen for the 2001 Nikon FM3A, widely considered one of the high points of manual focus SLR development.

** Canon has several designations for the matte field used on its screens (Laser-Matte, Bright/New Laser-Matte, Precision Matte, and Super Precision Matte). Which field is used for Ec-A, Ec-B, and Ec-L is not stated in the Canon materials, though all three models date back to the late 1980s and likely use the same matte as the standard screens of the time.

Last edited by stevebrot; 03-13-2018 at 07:19 PM.
03-13-2018, 09:21 PM   #6
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QuoteOriginally posted by stevebrot Quote
Nikon K3*, while not as sensitive to display of out-of-focus at wide apertures as the S-type screens, is equivalent to that used on the Ec-B
I know K3 has very good reputation, and that was one of the first screens I tried.
I have K3 screen installed on K5II, Ec-B on K5, and Ee-S on K30 and k10D. Ec-B is better in only showing the in-focus area "in focus", particularly for fast lens.

Steve, I have an off topic question here, since you know screen very well: Have you heard a focus screen does not work with 1.2 lens? I have two screens, Ee-S and Ec-B, both were very carefully calibrated and shimmed to ensure accurate focus. I have no issue with 35/1.4, 50/1.4 and 85/1.4 lenses. But, my K50/1.2 focuses a lot closer, although in the VF, it looks perfect. If I calibrate the screen using K50 1.2, my other lenses are off. I don't have a 2nd K mount 1.2 lens to test.
My other camera has a cheap eBay split screen does not have this problem. The one I took from Minolta camera also works fine.
Any thoughts?
03-14-2018, 10:35 AM   #7
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QuoteOriginally posted by grahame Quote
But, my K50/1.2 focuses a lot closer, although in the VF, it looks perfect. If I calibrate the screen using K50 1.2, my other lenses are off. I don't have a 2nd K mount 1.2 lens to test.
Tough one. My hunch is that you may be seeing focus shift on stopdown. This may be checked in live view. Given that calibrating with the K 50/1.2 results in everything else being off, I would simply calibrate with the 50/1.4. One thing to remember is that the Ee-S is intended for use with maximum apertures in the range f/1.8 - f/2.8. Calibrating with a faster lens may not buy any advantage and may introduce error.* The split-image on the Ec-B should be good to f/1.2, but if it does not work with the K 50/1.2, it does not work.

At the risk of sending you down a rabbit hole, you might want to do a thorough check of your K 50/1.2 using live view with the intent to detect centering problems and/or focus shift on stop-down at various subject distances.

Good luck.


Steve

* There is previous discussion on this forum regarding use of lenses faster than the known focus sensitivity of the screen. I have not tested the relative precision of f/1.2, f/1.4, and f/1.8 on the "S"-type or even on the Katz Eye, but suspect that there is no precision advantage to calibrating with or using a lens faster than the known performance of the screen being used. (Checking would require statistical evaluation and tools I don't own.)

Last edited by stevebrot; 03-14-2018 at 10:41 AM.
03-14-2018, 01:32 PM   #8
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QuoteOriginally posted by stevebrot Quote
you may be seeing focus shift
Its not focus shift. I focus through viewfinder to confirm, and take photos wide open.

I have something in memory that the distance and the size of rear element play some role, because it decides the angle of the light hitting focusing screen. I believe I read it maybe 20-30 years ago, memory is blurry and I couldn't find anything like this online to confirm. Maybe it says something about AF sensor? AF was new at that time.

Anyway, I did what you suggested, calibrate the screen using 1.4 lenses.

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