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Archive 2010 · Adjusting a 5D mirror box?

Cableaddict
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p.1 #1 · p.1 #1 · Adjusting a 5D mirror box?

After a recent mirror shave, my 5D manual focus went off. (Ughhh)

I was going to order a set of Canon washers, and do the shimming thing, but then I noticed that all of my AF lenses are also slightly off. - not as much as when I manually focus, but still off, and ALL are off in the same "direction."

I assume that the vibration from my Dremel cause the mirror box to move slightly.
So, the obvious thing to do, if possible, is to adjust the mirror box, then do shimming afterwards if needed.

But how? I have read online the 5D has two sets of screws. (possibly hex, possibly square-drive) One set moves the primary mirror, which aligns the AF, and the second set adjusts the secondary mirror, which aligns the VF in the same way shimming does.

OK, so is this true?

Inside my 5D, there are four round plastic tubes that the mirror rests on. Could these possibly have recessed screws in them?

If so, does anyone know which screw does what, and why there are 2 for each adjustment? Are they hex or square-head? (need to know, as I'd have to order L-shaped wrenches.
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Related Question:

With both AF and manual focus, I have to focus slightly FARTHER away than the item is, to get sharp pics. Is this called "front" focus or "back" focus?

Edited on Sep 26, 2010 at 03:16 PM · View previous versions

Sep 18, 2010 at 11:20 PM

phidong
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p.1 #2 · p.1 #2 · Adjusting a 5D mirror box?

http://photography-on-the.net/forum/showthread.php?t=345457

I looked in my 5D2 and I see the screw he adjsuted. I don't know if the 5D is different but from the wrong angle it does look like just tubes but if you look at an angle you'll see a small square or hex hole at the bottom. Not sure if fabricating a tool is the best move though

Sep 18, 2010 at 11:29 PM

Cableaddict
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p.1 #3 · p.1 #3 · Adjusting a 5D mirror box?

phidong.

Are you talking about those four plastic stops?

If so, I am now assuming that the front two adjust the main mirror, since that's what it sits on, and the back two adjust the sub-mirror.

- but I can't figure out what kind of tool goes in there. I'd kill for a dental mirror right about now....

Edited on Sep 25, 2010 at 01:39 PM · View previous versions

Sep 18, 2010 at 11:36 PM

phidong
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p.1 #4 · p.1 #4 · Adjusting a 5D mirror box?

The whole thing looks like the screw to me. If you look into the center of it you'll see the square or hex in the center. 5D might be different though..

Sep 18, 2010 at 11:58 PM

Cableaddict
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p.1 #5 · p.1 #5 · Adjusting a 5D mirror box?

Maybe you're right.

If the screw is de-centered, then turning it would cause the stop to change height. Thus, you are technically adjust the mirror STOPS, not the mirror box.

Surely someone here has done this?

Edited on Sep 25, 2010 at 01:39 PM · View previous versions

Sep 19, 2010 at 12:21 AM

AhamB
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p.1 #6 · p.1 #6 · Adjusting a 5D mirror box?

Cableaddict wrote:
Related Question:

With both AF and manual focus, I have to focus slightly FARTHER away than the item is, to get sharp pics. Is this called "front" focus or "back" focus?

If you have to focus further that means that you normally get focus in front of the subject (between the subject and the camera), which means your body is suffering from front focus. Back focus is when the focus ends up behind the subject.

Sep 19, 2010 at 07:18 AM

ersatz
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p.1 #7 · p.1 #7 · Adjusting a 5D mirror box?

I used a dental mirror to check and it's difficult to say but they look like hex holes. Coincidentally the dental mirror is the perfect height and it allows you keep the mirror propped up. You could use the sensor cleaning method but this exposes the sensor and you do not want to accidentally scratch it. I'd much rather damage the shutter which is a $250 replacement than the sensor or its filter.

Here's a quick pic, not the best but you can vaguely discern the hex pattern.

Sep 19, 2010 at 11:59 AM

Cableaddict
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p.1 #8 · p.1 #8 · Adjusting a 5D mirror box?

Thanks, Aham. So my body is front-focusing.

Ersatz - WOW, nice pic! Indeed, the bolt is off-centered, as I suspected. I must be a metric hex, as my Imperial ones don't fit.

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So why hasn't this been discussed before? An FM search turns up nothing.

Another obvious question: If one can indeed adjust the VF by turning the back set of screws, why does Canon bother making various-thickness washers? Something doesn't seem quite right here ...

Edited on Sep 21, 2010 at 10:55 PM · View previous versions

Sep 19, 2010 at 09:24 PM

thrice
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p.1 #9 · p.1 #9 · Adjusting a 5D mirror box?

Paul,

This is moving the mirror box, not adjusting the overall distance of the plane of focus.

It's a little complication to envision but this moves your mirror, not your sensor or viewfinder. Since the mirror is on a 45 degree angle it's a little complicated as to how it affects the VF image and AF, but suffice to say it is not quite planar.

This is the reason some mirrors will hit a lens while others will not. Many things working together and all need to be properly calibrated. You can probably still pay a Canon service centre to calibrate mirror box and viewfinder for you.

Sep 20, 2010 at 12:12 AM

Cableaddict
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p.1 #10 · p.1 #10 · Adjusting a 5D mirror box?

thrice wrote:
This is moving the mirror box, not adjusting the overall distance of the plane of focus.

Actually, I believe the mirror box does not move (it's glued-in, after all.) The off-center bolts cause the stops to raise & lower as you turn them. Hence, it probably should be called the "Mirror-Stop Adjustment"
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Adjusting the main mirror-stops ( the two in front) should be done (I assume) if all of your AF lenses are off, and in the same direction.

-Or if your AF-assist light is off with all your chipped lenses. see:
http://www.google.com/translate?u=http%3A%2F%2Fwww.astrosurf.org%2Fbuil%2Fautofocus%2Fadjust.htm&langpair=fr

NOTE: This article deals with a camera (30D) that has only ONE adjustment screw, so I assume it's affecting the entire mirror box. That means you'd surely have to re-shim your focus-screen afterward.
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Since the 5D has two sets (I have confirmed this) then the main mirror adjustment should not affect the VF.

Perhaps the 5D's separate sub-mirror adjustment is supposed to be the final VF tweak, after shimming the focus-screen gets you close.

Edited on Sep 20, 2010 at 01:08 AM · View previous versions

Sep 20, 2010 at 12:43 AM

Cableaddict
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p.1 #11 · p.1 #11 · Adjusting a 5D mirror box?

BTW, according to the above article, the proper key for the 30D is a #6 hex. I also says that a 1.3 - 1.4mm hex will probably work, as well as an Imperial wrench. The 10D needs a square-drive. No confirmation yet for the 5D, unless someone here knows, but probably the same.

---------------------------------

Also, according to that article, when adjusting the camera's AF:

To correct for FRONT-FOCUS: Turn the screw clockwise.
(the true focus point will get farther away.)

To correct for BACK-FOCUS: Turn the screw counter-clockwise.
(the true focus point will get farther away.)

Sep 20, 2010 at 12:48 AM

ersatz
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p.1 #12 · p.1 #12 · Adjusting a 5D mirror box?

So, what you're saying is that the bolts/screws are cambered so all you are really doing is moving the mirror up or down and there's no movement in the mirror box itself? The front adjuster will change the angle of the mirror as it rests upon it. The mirror does not sit or contact the rear adjuster so I'm not quite sure what it would adjust. The front screw will adjust the AF and the VF. But if you move the screw clockwise which would increase the angle of the mirror and project the image further back on the AF sensor would it have the opposite effect on the VF? Or does the additional mirror in the VF cause a reverse effect?

My screws are slightly rusted as evidenced by the photo so the 1.3mm seems too big. I think a 1.2mm wrench would work for my camera but alas I don't have one yet. I know that my camera front focuses in the VF now I'll see what turning the screw clockwise accomplishes in both the VF and the AF.

Sep 20, 2010 at 12:42 PM

Cableaddict
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p.1 #13 · p.1 #13 · Adjusting a 5D mirror box?

ersatz wrote:
So, what you're saying is that the bolts/screws are cambered so all you are really doing is moving the mirror up or down and there's no movement in the mirror box itself?

Yes, though it's only a guess until I try it.

This would certainly be the simpler way (cheaper manufacture, lighter camera) and the ONLY way to have a separate adjustment for the sub-mirror.

Edited on Sep 21, 2010 at 10:56 PM · View previous versions

Sep 20, 2010 at 04:35 PM

Cableaddict
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p.1 #14 · p.1 #14 · Adjusting a 5D mirror box?

ersatz wrote:
The mirror does not sit or contact the rear adjuster so I'm not quite sure what it would adjust.

The sub-mirror sits on the rear stops. (At least, on a 5D) Look underneath when you just slightly raise the main mirror, it's obvious.

If I'm understanding this correctly:

The main, semi-silvered mirror sends the image to the AF sensors. It has just enough silver to do this, without being too opaque.

The image also passes THROUGH this main mirror, to the sub-mirror, which is fully silvered. The sub-mirror sends the image back through the main mirror, but at a different angle, so it goes through the focus-screen & on to the viewfinder.

Thus, viewfinder accuracy is dependent upon both the focus-screen shims, and the sub-mirror position.

----------------------------

What's hard to understand is: Why is there a VF (focus screen) adjustment with the washers, and ALSO with stop-screws? Again, maybe the stop-adjust is for final tweaking after getting close with washers.

- But maybe the relationship between the main & sub-mirror is critical, for some other reason? Maybe the angle is important?

- Or maybe it's important to correctly adjust both the distance from focus-screen to mirror, AND focus-screen to pentaprism?

Edited on Sep 21, 2010 at 11:00 PM · View previous versions

Sep 20, 2010 at 05:44 PM

ersatz
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p.1 #15 · p.1 #15 · Adjusting a 5D mirror box?

Cableaddict wrote:
The sub-mirror sits on the rear stops. (At least, on a 5D) Look underneath when you just slightly raise the main mirror, it's obvious. If I'm understanding this correctly:

The main, semi-silvered mirror sends the image to the AF sensors. It has just enough silver to do this, without being too opaque.

The image also passes THROUGH this main mirror, to the sub-mirror, which is fully silvered. The sub-mirror sends the image back through the main mirror, but at a different angle, so it goes through the focus-screen & on to the viewfinder.

Thus, viewfinder accuracy is dependent upon both the focus-screen shims,...Show more →

You're right the sub mirror sits on the rear set of screws. But the sub mirror directs light towards the AF assembly. So, moving the front screw will adjust the mirror and effect the VF. But because the sub mirror is attached it will also move and affect AF accuracy. If they move counter to each other then you would adjust the rear screw as it would only affect the AF.

I've found an image of how light is directed through the VF and the red line would be if you adjusted the mirror up as it would strike lower on the mirror. It will cause backfocus on the AF assembly but would that be front focus in the VF? This is getting confusing and I just need to get the right allen and try it out.

Sep 20, 2010 at 09:52 PM

Cableaddict
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p.1 #16 · p.1 #16 · Adjusting a 5D mirror box?

^ Great stuff!

Makes me wonder why they didn't turn it upside-down, though, (in the original DSLR design with AF) so the fully-silvered mirror went to the VF. That should make the VF brighter.
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Anyway. I am STUNNED that there aren't more posts on this thread.

DOES NO ONE KNOW THE FOLLOWING? :
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1: Is it important to correctly adjust both the distance from focus-screen to mirror-, via washers, AND mirror to pentaprism, via the mirror-stops ?

2: Is the ANGLE of the main mirror important, or if it's simply a final VF tweak for after shimming? - Perhaps the correct angle is important for having both the top & bottom of your VF image in-focus?

3: Is the ANGLE of the sub-mirror important, with the AF distance calibration done electronically. Or, is it completely safe to adjust your AF lights by tweaking the back mirror-stops? - Perhaps the angle is critical if you use all of the AF points?

Edited on Sep 22, 2010 at 04:46 AM · View previous versions

Sep 21, 2010 at 10:46 PM

Cableaddict
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p.1 #17 · p.1 #17 · Adjusting a 5D mirror box?

Interesting thought:

Let's say you never, EVER use AF. - Or can afford to dedicate one camera to be MF only.

With some effort, I bet you could retro-fit a fully-silvered mirror into the main-mirror housing, - Or maybe remove the sub-mirror housing and glue that mirror directly to the main mirror.

I bet that would look nice in the VF.

Sep 21, 2010 at 10:51 PM

melanopsin
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p.1 #18 · p.1 #18 · Adjusting a 5D mirror box?

Cableaddict wrote:
Interesting thought:

Let's say you never, EVER use AF. - Or can afford to dedicate one camera to be MF only.

With some effort, I bet you could retro-fit a fully-silvered mirror into the main-mirror housing, - Or maybe remove the sub-mirror housing and glue that mirror directly to the main mirror.

I bet that would look nice in the VF.

Metering would be affected...

Angle of mirror shifts the viewfinder image up/down, no? Same with angle of AF mirror.

Sep 22, 2010 at 03:08 AM

Cableaddict
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p.1 #19 · p.1 #19 · Adjusting a 5D mirror box?

Oh, right. Metering. (thanks) I do enjoy AV mode.

----------------------------------------

Well, BUMP for the original query.

Fellas?

Sep 23, 2010 at 11:17 PM

ersatz
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p.1 #20 · p.1 #20 · Adjusting a 5D mirror box?

Have you tried to adjust the screws yet? I hope to have some time this weekend as I want to thoroughly test the effects on focus. I'm hoping to get my C/Y 85/1.4 back so I can use it's small DOF to test the accuracy of the VF.

Sep 24, 2010 at 09:25 AM

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