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Archive 2010 · MF Screen Calibration

jotdeh
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p.2 #1 · p.2 #1 · MF Screen Calibration

Mark Zwiesler wrote:
I'm really surprised that so may people were able to manually focus with their cameras without having to re-shim the focus screen.

Yeah, I'm quite surprised, too! Also by the number of people who just "feel" that their screen is calibrated correctly. I would challenge those to focus on their TFT screen manually, take a photo and then focus one using live view, to compare. That was enough to convince me I will have to calibrate mine... But to me it seemed like major hassle, especially since I would have to get the shims from Canon first. But I have to do it!

May 23, 2010 at 10:26 PM

jotdeh
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p.2 #2 · p.2 #2 · MF Screen Calibration

So here are the graphs again.


	http://farm5.static.flickr.com/4036/4635068394_2c9a2970a5_o.jpg

May 24, 2010 at 02:43 AM

Mark Zwiesler
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p.2 #3 · p.2 #3 · MF Screen Calibration

Johann;
Wish I could say I understand what those charts are saying.

I'm not sure what body you want to calibrate, but I still have the part numbers for both the 5D and the 5D2. The washers are inexpensive, I got a complete set for the 5D for about $22 with shipping. Canon has a different set of part numbers for the 5D2, however, I used washers for the 5D on my 5D2 without any problem, they fit fine.

Mark

May 24, 2010 at 09:14 AM

siriusdogstar
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p.2 #4 · p.2 #4 · MF Screen Calibration

Mark Zwiesler wrote:
Johann;
Wish I could say I understand what those charts are saying.

May 24, 2010 at 11:55 AM

jotdeh
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p.2 #5 · p.2 #5 · MF Screen Calibration

I ordered a set of washers for the 5DII today from the Service Centre. They didn't require the part numbers, only some explaining on the phone ("No, I already have a focussing screen. I want the washers!"). It's gonna take two weeks before they arrive...

There was a thread some months back with the 5D PNs, but maybe you can post here both for 5D and 5DII as reference...

As for the charts, I was going to modify this drawing, but no time now...
Wikipedia SLR Drawing

Basically if in my charts the focussing screen is "behind the film plane" it would be closer to the prism. This results in you pulling the lens closer in to the camera. On the focussing screen the image is in perfect focus, but for the film (sensor) the point of focus will lie further away (towards infinity). So there's your back focussing.

From the charts: if the screen is 0.2mm closer to the prism than it should be, and you focus a 35mm lens at a distance of 1.8m (1:50 magnification), the image on the film will be in focus about 0.7m further away, at 2.5m.

May 24, 2010 at 12:03 PM

wolfloid
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p.2 #6 · p.2 #6 · MF Screen Calibration

I understand the act of putting shims under the screen to compensate for front focusing, but how can you compensate for back focusing by lowering the screen? Or, to put it another way, how can you take shims out when there are none there?

Also, what do these shims look like, and how stable/secure are they?

May 24, 2010 at 12:52 PM

Cableaddict
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p.2 #7 · p.2 #7 · MF Screen Calibration

jotdeh wrote:
. If you choose Option 4 or 5, please share how you performed the calibration.

Mine was #4, so no calibration.

I had recently had my 5D at the NJ service center, and they shimmed the stock screen for me. (it was a hair off) I ran some tests to check it (the classic yard stick & batteries tests)

I then received / installed a Bill Maxwell brightened Ees, ran the same tests, and it was dead-on.

I was REALLY not looking forward to shimming, so whew....

Edited on May 24, 2010 at 04:01 PM · View previous versions

May 24, 2010 at 03:31 PM

Mark Zwiesler
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p.2 #8 · p.2 #8 · MF Screen Calibration

Here are the part numbers for the washers for the 5D and 5D 2

5D (last 3 digits represent the washer thickness)

CB2-0682-000 003
CB2-0682-000 005
CB2-0682-000 008
CB2-0682-000 010
CB2-0682-000 012
CB2-0682-000 015
CB2-0682-000 018
CB2-0682-000 020
CB2-0682-000 025
CB2-0682-000 030
CB2-0682-000 035
Catalog link

5D2
CB3-4823-000 003
CB3-4823-000 005
CB3-4823-000 008
CB3-4823-000 010
CB3-4823-000 012
CB3-4823-000 015
CB3-4823-000 018
CB3-4823-000 020
CB3-4823-000 025
CB3-4823-000 028
CB3-4823-000 030
Catalog Link

Canon Parts phone number (Jamesburg NJ): 1-866-481-2569

Mark

Edited on May 24, 2010 at 04:02 PM · View previous versions

May 24, 2010 at 03:58 PM

Cableaddict
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p.2 #9 · p.2 #9 · MF Screen Calibration

jotdeh wrote:
The only explanation I can come up with is that they are using different focussing "algorithms". One may always focus coming from infinity and stop as soon as it appears sharp (and maybe always overshoot slightly) while the other comes from the front etc...

There is definitely something that can cause this, as I experience it also: My screen is dead-on, of this I am sure, yet I tend to miss shots an awful lot with f/1.2 & f/1.8 lenses. Two of my photog friends have used my camera, with the same lenses, and nailed 95% of the shots.

Neither of them wear glasses, while I need +2.5 reading glasses. Maybe a diopter adjustment isn't a perfect solution? Perhaps it only brings "one plane" into focus, but messes with depth perception, or .... well, i dunno.

May 24, 2010 at 04:00 PM

siriusdogstar
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p.2 #10 · p.2 #10 · MF Screen Calibration

Thanks Mark for posting the part numbers!

May 24, 2010 at 05:08 PM

rnickl
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p.2 #11 · p.2 #11 · MF Screen Calibration

wolfloid wrote:
I understand the act of putting shims under the screen to compensate for front focusing, but how can you compensate for back focusing by lowering the screen? Or, to put it another way, how can you take shims out when there are none there?

Also, what do these shims look like, and how stable/secure are they?

I had this issue with my D200. No shim would front focus and the thinnest shim would back focus. I ended up using the thinnest shim I had (it got me the closest) and adjusting the mirror stop cam screw.

Going this route may have you adjusting the secondary mirror cam for auto focus also. Mine was close and I only needed to bump the primary mirror a touch, it didn't seem to effect auto focus.

Rick

May 24, 2010 at 05:29 PM

jotdeh
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p.2 #12 · p.2 #12 · MF Screen Calibration

Thanks Mark for the Numbers, and more importantly the parts catalogues - awesome!

wolfloid wrote:
I understand the act of putting shims under the screen to compensate for front focusing, but how can you compensate for back focusing by lowering the screen? Or, to put it another way, how can you take shims out when there are none there?

I would hope that the bodies are manufactured with a target shim thickness of say 0.15mm, and then manufacturing tolerances will cause deviation to either side, i.e. requiring thicker or thinner ones than 0.15mm. So there should always be a shim,only in the rarest of cases is no shim required (or worse, even no shim is "too much shim"). This is speculation, I don't know Canon's actual target dimensions and tolerances!

Cableaddict wrote:
Mine was #4, so no calibration.

I had recently had my 5D at the NJ service center, and they shimmed the stock screen for me. (it was a hair off) I ran some tests to check it (the classic yard stick & batteries tests)

I then received / installed a Bill Maxwell brightened Ees, ran the same tests, and it was dead-on.

I was REALLY not looking forward to shimming, so whew....

Even the focussing screens will be subject to tolerances in manufacture, is how I would explain this, especially if it was only off by "a hair".

Cableaddict wrote:
There is definitely something that can cause this, as I experience it also: My screen is dead-on, of this I am sure, yet I tend to miss shots an awful lot with f/1.2 & f/1.8 lenses. Two of my photog friends have used my camera, with the same lenses, and nailed 95% of the shots.

Neither of them wear glasses, while I need +2.5 reading glasses. Maybe a diopter adjustment isn't a perfect solution? Perhaps it only brings "one plane" into focus, but messes with depth perception, or .... well, i dunno.

Wow I'm getting curious as to what the effects at play might be. In the end it might be very simple phenomenon?

May 24, 2010 at 06:03 PM

jotdeh
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p.2 #13 · p.2 #13 · MF Screen Calibration

According to Canon's part diagram for 5DII, a thicker shim will move the screen away from the prism. So if you consistently front focus then you will need a thinner shim than the one installed.

May 24, 2010 at 07:11 PM

hjwhoub
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p.2 #14 · p.2 #14 · MF Screen Calibration

jotdeh wrote:
According to Canon's part diagram for 5DII, a thicker shim will move the screen away from the prism. So if you consistently front focus then you will need a thinner shim than the one installed.
Which is in line with my findings:
hjwhoub wrote:
I focused with a 1.4 50mm Planar c/y lens on a ruler at 70 cm with and without the shim in place and took two pictures. From the two focus points (with shim 2cm front focus without shim 8cm back focus) I calculated that my shim was 20% too thick. I had a .25mm shim which I exchanged for a .20mm shim. Now focus is spot on. I use an EE=S screen for my 5D.

May 25, 2010 at 12:30 PM

lextalionis
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p.2 #15 · p.2 #15 · MF Screen Calibration

Call Canon Internal Parts directly in Chesapeake, VA 9AM EST to 6PM EST at 732-521-7007

There are 11 washers (shims) in total available from .03mm to .30mm. The part numbers are cb3-4823-000-003, 002�030. $15.10 for all 11 plus $6 S&H, VA residents pay sales tax.

My 5DMK2 was way off. It had two washers (thick and thin) and using both, just the thick, or just the thin provide varying degrees of front/back focus. I needed to use the thin one that came with my camera and the 0.06mm shim and I�m pretty spot on now.

-Roy

Edited on Jun 02, 2010 at 08:12 AM · View previous versions

Jun 02, 2010 at 07:39 AM

cogitech
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p.2 #16 · p.2 #16 · MF Screen Calibration

wolfloid wrote:
Or, to put it another way, how can you take shims out when there are none there?

?

Carefully reduce the edges of the screen. This is what I had to do with my E-330, as discussed earlier.

All the shims do is add "thickness" to the edges. If you need to "remove shims that are not there" the answer is quite obvious; remove material from the screen itself.

IMO, this situation should never be necessary. Any screen produced for a particular body should be manufactured in such a way that it will always require a shim of some thickness and should never need to have its edges reduced. Unfortunately, this is not always the case.

Shims are either brass or plastic, and they look like:

(leftmost object)
http://www.camerahacker.com/Tools/Installing_Haoda_Screen_Pieces_Laid_Out.jpg

http://gallery.clubsnap.com/data/500/Shim.jpg

Jun 02, 2010 at 07:48 AM

jotdeh
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p.2 #17 · p.2 #17 · MF Screen Calibration

Man, whoever said changing focussing screen washers / shims was easy - I just ruined my screen and bent one of the washers!

Especially the foam gives me trouble as the shims just hang there and just don't wanna go in or come out...

Any tips?

Jun 15, 2010 at 07:32 AM

cogitech
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p.2 #18 · p.2 #18 · MF Screen Calibration

I guess "easy" is a relative term. What is simple for some may be next to impossible for others.

It takes a bit of fine motor skills (manual dexterity). Any time I have done it (on many different bodies) it is simply a matter of releasing the retaining clip and then tilting the camera so that the clip, screen and shim all flip down onto the mirror in a stack (a slight jiggle may be required). Then simply use some tweezers (preferably plastic or rubber tipped) to remove the shim and slide the next size into place. Finally, tilt the camera back and let gravity push the stack back into position (some nudging with a toothpick or tweezers may be required) and push the clip into place. BTW, all of this is performed with the camera upside-down.

I suggest taking it to a camera shop if you are having too much trouble.

Jun 15, 2010 at 07:42 AM

jotdeh
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p.2 #19 · p.2 #19 · MF Screen Calibration

Well I used to consider myself pretty skilled with these things. Anyway, I shall not be defeated quite that easily, and try again tomorrow... I don't really want to give this work away to anyone, because I want to be absolutely certain that I get the best accuracy, even if it takes me a lot of fiddling, sure it's worth it!

Jun 15, 2010 at 12:44 PM

ersatz
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p.2 #20 · p.2 #20 · MF Screen Calibration

Never had any issues with removing the focusing screen. Just ordered the shims from lextalionis' post. Hopefully they work better than trying to add layers of scotch tape to the focusing screen.

Jun 16, 2010 at 09:31 AM

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