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Continuing from my Focus Screen and Sensor Cleaning article which I had written when I had my EOS 5D, I saw an opportunity to follow it up with a more thorough post when a friend noticed a spot in the viewfinder. Having risked it all before on my EOS 20D, 5D and the 5D MkII I said I would take a look the next time he’s in town. So the day came and I knowing that he’s hands-on enough when it comes to small  PC-related tasks such as handling screw drivers, I threw the ball right back at him and had him tackle the problem himself. It was a great learning experience for him and at the same time allowed me to document the steps we took to complete the job. I’ve divided this post into two practical parts.

Part 1: Removing (or changing) the Focusing Screen

This step guides you to quickly examine if the dust or grime is merely on the Focusing Screen. After removal of the focusing screen and blowing both sides, reinstall the screen to check if dust disappears. If satisfied then Phase 2 isn’t necessary. Follow the same steps if you want to swap out the original focusing screen with a new one such as the Canon EG-D (Grid) Focusing Screen.

Place the camera on a flat surface with the lens mount facing up to avoid dropping the focusing screen. I take the extra step of removing the eyecup too for reason you’ll understand when you are at this stage.
You can actually use your fingernail or a small tool to lift the attachment hoot to release the focusing screen. If you previously bought a replacement focusing screen from Canon, a “Special Tool” is provided (see 2 pictures down). Yep, Canon doesn’t even know what to name it but calls it “Special Tool”
I replaced my 5D Mk II’s focusing screen with an optional Grid screen. In case anyone is interested, the Canon part number is SCREEN-EGD CZ6-C218 3356B001AA as printed on the box. Focusing Screens on the 5D Mk II are slightly larger than that of the 5D so make sure you order the right item.
Gently pull the attachment hook to release the focusing screen holder from the hook. When done right, the screen slightly “pops” out for easy removal.
Using the Canon special tool or tweezer, removing the focusing screen is a no-brainer task. If you’ve bought a kit from Canon the box is where you can temporarily keep the screen should you require to proceed to more advanced stages of cleaning. The focusing screen is extremely sensitive to touch and will smudge very easily.

Instructions on Canon Focusing Screen kit reads … “Never touch the screen with your fingers or hold the screen in your hand. If the screen becomes smudged with a fingerprint or a foreign substance, the smudge will be very difficult to remove. Also be careful not to smudge the mirror or other parts of the camera when changing the focusing screen.”

For the small price you pay for an optional Canon focusing screen the “Special Tool” has its use long after you’ve installed a new screen. The tool clamps the mounting tab of the focusing screen firmly and is ready to be inspection of dust or grime. Warning: DO NOT (I repeat) DO NOT at this stage use a blower on the screen just because there’s dust on it. This clamp is NOT STRONG enough to hold it against “Hurricane Katrina”. You’ve been warned. I will not be held responsible for any stupidity on your part.
Ignore the manufacturer’s instructions for a moment and use some common sense. If you spot dust on the focusing screen, blow it off with a blower (I use a Giottos Rocket). I do not suggest using air from your lungs for this assignment. You do not want to get any moisture onto the delicate screen. Believe me when I say it’s delicate. I have screwed one up before and pretty much lived with my mistake until the camera was sent in for shutter replacement only then I asked for a new screen replacement.

Part 2: Removing the Metal Shims and Superimposed Display Screen
If however after completion of Phase 1 and you still see spots on the viewfinder, proceed as follows:

If the dust spot isn’t removed using the above methods, chances are the spots are on the Superimposed Display ie the clear plastic screen with AF rectangles overlay. You’ll need a set of these mini screwdrivers and you’ll want magnetized ones too for obvious reasons (if you don’t know why, you’ll know soon enough—when you’re missing some screws and you happen to hear some rattling noises afterwards) 🙂
Using the smallest Philips screwdriver, remove the two micro screws that secure the metal plate. Remember to use a magnetized screwdriver here.
There are no cool looking tools here except the obvious one. I used a tweezer to grab the metal plate firmly and slowly disloge it from the fitting making sure I don’t accidentally drop it onto the highly sensitive mirror underneath it. You don’t want to add a scratched mirror to your list of pain.
Next comes the three-piece copper shims. These are sandwiched between the focusing screen and superimposed display each has a attachment hook that prevents them from dropping down during camera operation. The idea here is to carefully undo them starting with focusing screen, then the metal shims then finally the superimposed display screen.
The metal shims come off rather easily. The final bit in the triathlon of viewfinder cleaning is the removal of each of these components. Note that you should always remember how they come off because you need to put them back in the order they were removed. The focusing screen for instance cannot be fitted the wrong way. Doing so will leave you with a blurred viewfinder.
Of the three tasks, I find the attachment hook that holds the superimposed display a little difficult to remove. The idea here is to use something flat so that you can lift the catch to release the superimposed display.
Using a tweezer, gently remove the superimposed display (“SD”) to inspect for dust or in this case, I discovered something more stubborn—an oil spot. How it got in there I think that’s open to a multitude of guesses.
Isn’t this cool? I just placed the SD under my flourescent table lamp, tilt it a bit and suddenly the cheap plastic screen looks like expensive jewellery. Here, you can see the stubborn spot. The spot refused to budge even after given it a dozen blows. It’s decision time—wet clean or leave it be. The owner of this camera (being new and somewhat clueless and inexperienced) was :O by one lil black dot in his viewfinder and asked me for help. I took this opportunity to proceed with a tried and tested wet clean method with a purpose of documenting this procedure.
Applying Eclipse methanol fluid on a new Sensor Swab (two drops). Soaking the swab with too much fluids will leave unsightly streaks on the SD. You’ve come this far, don’t let streaks (should they appear) freak you out. You can fairly easily remove the streaks with a newly prepared swab and sweep the SD a few more times. It takes practice to get things right. The point here is that the Eclipse is safe to use and does not attack the plastic.
Here is a picture of me applying a second sensor swab on the SD. Although the oily spot had disappeared, I inadvertently left some streaks which needed a second application. — Photo by Gavin

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