DSLR secondary mirror stays down and causes a black band in photos — can I fix it myself?

Asked 4/17/2018

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The small secondary mirror behind the main mirror is not moving up properly during exposure. I can push it up by hand and it stays up, but when I take a picture it does not rise with the main mirror, and my images show a black band. Nothing looks obviously broken. Is this something I can safely repair myself, and is it usually worth fixing compared with the value of the camera?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

8y ago

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Mirrors and the assembly that they are attached to are very delicate. You need to be very careful when working with them. You should never touch the surface of a front silvered mirror, such as the two mirrors in your DSLR's light box.

This really is not a DIY type of repair. You're likely to just make things worse. There are a lot of delicate adjustments that must be perfectly right in order for the focusing system to work properly. The optical distance from the lens to the viewfinder via the main mirror, the AF array via the secondary mirror, and the sensor when the mirror is up must all be the same or focusing errors will occur.

In your image above there are fingerprints evident on the secondary mirror's surface. The surface with the prints is actually the reflective coating on the front of the glass. It's not like a more normal mirror where the reflective coating is on the other side of the protective glass plate. It is very difficult to clean smudges from such mirrors without damaging them and should only be done by someone who really knows what they are doing.

As it stands now, even if you get the mirror operating correctly, your AF system's performance will probably be impacted by the damage you have done to the secondary mirror. With the smudges left in place some of your AF points probably won't work at all. If you try to clean them you'll risk removing some or all of the reflective coating. With less reflective coating the light going to the AF sensor will be dimmer. With no reflective coating no light will reach the AF sensor for the spots on the mirror which have had the coating cleaned off along with the fingerprints.

Originally by user15871. Source · Licensed CC BY-SA 4.0

user15871

8y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

This is generally not a DIY repair. The main and secondary mirror assembly in a DSLR is very delicate, and the mirror surfaces are front-silvered, so touching them can easily cause damage. The secondary mirror is also part of the autofocus and viewfinder alignment system, so even a small error in mirror position can cause focus and calibration problems.

If the secondary mirror is staying down during exposure, the camera likely needs professional service. A repair center can inspect whether it’s a mechanical linkage issue or a known fault. In some cases, manufacturers have covered mirror-related repairs even on older cameras when the problem was due to a recognized defect.

Best next step: contact an authorized service center for an estimate before attempting anything yourself. If the body is older or lower in value, compare the repair quote with the camera’s replacement value.

UniqueBot

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8y ago

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