Arri SR3 Mirror Shutter Vs. SR2 Mirror

Mike Lyddon · October 15, 2015

I cracked the mirror shutter on my SR3 and have been having a hell of a time trying to find a new one. I did locate an SR2 mirror shutter so I thought I might be able to take off the mirror and replace the cracked SR3 mirror. I'm not talking about the whole mechanism, just the mirror.

Does anyone know if those two mirrors are compatible? They appear to be the same, but I've had difficulty finding exact specs on either.

Dom Jaeger · October 16, 2015

Replacing the mirror is honestly a professional job, many important settings such as ground glass focus and position and camera timing will need to be reset, not to mention the very crucial checking and adjusting of the mirror flatness - if this isn't set to within ten or so microns the image in the viewfinder will vibrate, making critical focus impossible and giving the operator a headache. I would strongly advise against trying to do this yourself, unless you don't mind spending time and money turning a professional camera into a doorstop.

Unfortunately it's a big job, and when you include the cost of a new mirror it may be cheaper to buy a new camera these days.

Kenny N Suleimanagich · October 16, 2015

Bernie O’Doherty might have the spare part, I’d contact him.

Simon Wyss · October 16, 2015

Curiosity, how did you crack that mirror?

Mike Lyddon · October 16, 2015

Replacing the mirror is honestly a professional job, many important settings such as ground glass focus and position and camera timing will need to be reset, not to mention the very crucial checking and adjusting of the mirror flatness - if this isn't set to within ten or so microns the image in the viewfinder will vibrate, making critical focus impossible and giving the operator a headache. I would strongly advise against trying to do this yourself, unless you don't mind spending time and money turning a professional camera into a doorstop.

Unfortunately it's a big job, and when you include the cost of a new mirror it may be cheaper to buy a new camera these days.

Dom Jaeger,

I certainly would not attempt to replace the mirror myself, but I was speaking in terms of parts. Do you know if the sr2 mirror is compatible with the sr3 mirror? Only the mirror itself, not the shutter mechanism it sits on.

Mike Lyddon · October 16, 2015

Here are the mirrors, the one on the left is from the sr3, the one on the right is a potential replacement. The mirror itself is detachable so the question is if the mirror is compatible as a replacement mirror for the sr3
At least I would have the part, then I could look for a tech to do the job..

Mike Lyddon · October 16, 2015

Curiosity, how did you crack that mirror?

PL adapter mounted wrong way on lens, inserted lens, ran camera, cracked mirror.

After I adjusted the mount I had no problem, I went ahead and ran a test roll of film and the camera ran perfectly. As for the film, I should get it back next week. Should be interesting;)

Mike Lyddon · October 26, 2015

Yeah so I got the test footage back, cracked mirror has no effect at all on the film, it looks fine. There could be a little more flicker in the viewfinder, no big whoop.
I did get a mirror (not expensive) which does match the existing cracked mirror, shouldn't be much of a problem replacing it if and when it is neccessary.

In other words, take any of these so-called "experts" advice with a grain of salt.

Dom Jaeger · November 2, 2015

No one said the footage would be affected, obviously it's only the viewfinder image that the mirror creates, the film is exposed when the mirror is out of the way. And if you can live with the flickery viewfinder image, if the mirror crack hasn't altered the ground glass focus, or there aren't tiny glass chips falling into the movement then the option of not replacing the mirror is certainly open.

But if you've found a cheap and effective way of replacing cracked mirrors on SR3s please keep us informed. Finding a mirror that seems the right shape isn't the hard part, it's fitting it so that the settings of the camera remain in spec that is difficult. You have to unglue the old one and re glue the new one, at the right height and perfectly flat. Saying that it "shouldn't be much of a problem" before you've even tried getting someone to do this is not exactly advice anyone should take without a large dose of salt either.

I do agree that any advice offered on an Internet forum like this should be taken with a grain of salt, it's only what people may have experienced themselves, and are freely passing on.

Simon Wyss · November 2, 2015

Is that why there are millions of tons of salt in the seas?

Mark Dunn · November 2, 2015

In other words, take any of these so-called "experts" advice with a grain of salt.

Gluing a replacement mirror on anyhow is a bit like nailing on a hat and expecting your head to work properly afterwards. Since you've already mounted an adapter the wrong way round, good luck with a chunk of glass rotating at high speed inside a camera.

The 'expert' who replied to your query is just that. He knows whereof he speaks and has been helping forum members out with expert advice for many years. He is too polite to take offence at your 'so-called' jibe but no doubt when you have been here a bit longer you will learn better.

Aapo Lettinen · November 2, 2015

one could make a replacement mirror with cnc machinery (lathe&milling machine) but it would probably cost more than buying a used SR body for spare parts :/

you'd have to be at least 1/100 mm accurate with the machining, probably much more. then you'd have to get someone to vacuum coat it with aluminium/silver/other good quality material and also add the protective layer on the finished surface.

please remember that the mirror rotates from 24 to 75 revolutions PER SECOND depending on frame rate so even a small glitch can cause a horrible cracking>exploding disaster or at least destroy the bearings :ph34r:

I would probably use aluminium if I would have to make a mirror by myself but as said it is not nearly as easy as it looks like <_<