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Kip Kubin

Aaton XTR Ground Glass has slipped down - can I adjust it? How?

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As time goes by my Ground Glass is no longer centered in the frame it has slipped downward as I look into the eyepiece.

Is there something I can do to adjust it "upward"

I have also noticed that when the top line of the ground glass is in focus the bottom is a little out.


Is there an easy way to adjust the ground glass back to factory setting without sending it away for service? I have a shoot this Tuesday and I'd like to fix it if possible


Thanks in advance.

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The ground glass itself is glued into a metal holder. The holder is screwed into the frame with two screws which have locktite on them, so it would be very difficult for them to come out. Most likely the glue has failed due to age and the actual glass element itself is "floating" in the holder.


If you take the lens off the camera and turn the motor by hand so the mirror is facing down and the gate is exposed. You should be able to stick a q-tip in there to tap on the glass and see if it moves. If it doesn't... then it COULD be something else. I've seen the prism at the top get un-glued as well and that would cause the same problem.

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The metal tab that rests on the top of the ground glass is not attached to the ground glass. - is that the issue? Should it be attached with glue?

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Metal tab eh... I'm not aware of any metal tab. The ground glass is glued and then screwed.

With symptoms like yours, the first step is to pull the viewfinder off the top of the camera, which is very easy. Then look straight down to the ground glass itself and you can see if there are any issues.

Here are some picts for you to look at from my camera, you can see how it's "suppose" to look.








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Actually, the first thing to do is determine if it is the groundless that is out of alignment or the viewfinder optics (mostly likely the prism). pull off the mag cover and the port cap. Shine a light into the viewfinder. Look through the lens port and slowly rotate the mirror. If the groundless is in line with the gate then the problem is with the viewfinder. If it is out of alignment it most likely just needs to be reseated.


Do you have a short eyepiece and a long eyepiece? It is possible that you stuck the eyepiece on the wrong way, with the registration pin not going into its little hole. That would cause the eyepiece to shift out of alignment and create just the issues you describe -- the framing would be off and focus would shift across the field. Check to make sure everything is seated properly. If it is seated correctly, try rotating the eyepiece a full 360 degrees, meaning spin the eyepiece so that the eyecup gpoints toward the front of the lens and then keep going around in a full circle until it lands back where you started. This can help reseat the eyepiece prism (the one that's right there next to your eye, not the one that is centered above the lens). If that doesn't fix it, try pulling off the camera lens and doing a 360 rotation at the other prism point (the one over the lens port). Note that many Aatons cannot do a 360 rotation at this location due to a patent issue with ARRI.


If these steps do not fix the issue, you really best take it in for service. Last things you want to have happen are (A) all your footage out of focus or misframed or (B) some part coming loose while rolling and dropping onto the spinning mirror (yikes!).

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Thanks Mitch


I tested both eyepieces. Seating correctly did solve the issue of the entire GG lines in focus


I tried rotating the eyepiece and nothing happened - the other part can't rotate


Depending on how put on the eyepiece is how the lines are shifted - one way its shifted upwards the other way downwards.


In a nutshell my center hash marks are not in the center. Im assuming they are supposed to be


I have shot this way and I believe its just a little misframed the footage was sharp


I'll send it off to be looked at.

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Some XTR,s .. after the Arri court case.. had a small screw in the top of the view finder . if you take that out.. the whole thing can be shifted over the other other side like the SR could.. it was a way of getting around the patent ..

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Mine has a tab that lays on the black strip that is on top of the ground glass




Does your camera have a built-in meter?


Have you tried pushing on the ground glass metal holder with your finger to see if it's loose?


Can you take a picture through the viewfinder and show us what it looks like?

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