Wierd backfocus issues - something new - is something wrong with our camera?

[David Wyatt]

I've also encountered this phenomenon, but only on later model cameras. I'm pretty sure this problem doesn't exist on our camera (#247). I wonder if anyone with the new mounts have this problem too?

[Brigham Edgar]

Same problem here but you can do it without it moving. All the time watch a monitor closely in case it does shift. Turn the screws very slowly little by little, constantly changing back and forth between the two. Even when it starts to get a little tight keep on going only very small turns bit by bit and still changin back and forth between the two.

Works well for me and if i try and do it any other way it just slips.:pinch:

[Mark Phelan]

Not having the opportunity to adjust backfocus yet, I might be out of turn with this idea but it occurred to me that after you have adjusted your backfocus and before tightening the screws, couldn't you apply a piece of tape to hold things in position while you tighten it up? Another idea would be to also apply two pieces of tape with a line marked between them spanning the gap, like Doug did to give you a visual reference to see if it had moved at all. Just a thought.

[jacknusa]

Mark,

The problem is not that the ring is moving, it's not - it's just the tightening of the screws that causes it.

Jack

[chuck colburn]

Mark,

The problem is not that the ring is moving, it's not - it's just the tightening of the screws that causes it.

Jack

Too much slop in the basic mechanisim I'd say.

[Stephen Williams]

Too much slop in the basic mechanisim I'd say.

Hi Chuck,

I quite like the idea of shims myself,

Stephen

[AIO Films]

Yup. The back focus changes when you tighten the screws. It takes some practice to get used to how far off you have to make it so that it will be right after you tighten them. Not fun.

Does this translate into bad engineering or bad machining? Will RED acknowledge the issue and fix it?

[chuck colburn]

Hi Chuck,

I quite like the idea of shims myself,

Stephen

Good morning Stephen,

I quite agree with you!
Although I think the concept of an adjustable mount standard could be made to work properly.

[Stephen Williams]

Good morning Stephen,

I quite agree with you!
Although I think the concept of an adjustable mount standard could be made to work properly.

Hi Chuck,

Don't you think it's a soloution looking for a problem? Unless the mount can be adjusted to be parallell to the sensor I don't think it's a real answer.

Stephen

[chuck colburn]

Hi Chuck,

Don't you think it's a soloution looking for a problem? Unless the mount can be adjusted to be parallell to the sensor I don't think it's a real answer.

Stephen

I do.

The way it's being done by using threaded pieces is a problem area no matter what the pitch is. There are however other ways of doing it, but they get complex and therefore pricy. Linear travel that is basically slop free and maintains parallelism requires complex mechanisims like the moving parts of a real zoom lens.