Thermally Stable Lens Mount ( this time around )

[Matt Uhry]

It's not so much the mount that's the issue, it's the 52mm of cast and machined aluminum that holds the mount and the sensor aligned. What's being suggested is that Red not screw the mount onto the body and instead onto a standoff that keeps it aligned with the plane of the senor made of invar or some other thermally stable material of their choosing.

That being said a steel mount front PL is a still good idea. I think invar may be a bit brittle for the actual mount, but I'm not sure of this.

Thanks for your care and attention!.

Matt Uhry
www.mattuhry.com

[David Mullen ASC]

I only had a back-focus problem once on the RED, oddly enough it was just two days after the initial prep where the back-focus had been checked at the rental house where the lenses came from. But by Day Two, I started noticing that one of our RED's seemed off in a wide day exterior shot and it turned out that the back-focus had shifted. But after we set it again, it never was a problem -- so perhaps we had a loose screw or something.

Now this was a movie shot in summer in warm to normal temp locations, never any cold situations.

Even if you focus by eye rather than measurements, a wide-angle wide shot can be hard to get sharp if the back-focus is off. On tighter, longer-lensed shots, sure, focusing by eye usually gets around this problem, or hides it. On the other hand, a lot of eye-focusing involves zooming in tight, focusing, and then zooming back wide, which doesn't work well if the back-focus is off (in fact, that's often how you spot that it is off...)

If you're shooting for projection on a 50' or 75' screen, these little issues become big issues.

In fact, one of the advantages I've found with shooting digitally on cameras like the RED is that I spot certain lens defeats and problems more easily rather than being surprised months later.

[Steve Sherrick]

It's not so much the mount that's the issue, it's the 52mm of cast and machined aluminum that holds the mount and the sensor aligned. What's being suggested is that Red not screw the mount onto the body and instead onto a standoff that keeps it aligned with the plane of the senor made of invar or some other thermally stable material of their choosing.

That being said a steel mount front PL is a still good idea. I think invar may be a bit brittle for the actual mount, but I'm not sure of this.

Thanks for your care and attention!.

Matt Uhry
www.mattuhry.com

Ah, this makes more sense why you guys are suggesting invar. The reason I asked if it would be strong enough is that I thought you were referring to using it for the mount itself, which made me wonder if it would be able to take the wear. This makes sense now.

[Dale Launer]

Any reason titanium isn't being considered as a lens mount?

[Steve Gibby]

On the other hand, a lot of eye-focusing involves zooming in tight, focusing, and then zooming back wide, which doesn't work well if the back-focus is off (in fact, that's often how you spot that it is off...)

In fact, one of the advantages I've found with shooting digitally on cameras like the RED is that I spot certain lens defeats and problems more easily rather than being surprised months later.

Definitely. Eye focusing with zoom lenses on RED does involve a lot of zooming in, hitting 1:1 image magnification (if you have time), racking focus, then pulling back to the framing. Experienced eye focusers get used to picking up nuances of the framings as they change from tight to wider - things like increased softness as you widen out, which tip you off to the possible need to reset back focus. Its obviously much better to notice that at the start of the shooting session, than later on, and have to re-shoot material. Experienced sight focusers will usually spot back focus problems quickly.

The addition of 1:1 image magnification on RED One has really enhanced sight focusing with the camera.

From f4 to more stopped down apertures I really enjoy sight focusing RED One if it works for the workflow and the needs of the shots. As you know, sight focusing obviously becomes much more of a challenge at apertures of 2.8 or wider open, which limits sight focusing to relatively static shots, and shots where subjects are not frequently moving toward or away from the lens.

I guess there is a time and place for everything. Experienced shooters develop an uncanny sense of when to do what, and when not to do what - and when to shift gears and move on to another solution.

[Jarred Land]

I wonder when people that are really worried about this are gonna start using Invar in lenses... The expansion that happens with the metal in most lenses is just as big of an issue as thermal expansion that happens in the mounts. Specially with the bigger zooms, like the big Optimos. People forget about that part. It's why Canon makes their long zooms White.

I guess minimizing the tolerance stacking as much as possible helps though.. which is why, like Jim said, for those that really want it, we will make it :)

[Fredrik Callinggard]

and instead use Invar or at least Stainless ?

Stainless is the only way to go

[Fredrik Callinggard]

I wonder when people that are really worried about this are gonna start using Invar in lenses... The expansion that happens with the metal in most lenses is just as big of an issue as thermal expansion that happens in the mounts. Specially with the bigger zooms, like the big Optimos. People forget about that part. It's why Canon makes their long zooms White.

I guess minimizing the tolerance stacking as much as possible helps though.. which is why, like Jim said, for those that really want it, we will make it :)

Absolutely but RED is infamous by now and one of the points for naysayers so why not go for stainless? It's proven itself to work for years and years.

I would also appreciate if we don't have a self adjustable mount. It has proven itself to be nothing but trouble.

[Steve Gibby]

I would also appreciate if we don't have a self adjustable mount. It has proven itself to be nothing but trouble.

I completely disagree with that. I own several RED One cameras and I've had no problems whatsoever with the new adjustable mounts. The ability for us to adjust back focus ourselves was a major advancement

What has proven itself to be nothing but trouble is the "never satisfied" attitude of some posters here. No matter how many improvement RED has made to RED One, and the excellent proposals for the new cameras, there are some nitpickers who are never satisfied no matter what advancements RED makes.

If you want to go back to mounts that can only be adjusted by a technician and not by the owner or operator, then IMO you should seriously consider buying your cameras from another company.

[Jarred Land]

I'm with Gibby on this one...

The attitude is frustrating. Specially after Jim bends and offers up a solution in this very thread.. people still bitch bitch bitch...