Thermally Stable Lens Mount ( this time around )

[Joel Kaye]

if we don't offer it, they continue to NEED it. As soon as it is available, they go silent. That is just human nature.

Free business advice they probably don't teach you at Harvard in that post.

 

[Brook Willard]

As far as I can tell, the "invar" obsession is as I posted earlier in this thread. When the RED ONE mount was being developed, somebody from RED posted that the mount would be invar. It eventually became aluminum and was notoriously unstable. The new mount was supposed to be stainless... but became aluminum and is less notorious but still somewhat unstable.

So when many of us thing "thermal stability," we think of "invar" because it was the metal behind the mythical thermally stable lens mount that never was. Ultimately we all aren't thermal engineers... but we sure know that aluminum doesn't quite seem to cut it. So if the word "invar" were replaced with "a thermally stable metal," I think the message behind this thread would probably be clearer. I bet that many of us wouldn't even have thought of invar as a good metal for lens mounts if we hadn't read it on REDuser [or DVXuser] that one day.

I suppose the same logic applies to the word "mount". If the mount were rock solid but the sensor block and front of the camera were thermally unstable... the mount is meaningless. The desire is more for a complete hardfront and sensor block made out of some sort of material that is more thermally stable than aluminum. If that material is stainless, awesome. If it's titanium or invar, perfect. If it's aerogel... that's cool too. Ultimately you have more lens building experience than most posters on these forums... and with our feedback in mind, I'm sure you'll find a stable solution for the mount.

As the end users, all we know is that the aluminum mount isn't quite cutting it. You guys have been cool enough to take that feedback... so the best we can do is sit back and wait... right?

Thanks for listening to the feedback. As much as we complain sometimes, we've sure never had to deal with the sensor flexing issues that the old D-20 did in the early days! Keep it up.

 

[Jay A. Kelley]

Wow!!! This is great.

Wow!!! This is great.

Jim, Jarred...
I FRIGGIN LOVE YOU GUYS (Don't take that wrong, I don't want to start picking out curtains or anything).

This thread, this one right here is what RED's all about.. And it's so damn fun and exciting to read and experience. Sure there are a couple of pissy people sometimes but what I see are a lot talented people from different parts of this industry speaking to the OWNER OF THE DAMN CAMERA COMPANY and each other about this and that lens mount. Customer feedback at it's best.

Rather than being an arrogant prick like so many other companys Jim says "Hey thanks for this, we're learning" and offers options for those that request it, not weeks or months later, but minutes. Even though you can tell he really doesn't agree with some of what's said his take is "you guys are the customers, and if it's that important to you, we'll get it done".

I really mean it.. This is special. I hope I'm not the only one that sees it.

As for my opinion on the type of lens mount... I have no idea, I'm not knowlegeable about this stuff, but I will keep reading and learn what I can, then depend on Jim to put a mount on Epic/Scarlet that does not cause me trouble later!

Jay

 

[Jens Jakob Thorsen]

Steel it is then? Please!...It has been used for decades and it works! I have had Backfocus issues and I would pay a "little" for anything that works....

 

[Deanan]

It eventually became aluminum and was notoriously unstable.

You get a very different picture when you dig into every customer issue versus what you hear around town. Almost all of the mount issues from the early days were because of mounts that weren't tightened or set properly. The adjustable mount made it alot easier to do both so there was less room for error.

Even the mounts as early CHE stayed solid through month of shooting and going from an AC'd camera truck to very hot ambient temps and direct sunlight.

"notorious" in no way implies factually correct.

 

[Michael Ragen]

true true. its quite frustrating going on shoots and suddenly all the nasty red rumors start flying around, or one guy on the shoot had a bad experience because someone fucked up and blames it on the camera.

haven't experienced any mount shifts yet, but i only took my camera into the snow for the second time today, and it was only around 30. but i'll still take whatever provides the most stability.

 

[Matt Uhry]

Yes it's true that lenses will change focus with ambient temp. but the camera has a built in heater in it - the processor. The problems I've experienced have had minimal external temp. swings, like shooting on a stage in El Segundo, during a summer day.

I'd accept some variances a shoot day included a frozen lake and a out of control sauna, but if it's going out of whack on a soundstage just while the camera warms up...

I've picked the brain of my material sciences Phd. brother in law - this is the amount of shift you can expect with the linear expansion of a 52mm piece of aluminum, if you calibrate the 52mm at "room temp" 25 deg C. It's enough of a shift to cause the problems I've been having. Depending on how the sensor is attached to the shell of the body the 52mm distance may be more or less.

Linear thermal expansion / contraction of 52mm of Aluminum:
5 Deg C 51.975
15 Deg C 51.988
25 Deg C 52.000 mm
30 Deg C 52.006
35 Deg C 52.012
45 Deg C 52.024

Using stainless parts to link the sensor plane to the sub mount ( the part we attach the user mount to ) should cut these #'s more or less in half which would probably be good enough for most people including me most of the time. Stainless mounts ( the PL part ) would be the cherry on top.

Matt Uhry
www.mattuhry.com

 

[Neil Duffy]

This is an excellent thread. Everyone is giving really knowledgeable feedback. This looks like a tricky issue, with the body being aluminum and the mount potentially being another material that has a higher price point. But everyone seems to be helping find a solution.

Very promising for RED's future.

 

[Brook Willard]

You get a very different picture when you dig into every customer issue versus what you hear around town. Almost all of the mount issues from the early days were because of mounts that weren't tightened or set properly. The adjustable mount made it alot easier to do both so there was less room for error.

Even the mounts as early CHE stayed solid through month of shooting and going from an AC'd camera truck to very hot ambient temps and direct sunlight.

"notorious" in no way implies factually correct.

You know, I'm actually glad to hear you say that. While I found the mount difficult in its factory calibration [throat too narrow, up to a dozen shims in the mount, sticky collar, loose screws, etc.], once the mount was milled out and collimated by Clairmont... it stuck as long as we had the mount. While it did shift in a similar manner to the current mount, it didn't explode and fall off like it did out of the box. I remember having Sam Druckerman's camera collimated at Clairmont before the first trip to Dubai... and it was SPOT on until the day he sent it back to get his X body. I've praised the general design of the mount multiple times on the forums... it was the factory collimation, tolerances and material [aluminum is what it is...] that weren't "up to snuff". :wink:

My choice of "notorious" was more relating to the reputation that the mount quickly gained across the industry in those first weeks and months. There were enough shoots and tests that were botched to make the concerns very real... back then. While those rather antiquated concerns certainly have vanished from that absurd oh-no-I-hear-the-RED-kills-your-shoot manner, there are still those little points that I'd love to see fine tuned.

Those points were originally squaring the mount to the sensor, centering the sensor and dealing with the thermal instability. The first two are guaranteed to be fixed by the inherent design of the new lens mount. I believe that this discussion and the work that you guys have no doubt been doing behind closed doors will lead to the third point being solved.

 

[Brent J. Craig]

We won't be happy until the entire camera is made out of unobtainium with mysterium accents.

 

[Dale Launer]

The only way to go?

The only way to go?

Stainless is the only way to go

Why is that? When Invar and titanium expand/contract less than stainless steel?

 

[Jannard]

Everyone seems to have an opinion on this topic. Why not make them all and let the customer have their choice?

Jim

 

[Matt Uhry]

Everyone seems to have an opinion on this topic. Why not make them all and let the customer have their choice?

Jim

It's not the mount itself but the material between the sensor plane and the part you bolt the mount to... Bolting 12mm of Invar or Stainless PL ring to 40mm of aluminum camera body is not going to fix the problem. *

I'm totally in for a Stainless PL mount for the gains in strength, stability and stickiness.

Matt Uhry
www.mattuhry.com

* I don't know the Epic's internals, but it looks like the user changeable front mount plates bolts onto the external body. Using a sub-mount that connects to the sensor plane to the front attach points would be one way to solve this. Imagine a squarish table with a rectangular hole cut in the center. That part would be made of something that is reasonably thermally stable.

 

[chuck colburn]

The advantage a video camera has over a film camera so far as error in the viewing system goes is, that the film plane is the ground glass. Now I know that in itself has it's own inherent problems but at least one does not have to worry if the flange focale depth is the same as the ground glass depth and vicea versa. I believe if the sensor and lens mount be it interchangable or not are mounted in a common machined block of whatever metal you will maintain a flange focale depth at least as accuret as what the lens is capable of. I also think that the lens seat and locking ring on the camera should be stainless even if the rest of the lens mount/sensor mount assembly is aluminum.
Just my two cents...

Another couple of reasons for having an "optical block" type of assembly are that it allows one to align the bore of the lens mount to the center of the aperture and garuntees parallelism of the lens seat to the film plane.

 

[chuck colburn]

as i understand epic and scarlet (like red one) will not have a hardfront. so even if the plate (with the 4 screws) plus the PL mount is made of invar, the body (made from aluminum) will still expand.

image of a hardfront (invar) where the PL or nikon mount is seated - not connected to the front housing made of aluminum

Is that the new Aaton 35 camera?

 

[Jannard]

You know... it is an absolute miracle that anyone is getting good images out of a RED ONE. Really. If you look at it, it just doesn't make any sense. The whole body should technically be Invar, including the mount. Anything else just... well, sucks! If I do the math, the RED ONE, along with every other camera just can't make good images. The laws of science prohibit it.

I'm with you guys. Make an option where everything just can't move one iota. Then we would all be happy and be able to shoot feature films again instead of just fooling around with this other crap.

How many vote for an all Invar camera body and mount? Too heavy and much $$$? How about an all stainless steel body and mount? We are all in. Just tell us what you want and put up your deposit.

Jim

 

[Jannard]

We will make an optional Invar front body plate (integral with the sensor mount) and lens mount. We will also make an optional stainless steel front plate and lens mount option. Obviously they both will cost more money. But it now puts this thread to rest.

Oh, and you want a titanium set instead? No problem. We'll do that too. We aim to please. God loves a modular system.

Jim

 

[Fredrik Callinggard]

I here you Jim it's frustrating hearing all this voices, but no one is complaining about the image of RED One. Well, except for now and then , but mostly not.

See all this as us trying to be constructive not complaining. After all your learning and so are we. The mount as it is now is functional but it's definitely not perfect. The amount of times I've been standing swearing on set when backfocus been an issue are plenty.

At those times I've not immediately been able to say if it's the lens, the camera or the temperature.

So all we're trying to put in our suggestions in how to make it better. Letting us all sleep better at night, except for you guys who has to put in overtime back at the shop :w00t:

I for example suggested stainless steel, because it's the cheapest that has proven itself to work. Although that is with film and it's more forgiving.

Depending on price I wouldn't be against for example invar.

No ones asking for the whole body to be in invar but BTW didn't you promise that Epic is an all titanium body :innocent:

and as a last word I want to say... that don't think we appreciate your hard work and your crazy idea about a camera for everybody. We just want to chime in so we can pretend we're a part of it.

 

[Jarred Land]

We will make an optional Invar front body plate (integral with the sensor mount) and lens mount. We will also make an optional stainless steel front plate and lens mount option. Obviously they both will cost more money. But it now puts this thread to rest.
Jim

and with that.. lets close this one down