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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Birger Lens Mount & Follow Focus

Hi Erik, Curt

I can't promise an order yet, as I'm still waiting for a contract from a customer, but if all goes well, I'll be looking for a motorized zoom for Canon lenses soon. I have seen a rendering for the Red Motor and I was hoping I might offer a design suggestion. We'll be sticking the lens in a custom underwater housing, which means we need to keep things fairly small (the housing will probably have less than 125mm ID). Would you consider changing the motor design from a big flat thing to something small like this: http://www.heden-engineering.com/default.asp?m=0,56,57,93&i=93&n=

Thanks,
Brendan
 
Since they're pretty close to delivery I doubt they will make such a drastic re-design. However if you are useing a Canon EOS AF lenses you could mount the motor under the lens where the body has to decend anyway. This might make the whole package thinner. Also what about a mechanical linkage, this is what they do in DSLR housing no?
 
Evin Grant said:
It's fairly simple, they bench test a bunch of different SLR zoom lenses and create a data base that corresponds to the amount of zooming that's needed to counteract the breathing. This won't work at the very ends of the zoom but should be fine.
Click to expand...
"at the very ends of the zoom"..

as for instance?..
 
Well if you're pulling from close to far, your image will need to be zoomed slightly in to compensate, if you're at 70mm on a 28-70mm zoom this can't be done so you would need to zoom out slightly to allow for the correction. The same would apply in reverse at the wide end.
 
sure.. it does make sense now.
 
Evin.. correct. Our thoughts were that when your using lens breathing compensation (LBC) mode it would limit the zoom to positions that can be compensated for. If you need that extra range then you'd have to tun off the LBC mode .
 
Curt, is the motor going to do some kind of calibration at power up so it knows where the ends of the zoom are. If so you could limit the motors ability to go past safe "soft stops" so that in LBC mode you never have to worry about zooming too far in or out. Think that's possible?
 
Yup, as mentioned at NAB, the calibration is already a feature. You press the button on a motor and it finds the limits. Just to clarify, all off of the compensation is done in the remote/receiver... so basically the receiver would look up the current lens data and not command the motor to go further than the database allows for that particular lens (if in LBC mode). we are going to have a serial port as well so we may be able to tap directly into Eriks mount and issue move commands. This all depends on who gets to it first :)
 
Evin Grant said:
Why would you consider them rivals? Curt's products directly complement the Birger mount and both need to interface as seemlessly as possible into the Red package. Even if you were using the electronic focus of the Birger you would still need a Red Motor to do the breathing compensation on the zoom. They are joined at the hip on this it seems.
Click to expand...

I only considered them potential rivals, as they have similar expertise. Just because different manufacturer's make products that can work with products made by others, doesn't necessarily mean they won't make products that overlap or directly compete with each other. But yes they are very complementary, and cooperation sounds like a very good idea in this instance.
 
CVB said:
Evin.. correct. Our thoughts were that when your using lens breathing compensation (LBC) mode it would limit the zoom to positions that can be compensated for.
Click to expand...
How much would you estimate?
 
Akube said:
i want to pre-order this thing already, wheres the page?
Click to expand...

Yeah where is the page amigos??
I've read previously that the cost wth accessories would be $1400 and that very early reservers would get a free wireless controller. Ok so how do we buy the thing? It's the 20th of August already.. Also, will we see the Birger mount in the RED booth at IBC?
 
Dear birger, how are the ergonomics of the mount thought out with regard to handheld shots?
Much of the input on this board regards the focus puller and dp both being able to fumble around simultaniously, but have you tested the mount in a simple shoulder mounted setup?
Is it up to the user to find a configuration that suits him well, or is there a basic plan, as to what your left and right hand should be doing?
 
Eddie said:
Is it up to the user to find a configuration that suits him well, or is there a basic plan, as to what your left and right hand should be doing?
Click to expand...

As long as it mounts on rods and the cable is long enough we should be able to put it anywhere needed - which is more flexible than a lot of FF units out there.
 
Did an answer ever come back to Evin's question about whether the Nikon mount version is still on track for October release?
 
A couple questions that I haven't found answers to yet...

1.) If you power off the RED and power it back on, do the iris and focus stay at the same settings as before power off?

2.) If yes to the above, do either the iris or focus cycle (open/close near/far, etc.) back to the desired position or truly stay where they were last set?

3.) I think I read 4048 encoder points on the focus... I'm wondering exactly how smooth focus will be, and are all these encoder points referenced up to 1:1 on the lens itself? Does a lens with a short focus throw (say 1/3 rotation) have the same amount of precision as one with a longer throw?

Regards,
 
Digging into the website a bit more I see an example for a Canon EF50mm f/1.4, which returns 664 steps from min to max focus... now I wonder does that mean there is 664 discreet steps in the focus, or some sort of averaging over the full encoder range of 4048? Also, will all lenses have the same number of steps, or is there greater variation?

IMO, this whole system will live or die based on the smoothness of focus... and I'm just trying to figure out what this means in actual conditions...
 
birger mount

birger mount

Jim Arthurs said:
Digging into the website a bit more I see an example for a Canon EF50mm f/1.4, which returns 664 steps from min to max focus... now I wonder does that mean there is 664 discreet steps in the focus, or some sort of averaging over the full encoder range of 4048? Also, will all lenses have the same number of steps, or is there greater variation?

IMO, this whole system will live or die based on the smoothness of focus... and I'm just trying to figure out what this means in actual conditions...
Click to expand...

Jim: The various lenses have different numbers of steps. I copied some info Erik posted in another thread so you can see most lenses have a very high number of steps. (also some interesting stuff on autofocus possibilities). I'm pretty sure the encoder would translate the 4048 steps on the knob into whatever the lens max-min would be. As far as smoothness of focus clarify for me - but I'm not sure that it matters much since the lens can only do what it can do - in other words if the 70-200 has 2500 steps it has to stop on a discrete step, but more steps means more precision, so more precision than the 10-22 which has about 1200. He also states it is more logarithmic so more steps in the close focus range.

We won't know for sure until we try it on the red but from some of the things Erik said in my only conversation with him, I think the focus is going to be very smooth. (PS this response from erik is months old so they may have new things as well)

Quote from other thread (he was responding to my question about focus repeatability)

"With lenses that have ring-type USM motors we are seeing repeatability on the order of a few steps. The step counts for some of these lenses:
85mm f/1.2: 4200 steps
14mm f/2.8: 1400
70-200mm f/2.8: 2500
200mm f/1.8: 3750
200mm f/2.8: 2100
35mm f/1.4: 2500
60mm f/2.8: 2000
100mm f/2.8: 2500

On all of these lenses we have repeatability on the order of 0.1%. Steps correspond to more of a log than a linear scale of focus distance. Half of the steps might be used for the first meter or two of focus on some lenses. Steps are linear in terms of the rotation of the mechanism.

The 10-22 f/3.5-4.3 has about 1200 steps. We have played with this lens for about five minutes. It is not one of the ones that works really well with servo mode, yet. We will add it to our set. Give us a few weeks... It is extremely repeatable with our normal mode of operation, move stop move stop etc. Servo mode is really new.

Basically the lenses are more accurate in their positioning than a typical human being is capable of by simply turning the dial manually. This offers some really interesting possibilities if Graeme's radical new focus assist were to be the basis for an auto-interactive focus mode for ENG users. We can all guess what the focus assist is going to offer.

But if this is even just a texture based quality of focus (maximized high frequency component means better focus) it has enough information to keep a "talking head" in focus as the 3D path of the head relative to the focus plane can be understood. If best focus is near the middle of the object (think nose) focus is too close. If best focus is near the outer edges, focus is too far away. Blob analyze the scene... blob analyze the focus quality... apply Newton's second law (i.e. a PID loop)... voila... auto-interactive focusing...

I call this auto-interactive focus, as the camera operator just has to pick which blob to start tracking."
 
AquaVideoRed206 said:
"...The 10-22 f/3.5-4.3 has about 1200 steps...Basically the lenses are more accurate in their positioning than a typical human being is capable of by simply turning the dial manually..."
Click to expand...

Well, even if the throw of a lens was a whole 360 degrees, and we only had the lowest quoted 1200 equal steps - that is 0.3 degrees per step! Then given that those steps are weighted towards the closer more critical focus end, I don't think we need to worry that we will see steps in the focus.

Or maybe I'm misunderstanding the maths - always a possibility in my little brain! :waaa:
 
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