Birger feedback

[Billy McCannon]

It is difficult to draw a user experience consensus of Birger/VF because the gestation period was so protracted. It is a great pity it didn't come out of traps when the Red One was released.

It is only in the past six months that it has really come out of beta and anyone whose experience predates that would have had a less than satisfying experience. The mount itself is bombproof while the controller, being made of plastic gives the wrong impression in a professional environment, however it is in fact, very robust.

I found that when I had mastered the system it was virtually error proof - repeatable and accurate to echo's Paul's assessment. Its weakness, if it is a weakness, is that you have to take the time to learn how to use it if you want to fully exploit its functionally.

If the focus puller hasn't mastered the unit before the the shoot - s/he will suffer but a good focus puller will know the gear.

The downside is that it doesn't offer a fast lens wider than 24mm and the learning curve is steeper than I'd like. That aside, with a set of L lenses it makes a great system.

I would be very interested to hear more of Paul's experience of its limitations and advantages on those shorts.

[paul engstrom]

You've pretty much nailed it with earlier experience vs. later experience, the importance of AC (or DP) knowing what all the buttons and beeps can do and also the lack of a fast wide lens.

I DP'd the short and set up the system for my AC. She did awesome and the mount did awesome. We used 2 lenses the whole time: 17-55 and 70-200. Glass worked great. Focus was great. It definitely helped that I knew you had to press and hold the Focus button until it made a beep with a descending tone in order to get great performance out of the 17-55. But that special setting is there because Erik heard those of us that saw the 17-55 (with image stabilizer) as an especially useful lens and therefore created a special setting for its unusual lens behaviour.

DPs here in Vancouver are just blown away when I show them 720 degrees of smooth, accurate, quiet lens pull using a still lens. And then more impressed when I hit a button to set that range to 1/8 of that for a shot requiring a quick focus rack.

The Canon 85L is a fantastic lens.

I am so hoping that RED doesn't just have Canon and Nikon mounts but also has a focusing knob that is nothing less than the Birger/Impero system for the Epic system.

There's a huge weight savings here too, I should add. I just collimated a mount for some guys working here in BC, Canada that are doing some unbelievably awesome backcountry shooting with an extremely lightweight rig--and a Birger mount. I was able to carry my camera and lenses--covering a range from 10mm - 400mm yet weighing less than 2 RED prime lenses--up our steep Coastal mountains for some footage I was after. Needless to say, there are some big benefits for doco and various types of run and gun cinematography.

All that to say, electronics scare me. In my perfect world I own both electronic and mechanical lenses and follow focusing systems.

Regards,
Paul

[Jason Sinclair]

Thanks guys, i don't want this to go into a for or against fest. Not my objective at all. Your feedback is really appreciated.

Looking over the dslr forums on the internet it seemed that even canon and nikons own software and the embedded raw content could not show exact focusing.

From what those guys on the forums are saying is: this is because they only (on some of the better lenses) have 8 point encoder on the lens barrel. Now 8 points is not talking 2000 steps. Sure enough people have tested this and the focus data is often out. For photography, this data isn't so important but for our application it is critical.

Now, this begs some interesting questions. If Canon have encoders on the motors and can access this data then why add more encoders to the barrel in order to introduce less reliable data? It just isn't making sense to me.

Almost universally across the internet dslr owners are saying that the lens motors don't have encoders. Sure enough when you see an opened USM lens you don't see any encoders on the motors. What you do see is the photocoupler CLICK HERE and that is according to the article, the mechanism which tells the lens when an object is in focus after searching for it. However it doesn't seem to be a positioning devise.

If anyone can provide any precise information regarding encoders on the motors it would be really appreciated (the kind that provide precise positioning-not the 8 point encoders). Has anyone had it verified or seen the encoder with their own eyes?

Now considering all the above info, some things are just not adding up here.

We have had someone said the lens data on the red read out is precise. How precise are we talking? sub inches? mm? What does it read in and what is it's lowest denominator? .000?? Has it been tested thoroughly against tape? If we are talking 2000 steps then it should be mm's at the least.

We assume for certain though, its more than 8 readouts.

So given all that information and the programming difficulties expressed (if Birger was using the canon protocol then his unit shouldn't have anymore of a hard time "talking" to the lens motor than the cameras own system uses itself and we know focus systems in dslr's are very precise.) then how can anyone explain all this?

Without encoders how can Michael achieve precise positioning to 2000 steps??

Like i have said before if anyone can give evidence to the contrary, like a white paper or a photo or even personally seen one themselves, then i will stand corrected. I want so much to have encoders in those motors but there is conflicting information i want resolved first.

[Michael Hastings]

Jason:

Your application sounds much more precise in terms of the positioning information than I had understood. You really just need to talk to Erik at Birger - he's the expert on the lenses, and the kind of stuff you are talking about. Red was just a sideline to the industrial/scientific stuff Birger has been doing with the Canon lenses for 7 or 8 years.

My point was geared toward the idea of doing repeat focusing using marks on the impero knob on normal movie/video shoots where you are shooting a scene a few times and then moving on to another. I think my info on the steps for how the focus moves is correct, but I have no idea of the accuracy of the encoders (or whatever it is in them that I think of as encoders) and how that relates to the number of steps. Most of the time I am shooting in an underwater housing with a dome port that completely changes the focus anyway, so I have never relied on the focus data except to see whether focus is changing.

You should also be aware that Canon lenses do not have smooth iris, I think it is 1/3 stop steps, and I think Erik said you may be able to get 1/4 stops through some sort of software interpolation.

[paul engstrom]

Yeah I'm not sure what exactly you're after Jason.

I have the readout in inches rather than metric and it gives me accuracy down to inches--ie. the same as mechanical cinema lenses. So a readout like 7'4", for example. Tape verifiable (that's how you collimate the system). And repeatable (again, that's how you collimate the system). I have seen it. On my own camera and on other cameras.

Our point is that your eyeball is able utilize the focusing knob and Birger interface to accurately accomplish and repeat focus with Canon lenses to the same degree that can be accomplished with a Cooke S4i and Arri FF4

I did want to add one thing to an earlier post. For ACs, the distance readout in the monitor is not the same as having markings on a lens barrel, because you're not able to anticipate focus quite the same way with a readout (which has just the distance you're at and not the range), that you are with a well marked lens. It would be like using the S4i data and not the markings on the lens. So relying solely on the readout for a rack focus is difficult...

However, putting near/far marks on the marking disc works perfectly. Repeatedly. Accurately. As it would with an FF4 (in other words, mechanical follow focus)

re: the steps...that has more to do with smoothness of pull. There are so many focus steps that you don't notice the increments between steps--which had initially been the main concern of many of us. Because of the huge number of steps they are imperceptible.

In contrast, the Iris only has 3 steps per stop, so it is not smooth. You cannot achieve a smooth (ie. non-steppy) iris pull using this system.

Again, your particular application seems to be something different than regular cinema production-no? Good luck with your inquiries. Please share the knowledge with us as you go.

P

[Stephen Strangways]

For ACs, the distance readout in the monitor is not the same as having markings on a lens barrel, because you're not able to anticipate focus quite the same way with a readout (which has just the distance you're at and not the range), that you are with a well marked lens. It would be like using the S4i data and not the markings on the lens. So relying solely on the readout for a rack focus is difficult...

I also find there's a delay of about half a second from when the lens stops moving to when the distance readout on the camera monitor updates. That makes it pretty much impossible to use the distance readout to determine when to stop a focus pull, but as Paul says, marks on the Impero disc work perfectly and repeatedly.

It's always a good idea to mark a "zero" point on the Impero disc so that if you get completely lost and want to reset focus, you can do so at the same zero point each time so your markings line back up perfectly after the reset.

[Jason Sinclair]

Conclusions:

Touch screen autofocusing is going to be very difficult to implement.

For motion control and precise digital focus Red needs to include full high resolution barrel encoders on their electronic lenses.

EDIT:

I am hoping that the phase detect system is in the round thing at the front of the gunner, I am also hoping there is an external lens motor with encoder just above it and the side electrical contacts supplying lens data to the touchscreen. Then we have a very valuable system and can use all lenses.



EDIT 2

Here is a vid which shows Ted and the touch screen autofocus using Canon which looks like a good idea for small screen shooting, to set focus. It does look handy, so i am assuming it talks to photocoupler.
http://www.youtube.com/watch?v=7AkdqY2NbY0&hd=1