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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 Reservations

More on intallation

More on intallation

I checked the back focus again today with all my zooms. Yesterday I set back focus with a 16-35 2.8L II. Today I started with my 28-70 2.8 L and it was a little off. I checked my 70-200 2.8L and it seemed a little off. Then I decided to redo the back focus using the 28-70. I tried just loosening the four screws that hold on the mount and putting my hand inside it's throat to rotate the back focus ring. Very easy. Easier than removing the mount. It took about four more adjustments. After that all lenses were spot on, even the 16-35. I guess that a such a wide mm as 16 there is just too much DOF even at 2.8. A little bit one way or the other was just not noticible. But on the other lenses just a little bit of focus adjustment was a mile. Now every lens seems to have perfect back focus. Even my Tokina 11-16 2.8 is also spot on. I am very happy about this. Now I can do what I have always done with my ENG style lenses, zoom in and get focus and then zoom out. Nice. These zooms are all L series, except for the Tokina, so don't expect to get this gift from the cheapies. But you could get lucky. I am using a back focus chart at about five feet from the sensor plane. Iris control is good on all zooms. Tomorrow I'll check the primes.
 
have you any sigma's? curious to see if these guys work at all--and also how the tokina cuts with the canons...and how the canons cut with each other. so many questions :)

glad to see its working so well for you!

p
 
I have been beta testing since late January. I've posted a bunch of stills in the past seven months. I have tons of clips. I'll work on getting some uploaded. The Tokina's color cuts perfectly with Canon L series. Before I left the studio tonight I tried my 85mm 1.2L and unfortunately it wouldn't focus. The mount would control the focus when you press the center button as it learned the lens, but I had no manual control. This particular lens requires auto focus power from the camera to manually focus using the len's focusing ring. I called Erik at around 7:30PM. I'm going to send him the lens next week so he can fix a bug in the software. That's the great thing about going Birger, new lenses are just a software fix. More later.
 
Mark, Can you point me to where there's more on how to do the back focusing you're doing? Thanks!
 
Thanks, Mark.

I didn't realize you'd already posted grabs. I may have seen some and just not recalled that it was you who posted them, as I try to keep up daily at the forum and stay aware of any grabs or clips shot with still lenses. I'll check your post history and see if I can find those you've already uploaded.:wink:
 
NuclearNerd said:
It's not just the internal diameter you have to worry about. Every lens mount has a specific "flange focal distance", or distance between mount and sensor. The Canon EF is 44mm, and Arri PL is 52 mm. 8mm is not much to fit an adapter. You couldn't really nest the two either, since the OD of the PL mount is exactly the same as the ID or the EF mount, so again, there's no room for an adapter.
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8mm is plenty of depth for an adapter. There are EF to nikon adapters and the difference in FFD is only 2.5mm; 44mm for EF, 46.5mm for Nikon F. Also, the internal diameters of EF and PL mounts are both 54mm, so I'm not sure what you're saying about the outer diameter of the PL mount being the same as the internal diameter of the EF mount. Theoretically, all one would need would be a male EF mount attached to an 8mm deep (or whatever the measurement would actually need to be based on the thickness of the mount flanges, etc...) tube with a 54mm internal diameter and an outer diameter of whatever size would be necessary to attach the PL mount, and a female PL mount. The only thing that might cause a problem is the internal "lip" that is in the Birger EF mount where the electronic contacts are located. It could get in the way of PL mount lenses with protruding rear elements.

The other route would be to remove the "smart lens mount" piece from the base Red/Birger camera adapter, as you would if switching from the EF to the forthcoming Birger Nikon mount or FourThirds mount, etc..., and make a mount with the same dimensions on the back half as these other mounts, where it attaches to the base adapter, and then whatever dimensions necessary on the front half (plus the 8mm over the EF mount) to accommodate the PL mount. I know that Erik has said that the base mount was not made to support a PL mount, but I'm not sure why it would be that much more stressful on the 4 screws that hold the mounts in place to have a PL mount over any of these others. And, again, even with this route, the electronic contacts in the base mount could get in the way of deeper PL mount lenses.

But we'll see. I talked to Doug Underdahl several months ago about making a simple nested adapter and he didn't think that it would be a problem. So, if and when I get my mount, I'll see if he still wants to make one and we'll see if it works. Then we won't have to debate about it's viability anymore.
 
very very neat. need to sleep. more info soon. all seems well with the mount. we leave in about 40 hours. We for sure tested the 17-55 and the 100-400. Stephen Lucas who will be shooting with us out at Burning Man is testing tonight.... Erik you have shed the light on our project. thank you. Canon lenses were geared by the team at Duclos

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MikeHedge said:
I had a dream last night. I was swimming... and was drowning.... someone was like "Mike!!!!" and I was swallowing water..... and at the last moment they threw me out a Birger mount, I grabbed onto it and was saved....
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A prophetic vision?
 
Collimation advice

Collimation advice

I know I'm not the only one who is frustrated on this thread, however...

Trying to be a little more constructive, hopefully the day is soon here. I'm sure I'm not the only one who will be collimating a lens/camera for the first time. Total newbie...

Perhaps we can have some suggestions on the process?

General Questions :

I have downloaded a PDF res chart ( I'm reluctant to buy a $1000 res chart, so other solutions would be helpful) There are lots of charts out there, what type are the best? Is there anything that I should be looking for to help me?

What size should I print my test Chart. A4 or A3 ok?

What is the process of collimation? Do we place a chart at say 3ft, then focus the lens to 3ft and then adjust the backfocus till everything is sharp?

I have read that using a wide angle lens would be best, but surely a wide angle has more error tolerance. Wouldn't using a 50mm for example give a more accurate result as the focus is much more critical? I'm a bit confused here as a wide angle could be off slightly and it would still look sharp. Perhaps a zoom lens and check it throughout the range?

Birger specific :

Reading the assembly instructions it looks like you adjust the collimation ring before you put the lens mount and lens on? So how does that work? Does that mean you have to take everything apart again to adjust the backfocus? This leads me to believe I have misunderstood it's use here, as that just doesn't sound right.

Some more explaination of the collimation ring, and its markings would be helpful from Birger.

Sorry if to some of you this is bread and butter, but I think I'm not the only one who would benefit from some info. I've never had to collimate my DSLR so it's all new territory. I'm sure I can do it, but I don't want to be guessing.

Here's hoping the first batch does indeed ship before the end of this week. Thanks for any advice you can offer.

best
 
Read mark crabtree's post on the collimation. You don't have to remove the whole mount to adjust, you just loosen it so you can rotate the adjuster. Right now you have to do it manually but Erik has been working on a software way of using particular lenses to help you find precise backfocus. The lenses give focus position info and it can be used to set the backfocus with a few tries to zero in.
 
Thanks Aqua, I went back to re-read and it will probably make more sense when I have one in my hand.

I would still be making it up as I went along, and I think its important to nail perfectly as we see what can happen at 4K if youre a fraction off.

What do the markings on the ring mean, how do they help you to adjust what you see in the viewfinder mathematically?

Hopefully Birger can post a comprehensive collimation procedure when the mount ships and if anyone can give me some advice on the best way to visually collimate (i.e chart type/size, distances, lens focal lengths/apertures) then I'd appreciate it. looks like Marcs 16-35 was giving inaccurate results. I have the 17-55mm - would that be a good lens to use for the adjustment?
 
The 16-35 was accurate, it is just that at 16mm you are too wide to accurately set focus, too much DOF. Better to set back focus with a medium zoom like the 24-70.
 
Congrats there Hedge!!! Looking good.
 
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