SHIM Set ups in URSA Mini Pro PL and EF

Hi all,

Keen to hear what shims you are using across PL and EF set ups.

I've been starting to test the shims supplied with the PL mount kit to make sure there is accuracy across mounts and lenses.

The instructions say in EF "when removing the original EF mount, make sure the 0.50mm and 0.10mm shims always stay attached to your camera." So my assumption is, how it is shipped with EF is how it should be with EF lenses.

However I've been doing some tests with Canon Cine Primes (35, 50, 85) testing their infinity focus and focus marking accuracy. From the tests 3-foot (for example) on the lens doesn't give a sharp lens chart at 3-foot measured from the focus point on the camera.

When switching to PL it says "add 0.10mm to your camera." Does that mean in addition to the existing two that you use for EF? So there would be 3 shims on your camera for PL? I used this method recently for a TVC with Cooke S4s. The focus is fine but I didn't have the 1st AC pulling from the lens markings so I can't confirm if there were any issues.

A friend who has a UMP tested his PL shims with RED primes lenses and found that the .50+.10+.10 doesn't give accurate focus marks according to the lens.

Keen to hear what you guys know and have tested. I will be testing more on Monday with Zeiss Standards in PL.

Final thing. I had a black shim on my UMP when it shipped with no marking. Every other shim has a mm marking. I measured it and it is probably a 0.10. However two other UMP owners I know do not have a black shim in their set. They only have 1 x .10. Did I win the Black Magic Golden Ticket?

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If a wide zoom is parfocal I'd trust that more than it's focus marks. After all, this is great glass, but not a true cine lens with carefully tested witness marks.

A few things.

Each mount shims differently. So what you get from the factory is very possibly different camera to camera because the tolerance of the mount changes camera to camera. This is the whole point of shims. To make the camera mount conform to a standard. You use a shim to make sure the variances of manufacture from camera to camera can be accounted for.

It makes sense that there would be different shims in each mount no ?

THEN

On the lens side, it's usually considered good practice to shim to a known good lens if you don't have a way of measuring your flange depth. Wide lenses are best to use for this as they have less tolerance in the focus depth.

Normally you use something like this to check you camera.

http://www.denz-deniz.com/premium-produ ... -pl-mount/

If you don't have access to something like this or can't have a local lens tech check your camera using one, then you can start to use a lens, BUT it's fraught because many lenses aren't "collimated", especially if they're EF mount.

That means that the lens is set to focus at infinity when the lens focus line is on infinity.

Checking a lens at 3' is not a good way to check the FFD of your camera. It's entirely possible to have a lens not be collimated OR, equally likely, be collimated but not have accurate witness marks for short distances like 3'. So you can have you out of whack camera shimmed to get a out of whack lens focused at 3', but the lens will then maybe not hit infinity or hold through the zoom range or at other distances OR maybe only be accurate for that one lens but not other.

You can really start chasing you tail if you don't get methodical and know what you're doing.

Best to get some professional help, because if you haven't done it before you can screw things up really fast.

JB

Thank you John. That's really helpful.

Thanks to everyone who replied.

Very informative, thanks John.

So in a situation where you would be regularly changing mounts depending on what glass is hired in for that particular shoot (in my case PL, EF and the upcoming F mount) what would be the procedure regarding shimming if the hired-in glass is of an unknown quantity i.e. you don't whether they're 'collimated' or there isn't the time for the whole package to be checked over by a lens tech? For one day shoots, at best, the glass might arrive the evening before for a quick tech setup the evening before.

Thanks in advance!

Well, you're pretty much out of luck then.
The only possibility might be FF and your own marks. But zooms might not be parfocal and wides with floating focusing will not show their full quality.

Very informative, thanks John.

So in a situation where you would be regularly changing mounts depending on what glass is hired in for that particular shoot (in my case PL, EF and the upcoming F mount) what would be the procedure regarding shimming if the hired-in glass is of an unknown quantity i.e. you don't whether they're 'collimated' or there isn't the time for the whole package to be checked over by a lens tech? For one day shoots, at best, the glass might arrive the evening before for a quick tech setup the evening before.

Thanks in advance!

Regularly changing mounts is always going to be hard. You can do it, but it's not really meant to be a daily activity. You best bet would be to get a known "good" lens that you can trust as use that to set your mount to. In other words, get a good lens, preferably wide that has accurate witness marks or get it set by a technician and then use THAT lens to set your shims on the other mounts (presuming you can adapt those lenses to those mounts or get a "known" lens for each mount.

JB

Should work reasonably well for PL mount, but EF is a gamble. Lenses themselves are all over the place.

Thanks John and Uli, very useful info!

Paul,

Did your kit come with 2 x .10 and was one of them black without markings?

I have two of them which makes sense considering the instructions indicate to use both for PL. However a mate of mine only received 1 x .10mm shim.

I'm just trying to work out some kind of standard.

Anyone else?

Regards,

Brad

[Tim Schumann]

The cameras are all shimmed at the factory to within + or - 0.02mm which is the same tolerance many lens manufacturers use.

Yes to go from the default EF to the PL, B4 or F mount you should add the 0.1 shim meaning you will have a plastic 0.1, a metal 0.5 and then add a metal 0.1. If you do this and you are not hitting your marks then you can reshim with the shim kit that comes included with each mount or can be purchased on its own as the URSA Mini Pro Shim Kit.

Each of these kits should have a 0.025mm, 0.05, 0.1, 0.12, 0.15, 0.18, 0.2, 0.3 and a 0.5mm shim in the kit. If you also got a plastic 0.1 in the shim kit then it might be a bonus shim so you got lucky!

With that combination in the shim kit you should be able to adjust get your camera shimmed perfectly. Tools like the Denz FDC that John linked to are excellent for checking this as they take the lens out of the equation and ensure the camera & mount are bang on. There is also a EF attachment for the FDC which works well.

If you know your lens is shimmed correctly then you can shim to that or a decent FDC can help. Wear and tear over time, as well as temperature changes can have effect on your shimming so just because your lens is a PL lens doesn't necessarily mean it hasn't shifted over time.

Following the simple instructions in the kit or the URSA Mini Manual will have you very close to correct for PL, F Mount and B4. We have found that some EF lenses also work better with the 0.1 added to the shipping configuration but as there are so many EF lenses out there and as the EF lenses themselves are generally not shimmable you are able to adjust precisely using our shims provided you are methodical with your adjustments.

Hope this helps.

Hello everyone.

It's a probably useful post for the UM4.6K Pro owners and those who use the PL mount and wonder about how many shims to use.

I recently put on Cooke s4 and Genesis lens on my UM4.6Pro using the manual-recommend 0.10mm shim. In both cases the infinity was on 6 meters.

Then, courtesy to the ATM System (a great rental in Poland with great and helpful people working there) I could test the sensor distance calibrator.

It appears that you need to use 0.10 + 0.18 shims to make it work correctly (in addition to the shims you have already there for the EF mount). Unless your lenses are calibrated in any non-standard way.

Hope this solves a bit

Hello everyone.

It's a probably useful post for the UM4.6K Pro owners and those who use the PL mount and wonder about how many shims to use.

I recently put on Cooke s4 and Genesis lens on my UM4.6Pro using the manual-recommend 0.10mm shim. In both cases the infinity was on 6 meters.

Then, courtesy to the ATM System (a great rental in Poland with great and helpful people working there) I could test the sensor distance calibrator.

It appears that you need to use 0.10 + 0.18 shims to make it work correctly (in addition to the shims you have already there for the EF mount). Unless your lenses are calibrated in any non-standard way.

Hope this solves a bit

You can’t really extrapolate about all PL mount cameras needing the same shim. This is something that needs to be checked for each camera. It’s never going to be the same amount.

JB