BMPCC Speedbooster backfocus adjustments...

Hello again guys !

I recently received my mosaic OLPF filter for the BMPCC. I'm very pleased with it so far. I think it's a very necessary feature BM cameras should have from the go. I love my bmpcc but the aliasing (even more than the moire) is all over the place and used to prevent me from using this cam on a pro level. Anyway you have the mosaic filter or a blackpro mist filter to get pretty much rid of it (I haven't figured out which combination works best yet) but they have their drawbacks.

So, as you probably know, installing the filter introduces a slight shift in the focal distance which can be corrected if you use a speedbooster. I have the specific bmpcc EF speedbooster and tried to adjust this backfocus by unscrewing basically the only screw I see on the bottom right of the rear optical block. But the optical block won't turn at all. I see what appears to be another screw at the exact opposite but it lacks a screwdriver slot.

So has anyone done it before ? Do you think I should try harder turning the block ? It seems quite stuck. Do I need to do something else ?

Thanks ! Cheers !

The Mosaic OLPF filter should have come with a shim kit to get the lens mount back to where it needs to be. If your filter kit did not come with this shim kit just contact them and they'll send you one (likely for free).

Thx for the info !

There was no shim kit. Maybe it's a new addition to their very recent customers ? Cause I haven't heard of it. I have the exact same box that you can see in their video where they show how to install the filter.

And by e-mail, Mr Vasilyev from the company, never told me about it. He advised me to adjust the back focus of the speedbooster. But that was even before I received my filter. Maybe they've added this kit now.

I'll send them an e-mail about it. But it doesn't change the fact that I can't make this optical block turn. I'm sure someone has done it before !

Hi Olivier,
I have had the opposite problem. Sometime ago I adjusted a Speed booster and found that the thread on the lens block was a loose fit in the mount. It was so loose that you could see the lens block move sideways when the retaining screw was tightened. I sent it back to the manufacturer for modification. When it was returned I made my adjustment with the assistance of an autocollimator left over from my 16mm film days.

Thx for the info !

There was no shim kit. Maybe it's a new addition to their very recent customers ? Cause I haven't heard of it. I have the exact same box that you can see in their video where they show how to install the filter.

And by e-mail, Mr Vasilyev from the company, never told me about it. He advised me to adjust the back focus of the speedbooster. But that was even before I received my filter. Maybe they've added this kit now.

I'll send them an e-mail about it. But it doesn't change the fact that I can't make this optical block turn. I'm sure someone has done it before !

The optical cell is prevented from rotating by a small set screw in the side of the m43 bayonet. See this page on the Metabones website for a visual: http://www.metabones.com/article/of/inf ... oster-only . Focusing the Speed Booster in this way is equivalent to using shims, but is much more convenient. Of course you can still use shims under the lens mount attachment screws. I normally cut my own from standard plastic shim stock. One advantage of using shims is that you can correct any lack of parallelism between the sensor and the lens mount - which I had to do with my BMPCC.

The optical cell is prevented from rotating by a small set screw in the side of the m43 bayonet. See this page on the Metabones website for a visual: http://www.metabones.com/article/of/inf ... oster-only . Focusing the Speed Booster in this way is equivalent to using shims, but is much more convenient. Of course you can still use shims under the lens mount attachment screws. I normally cut my own from standard plastic shim stock. One advantage of using shims is that you can correct any lack of parallelism between the sensor and the lens mount - which I had to do with my BMPCC.

Thanks Brian for the info.
I already went on metabones website though but I think something might be wrong with my speedbooster. I posted a photo of mine on bmcuser forum and someone told me it has a problem.

You can see on the picture the bottom right screw that I can unscrew and which does nothing. And top left, a bar/screw that might block the optical cell. Should my speedbooster looks like the photo ? Is everything at the right place ?

About shims, I'm very interested in it. What kind of plastic can I use for it ? Where do you exactly place your shim ?

Thank you for your expertise !

Mosaic Engineering sells shims for the BMPCC mount made to be paired with their OLPF. See their install video here:

The optical cell is prevented from rotating by a small set screw in the side of the m43 bayonet. See this page on the Metabones website for a visual: http://www.metabones.com/article/of/inf ... oster-only . Focusing the Speed Booster in this way is equivalent to using shims, but is much more convenient. Of course you can still use shims under the lens mount attachment screws. I normally cut my own from standard plastic shim stock. One advantage of using shims is that you can correct any lack of parallelism between the sensor and the lens mount - which I had to do with my BMPCC.

Thanks Brian for the info.
I already went on metabones website though but I think something might be wrong with my speedbooster. I posted a photo of mine on bmcuser forum and someone told me it has a problem.

You can see on the picture the bottom right screw that I can unscrew and which does nothing. And top left, a bar/screw that might block the optical cell. Should my speedbooster looks like the photo ? Is everything at the right place ?

About shims, I'm very interested in it. What kind of plastic can I use for it ? Where do you exactly place your shim ?

Thank you for your expertise !

The screw on the lower right functions as a stop to prevent the bayonet from spinning on too far. The upper left screw is the one you need to loosen in order to turn the threaded optical cell.

I normally use color-coded plastic shim stock like this: http://www.zoro.com/precision-brand-shi ... lsrc=aw.ds , although I also use brass and steel shim stock for certain applications. Shims should be placed close to the screws to minimize any warping of the flange. Ideally you would make a complete ring-shaped shim with holes and cutouts in all the correct places, but I generally just cut little rectangles with a pair of scissors. Another useful shim material is Scotch tape, which is about 0.002" thick.

I didn't find a source for Zoro in Europe, so may I ask if Scotch tape will not change it's thickness under pressure, with the adhesive layer being squeezed? Or does this not happen in your experience?

Unfortunately the top left screw has no head on my speedbooster... I'll send an e-mail to Metabones. But I also ordered the shim kit from mosaic. Thank you for all your advice guys ! And I'll try Scotch tape (on a RJ speedbooster FD/M43 which has a little loose mount)

I didn't find a source for Zoro in Europe, so may I ask if Scotch tape will not change it's thickness under pressure, with the adhesive layer being squeezed? Or does this not happen in your experience?

There must be some sort of shim stock available in Europe. I'm sure that Scoth tape will change thickness under pressure - but you're talking a tiny change at worst. You just don't need micron accuracy for shims.

Unfortunately the top left screw has no head on my speedbooster... I'll send an e-mail to Metabones. But I also ordered the shim kit from mosaic. Thank you for all your advice guys ! And I'll try Scotch tape (on a RJ speedbooster FD/M43 which has a little loose mount)

I'm having the same problem with the BMPCC speedbooster. The screw I'd need to loosen to adjust backfocus appears to have to head. Did you ever find a solution to this?

has anyone out there managed to adjust the backfocus on a bmpcc speedbooster?

It is adjustable and there safe seversl discussion on this previously posted, try doing a search here and via Google.
Cheers

Brian.

Slightly off-topic. Have you contemplated making the 0.71x Ultra optical cell alone available for people to buy to install in their 4K URSA cameras? A few who are doing this have been buying new or used Ultra Speedboosters and ratting the optical set from within them.

Brian.

Slightly off-topic. Have you contemplated making the 0.71x Ultra optical cell alone available for people to buy to install in their 4K URSA cameras? A few who are doing this have been buying new or used Ultra Speedboosters and ratting the optical set from within them.

Occasionally we've sold small batches of optical cells (50-100 units) for various purposes. However, I'm not sure it would be worthwhile making individual cells available for a DIY market.