BMPCC4K Infinity Focus issue

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STUDIOSECHZEHN

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BMPCC4K Infinity Focus issue

PostThu Apr 01, 2021 12:20 pm

Hi. I hope, that I´m not totally wrong, but I can´t find a similar post on this forum.

I´m totally new to the BMPCC4K, coming from the GH5s which I use since its first days.

I bought the Camera and the Metabones Cine Ultra 0.64 Speedbooster and I´m not able to get the infinity Focus with this system right.

It doesn´t matter which lens I use.
I´ve tested it with the following Lenses:
Zeiss Distagon 28mm f 2.8
Zeiss Planar 50mm f 1.4
Zeiss Planar 85 mm f 1.4

The thing is, that all lenses work like a charm with my MFT Ultra Speedbooster on my GH5s.
What i also notice is, that the Focus distance is totally out of range. I have a close focus distance in the 28 mm which is around 5 cm, which is totally uncommon.

It Seems that the Sensor/Mount Distance on the Pocket is totally wrong. I tried to contact BM-Support three days ago, but there wasn´t any answer until now. :roll:

Did anyone of you recognized such or a similar problem? thanks for your help.
Attachments
Speedbooster-Ultra-BMPCC4K-85mm-1.4-Infinity.jpg
Speedbooster Ultra BMPCC4K 85mm 1.4 Infinity
Speedbooster-Ultra-BMPCC4K-85mm-1.4-Infinity.jpg (475.02 KiB) Viewed 803 times
Speedbooster-Ultra-BMPCC4K-50mm-1.4-Infinity.jpg
Speedbooster Ultra BMPCC4K 50mm 1.4 Infinity
Speedbooster-Ultra-BMPCC4K-50mm-1.4-Infinity.jpg (484.36 KiB) Viewed 803 times
Speedbooster-Ultra-BMPCC4K-28mm-2.8-Infinity.jpg
Speedbooster Ultra BMPCC4K 28mm 2.8 Infinity
Speedbooster-Ultra-BMPCC4K-28mm-2.8-Infinity.jpg (632.58 KiB) Viewed 803 times
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John Griffin

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Re: BMPCC4K Infinity Focus issue

PostThu Apr 01, 2021 1:50 pm

The speed booster is adjustable to correct for this but it means when you use these lenses on your GH5s they will overshoot infinity which is less of a problem than not reaching infinity on the P4k.
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Mark Foster

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Re: BMPCC4K Infinity Focus issue

PostThu Apr 01, 2021 5:38 pm

cMP 5.1 2x3,46/96GB/2x2TB 860pro/4x4TB HGST/SSD7101A 4x2TB 970evoplus/HP1344/BMD4k/Radeon VII
macOS 11.2.3

BMPCC4k (7.3)+ MB speedbooster ultra 0.71 (3.60)
resolve 17.2
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STUDIOSECHZEHN

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Re: BMPCC4K Infinity Focus issue

PostSun Apr 04, 2021 8:00 pm

Thanks. I know about the possibility to readjust the Speedbooster, but what confuses me the most is, that exactly my setup works perfectly on the Bmpcc4k from a friend. We did a side-by-side test and his pictures are sharp, while mine are not..

And after 7 days, I still don’t have a message by. BM- Support. Is this common?
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STUDIOSECHZEHN

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Re: BMPCC4K Infinity Focus issue

PostThu Apr 15, 2021 8:32 am

I´ve sent it in yesterday. BM will measure if there´s any tolerance. let´s see what happens.
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Frank2021

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Re: BMPCC4K Infinity Focus issue

PostFri Apr 16, 2021 8:40 am

This is a severe flange focal distance quality issue with the BMPCC4K.

I tested two (!) cameras (my first was replaced) with 3 (!) native MFT lenses at full aperture:

* Olympus M.Zuiko ED 12mm f2.0
* Meike 12mm f2.2 Cine Lens
* Samyang 12mm T2.2 Cine NCS CS

Infinty focus was impossible in all 6 (2x3) combinations.
In all 6 cases you had to set the lenses to infinty to focus an object in 1 meter distance!

Since this happens with all 6 (2x3) combinations, the flange focal distance of the cameras must be wrong.

My second camera is now under test at BMD UK.

It took more than 2 weeks to get it from Germany to the UK (I love BREXIT)
The test is going on now for one week (I can do this in 10 minutes)
Hope to get the camera back one day.
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John Brawley

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Re: BMPCC4K Infinity Focus issue

PostSat Apr 17, 2021 12:04 am

Might be worth a read of this.

There have always been copy to copy variations of FFD in both cameras and lenses. Seems fro this survey below BMD err on the side of being closer to zero, which means ironically if the lenses are out by more than usual, you can be in trouble.

https://www.lensrentals.com/blog/2020/0 ... o-cameras/

JB
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Frank2021

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Re: BMPCC4K Infinity Focus issue

PostSat Apr 17, 2021 10:30 am

This link for cine cams clearly shows the low precission of the BMPCC4k:

https://www.lensrentals.com/blog/2020/0 ... e-cameras/

They measured the Flange-to-Sensor Distance for 22 samples of BMPCC4K !
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drknsss

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Re: BMPCC4K Infinity Focus issue

PostMon Apr 19, 2021 5:06 pm

Frank2021 wrote:This link for cine cams clearly shows the low precission of the BMPCC4k:

https://www.lensrentals.com/blog/2020/0 ... e-cameras/

They measured the Flange-to-Sensor Distance for 22 samples of BMPCC4K !


Thank you for sharing this link. I have seen so many examples of this flange to sensor distance issue. I have also seen many reviews of lenses that didn't look so great, now I can see how these tiny variances from body to body can change the properties of a lens on a particular camera body.

I used to PA at a commercial house back in the day and the Camera Ops spent a lot much time testing the rented lenses and film bodies so there will be no surprized in editing. Nowadays these young whippersnappers want their camera to do everything perfectly.
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John Brawley

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Re: BMPCC4K Infinity Focus issue

PostTue Apr 20, 2021 11:24 pm

Frank2021 wrote:This link for cine cams clearly shows the low precission of the BMPCC4k:

https://www.lensrentals.com/blog/2020/0 ... e-cameras/

They measured the Flange-to-Sensor Distance for 22 samples of BMPCC4K !



Huh ?

It shows that ALL cameras have the same lack of precision. If anything the PC4K is closer to ZERO than most, with Zero being the exact spec distance.

In the case of people using the P4K with third party adaptors and other non-native lenses, you generally find that being less close to zero is actually better to accomodate those adaptors but you can hardly blame BMD for being closer to the spec than most.

JB
John Brawley ACS
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John Griffin

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Re: BMPCC4K Infinity Focus issue

PostWed Apr 21, 2021 7:12 am

Although the actual M43 flange to focal plane distance is known the actual tolerance it can be under and over is not. It's quite possible this is not that 'tight' and any variation would be expected to be taken up in the lens design which for M43 native lenses that have no fixed infinity stop will cope with. From a technical standpoint the lesser the focal length the narrower the depth of focus so the more critical the flange to focal distance will be for lenses like 12mm. Any manufacturer putting a non adjustable hard infinity stop into such a design is therefore creating a big problem as at the dimensional tolerance required you will run into both manufacturing tolerances and thermal expansion. +/-0.1mm is a pretty normal manufacturing tolerance but to get a 12mm lens to hit a hard infinity stop may require +/-0.01mm tolerance and this gets very expensive. I'm not familiar with cine lenses but all legacy stills lenses have adjustment for infinity stops that are fairly easy to DIY with a few simple tools. I would have though cine lenses would have even easier user adjustable stops considering the use of focus scales in focus pulling?
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Frank2021

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Re: BMPCC4K Infinity Focus issue

PostWed Apr 21, 2021 7:49 am

It is not alt all an issue of infinity stop, my three lenses do not have one:

I tested two (!) cameras (my first was replaced) with 3 (!) native MFT lenses at full aperture:

* Olympus M.Zuiko ED 12mm f2.0
* Meike 12mm f2.2 Cine Lens
* Samyang 12mm T2.2 Cine NCS CS

Infinty focus was impossible in all 6 (2x3) combinations.
In all 6 cases you had to set the lenses to infinty to focus an object in 1 meter distance!
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John Griffin

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Re: BMPCC4K Infinity Focus issue

PostWed Apr 21, 2021 10:19 am

Frank2021 wrote:It is not alt all an issue of infinity stop, my three lenses do not have one:

I tested two (!) cameras (my first was replaced) with 3 (!) native MFT lenses at full aperture:

* Olympus M.Zuiko ED 12mm f2.0
* Meike 12mm f2.2 Cine Lens
* Samyang 12mm T2.2 Cine NCS CS

Infinty focus was impossible in all 6 (2x3) combinations.
In all 6 cases you had to set the lenses to infinty to focus an object in 1 meter distance!

Well obviously some cameras are way off spec which should be a BM service issue. As most people don't seem to have this problem it would seem not to be a widespread issue with BM QC. Also mounting a heavy lens without lens support or a knock could be enough to distort the camera structure.
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Frank2021

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Re: BMPCC4K Infinity Focus issue

PostThu Apr 22, 2021 7:36 am

John, you are right!

I had a 70kg lens on both cameras and dropped them on stones 25 times!
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John Griffin

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Re: BMPCC4K Infinity Focus issue

PostThu Apr 22, 2021 7:57 am

Frank2021 wrote:
I had a 70kg lens on both cameras and dropped them on stones 25 times!

I wouldn't mention this to BM when you send it in for fixing.....
Seriously though - the M43 mount is inherently weak and on the P4k secured onto a plastic frame which is OK for most native M43 lenses but when people start loading it up with adapters and heavy cinema lenses it needs support as only a slight amount of overload would be enough to distort the flange to focal plane setting. It's also worth checking the tightness of the 4 flange securing bolts.
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