BMPC4K Mount Issues - Infinity Focus, Wobble

Hi everyone. I recently bought a Pocket 4K and I'm experiencing a number of issues. One of the biggest is the inability to make lenses+MFT adapters I used for roughly 10 years with other MFT cameras (BMPCC OG, GH4..) work properly. Two things I noticed are an increased play/wobble on the mount (whereas the grip of all my MFT adapters is rock solid on the BMPCC OG) and the seemingly wrong flange focal distance.

I used for years C-mount zooms+C7Adapters's high quality C-to-MFT adapter on my BMPCC OG and all zooms had parfocality and correct infinity. None of them has either one, with the same adapter, on the Pocket 4K. I tried the cheap Fotodiox C-mount adapter and the parfocality improves, but still isn't right. Setting aside C-mount zooms and parfocality which probably require a design refinery this 1,300€ camera probably can't have, I switched to try Canon FD lenses, which I also used for 10 years.

I had a FD-MFT cheap adapter from 2013, with which all my FDs reach infinity focus on the BMPCC OG; I tried it on the 4K, and while infinty seem to work okay (maybe a little further away than it would seem right) I noticed the adapter had a noticeable wobble on the Pocket 4K mount. So I said: let's buy a new, more serious, well-reviewed FD adapter for my new camera. I bought the K&F Concept FD-MFT which is among the best reviewed.

The K&F Concept adapter arrived and I tried it with my Canon 28mm FD.

Firstly, the adapter's play on the BMPC4K mount is the exact same of my old cheap FD/M43 adapter from 2013, so it's either my BMPCC4K own MFT mount that is faulty, or this amount of play is normal. Check the video on this link: https://drive.google.com/file/d/1emoL-lPlKfEFM4Y1qxFAVHzazxeO4SsJ/view?usp=drive_link; does this amount of wobble seem normal to you? Maybe it is, but if it's not, should I contact BMD support about it?

Secondly, but that's big deal, infinity focus can't be reached at all. With my old FD/M43 adapter from 2013, there is a rough correspondence between the actual focus distance and the focus ring markings. If I stop the 28mm to f4 and focus at 3 meters according to the lens markings, on an object that's 3 meters away, it roughly checks out; with the K&F concept adapter, 28mm stopped f4, I focus on the same object that's roughly 3 meters from the camera and it is way out of focus; turns out it comes in focus if I pull the wheel to 80cm [0,8 meters] according to the lens markings. Infinty focus is, instead, way beyond anything on the horizon.

Am I doing something wrong? Has someone experienced this or the K&F adapter?

I have a similar issue with a Minolta MD to MFT adapter, which again works fine with the BMPCC OG.

I tought it was an adapters-related issue but I am starting to see a pattern here and the hypothesis of the Pocket 4K's flange focal compliancy to the MFT standard + camera's physical MFT mount being trash is becoming not that improbable.

Can you help/make suggestions?
It's getting very frustrating :/

Thanks everyone in advance

I have had zero issues with any MFT lens or adapted lens, even at infinity focus. I've used cheap and expensive MFT lenses, adapted M42 and FD manual lenses, and even adapted RF lenses without issue.

There's no front/back play on any lens I've used. Rotational play happens a little bit with the cheapest adapters but otherwise isn't there.

Contact support. This sounds like some sort of manufacturing issue.

On today’s shoot I took measurements with a tape measure to various locations on the stage for both the BMPCC4K with SPL Magic 32mm APO PL mount (original now called Hyperprime) and the UM4.6K original with B4 mount and the 30
year old Fujinon 20x7.8BRD Cine Zoom. Then I used the handy Focus Chart app with minimal Focus Assist coloured lines.

The witness marks on the prime lens were not reliable although the prime lens does focus everywhere. The witness marks on the Fujinon were quite reliable. As part of my prep for the shoot, I considered using the Tokina ATX Cinema zoom and found its witness marks weren’t reliable. I’m beginning to suspect my PL-MFT adapter to be the problem and will look into that further as I have a different adapter.

I have had zero issues with any MFT lens or adapted lens, even at infinity focus. I've used cheap and expensive MFT lenses, adapted M42 and FD manual lenses, and even adapted RF lenses without issue.

There's no front/back play on any lens I've used. Rotational play happens a little bit with the cheapest adapters but otherwise isn't there.

Contact support. This sounds like some sort of manufacturing issue.

It indeed seems a manufacturing issue. The only adapter that doesn't have any rotational play is the C7Adapters' C-mount to MFT. All the others --Nikon G, Canon FD, Minolta MD... have rotational play; and they don't have it on my Pocket OG mount which is still rocking it from 2013.

I guess what would mean tough --will I have to send to BM Support at my expenses and then wait months to have it back? I wonder if the authorized seller can just swap it with another unit (I bought it in September, and as a first funny surprise it came without the protective plastic on the LCD screen, with finger marks on it. But support assured me it's a new unit, it was a packaging error and they won't in any way extend warranty; such a great support)

On today’s shoot I took measurements with a tape measure to various locations on the stage for both the BMPCC4K with SPL Magic 32mm APO PL mount (original now called Hyperprime) and the UM4.6K original with B4 mount and the 30
year old Fujinon 20x7.8BRD Cine Zoom. Then I used the handy Focus Chart app with minimal Focus Assist coloured lines.

The witness marks on the prime lens were not reliable although the prime lens does focus everywhere. The witness marks on the Fujinon were quite reliable. As part of my prep for the shoot, I considered using the Tokina ATX Cinema zoom and found its witness marks weren’t reliable. I’m beginning to suspect my PL-MFT adapter to be the problem and will look into that further as I have a different adapter.

I'm wondering: is there a reliable way to test if a lens is working right while focusing? The thing with infinity focus that I don't get with adapted lenses is, if stopped down to f4/5.6 or above, where should the sharp focus start? Because with prime photo lenses stopped at f4 or above, focusing to infinity will make focus peaking tell me it's all in focus like 50 meters away, but, say, a building 30 meters away is not as sharp; if I turn the wheel slightly back prior to infinity, the focus peaking gets the "closer" building as in full sharp focus; with cine zooms like my Angenieux, stopped f4 or similar, pulling to infinity will give me everything in focus from my window 2 meters away to the bulding 30 meters away and anything beyond; I think that is how it's supposed to work; in fact, if I shoot in a small room and I'm doing a master shot (not a close-up), focusing to infinity would give me everything in focus. This is not true with still lenses, even stopped down, where if the small room is, say, 5 by 5 meters, I have to focus accordingly, 5 meters away and not to infinity; PS: all these focusing doubts refer to my experience with the BMPCC OG and other older MFT cameras, as my new Pocket 4K can't seem to do anything properly to this date.

How do you realiably test if a lens is focusing right, and how does infinity focus is really supposed to behave?

Thanks

I have three P4k, one of which is unable to focus to infinity with 2 of my Kamlan lenses.
I have a more or less fixed config on 1 cam, with a DZOfilm Linglun20-70, with an extra plate and lens support, so the lens has no play/wobble.
The DZOfilm is parfocal, and has a built-in adjustment to achieve this. I notice regularly that transporting the cam/lens (in its dedicated suitcase, so I basically do NOT take it apart and reassemble) makes it NONparfocal (changes in temp mainly ?). I then need to adjust on the lens (with this particular lens you can do that without taking it off the cam) to make it parfocal again. In most circumstances I end up at almost exactly the same adjustment, but sometimes it can be quite off.

This proves that even a known and correct P4K cam (mostly this lens needs to deviate almost nothing from its calibrated position / and the Kamlan lenses focus fine on this body) can STILL behave badly with its mount...

Or is this a known issue with all cams ? I don't know.
But I do know infinity focus on manual lenses can be problematic/impossible.

You are correct in a small room you’re never going to want to focus at infinity! Just a reminder infinity is very far away but as we rotate the lens gear toward longer distances, as you know a very tiny amount of rotation changes the focus hundreds of meters. When shooting landscape stills, we naturally just focus at infinity because it’s easy, but it’s not necessary.

There are many apps that quickly illustrate the depth of field with a given lens at a given focal length at a given f/stop on a given sensor/window. I use Lens Toolkit f8. That’s for planning my approach. For example my subject may be 6 meters away typically but may move forward and backwards from 5 meters to 8 meters. Focusing at roughly 6 meters gives me focus on the entire stage say at T5.6 with a wide focal length. When you zoom in on the subject you’ll get much less depth of field and should be prepared to alter your focus.

When shooting with the camera, best to actually test focus to the various stage distances (using the Focus Chart app) and the Focus Peaking on the BMD camera. You can set the Near and Far focus points on your focus gear (I use PD Movie to control my focus motor) and you’re ready to shoot and follow the action. Manually.

Focus depends upon setting the mysterious “centre of confusion” which gives you a number such as 1500 that defines how critically you want to define what you consider to be in focus. I typically use a higher value 1700 to be fussier about focus. The value I believe changes depending upon the size of the sensor, but I’d need to look it up to be sure.

The Lens Toolkit app illustrates clearly what will be in focus for near and far positions from the desired focus say from 5 to 8 meters while focused at 6 meters for a wide angle. A long telephoto focal length may only have a few centimeters in focus from near to far positions. So that focus peaking while shooting is necessary.

Thinking about Focus Peaking in a BMD camera, set the intensity to a Low value rather than High to be more accurate. If your subject moves a lot, use Medium and pray. Play with it until you see what’s working for you. My last shoot I think I had the BMPCC4K at Focus Lines 15, but if the subjects are relatively stationary, even Focus Lines 1 will work! I don’t know for sure the programming techniques being used by BMD but it’s like the different strength settings vary the circle of confusion. High is dangerous as it will pretend something is sharp when it’s not really. Low values are trustworthy, but difficult to work with when there’s significant motion such as sports where Medium is required.

Lensrentals did an exhaustive evaluation of flange depth for various cameras. The P4k did have a wide range of tolerances, but they were all <19.25mm which means that the lens might hit infinity before the mark but it will still hit.

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

Keep in mind these are native camera mounts, with adapters there is going to be additional variance. The C7 MFT-PL adapters were typically about .05mm short to ensure infinity focus.

Then there’s the lens. On my OG Pocket I had to try 3 copies of the SLR Magic 12mm before I got one that would mount let alone hit perfect focus.

Without shimmable mounts and lenses there’s not much to be done except for trying out combinations of stuff and seeing what works best together.

Good Luck

Sounds to me like you got a copy of the 4k that has a mount that’s either out or close to the tolerance.

Has Howie say, multiply that with some adaptors and lenses that are biased in the the same way and then you have an issue.

The huge downside with mirrorless mounts is that they can’t be user shimmed.

Some adaptors do offer shimming so you can probably make it up in the adaptor but for native lenses you might be out of luck.

If the camera is just purchased then ask to swap for another copy or RMS is.

JB

I guess what would mean tough --will I have to send to BM Support at my expenses and then wait months to have it back? I wonder if the authorized seller can just swap it with another unit (I bought it in September, and as a first funny surprise it came without the protective plastic on the LCD screen, with finger marks on it. But support assured me it's a new unit, it was a packaging error and they won't in any way extend warranty; such a great support)

I'd check with the seller first. If they're unwilling to help out, get with BMD and sort it with them. Make sure they know their authorized seller wouldn't help you with what should be a warranty issue if it comes to that.

Thanks everybody for the previous answers, I really appreciate.

Sounds to me like you got a copy of the 4k that has a mount that’s either out or close to the tolerance.

Has Howie say, multiply that with some adaptors and lenses that are biased in the the same way and then you have an issue.

The huge downside with mirrorless mounts is that they can’t be user shimmed.

Some adaptors do offer shimming so you can probably make it up in the adaptor but for native lenses you might be out of luck.

If the camera is just purchased then ask to swap for another copy or RMS is.

JB

Yes, I see what you mean. In fact, I shall split my inquiry in two parts, one is the wooble problem and the other is the flange focal distance problem; I tought they were related but I don't think so anymore, here's why:

I returned the K&F Concept FD-to-MFT adapter (new version) that didn't reach infinity with any of my FD lenses and then I bought the "Urth" one instead, another one that is deemed to be good-quality.

Wobble problem: there is the same amount of wobble/rotational play of the K&F and my old FD/M43 cheap adapter from 2013. So be it, I'll adress my seller or BMD support on that, see if it's normal (you can check these videos: https://drive.google.com/file/d/1emoL-lPlKfEFM4Y1qxFAVHzazxeO4SsJ/view?usp=drive_link, https://drive.google.com/file/d/1emarWP6fKXohcxQg75O2LWbADs74DgQm/view?usp=drive_link, https://drive.google.com/file/d/1gJXdC2tNZJL9pd_Cq8RTyrjUGWt0bh68/view?usp=drive_link, https://drive.google.com/file/d/1gD25MS8ORzOnG4jWUHtUBSzuZpA47nN4/view?usp=drive_link)

Flange tolerance problem: the Urth adapter shows the same behavior of the K&F Concept adapter: infinity focus can't be reached and focus marks are completely off.
With my old cheap, brand-less FD/M43 mount from 2013 [that I wanted to replace, funnily] there is a rough correspondence between the actual focus distance and the focus ring markings (3 meters according to the lens markings does mean focusing 3 meters away from the camera).
With the K&F concept adapter, and now with the Urth adapter, pulling the focus wheel to 0.8 meters (80cm) does focus on objects 3 meters away, and infinity can't be reached no matter what.
This got me thinking. I tried the Urth adapter with my old BMPCC OG and it does have roughly the same behavior it shows with the Pocket 4K (but it does not have rotational play, hence the two problems are unrelated);

I really don't know where the problem is, I'm trying to rule out possibilities:

- Can all my FD lenses be off-tolerance? A bit unlikely, they where used for photography since the 90s and I used them seamlesessly for years [with good correspondence to focus markings and reaching infinity focus] with my old brand-less FD/M43 adapter on my BMPCC OG;

- Can my BMPC4K and my BMPCC OG be off-tolerance and biased the same way? Kind of unlikely, and I can say with sufficient confidence my BMPCC OG mount is compliant as it worked perfectly with several adapters (C-mount parfocal zooms being parfocal, Nikon still lenses, Minolta still lenses...)

- Can the new FD/M43 from K&F and Urth be off-tolerance, in the same exact way? That's extremely unlikely. They are deemed good quality by the online community and I didn't find reports of the problems I am experiencing; I think in this very group there are people who use these exact adapter models with the Pocket 4K and their FD lenses without any trouble, focusing according roughly to lens marks and reaching infinity focus: can somebody confirm this?

Which of the three possibilities is the most likely one? I really don't know what to do, can you suggest some lens tests/measurements I can take to identify what the problem really is?

Thanks a lot to everyone

Sorry to resurrect this thread from the dead, but did you ever solve this issue?

I'm having the exact same issue with all of my adapted lenses on the BMPCC 4k, no problems with the OG BMPCC.

Apologies for resurrecting this thread, did you ever resolve this issue?

I'm having the exact same issue with my BMPCC 4k and all adapted lenses that work fine on my OG BMPCC.

Apologies for resurrecting this thread, did you ever resolve this issue?

I'm having the exact same issue with my BMPCC 4k and all adapted lenses that work fine on my OG BMPCC.

Hi! no problem. I "solved" the issue by giving up; sent the camera to BMD support UK, they tested it with their instruments (a tool that determines if the sensor is within a certain range in respect to the MFT flange standard, but gives no direct measurement) and they said it tested ok.

For the wobble, they said it's by design, and also within the expected "wobble" range.

My thoughts on this full debacle is that the BMPC4K is a budget camera with less build quality and larger tolerances, while the BMPCC was a top-notch experiment engineered to win a market, and it won it. I still use the BMPCC OG after more than 10 years and it still rocks.

So, the only way is to find workarounds; for the flange, you'll have to browse or customize adapters; for the wobble, you'll have to use locking mechanisms attached to rails or to the cage; that's the best I could come up with anyway!

Have a nice day