Thread: OLPFs for BMPCC and BMMCC - Mosaic & RawLite

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  1. #81  
    Senior Member shijan's Avatar
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    First attempt to install the shim:
    3 screws unscrewed but hex holes are slightly deformed now. Fourth screw hex holes is deformed and it can not be unscrewed at all. It seems it was overtighten in the factory during camera assembly. Even Mosaic custom made hex bit don't helps.

    Conclusion:
    Screws are made of unknown crappy soft metal. It seems hex holes have custom shape that protects from unscrewing them. They holds hex key very well when you screw them, but slips when you unscrew them. This is build like cheap unrepairable thing in mind. What a shame Blackmagic, what a shame...
    Need to find a way to unscrew that sticked screw.
    Need to find new M3 screws made of hard stainless steel and with more reliable Phillips or Torx hole to replace those crappy ones.


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  2. #82  
    Senior Member shijan's Avatar
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    Sorry for double posting but i can not hold my emotions.
    Finally I was able to unscrew fourth screw with help of a pad cut from Nitrile glove. Nitrile is very strong material and same time very grippy rubber-like. I need to add enormous force to unscrew that screw. It was very hard to unscrew all the way compare to other screws. When i finally get it out of camera i find that a drop of Loctite adhesive in the end. This kind of adhesive used to protect screws from self unscrewing in heavy duty situations. This is madness.

    Last edited by shijan; 09-10-2017 at 07:15 AM.
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  3. #83  
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    Quote Originally Posted by shijan View Post
    Sorry for double posting but i can not hold my emotions.
    Finally I was able to unscrew fourth screw with help of a pad cut from Nitrile glove. Nitrile is very strong material and same time very grippy rubber-like. I need to add enormous force to unscrew that screw. It was very hard to unscrew all the way compare to other screws. When i finally get it out of camera i find that a drop of Loctite adhesive in the end. This kind of adhesive used to protect screws from self unscrewing in heavy duty situations. This is madness.

    It depends on how you look at it. They weren't intending for you to take apart the camera. This is a choice you(we) are making. So the Loctite is not all that surprising, especially if they feel it would prevent things from becoming loose in the field. We always have to keep in mind that just because we have the ability to modify the cameras doesn't mean the company making the cameras thought of making it easy to do so.

    Having said all that, yes it can be frustrating when you want to modify something and you risk damaging it. That's why I have encouraged people to be careful with installing their own leitax mounts on C/Y lenses because sometimes the screws are cemented and it can be a bear to get the screw out. Sometimes it's best to just have someone with the right tools do it.
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  4. #84  
    Senior Member shijan's Avatar
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    Here is a quote from Mosaic support regarding this problem:

    First of all, just about your immediate situation, maybe I have one suggestion: Since you have managed to remove the difficult screw, and also you seem to be a resourceful person, if I were you, before replacing it, I would use a dremel tool or some similar cutting tool, to first cut a slot in the top of your damaged screw. This would allow you to at least replace the screw into the camera right away, without having to wait to find some replacement; with a slot in the top of the screw at least you can use a normal flat-bladed screwdriver to turn the screw reliably for the time being.

    Second: We actually have here, replacement screws with the same head design as Blackmagic uses in their cameras. If you would like, we are happy to send you some of these new screws, at no charge.

    Now for a bunch of additional details:

    These screws that Blackmagic uses in the lens flanges of all their cameras - they are a significant complication; I am not sure why Blackmagic has chosen to use such screws as these. As you have found, the design of the screw head shape is non-standard, so we have found it to be impossible to buy replacements from any common source. Also there are other problems with these screws: The hex sockets are slightly over-sized, but at the same time the hex sockets are also very shallow. The result is that these screws cannot be turned strongly with a normal 2mm hex driver - a normal driver will just strip the screw socket, as you unfortunately have found.

    I think, that this is the reason why Blackmagic has sometimes used a thread locking compound on these screws: I think, they are not using Loctite on these screw for the "normal" reason - i.e., it is not because the cameras are subject to high levels of vibration and shock. Rather, I think they have decided to use Loctite on these screws, because they have recognized, that it is not possible to tighten the screws strongly during the assembly of the cameras. Since they can't strongly tighten the screws, I think their solution was to put Locktite on the screws, to keep them from falling out later.

    Here is some history as we have observed, just from seeing various customers' cameras come through here over time:

    -- On the original EF and MFT 2.5K Cinema Cameras, we have found Locktite on ALL flange screws of ALL of these cameras which we have had the opportunity to examine.

    -- On the Pocket Camera, we OFTEN see Locktite on the flange screws. But not always - we have some Pocket cameras come through here with no thread locking compound of any kind on these screws.

    -- On the Micro Cinema Camera, actually up until now we have NEVER seen Locktite on the flange screw threads. But obviously you have found it - yours is the first camera where we have seen thread locking compound used in this location. So I am not sure exactly, how and when Blackmagic decides to use it or not use it.

    About the design of the screw heads on these special screws, here is what we have found: The Blackmagic lens flange screws, seem in fact to be standard metric, socket head, flat-head screws, except that the outer diameter of the screw threads has simply been reduced. When I stated before that we have replacement screws here, we have just made them ourselves in our machine shop: we have simply bought standard flat-head screws, and set up our lathe here to cut the screw heads to a smaller diameter. This gives the exact same form and shape of head, as the original Blackmagic flange screws have. So I think that probably, this is the same way that Blackmagic is having these screws made; I think they are a simple modification of a standard flat-head screw.

    This means, by the way, that you might be able to make some of these screws yourself, easily: If you just take a standard flat-head screw of the correct length, and screw two hex nuts on the shaft of the screw, you should be able to mount the screw in the chuck of a normal drill without damaging the threads. Then you should be able to rotate the screw in the drill, and cut the head smaller with a flat file. If you do this, you will find, that the screw head shape will be exactly right, and the screw will fit perfectly in its position in the lens flange.

    Lastly, I note your suggestion to use Torx screws in place of hex-socket screws. This is an excellent suggestion. We have found, as you have, that the metal of the stock Blackmagic screws seems to be quite soft, and therefore the sockets easy to strip. However, I will say, that even when we have bought standard screws and cut the heads smaller, we have found the situation unfortunately to be quite similar - the sockets are still easy to strip. I think now, that this is because in standard flat-head socket-head screws of this size, the socket heads are not very deep; much less deep than in a standard socket-head cap screw. It is for this reason, by the way, that we started shipping the special tapered driver. Which has worked very well so far, by the way; since we have started shipping this tapered driver tip, we no longer have had customers reporting stripping these screws. However, you have clearly had a problem, so I think our solution is not yet perfect. Anyway, a
    Torx
    screw as you say, would be much better - we will plan to look for these soon, hopefully they are easy to find as a standard part.

    Okay - sorry for this long explanation. Please feel free to post this reply into the forum thread that you have made, in case it can be helpful to anyone else.

    Thanks again and best regards--

    --dave cubanski

    Also i done explanation image for this. Currently I plane to use Torx screws, because they have smaller head size. Will test Torx screws as well.


    Last edited by shijan; 09-10-2017 at 02:04 PM.
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  5. #85  
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    Quote Originally Posted by shijan View Post
    Here is a quote from Mosaic support regarding this problem:




    Also i done explanation image for this. Currently I plane to use Torx screws, because they have smaller head size. Will test Torx screws as well.


    Possibly, however it might be they are using a custom head and perhaps that is to discourage people taking apart the camera outside their control. I can't be certain of this but it wouldn't surprise me. As to the quality of the screw itself, I find in general that many screws these days are "soft". I have 30 year old screws that work better than most I can find in hardware stores, especially places like the big box stores. So, that aspect of things doesn't surprise me. In terms of loctite, I think they do expect the camera to be subjected to vibration, because the BMMCC can be put in places it's hard to put other cameras. However, the theory that it's the screws themselves that are the problem and needs it could be possible.
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  6. #86  
    Senior Member shijan's Avatar
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    I think they just wanted to make the camera look pretty and cool and got some design awards for it. Thats the only logical explanation of those custom made hex screws and user unfriendly buttons as well. But just a cool look is not a design. It should be all together in equal parts: ergonomics, external look, engineering, economy manufacture, convenient repair, recycling.
    Last edited by shijan; 09-10-2017 at 02:50 PM.
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  7. #87  
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    Thank you for the heads up shijan! It's very useful to know all this for anyone who is getting involved in OLPFs. The people I've seen online that put shims onto the BMMCC's mount didn't have the loctite problem, or at least didn't report it, so maybe it's only just a few BMMCCs that have this 'issue'.

    I'm very interested in your opinion about sharpness loss. For all the research that I've done, sharpness can be recovered with post sharpening in resolve. But everyone always shoot in RAW, and TBH Prores pays the bills, is the everyday codec. It would be great to see how the loss of sharpness gets affected in prores and with what filter (unsharp mask, sharpen) we can recover it best.

    Best thing in the world would be if Blackmagic added a sharpen threshold into the settings, like ALL cameras do... doubt they'll do it, though been thinking about submitting a very thorough feature request.

    Thank you and good luck with the screws!!!
    (i bet you can use the camera with 3 screws until you get the new one, unless you use VERY heavy lenses)
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  8. #88  
    Senior Member shijan's Avatar
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    Probably TORX screw should fit! Regarding tech specs cap height is 1.65mm, this is the exact same as Blackmagic camera screws. So only need to grind outer diameter from 5.5 to to 4.4mm.

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  9. #89  
    Senior Member DPStewart's Avatar
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    Can't tell if you guys are on to something....or if you're just screwing around.
    Cameras: Blackmagic Cinema Camera, Blackmagic Pocket Camera (x2), Panasonic GH2 (x2), Sony RX100 ii, Canon 6D, Canon T2i,
    Mics: Sennheiser, AKG, Shure, Sanken, Audio-Technica, Audix
    Lights: Every Chinese clone you can imagine
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  10. #90  
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    mmm this is very concerning. For those of us with a v2 ordered what would you say the best way to go about taking the screws out from what you've learnt Shijan?
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