URSA ( FULL SIZE ) SPEEDBOOSTER.

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robert Hart

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URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Jun 18, 2017 9:29 am

There has been a bit of discussion on the practicality or otherwise of using a focal reducer situated in the throat of the big URSA to enable a closer visual match to the identical lenses used on the 4.6K cameras.

For those who are tempted to dig and delve, I suggest you DON'T, unless you have seriously developed fine engineering skills. That said, here follows, a bit of information. Please do not ascribe accuracy or validity to the following comments.

During the course of designing a one-off Nikon F-Mount for a big URSA PL v1, I also examined the possibility of an integrated Speedbooster optic. For the Big URSA, for Nikon lenses, there is a possibility because there is ample real-estate in the camera design to permit this. For the URSA Mini cams, I don't think so. There appears to be insufficient workroom to relocate a Nikon mount the necessary distance rearwards which is about 8mm when the BMPCC Speedbooster optical cell is tested.

The filter/cover glass in the throat of the BM URSA is situated too close to the front of the camera body for a Speedbooster optical cell to be located within the throat of the camera without this filter having to be relocated rearwards. That may introduce other optical and colour issues. As with the RED camera experiments thus far, the filter glass would have to be remade to a smaller diameter and installed closer to the sensor on the rear of the redesigned Speedbooster optical cell.

Unlike the recent RED experiment in which the optical elements themselves had to be ground flat on the edges to permit fitment within the throat of the RED camera, there is generous workroom within the big URSA's throat to fit the optics and reposition the Nikon Mount. With a PL-Mount and a modified clamp ring to permit a working clearance, this might also be possible, except with lenses which have a deep rearwards penetration into a camera throat.

With the aggressive BMPCC Speedbooster optical cell installed within the throat of the big URSA and the filter glass removed, Nikon lenses can be offered up and achieve infinity focus.

There is as I expected, a significant corner vignette from the BMPCC Speedbooster optical cell along with significant edge distortion. The optical cell from the 0.71 "Ultra" Speedbooster series may yield a wider image circle and maybe less edge distortion. It may not need to protrude so far back in the throat of the camera as the BMPCC optical cell which is about 13.25mm rearwards of the M/43 flange, therefore about 4mm from the sensor itself.

If the 0.71 optical cell can perform to the 21mm V1 URSA 4K sensor without a vignette, then it would be a relatively simple matter to remake the anti-reflection cone to carry the optical cell or the elements themselves in a custom assembly, to screw straight into the throat of the big URSA camera and shim between the rear shoulder of the BM throat and the rear face of the cell barrel for collimation.

As for removing the filter glass, I do NOT recommend that people tackle this. This element is surface-coated and could be easily damaged. The neoprene "O" ring retainer is a challenge to re-install correctly.

I have enquired with the folk who make and sell the Speedboosters to see if they will sell me a 0.71 optical cell. As a kitchen-table engineer, I do not like my chances but who knows.

There is probably not a lot of point to this exercise except as an option for folk who retain the big URSA and intend to use it in controlled lighting environments alongside the URSA Mini 4.6K or Pro, for a 4K or HD finish. Then the images conferred by the lenses may be a better match.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Jul 15, 2017 4:46 pm

For what it is worth. initial offer up of the Metabones speedbooster "Ultra" 0.71 optical cell appears to convey a near-perfect image to the sensor WITHOUT need to interfere with the blue filter in front of the sensor which is an unexpected bonus. The optical cell has to be rearwards in the throat of the camera almost to the blue filter disk.

I have offered up two Nikon F-Mount wide-angle lenses, the Nikon DX 12-24mm zoom which only "just" covers the sensor and 14mm Sigma-for Nikon.

The bad news is that a PL-Mount option is unlikely. Certainly old Cooke Speed Panchro lenses penetrate too deeply rearwards. The PL-Mount shoulder is also going to create workspace problems at my skill level. Although more competent optical engineers might find a solution, many PL-Mount lenses with rearwards penetration into the throat of the camera may clash with the Speedbooster optical cell.

The Speedbooster version I have borrowed the optical cell from is the Canon EF version. It would be theoretically possible for an EF-Mount Speedbooster for the USA 4KV1 to be made. A limitation will be the physical width of the rear of the EF mount lens which might interfere with the body of the camera.

As with my Nikon adaptor for the big URSA, there is no practical workspace to enable the pin latch to be fitted and corrugated spring friction alone will resist the tendency for the lens to turn in its mount during focus movements. This would preclude usage of motorised focus as the focus motor will hit stop points and turn the lens out of its mount during calibration.

There is only 1mm of workspace in front of the intermediate adaptor disk which fits within the URSA body, so this would have to be remade slightly thinner to enable a genuine Nikon F-Mount and corrugated spring to be fitted.

A professional engineering approach would be to remake the intermediate adaptor with a shoulder penetrating inside, replacing the anti-reflection cone entirely and containing the Speedbooster optical cell.

My approach will be to remake the anti-reflection cone as a support for the Speedbooster optical cell and remake the intermediate adaptor as two separate components, purely because of my incompetence at fine engineering.

You can see a phone photo of the Speedbooster cell, offered up rather crudely to the big URSA by means of cardboard disks in the anti-reflection cone at this web address.

http://www.bmcuser.com/showthread.php?2 ... post239903

If Blackmagic design got into bed with Metabones and offered a replacement intermediate adaptor/mount assembly containing the 0.71 "Ultra", I imagine they might sell a fair number if the price was comparative with the other Speedbooster "Ultra" versions in the ballpark of US$499-00.

The kit would need to be supplied in two pieces, the intermediate adaptor and the Canon EF-Mount as the replacement intermediate adaptor containing the optical cell would have to be installed first, then the Canon EF-Mount, due to the mount ring being wider than the Nikon F-Mount and will partially cover the attach screws for the intermediate adaptor.

Due to the fitment of the ND filters in the UMP cam, there is no workspace remaining to install a Speedboster optical cell. Due to the size of the 4.6K sensor, there is no need to.

PLEASE NOTE THAT THIS EXPERIMENT HAS ONLY BEEN CONDUCTED WITH THE PL-MOUNT TURRET VERSION OF THE BIG URSA CAMERA. IT MAY NOT BE WORKABLE WITH THE EF-MOUNT TURRET VERSION. CERTAINLY, THE PASSTHOUGH CONDUCTORS AND ASSOCATED INTERNAL STRUCTURES FOR POWERING AND CONTROLLING THE ELECTRONIC LENSES MAY INTERFERE WITH ANY SPEEDBOOSTER INSTALLATION AND COMPLICATE THE ENGINEERING.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Jul 16, 2017 9:23 am

For interest, here is a link to the bmcuser forum where I have posted some comparitive frames with and without the 0.71 "Ultra" speedbooster optical cell in place, using the same 20mm f1.8 Sigma-for-Nikon lens with the same aperture settings across the comparative shot pairs.

I could not get the images to show up here on this page.

http://www.bmcuser.com/showthread.php?2 ... ROUP/page5
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostWed Jul 19, 2017 8:48 am

I am in the process of making a special insert for the BM URSA 4KV1 PL camera to accommodate a 0.71 "Ultra" optical cell from a Metabones Speedbooster.

Does anyone by chance know what the pitch of the threaded section of the optical cell is. It is very fine and likely to be a nightmare for a backyard engineer like me to reproduce. I could machine a piece of Delrin and use its inherent compliance to screw the optical cell into without having to cut an actual thread. I would prefer to do the job properly.

Metabones simply does not reply to messages so there is not much point to trying for info from them forever.

I would like also to get hold of a spare anti-reflection cone for the URSA. I may go the nolathane casting route for mounting the speedbooster optical within a spare cone. With care and use of a suitable separation material, I should be able to preserve the functionailty of the thread for fine backfocus adjustments.

Does anyone know how best to go about getting hold of BM spares. Navigating to someone who can actually help, assuming the company would want to is proving an enigma.
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Denny Smith

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostWed Jul 19, 2017 4:13 pm

Robert, you can get or borrow a machinist thread pitch gauge to determine the thread pitch and count.
As for BM parts, they have traditionally not been selling them, but contact BM Support Technical USA, and you might get lucky. That said, the lens mount baffle is a part that would have been a non-repair part, expected to last the camera's lifetime, so spares might not be available, unless BM has some unbuilt cameras kicking about.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostWed Jul 19, 2017 4:50 pm

Denny. I'll give it a shot but the rear wall of the retail storefront has been about as deep as I have been able to penetrate thus far.

Metabones does not even bother to reply. - No reply is obviously reply code for "No".
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Jul 30, 2017 5:41 pm

How's this for a bit of fortuitous coincidence. It seems from calculations and from offer-up tests that the front face of the big URSA PL's intermediate adaptor is exactly spot-on for the rear mounting face of the Nikon 5-screw mount with a Speedbooster optical cell in the throat of the camera. The internal diameter is too wide for the Nikon F-Mount to be directly attached by screws. However for test purposes the mount can be clamped with a thin hard spring-steel grade washer arrangement with screwholes in the PL-Mount pattern.

The washer has to be thin enough that the 1.2mm rear overhangs on the Nikon iris ring clear the washer. The Nikon mount ring also need so have the 2mm deep AI clearance of the FM2n style mount. The later mounts have a shallower clearance. For a substitute intermediate adaptor with correct internal diameter for a Nikon mount, there is a space required behind for the small 1.5mm deep rear shoulder of the Nikon mount ring and the corrugated spring, which requires some clearance channels to work properly.

I also offered up an old Angenieux T3.9 25-250mm zoom lens. It is not viable for a speedbooster because its image circle is too small and vignettes to the big URSA's 4K sensor with speedbooster in place. It would be sort-of okay with a faux-cinemascope top and bottom of frame crop but it appears there would remain a subtle side edge darkening of an apparent half-stop.

Interestingly, the Sony FS7 sensor is quoted as 25.5mm wide and the BM4.6K sensor as 25.34mm wide. I have been advised of anecdotal accounts of the Speedbooster "Ultra" EF-Mount to Sony E-Mount version, conferring a full image to the sensor of the Sony FS7 camera. I think the lenses used were Nikons via adaptors and Zeiss CP2. I have not seen it working myself.

Depending upon the intermediate adaptor arrangement of the BM URSA Mini 4.6K, it may be possible for this camera to also provide a useful image with a 0.71 Speedbooster but the chances of corner and side edge image softness may be greater with some lenses.

I have not yet been able to get my greasy hands on a URSA Mini 4.6K.

NOTE: The URSA Mini Pro 4.6K is not viable for a speedbooster optic being installed in the camera throat because the workspace is occupied by the inbuilt ND filter system.
Last edited by robert Hart on Mon Jul 31, 2017 2:27 pm, edited 1 time in total.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostMon Jul 31, 2017 11:15 am

The making of the mount for the speedbooster arrangement was an easier go than I thought it would be. It was possible to use my original Nikon adapter mount with just a mere 2.5mm shaved off the rear locator shoulder which fits inside of the intermediate adaptor when that is in its normal place and the speedbooster optic not installed. Drilling and countersinking six new holes to match the fastener pattern of the intermediate adaptor and it was done.

In the images on the bmcuser site, you will observe that the face of the Nikon adaptor piece is now recessed into the body of the camera and the front face is now coincident with the normal face position of the intermediate adaptor. I shaved the rear face a whisker more than the 2.5mm to give me some shim space if I need it. It remains a prototype. Some time when I am not lazy, I will remake the piece as two separate adaptors, one for the speedbooster, one without.

This will enable me to maintain best accuracy in keeping the optical axes of the lens and speedbooster optical cell coincident.

This is the web address of the bmcuser page with the images.

http://www.bmcuser.com/showthread.php?2 ... post240350
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostMon Jul 31, 2017 4:17 pm

I now have a speedbooster arrangement working with the "big" URSA camera PL-Mount model. The optical cell from the 0.71 "Ultra" Metabones Speedbooster products has been fitted within the throat of the camera and can be used with a modified Nikon F-Mount. Other lens types are not suited to this arrangement due to available workspace within the camera body.


The arrangement requires two custom components to be made. These are :-

Replacement for the anti-reflection cone in the form of an internally threaded barrel to accommodate the 0.71 optical cell.

Remake of the inner "intermediate" adaptor to become a Nikon F-Mount positioned rearwards of its normal position with flange now 42.0mm from focal plane, compared to the normal position of 46.5mm from focal plane.

In view of some interest by owners of big URSA 4K, URSA Mini 4K and URSA Mini 4.6K cameras of the PL-Mount type I would like to enquire of people their interest in buying two-piece mod kits for these cameras.

If sufficient folk were interested to commit, then it might be possible to persuade a third party optical manufacturer, even Metabones, to do a limited production run of kits using the 0.71 "Ultra" optical cell.

I have absolutely no idea of the price involved and would field this whole project to a manufacturer/vendor as I have not the engineering or business skills to take on something like this.
Attachments
URSA 4KVA SPEEDBOOSTER1 (7).jpg
URSA 4KVA SPEEDBOOSTER1 (7).jpg (693.13 KiB) Viewed 5322 times
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 01, 2017 3:37 pm

For what it is worth, here is link to bmcuser.com which in turn will link to a rough and ready twilight test with the big URSA 4KV1 PL, an added Metabones Speedbooster 0.71 "Ultra" optical cell added into the throat of the camera body and a custom Nikon F-Mount. I tried to use the embedding feature on this site but I think I broke it. The web address will not copy either so only the web address is copied below.

The recording was made at HD resolution on a BM recorder via HD-SDI as I did not have a media card available.

The lenses used were :-
Sigma-for-Nikon 14mm f2.8
Nikon 35mm f1.4
Nikon 50mm f1.4
Nikon 85mm f1.4
Nikon 105mm f1.8
Sigmatel-for-Nikon 135mm f1.8
Peleng 8mm f3.5 Fisheye.

You will observe in the 14mm and the 35mm lenses, some corner softness, noticeable with the 14mm, less so in the 35mm but a known issue with this lens on some speedboosters for some users. This might be remediable with fine adjustments of the position of the speedbooster optical cell.

http://www.bmcuser.com/showthread.php?2 ... er-project
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Aug 06, 2017 6:00 pm

For curiosity only. The accompanying diagrams are not engineering drawings and measurements have not been meticulously checked. The diagram on the right is an estimation of the section of a replacement mount for the speedbooster which would replace the anti-reflection cone in the URSA 4K PL camera turret.

A reminder. This is most definitely not a BM approved adventure into the working of the camera. Any such adventure by you into your camera will void your warranty.
Attachments
BMURSA4KPLSPEEDBOOSTERINNERresized.jpg
Modified BMURSA4KPL anti-reflection cone re-purposed as speedbooster optic mount.
BMURSA4KPLSPEEDBOOSTERINNERresized.jpg (181.78 KiB) Viewed 5204 times
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 08, 2017 8:09 am

You will need to scroll the image downwards with the click and drag doover on the right of the image frame to view the actual fitting. Sorry about that. I am a bit of a computer illiterate.

Now that the internal piece is complete and the speedbooster optical cell can be easily adjusted, I found that movement of the optical cell forward one and a half turns away from near-contact with the IR filter restored true focus for the Nikon lenses I am using.

Because the fitment is inside the camera body, there can be no provision for locking the optical cell with a screw after adjustment without disturbing the adjustment by removing the whole assembly. I will have to make do with a dot of some semi-hardening material at the front-edge of the optical cell and the custom housing.

I have been asked by a few folk if this arrangement will work on a URSA Mini Pro? - Most definitely no. The ND filter system occupies the same internal workspace.

Will this arrangement work on the URSA Mini 4K PL or URSA Mini 4.6K PL? - I have been asked by a few folk about this as well. The truth is that I do not know. I do not have examples of the cameras to examine. I am not about to pull some owner's camera to bits for a look-see because of the obvious risk of damaging someone's functional camera.

I am hopeful of finding a wrecked one which has a surviving front end. I am not going to buy one just to find out.

The little guys in Dongguan China could probably put together something affordable but there is no prospect of me making and selling these things. I don't have the skill sets, engineering or business-wise.

This arrangement has only been proven for Nikon F-Mount lenses. A PL-Mount arrangement could be arranged for the big URSA but the mount clamp ring would have to be substantially altered to clear the body due to the 4.2mm rearwards relocation of lens mounts caused by the optical characteristic of the speedbooster.

A final CAUTION. Whilst this arrangement in itself is non-destructive of any part of the big URSA 4K PL camera, owner-disturbance within the camera body may void the warranty, especially if by mishap of adjusting the optical cell too far rearwards, the IR filter glass becomes cracked or marked by contact.
Attachments
URSA 4KV1 SPEEDBOOSTER INTERNAL ASSY.jpg
INTERNAL ASSEMBLY OF SPEEDBOOSTER 0.71 "ULTRA" OPTICAL CELL.
URSA 4KV1 SPEEDBOOSTER INTERNAL ASSY.jpg (176.32 KiB) Viewed 5162 times
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Nick Gombinsky

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 08, 2017 12:18 pm

Great job, man!
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 15, 2017 10:34 am

For interest of anyone who would like to have a speedbooster in their URSA, I have obtained some numbers from a local machinist.


Costs thus far :-

For both the internal support for the speedbooster optical cell and Nikon F-Mount base only = AU$460-00, plus material.

GST if in Australia = AU$46-00.

Nikon F-Mount supplied separately by camera owner. = Cost unknown. Cost $AU Zero if the Speedbooster is Nikon Mount type.

"Ultra" 0.71 Speedbooster optical cell supplied by camera owner. = AU$610-89.


With used big URSA cams going inexpensively on eBay, a cost of about AU$1010-89, plus AU$102-00 GST, probably represents over-capitalisation for the benefit of near-to full stills frame fields-of-view and being wedlocked to Nikon F-Mount lenses.

I have not been able to obtain any information regarding permission related to fitments designed to match registered design and separate supply of the 0.71 "Ultra" optical cell from either Metabones or Caldwell. Each entity seems unwilling or incapable of replying to email queries.
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Tristan Pemberton

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 15, 2017 10:52 am

robert Hart wrote:For interest of anyone who would like to have a speedbooster in their URSA, I have obtained some numbers from a local machinist.


Costs thus far :-

For both the internal support for the speedbooster optical cell and Nikon F-Mount base only = AU$460-00, plus material.

How about Canon EF mount?
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Aug 15, 2017 5:32 pm

Canon EF-Mount so far as I can tell, may not be doable because the 4.2mm setback of the flange face places it too far rearwards in the camera body. It might be doable with a PL-style positive lock threaded clamp ring. I have only modded the PL version of the big URSA and Nikons are the only lenses which seem to be workable. I have not had my eyes on an EF-Mount big URSA to study it closely.
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Tristan Pemberton

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Aug 19, 2017 7:03 am

robert Hart wrote:Canon EF-Mount so far as I can tell, may not be doable because the 4.2mm setback of the flange face places it too far rearwards in the camera body. It might be doable with a PL-style positive lock threaded clamp ring. I have only modded the PL version of the big URSA and Nikons are the only lenses which seem to be workable. I have not had my eyes on an EF-Mount big URSA to study it closely.

Sorry, I meant an EF mount for URSA Mini 4.6k PL mount?
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Sep 09, 2017 6:35 pm

Noted your comment referred to the URSA Mini and sorry for my delay in responding. I have not had my eyes and hands upon an URSA Mini PL to see if an EF-Mount could be made to work on one. I had a request in to BM to see if they have any broken cameras I might be able to use as references but after a few weeks, I have had not received any furthur emails. In absence of any specimens to study I cannot say if it can be done satisfactorily or not.
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Tristan Pemberton

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Sep 10, 2017 12:28 pm

robert Hart wrote:Noted your comment referred to the URSA Mini and sorry for my delay in responding. I have not had my eyes and hands upon an URSA Mini PL to see if an EF-Mount could be made to work on one. I had a request in to BM to see if they have any broken cameras I might be able to use as references but after a few weeks, I have had not received any furthur emails. In absence of any specimens to study I cannot say if it can be done satisfactorily or not.

Where are you based?
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Sep 12, 2017 9:17 am

QUOTE: "Where are you based?"

I am based in the Perth outer metro area in Western Australia.

BM has responded that they are unable to assist me with any wrecked URSA Mini cameras for test purposes.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Oct 08, 2017 7:56 pm

If anyone is going the internally located Speedbooster route for the big URSA PL cam, here is an eBay listing for an Ultra series Speedbooster which looks a reasonable for price for a 0.71 optic and a Nikon Mount.

The front to rear dimensions of the Metabones version of the Nikon mount ring may differ from the genuine Nikon FM2n mount I designed my intermediate adaptor to comply with. The front end of the intermediate adaptor design would need adjustment so that the actual flange face of the Nikon mount remains the correct distance from the sensor.

http://www.ebay.com/itm/Metabones-Speed ... SwV4BZ0l5f
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostThu Oct 12, 2017 12:02 pm

Matthew Duclos, master lens-smith in the US has apparently been involved with a similar development with the RED DSMC2 camera family to yield vistavision fields of view to the RED sensors.

I sent him an email regarding in-built focal reducers in Blackmagic cams. He has no plans for a Blackmagic project but he is not opposed to exploring additional avenues wherein only minor changes are required.
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Tristan Pemberton

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Oct 14, 2017 9:42 am

robert Hart wrote:QUOTE: "Where are you based?"

I am based in the Perth outer metro area in Western Australia.

BM has responded that they are unable to assist me with any wrecked URSA Mini cameras for test purposes.

Hey Robert, I'm on the other side of the continent - Wollongong, NSW. Pity you aren't closer. I don't know any BM camera owners in WA.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Oct 14, 2017 7:34 pm

There's two folk I know fairly nearby who trade as 2D films. Their kit is the UMPro which cannot accommodate a speedbooster, nor does it really need to because it has the wider sensor. It was their BM4KEF which I also examined regarding a speedbooster. I know of no other BM URSA operators here in WA but other than posting on this forum and BMCuser, I have not been enquiring with any vigour.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSun Nov 05, 2017 3:25 pm

For the sake of those who are curious, I have been a bit slack but finally got around to trying the speedbooster arrangement outdoors in near to real-world conditions at an air show with a Sigma-for-Nikon 50mm-500mm zoom I have used previously on the SI2K camera for ground-to-air vision of aircraft.

Like the SI2K/P+S Technik camera-recorder, the big URSA is a struggle and grunt to cart around and set up on one's own. The URSA mini is obviously a better choice for agile portability. An assistant would make a lot of difference. An eyepiece viewfinder would also make a lot of difference.

The inbuilt mikes work better than I thought they would for ambient sound. To minimise wind buffet, I shoved a sort of fluffy seatcover moustache under the lens mount where the small mike ports are. The audio levels remained fine and the camera's audio recorder also seems to tolerate excessive levels better than I expected.

Except for a small speck on the sensor which indicates I have been careless, there seemed to be no vices with the lens compared to using it without a speedbooster a few months ago. I had to fit an ND.9 filter to keep the exposure level within reason.

When I can muster a greater horsepower computer to reproduce the 4K image, I will assemble and upload a clip.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Nov 07, 2017 11:56 am

Here is a link to a youtube clip shot on Sunday with 3:1 RAW, the Speedbooster in place and using a Sigma-for-Nikon 50mm -500mm f4-f6.4 zoom lens. ND.9 was used on front of the lens to keep the exposure levels civilised but because the lens is not constant aperture through its range, one has to ride the iris or the level can get away.

The image is not as good as it could be because my poor old computer cannot manage 4K. It went through three stages of conversion, from 3:1 RAW in Resolve to H264 so Premiere can digest the vision and export it as .wmv 1920x1080.

My follows are not all that good either. I am too much out of practice and the mass of the camera, whilst around the same as the SI2K behaves a little differently coming off steep tilts.

Please note that this link is not clickable, in fact it cannot even be made to be readable. BM forum and my computer collude to stop me doing that. You'll have to copy and paste by right-clicking in the middle of the grey frame
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Patrick Acum

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostTue Nov 07, 2017 1:28 pm

Has anyone tried the speed booster from Luca Butrera at Lucadapters? I've been speaking to him on Facebook, it's all a little sketchy but he claims to have a working booster for the ursa ef and the mini 4k...
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostMon Apr 23, 2018 8:09 am

Because I only have Nikon lenses capable of covering the 4K sensor via a Speedbooster I have not bothered to examine closely the possibility of resetting the Big URSA's PL-Mount 4.2mm rearwards to restore infinity focus once the Speedbooster optical cell is fitted.

Whilst checking something else I decided to offer up the PL-Mount with a lens attached and it seems my original comments relating to the BM URSA PL-Mount and Speedbooster were incorrect for which I apologise.

The rear outer shoulder of the PL-Mount will fit within the body of the big URSA. It is the same diameter as the intermediate piece the PL-Mount fastens onto.

The PL-Mount's clamp ring will still work. The clearance between the camera body and the wings on the clamp ring is closer and might nip fingertips painfully in the smaller gap if the operator becomes excited and careless on a cold day.

There are significant alterations required for the BM PL-Mount itself.

The locator pin inside the camera body reaches the closed end of the matching hole in the rear of the PL-Mount. Therefore the mount rides on the end of the pin before it can slide rearwards enough into the camera body for infinity focus to be restored.

To fix this would require the hole in the rear of the PL-Mount to be deepened. The pin may then protrude far enough through the deepened hole to run foul of the flange face in which case, the pin would have to be slightly shortened.

That may introduce a problem if the pin then becomes too short for the PL-Mount to be attached in its original arrangement on top of the intermediate mount ring.

This would not be a deal killer but might introduce inconvenience when re-installing the PL-Mount without the Speedbooster, or the B4-Mount as the pin might no longer be long enough to make the job of orienting the mount in correct relationship to the screwhole pattern.

A custom shim would have to be made to hold the PL-Mount forward inside the body at correct flange to focal plane distance. Blackmagic's own shims for the 4K version of the B4-Mount could be stacked but new holes would have to be punched or drilled in them to match the screwholes in the body.

New screwholes would have to be drilled in the PL-Mount to match the pattern of the screws which attach the intermediate adaptor to the camera body.

Care needs to be taken with the attach screws. The threads tapped into the metal material in the camera body were not intended for frequent removal and re-attachment of the mounts.

BM's instructions relating to tension in tightening the screws should not be ignored or the thread inserts may pull or the threads may strip.

The 0.71x Speedbooster optical cell occupies space in the camera throat and some PL-Mount lenses will protrude far enough rearwards to strike the front of the optical cell.

Modern PL-Mount full-frame lens offerings as approved on the Metabones website will be fine. The Cinevised Rokinon/Samyang and the Xeen range of lenses should be okay but a protrusion on the side of the rear of the Xeen lenses may foul the camera body. I do not have any specimens to check with.

Older PL-Mount lenses which were intended to cover the original 35mm film frame may vignette with the 0.71x speedbooster optical cell in place. The original Angenieux T3.9 ( f3.2) 25mm - 250mm zoon does vignette the corners. It might be okay for a faux-cinemascope crop in post. The speedbooster does improve the "apparent" sharpness of this character lens.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostMon Apr 23, 2018 4:20 pm

Furthur to the previous post, the thin shoulder on the rear of the PL-Mount will need to have a small amount skimmed off the rear. It rides on the inner camera body and holds the mount forward of infinity focus.

If the original short screws which fasten the PL-Mount to the intermediate mount ring are to be used, clearance holes for the screw heads will need to be drilled deeper into the mount. Alternatively, longer screws can be bought and used.

The original arrangement of an intermediate mount ring might be retained with a thinner ring made and threaded but the material will need to be more robust than the original aluminium. It may otherwise bend and droop if heavy unsupported lenses are fitted.

There will also be less thickness of metal in which the threads for the screws holding the PL-Mount are tapped.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostThu Apr 26, 2018 11:52 am

Furthur to the previous posts, with a Metabones 0.71x optical cell installed, I have found that to enable infinity focus with the PL-Mount, as well as skimming the rear inner shoulder of the mount shorter forwards, extending the locator pin hole forward, drilling a new pattern of screw holes and head clearances, there remains another task.

That is, the rear face of the clamp ring and the two handles have to be skimmed forward to restore working clearance of the camera turret front body. One could dress the front of the turret body rearwards to produce the necessary clearance but with the thickness of the metal unknown, this would be risky and would spoil the original aesthetic. If there remains any warranty available for a particular camera, the warranty would be voided.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostThu Apr 26, 2018 3:02 pm

Furthur to my posts above, I found that the PL-Mount clamp ring must have about 2.5mm skimmed off the rear and about 1mm off the rear mounting faces of the handle on the clamp ring to enable clearance of the front of the "big" URSA PL turret. The head of the limit screw for the clamp ring fouls the front of the turret body, so sadly that has to be taken out.

There is just enough workspace in all the parts for modifications to make the PL-Mount work with the 0.71x speedbooster without destroying the mount for normal use without the speedbooster optic in place. I have arranged it so that the lens is a fraction closer to the sensor than true infinity to give some opportunity for shimming the mount forward to the correct position.

I tested with an old Angenieux 25-250mm T3.7 and found the vignette to be quite severe. The 0.71x speedbooster arrangement is probably best regarded as suitable only for full frame lenses.
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Savannah Miller

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostFri Apr 27, 2018 9:08 am

youtube.com/watch?v=3DXDyudvCYg&t=603s

That's a review of the Lucadapter
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Apr 28, 2018 7:50 am

The telling of truths will be when somebody puts an ultrawide wide lens on the Luca adaptor. It seems to be producing the result for its users which is what counts.

With my arrangement for the Metabones Ultra 0.71x cell, an ultra-wide Sigma-for-Nikon 14mm f2.8 lens yields image softness in the corners. Some lenses play nice with focal reducers, some don't.

I used the witness marks on the focus barrels of a wide range of Nikon lenses and a "majority vote wins" method to adjust the position of the optical cell. I adjusted to suit a measured 1 metre or near distance and tested again at infinity focus. This is not the ideal way of doing things. I am also not an optical engineer with the proper equipment so one does one's best with the resources at hand.

I used the known flange to focal plane distance for the Metabones adaptor as my reference and adjusted the position of the optical cell within the adaptor I had made to those measurements.
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostSat Apr 28, 2018 6:00 pm

Here and hopefully viewable are some images of the modified PL-Mount as installed to the "big" URSA 4K PL camera. I had to degrade the images considerably to get the down to the smaller file size required for posting.

Whilst the mount has had some material machined from the rear to allow mounting rearwards the 4.2mm required for the Speedbooster, it remains capable of being mounted normally without the Speedbooster. It is a very, very snug fit.

I should have taken another 0.3mm off as dust may get in the gap and grind the paint finish off the camera front.
Attachments
BMURSA4KSPPL1REDUCED.jpg
10" screen image. Standard 35mm lens image becomes vignetted with Speedbooster optic in place.
BMURSA4KSPPL1REDUCED.jpg (710.39 KiB) Viewed 1169 times
BMURSA4KSPPL2REDUCED.jpg
Top view. Note very snug fit against front of turret body.
BMURSA4KSPPL2REDUCED.jpg (746.1 KiB) Viewed 1169 times
BMURSA4KSPPL3REDUCED.jpg
Front view. The tail of the mount has been shortened but sufficient depth remains for normal fitment.
BMURSA4KSPPL3REDUCED.jpg (795.42 KiB) Viewed 1171 times
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robert Hart

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Re: URSA ( FULL SIZE ) SPEEDBOOSTER.

PostThu May 10, 2018 12:27 pm

Furthur to above, I went down to our local production equipment rental place, Location Equipment in Leederville and had a play with some of their rental lenses on the big URSA with Speedbooster and PL-Mount. Hanging from the ceiling in their test room is a big resolution chart published by Duclos lenses.

Due to the closeness of the front element of the speedbooster optical cell, The ARRI Ultra lens set cannot be used, at least not without some modification. To alter pristine ARRI T1.9 lenses is not good manners and simply not done. I mean, who would put dragster tyres and a supercharger scoop on a Rolls Royce?

There is half a chance that if the shield cones on the rear of the ARRI set can be removed, then there may be in some instances, a working clearance between the rear element of the ARRI lenses and the front element of the speedbooster.

The next cab off the rank was a set of Zeiss CP2 primes. They offer up and fit fine, as Metabones suggest they should by putting them on their approved list.

My objective was to test just how far off infininty focus my relocated fitment of the PL-Mount is. With the CP2 lenses, across their range of focal lengths, infinity focus came in at about 50ft so I do have some shims to make up, which I expected.

With the 85mm lens and the Duclos chart tightly framed, a very slight "donut" effect was observed when trimming focus. This may be attributable to the very slight rearwards position of the lens due to shims being required in the mount.

The 50mm, lens image appeared sharp across its width. There is a small barrel distortion in the image. Again, this may be reduced by correct collimation of the mount.

The 35mm, 28mm and 21mm images also have barrel distortion with a curious astigmatic distortion appearing in the 35mm image. I may need to check again just how straight in the adaptor my mounting of the speedbooster optic is.

I pointed the camera outdoors when I tested for infinity focus. The image from these lenses compared to my old Nikons is of improved apparent clarity and sharpness, just plain sweet to look at.

The image area of field-of-view "as seen" via the camera is close to full frame in width, with probably about 1.5mm missing from the sides.

Location Equipment will be receiving some rehoused Kowa anamorphic lenses soon. So long as they can fit, I will be trying them.

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