Ursa 12k ef versus pl

The place for questions about shooting with Blackmagic Cameras.
  • Author
  • Message
Offline

thefilmaddict

  • Posts: 120
  • Joined: Sun Oct 27, 2019 9:58 pm
  • Real Name: Jason Morris

Ursa 12k ef versus pl

PostTue Nov 23, 2021 11:53 pm

I have a lot of canon ef glass. They are all photo lenses. The main one is the sigma art 18-35. I’ve been thinking a lot about changing to the ef mount and using those lenses on the ursa 12k. I only have one pl mount lens — the dzo film Pictor 20-55. I like it, but it does suffer from lens distortion and some softness on the edges all the way open. What it does well is focus breathing. I know that the sigma is terrible at that, however, as far as sharpness and other qualities, how will the sigma compare to the dzo film zoom on the 12k?

I just can’t afford really expensive pl lenses, even though I know the good ones are superb for a number of reasons.

Thanks!
Offline

John Brawley

  • Posts: 4267
  • Joined: Tue Aug 21, 2012 7:57 am
  • Location: Los Angeles California

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 3:19 am

thefilmaddict wrote:I have a lot of canon ef glass. They are all photo lenses. The main one is the sigma art 18-35. I’ve been thinking a lot about changing to the ef mount and using those lenses on the ursa 12k. I only have one pl mount lens — the dzo film Pictor 20-55. I like it, but it does suffer from lens distortion and some softness on the edges all the way open. What it does well is focus breathing. I know that the sigma is terrible at that, however, as far as sharpness and other qualities, how will the sigma compare to the dzo film zoom on the 12k?

I just can’t afford really expensive pl lenses, even though I know the good ones are superb for a number of reasons.

Thanks!


It's very easy too hence mounts on the camera and have both isn't it ?

JB
John Brawley ACS
Cinematographer
Currently - Los Angeles
Offline
User avatar

Travis Hodgkinson

  • Posts: 518
  • Joined: Fri Jun 20, 2014 9:30 am
  • Location: Brisbane, Australia

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 6:16 am

I do find it amusing that so many think shooting at wide open is the best choice. When most lenses produce their best images between T4-5.6

I’m sure the DZO looks better at those ranges than at the 2.8 you’ve been using.
Freelance Camera Op & Cinematographer based in Brisbane, Australia.
-----------------------------------------------------------
Weapons: URSA 12K + Canon XF605 + Hero 10 + Pocket 6K Pro
Optics: DZO Pictor Zooms + SLR Magic Hyper Prime + Tokina Cinema Zoom
Offline

thefilmaddict

  • Posts: 120
  • Joined: Sun Oct 27, 2019 9:58 pm
  • Real Name: Jason Morris

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 12:02 pm

No doubt that dzo film zoom looks better when stopped down a little. I do like it overall, just would love to use my ef glass, too.

As far as changing the mount, is it easy to do?

I found this video:


The guy suggests buying a torque screwdriver for $125 and bits for $11. Are those additional purchases really necessary? He also removes 1 of the shims. Does this sound right?

Thanks!
Offline

Ryan Earl

  • Posts: 517
  • Joined: Sun Jan 17, 2016 6:56 pm

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 12:27 pm

thefilmaddict wrote:The guy suggests buying a torque screwdriver for $125 and bits for $11. Are those additional purchases really necessary? He also removes 1 of the shims. Does this sound right?


UGGH YES! Get a screwdriver that won't let you apply too much torque. I bungled a screw on mine changing the mount to PL and luckily spread pliers into the slot and extracted the screw. Then used a fresh set of screws to lock in the mount. They are pretty soft screws. It won't take much force to rip the head off then you're really 'screwed.'
Offline
User avatar

rick.lang

  • Posts: 17175
  • Joined: Wed Aug 22, 2012 5:41 pm
  • Location: Victoria BC Canada

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 2:23 pm

No question, I’d recommend a Wera Torque Wrench. One that includes support for the correct torque strength. I can post a photo if needed but they’re easy to find. I posted years ago about the adventure I had getting the proper bit locally but finally found a set in a hobby store downtown specializing in model kits and men’s grooming, BC Razor.
Rick Lang
Offline
User avatar

timbutt2

  • Posts: 2840
  • Joined: Tue Nov 12, 2013 10:32 am
  • Location: St. Petersburg, Florida, United States of Amercia

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 4:55 pm

Yeah, first thing I bought was the torque screwdriver. I've changed the mount on my camera countless times now. It's super easy. Also, Hook of BMD confirmed you can keep the shim from the PL mount in for the EF mount.

DZOFilm wise it is soft wide open, but not too terrible. I often try to shoot at T4-T5.6 on any lens in general anyways. Usually makes focus pulling easier as well to not be wide open. With primes I'm the same way, but with the Vespids I feel good about shooting T2.8 and having a good image. I have also shot open at T2.1 and been very pleased with the image. I love the bokeh wide open. However, it is a pain pulling focus wide open as I stated.

There's a great meme about trying to pull focus at 85mm T1.5... I'll have to see if I can find it.
"I'm well trained in the art of turning **** to gold." - Tim Buttner (timbutt2)

Cameras: URSA Mini Pro G2 & Pocket 6K Pro
Past: UM4.6K, P6K, BMCC 2.5K
Computers: iMac 5K (Mid 2020) & MacBook Pro Retina 15.4in (Mid 2018)
Offline
User avatar

timbutt2

  • Posts: 2840
  • Joined: Tue Nov 12, 2013 10:32 am
  • Location: St. Petersburg, Florida, United States of Amercia

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 5:01 pm

Image


Sent from my iPhone using Tapatalk
"I'm well trained in the art of turning **** to gold." - Tim Buttner (timbutt2)

Cameras: URSA Mini Pro G2 & Pocket 6K Pro
Past: UM4.6K, P6K, BMCC 2.5K
Computers: iMac 5K (Mid 2020) & MacBook Pro Retina 15.4in (Mid 2018)
Offline

thefilmaddict

  • Posts: 120
  • Joined: Sun Oct 27, 2019 9:58 pm
  • Real Name: Jason Morris

Re: Ursa 12k ef versus pl

PostWed Nov 24, 2021 11:42 pm

That's hilarious and so true!

I ordered the wrench and bit. So unlike what that video says, I'll leave on all of the shims that were on the pl mount when I change it to the ef mount.

Thanks!
Offline
User avatar

Uli Plank

  • Posts: 21292
  • Joined: Fri Feb 08, 2013 2:48 am
  • Location: Germany and Indonesia

Re: Ursa 12k ef versus pl

PostThu Nov 25, 2021 12:32 am

You can never be sure of back focus being correct as long as you don't have a properly collimated wide angle to check. It can be right to leave that shim in, but you'll need to check, in particular for a parfocal zoom. You may need to take some shim out or even add another.

EF is notorious for lack of precision, photographers don't need to care that much. That's why PL is considered the professional solution for film.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

Studio 18.6.5, MacOS 13.6.5
MacBook M1 Pro, 16 GPU cores, 32 GB RAM and iPhone 15 Pro
Speed Editor, UltraStudio Monitor 3G, iMac 2017, eGPU
Offline

thefilmaddict

  • Posts: 120
  • Joined: Sun Oct 27, 2019 9:58 pm
  • Real Name: Jason Morris

Re: Ursa 12k ef versus pl

PostThu Nov 25, 2021 1:01 am

It took many tries to get the right amount shims in the DZO films zoom with the pl mount. All of my ef glass are photo lenses, which every time I zoom, I have to readjust focus, so shims shouldn't matter as much, right?
Offline
User avatar

Uli Plank

  • Posts: 21292
  • Joined: Fri Feb 08, 2013 2:48 am
  • Location: Germany and Indonesia

Re: Ursa 12k ef versus pl

PostThu Nov 25, 2021 1:16 am

Photographic parfocal zooms are the rare exception.
Some modern AF lenses solve the problem by re-focusing unnoticed, but normally only with the right camera.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

Studio 18.6.5, MacOS 13.6.5
MacBook M1 Pro, 16 GPU cores, 32 GB RAM and iPhone 15 Pro
Speed Editor, UltraStudio Monitor 3G, iMac 2017, eGPU
Offline

Howard Roll

  • Posts: 2506
  • Joined: Fri Jun 03, 2016 7:50 am

Re: Ursa 12k ef versus pl

PostThu Nov 25, 2021 4:25 pm

thefilmaddict wrote:So unlike what that video says, I'll leave on all of the shims that were on the pl mount when I change it to the ef mount.


The .1mm shim is .004 imperial which would be way out for a PL zoom. Since the offset is a positive number the lens will be required to rotate past the infinity mark to achieve infinity focus. Some wides may never achieve critical focus.

Good Luck
Offline

Tom Roper

  • Posts: 521
  • Joined: Sat Apr 14, 2018 4:59 pm
  • Real Name: Tom Roper

Re: Ursa 12k ef versus pl

PostThu Nov 25, 2021 8:51 pm

What screw torque is recommended for the EF mount?
Offline
User avatar

rick.lang

  • Posts: 17175
  • Joined: Wed Aug 22, 2012 5:41 pm
  • Location: Victoria BC Canada

Re: Ursa 12k ef versus pl

PostFri Nov 26, 2021 12:33 am

thefilmaddict wrote:It took many tries to get the right amount shims in the DZO films zoom with the pl mount. All of my ef glass are photo lenses, which every time I zoom, I have to readjust focus, so shims shouldn't matter as much, right?
Once you get a parfocal zoom shimmed correctly, it’s a huge advantage operationally over a lens that is not parfocal as you now have the flexibility to change your focal length (while you continue to record a subject) without losing focus. A non-parfocal lens should be referred to as a Variable Prime lens when used for cinematography; nothing wrong with that behavior if you never change focal length while recording.

I’m oversimplifying things a bit. If you are planning to zoom into a subject in a shot, you should focus with a long focal length to get a critical focus first, then do your shot say from wide to telephoto with confidence. If you focus with a wide angle first and then zoom to a telephoto, your depth of field changes dramatically and the telephoto end could miss critical focus. Less likely a problem if you shoot at T8 but very likely a problem at T2. Critical focus with the longer focal length perhaps even at T2 or so adjusting shutter angle temporarily if you need to see the image correctly, and then record beginning at the shorter focal length at T4-T5.6 for example and all your telephoto CU zooms will be good.
Rick Lang
Offline
User avatar

rick.lang

  • Posts: 17175
  • Joined: Wed Aug 22, 2012 5:41 pm
  • Location: Victoria BC Canada

Re: Ursa 12k ef versus pl

PostFri Nov 26, 2021 12:37 am

Tom Roper wrote:What screw torque is recommended for the EF mount?
Tom, best to check the relevant camera manual. I believe BMD recommends the same force for all their mounts but I can’t verify that now. It’s an adjustment you make on the Wera once and then forget it.
Rick Lang
Offline
User avatar

Jamie LeJeune

  • Posts: 2012
  • Joined: Tue Feb 26, 2013 4:33 am
  • Location: San Francisco

Re: Ursa 12k ef versus pl

PostFri Nov 26, 2021 5:53 am

It's covered on p213 of the current URSA Mini manual:
CleanShot 2021-11-25 at 21.38.10.png
CleanShot 2021-11-25 at 21.38.10.png (30.66 KiB) Viewed 2704 times

The is the adjustable torque tool I bought that can be set to .45Nm
https://www.wihatools.com/adjustable-torque-vario-s-0-1-0-6nm
plus 2mm hex driver
https://www.wihatools.com/hex-metric-torque-blades-2-0mm
www.cinedocs.com
http://www.imdb.com/name/nm4601572/

Return to Cinematography

Who is online

Users browsing this forum: Phil999 and 83 guests