Lack of back focus adjustment on PMW350 Fujinon lens at DVinfo.net

Steve Phillipps · January 31st, 2010, 08:58 AM

Just seen Andy's review of the new PMW350 Fujinon lens at the Abel blog.
Turns out it'll only work with the 350 due to not having a back focus adjustment on the lens!
Can anyone convince me there is a genuine reason for this other than the fact that people would buy it and put it on Varicams and F900s as it only costs about £1500 instead of buying a £10,000 Fujinon?
Steve

Alister Chapman · January 31st, 2010, 10:57 AM

I've been told that there will be a firmware update and software routine to allow manual backfocus adjustment of the lens making it possible to use it on other cameras. Hmmm we'll see.

Being honest I'm not sure how this would work and I'm not convinced it will happen. If your very lucky you might find the settings for 350 will work on another camera. I've been playing with it on my PDW-700 and the backfocus appears OK.

Chris Hurd · January 31st, 2010, 11:15 AM

Thread title changed from:

"Sorry, more cynicism!"

to:

"Lack of back focus adjustment on PMW350 Fujinon lens"

A friendly reminder here that DV Info Net is a technical resource and great care should be taken when choosing a title for a discussion thread. Please avoid ambiguous titles as they are worse than useless. The thread title should reflect the subject of the discussion, and the subjects we discuss here are technical and creative matters exclusively. Thanks in advance,

Mike Marriage · January 31st, 2010, 11:30 AM

Steve, I think it is more to do with the design of the lens and how it focuses.

If I understand it right, the lens is able to perform so well partly because it focuses using elements at the rear rather than the front. Correct me if I'm wrong but the focus is not mechanically attached the the lens elements and these are driven by a servo. This makes the design simpler and able to outperform the price point. It also explains how the lens hardly breaths at all when pulling focus.

That is how I understand it anyway, I may be wrong.

Alister Chapman · January 31st, 2010, 01:04 PM

Yes Mike the rear elements are moved to focus the lens. It is a varifocal lens, so as you zoom the focus of the lens changes. By using a look-up table the lens is able to adjust the focus to compensate and thus hold focus as you zoom. The optical design of a varifocal is simpler than a regular zoom lens. This makes it cheaper but also offers some advantages as with fewer elements there should also be less CA.

Steve Phillipps · January 31st, 2010, 04:24 PM

Quote:

Originally Posted by Mike Marriage

Steve, I think it is more to do with the design of the lens and how it focuses.

You may well be right Mike. I still don't think that's any reason why it couldn't have back focus too, but if you're right maybe my cynicism is misplaced after all!
Steve

Daniel Epstein · February 2nd, 2010, 06:08 PM

My guess is Sony wants people to use the electronic back focus method not a manual back focus method for this lens. Cost savings are an important consideration at the price they are trying to hit.

Tom Roper · February 2nd, 2010, 08:31 PM

No cynicism about the appeal of the kit lens for me. Quite simply it brought the package within reach for me, has the CA correction and auto focus. Without the kit lens, I would not have afforded the camera. So to me, it was a shrewd move by Sony to bring people like me on the fringes into the fold. I expected it to work reasonably well, on par with EX1/3 lens, and it does. If it was utter junk, it would do more harm to Sony's reputation, and Alister and others had already given favorable reviews of it so I felt comfortable. Obviously, you can spend more and get more, but it is still sharp and contrasty, with a useful focal range, doesn't breathe due to the varifocal back focus design. So it works and is a solid entry level value.

January 31st, 2010, 08:58 AM	#1
Steve Phillipps Inner Circle Join Date: Apr 2006 Location: Wales Posts: 2,130	Lack of back focus adjustment on PMW350 Fujinon lens Just seen Andy's review of the new PMW350 Fujinon lens at the Abel blog. Turns out it'll only work with the 350 due to not having a back focus adjustment on the lens! Can anyone convince me there is a genuine reason for this other than the fact that people would buy it and put it on Varicams and F900s as it only costs about £1500 instead of buying a £10,000 Fujinon? Steve

January 31st, 2010, 10:57 AM	#2
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	I've been told that there will be a firmware update and software routine to allow manual backfocus adjustment of the lens making it possible to use it on other cameras. Hmmm we'll see. Being honest I'm not sure how this would work and I'm not convinced it will happen. If your very lucky you might find the settings for 350 will work on another camera. I've been playing with it on my PDW-700 and the backfocus appears OK. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

January 31st, 2010, 11:15 AM	#3
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Thread title changed from: "Sorry, more cynicism!" to: "Lack of back focus adjustment on PMW350 Fujinon lens" A friendly reminder here that DV Info Net is a technical resource and great care should be taken when choosing a title for a discussion thread. Please avoid ambiguous titles as they are worse than useless. The thread title should reflect the subject of the discussion, and the subjects we discuss here are technical and creative matters exclusively. Thanks in advance, __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

January 31st, 2010, 11:30 AM	#4
Mike Marriage Major Player Join Date: Sep 2005 Location: NE of London, England Posts: 788	Steve, I think it is more to do with the design of the lens and how it focuses. If I understand it right, the lens is able to perform so well partly because it focuses using elements at the rear rather than the front. Correct me if I'm wrong but the focus is not mechanically attached the the lens elements and these are driven by a servo. This makes the design simpler and able to outperform the price point. It also explains how the lens hardly breaths at all when pulling focus. That is how I understand it anyway, I may be wrong. __________________ www.mikemarriage.com

January 31st, 2010, 01:04 PM	#5
Alister Chapman Inner Circle Join Date: Dec 2005 Location: Bracknell, Berkshire, UK Posts: 4,957	Yes Mike the rear elements are moved to focus the lens. It is a varifocal lens, so as you zoom the focus of the lens changes. By using a look-up table the lens is able to adjust the focus to compensate and thus hold focus as you zoom. The optical design of a varifocal is simpler than a regular zoom lens. This makes it cheaper but also offers some advantages as with fewer elements there should also be less CA. __________________ Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com

February 2nd, 2010, 06:08 PM	#7
Daniel Epstein Trustee Join Date: Jan 2006 Location: New York, NY Posts: 1,267	My guess is Sony wants people to use the electronic back focus method not a manual back focus method for this lens. Cost savings are an important consideration at the price they are trying to hit.

February 2nd, 2010, 08:31 PM	#8
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	No cynicism about the appeal of the kit lens for me. Quite simply it brought the package within reach for me, has the CA correction and auto focus. Without the kit lens, I would not have afforded the camera. So to me, it was a shrewd move by Sony to bring people like me on the fringes into the fold. I expected it to work reasonably well, on par with EX1/3 lens, and it does. If it was utter junk, it would do more harm to Sony's reputation, and Alister and others had already given favorable reviews of it so I felt comfortable. Obviously, you can spend more and get more, but it is still sharp and contrasty, with a useful focal range, doesn't breathe due to the varifocal back focus design. So it works and is a solid entry level value.