View Full Version : Lens problem or adapter problem ?
May 6th, 2012, 01:54 AM
Recently filmed a sequence in a building which was to be demolished the following day. In the rush to shoot, I rented the only handy lens available regionally to use with the HZ-CA13U adapter. It's a Super 16 Optex/Zeiss Vario Sonnar 12-120 T2.4 with PL. Suppose it was rehoused by OPtex.
The image was dreadfully vignetted when stepped down. Luckily, the shoot was at night and the lens fully open so we got by and the rushes are allright.
But I'd like to understand what happened (my local DP didn't).
Below are some images I shot the next day (never mind the wrong WB) that show the vignetting.
Never encountered such extreme vignetting before.
I'd be very grateful for any feed-back.
May 6th, 2012, 05:36 PM
Could it be that there is something wrong with the internal ND filter? I ask because the vignette seems to be quite distinctive in it's shape as apposed to a softer and more evenly spread vignette.
I have had times when I accidentally positioned the filter between two settings and it looked a bit like the photos you posted.
May 7th, 2012, 12:36 PM
I think I read somewhere that a Zeiss 16mm film camera zoom lens required an extra optic on the rear to yield an image to a Super16mm gate without vignetting as it was originally for a standard 16mm gate coverage only. Whether your rented specimen was one such is another matter. It might have been modified for PL-Mount and not for Super16mm. Was it marked as Super16mm?
There is a similar vignette which intrudes and then widens away with the Angenieux 10mm x 150mm initially at wide, then creeps out and then creeps in again through the range about 25mm to 25mm and then widens away for the rest of the movement.
With the Angenieux there were two sources for the vignette, the front rim of the lens and the moving optical group within the lens. Even on the CP16R camera with a standard 16mm frame, a Series 9 filter and rubber Tiffen shield were enough to vignette the corners on wide.
May 7th, 2012, 03:03 PM
Thanks my friends
Gavin: first still, indoors @ 5.6, is without ND but still vignettes. We went through the ND levels and saw no real change. Only change was with aperture.
Bob: the vendor rents this lens out as a Super-16 but it is really only marked "OPTEX" on the housing. This might be the cause of the problem. I also found that the lens breathed an awful lot - luckily no rack focussing necessary for this shoot.
Part of the problem might stem from the fact that I was explicitely looking for a not-too-modern lens, sharp but still yielding softness, yet had no time to do amy testing, alas. So it might weel just have been a standard-16 re-mounted by Optex for PL. Also, the maximum aperture was smaller on the ring than on the lens id. The softness I got, but also the drawbacks.
In truth, I mostly use 35 or S-16 primes so far with the JVC adapter, so the vignetting never came up.
So maybe standard-16 lenses do provoke vignetting in the adapter. Maybe someone from JVC could fill me in ?
Again many thanks.
May 8th, 2012, 11:39 PM
There was a list published a while back I vaguely recall, on something like "cinematographer.com" or some similar site of which older standard 16mm lenses would throw an image able to cover a Super16mm frame. LATE EDIT thanks to the marvels of Googe Search, found in about five seconds - http://www.cinematechnic.com/resources/optics_for_super-16.html
The Kinoptik 5/7mm f1.8 ultra-wide was a surprise. One expects wide lenses to be the worst. I think I have previously mentioned the Angenieux 17.5mm to 70mm zooms which are new-old-stock being vended by Ken Hale at Whitehouse AV.
The Angenieux 16mm - 64mm was a faster lens, also very good but hard to find these days. A specimen I got hold of had been ruined by bad repair of separated elements and was unusable. If you find one for sale, be careful to get the vendor to let you look through it for flare from bad repair or yellowing from separating elements.
There is a 9mm Cinema Products Ultra T* T1.3 prime with CP-Mount relisted on eBay. These were made by Kowa. The 9mm "will" vignette but can be modifed. Ken Hale can do it for you then fit and properly collimate a PL-Mount whilst he is at it.
It is a simple mod, the milling out of clearances in the front retainer of the foremost element. In a PL-Mount you have to remember it only goes in two ways otherwise the vignette comes back.
I think the adaptor will not be the problem. JVC have previous experience in optically based in-camera format adaptors so your adaptor has to be at least second generation.
Their older KY-F23 and KY-F50 camera heads of the mid 1990s used such techology inbuilt to convey 1/2" and 2/3" lens images to 1/3" sensors to broadcast standards in what were then small camera bodies.
May 9th, 2012, 12:44 AM
The lens I used is indeed included in the list in this category:
«Zoom Lenses Converted to Super-16
.... They are converted to Super-16 by using a range extender. .... These lenses have had 1.15x or 1.2x extenders installed behind their rear elements. The 1.2x extender optics increase the diameter of the lens' image circle by 20% thereby extending coverage to the Super-16 frame»
Meaning that this Optex conversion should fit properly without vignetting. But this is not the case, at least using the JVC adapter..
The problem may be of my own making, because I am looking for a softer image in the cam (not in post) for my many night shots. I probably would stay out of trouble with the JVC adapter if using recent S16 lens technology.
But then, why bother with digital S16 ? And 720p ?
Any thoughts ?
May 9th, 2012, 05:31 AM
But then, why bother with digital S16 ? And 720p ?
I think bought and paid for is a pretty powerful argument along with fact that the JVC ProHD image is still sweet and a few features have been done on it.
May 15th, 2012, 07:34 AM
Agreed, Bob, but I'm just wondering if on feature films such as I have presently going, it's worth the hassle piecing and fitting and calibrating everything together when we could use ready-to-go solutions ranging from F3 via Alexa to Ikonoskop.
What makes me linger with the JVC HD-GY251 is the wonderful image which the captor produces, so gentle with colors and so progressive, like the sweep of the shutter.
I ran a Nanoflash @ 100 mBit/sec along the with the JVC HD recorder. It'll be interesting to compare 4:2:0 vs. 4:2:2 night shots on the big screen.