cyvideo
Veteran
A colleague of mine borrowed my Sony SEL20TC. For those not familiar, it's Sony's 2 x teleconverter which can be used with Sony's A7 series cameras and a number of Sony's longer lenses, starting with their 70-200 mm.
On returning it, he asked me, "Have you tried it on the FX6?" "No." I replied. Which got me to thinking. Be it madness or not. But being an old 2/3" shooter, I've always the hankering for the flexibility and range in one lens that a B4 servo zoom can offer. What does a B4 lens offer? It can offer a cheap solution to fill the need for a long range parfocal constant aperture lens. I've played around with adapting a B4 to an FS7, FX9 and now an FX6 before. So the two of us decided to chase this Unicorn. This is an experiment down that path.
NOTE! To be able to fit the Sony SEL20TC to the back of MTF's S16 B4 to E-Mount adapter meant, after careful measurements and calculations, I had to shim the rear flange of the MTF unit with a 0.7 mm shim. This prevents the protruding front element of the SEL20TC from meeting the rear element of the MTF S16 adapter. This still leaves sufficient back focus adjustment on the B4 lens. Though, the adjuster ends up about 50% through its adjustment in an anti-clockwise direction.
On the way back from a shoot, I diverted for a coffee at a local scenic observation point and shot the following clips using a variety of configurations that this MacGyver rig can be used in.
A B4 lens creates am 11 mm image circle without it's 2 x doubler engaged.
Add an MTF B4 S16 adapter, and we end up with an image circle expanded to 14.55 mm. The Abakus '132' S16 PL Adaptor will do he same. With either of these adapters, we generate a 14.55 mm image circle for use in the S16 crop mode offered in the FS7 and X9. The name of the Abakus '132' S16 adapter derives its name from this 1.32 expansion factor.
Let's now add a Sony 2 x E-Mount teleconverter lens, the SEL20TC behind this S16 adapter.
The image circle result of combining a B4 lens with a S16 adapter and a Sony SEL20TC 2 x teleconverte will be the creation of 29.1 mm image circle.
All Sony S35 sensors require a 27.1 mm lens image circle to cover the sensor. This 27.1 mm image sensor circle when taken from the 29.1 mm image created by the adapters above gives us a very clean OPTICALLY CORRECTED image circle with very clean crisp edges, minimal distortion and minimal CA and Coma artefacts. These two S16 adapters listed above have been optically corrected to converge and focus a B4 lens' light paths onto a single sensor plane. B4 lenses are designed to split and focus the light through a prism to three individual R, G and B sensors.
Think one step further. Now introduce the B4 lens 2 x converter into the equation. The S16 adapter is now receiving a 22 mm image circle. The Sony 2 x teleconverter is now doubling this to 44 mm. A full frame sensor needs an image circle of 43 mm to cover it. Though in reality, there is a slight amount of vignetting if using both the B4 Lens 2 x and the SEL20TC 2 x together in front of and behind the MTF S16 adapter.
What we have here is a 100% optically corrected 44 mm image circle that can work with any Sony FF sensor.
If we take an FX6 for example which has CIZ (Clear Image Zoom) the above B4 lens combo can be used in a variety of ways.
1) Optical + CIZ solution
.
The B4 lens without its 2 x doubler engaged plus a S16 adapter plus a CIZ of 1.5 will cover the FX6 full frame with a 2.7 stop light loss. You end up with a 0.7 of a stop loss from the S16 adapter and a 2 stop loss from the 2 x teleconverter. This works in FF mode in either HD or UHD / 4K. In FF HD mode, you actually have access to a 2 x range of CIZ, further extending the reach of the lens by a further 50%.
2) Optical only solution.
The B4 with its 2 x doubler engaged plus the S16 adapter and the Sony 2 x teleconverter gives you a 100 optical coverage of the FF sensor. On top of this you can add in 4K CIZ of 1.5 x. Or in HD a CIZ of 2 x.
Question? How does this actually look in reality?
Chris Young
On returning it, he asked me, "Have you tried it on the FX6?" "No." I replied. Which got me to thinking. Be it madness or not. But being an old 2/3" shooter, I've always the hankering for the flexibility and range in one lens that a B4 servo zoom can offer. What does a B4 lens offer? It can offer a cheap solution to fill the need for a long range parfocal constant aperture lens. I've played around with adapting a B4 to an FS7, FX9 and now an FX6 before. So the two of us decided to chase this Unicorn. This is an experiment down that path.
NOTE! To be able to fit the Sony SEL20TC to the back of MTF's S16 B4 to E-Mount adapter meant, after careful measurements and calculations, I had to shim the rear flange of the MTF unit with a 0.7 mm shim. This prevents the protruding front element of the SEL20TC from meeting the rear element of the MTF S16 adapter. This still leaves sufficient back focus adjustment on the B4 lens. Though, the adjuster ends up about 50% through its adjustment in an anti-clockwise direction.
On the way back from a shoot, I diverted for a coffee at a local scenic observation point and shot the following clips using a variety of configurations that this MacGyver rig can be used in.
A B4 lens creates am 11 mm image circle without it's 2 x doubler engaged.
Add an MTF B4 S16 adapter, and we end up with an image circle expanded to 14.55 mm. The Abakus '132' S16 PL Adaptor will do he same. With either of these adapters, we generate a 14.55 mm image circle for use in the S16 crop mode offered in the FS7 and X9. The name of the Abakus '132' S16 adapter derives its name from this 1.32 expansion factor.
Let's now add a Sony 2 x E-Mount teleconverter lens, the SEL20TC behind this S16 adapter.
The image circle result of combining a B4 lens with a S16 adapter and a Sony SEL20TC 2 x teleconverte will be the creation of 29.1 mm image circle.
All Sony S35 sensors require a 27.1 mm lens image circle to cover the sensor. This 27.1 mm image sensor circle when taken from the 29.1 mm image created by the adapters above gives us a very clean OPTICALLY CORRECTED image circle with very clean crisp edges, minimal distortion and minimal CA and Coma artefacts. These two S16 adapters listed above have been optically corrected to converge and focus a B4 lens' light paths onto a single sensor plane. B4 lenses are designed to split and focus the light through a prism to three individual R, G and B sensors.
Think one step further. Now introduce the B4 lens 2 x converter into the equation. The S16 adapter is now receiving a 22 mm image circle. The Sony 2 x teleconverter is now doubling this to 44 mm. A full frame sensor needs an image circle of 43 mm to cover it. Though in reality, there is a slight amount of vignetting if using both the B4 Lens 2 x and the SEL20TC 2 x together in front of and behind the MTF S16 adapter.
What we have here is a 100% optically corrected 44 mm image circle that can work with any Sony FF sensor.
If we take an FX6 for example which has CIZ (Clear Image Zoom) the above B4 lens combo can be used in a variety of ways.
1) Optical + CIZ solution
.
The B4 lens without its 2 x doubler engaged plus a S16 adapter plus a CIZ of 1.5 will cover the FX6 full frame with a 2.7 stop light loss. You end up with a 0.7 of a stop loss from the S16 adapter and a 2 stop loss from the 2 x teleconverter. This works in FF mode in either HD or UHD / 4K. In FF HD mode, you actually have access to a 2 x range of CIZ, further extending the reach of the lens by a further 50%.
2) Optical only solution.
The B4 with its 2 x doubler engaged plus the S16 adapter and the Sony 2 x teleconverter gives you a 100 optical coverage of the FF sensor. On top of this you can add in 4K CIZ of 1.5 x. Or in HD a CIZ of 2 x.
Question? How does this actually look in reality?
Chris Young
