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B4 Lens on Panasonic GH4




After much research and study I finally "pulled  the trigger" and I bought a Canon B4 lens for the GH4 camera.


I was quite hesitant at first, but thenI went for it. First I go the lens, which it looks like new and then I searched on ebay for the lens adapter, the connecting cables and the 12v battery, and they all work together well.
I got the B4 adapter to m43 with the tripod mounting plate, it is the short version, and that din't work to mount it to the tripod, so I had to manufacture an adapter to rise it up a bit, and that works really well now.
I also made a second tripod plate that is permanently mounted on the adapterThat goes on the tripod.

The lens I am using is 9 to 171 mm, with the 2x extender it becomes 18 to 342mm.
I am using this lens + GH4 to film live events in a multi camera set up and having the power zoom it ads a nice dynamic to the production.
The 2nd camera is GH4 + 14-140 and the 3rd camera is a GH2 + Canon 17-40mm with a pasive adapter.

Back to the B4 lens, it is known that you have to have a 2x extender buit in the lens in order to get the full screen image. If the lens doesn't have the extender you see a full circle and a big vignette.
The trade off when you engage the extender, there is a light loss of 2 stops. Also it's good to know that this SD lenses work best on the 5.6 f stop and when you loose 2 more stops with the extender, it makes the lens a bit slow regarding the light.

Usually when I film a concert, a theater play, or church service, there is usually good lighting and it works well.
There is a little secret, it I have the lens on the 1x and I zoom all the way to about 155mm the image is full screen and I have the native fstops, so I get more light.
Even better when I use the 4K mode, there is more crop from the sensor, this means that I get full screen from 80 to 171mm.

Cables and 12v battery
I got the Hirose cable, the lance cable and a 12v battery. I plug the lance cable in to GH4 and this allows me to start/stop recording from the lens start/stop button.
The battery comes with a charger, and it lasts several hours, I can shoot few events and is still working.

Is the B4 lens for you?
This is a very good question. I will try to write as much as I know hopefully it will give you a better idea and decide if this lens will work for your need.
First of all this combination Canon B4 or Fujinon B4 lenses with the Panasonic GH4 will work very well on a tripod, or a good camera stabilizer like a shoulder mount.

It has a very good zoom range, and is constant aperture and focus stays the same through out the zoom range, unlike the DSLR lenses that change focus whe you zoom in or our and you need to readjust. You get nice power zoom, variable speeds, this is useful for live events.

If the lens is open to from F4 and up it becomes a bit softer, the optimum is 5.6 and down. When you engage the 2x extender you loose 2 stops of light. This set up is heavy.

What projects is this set up suited for:
As I mention earlier, this lens will give you really nice image for live events, conferences, concerts, church services, sports, TV and broadcast style work.
Can you use this lens for weddings? Yes and no! I have used the lens on weddings, but as a second camera for close ups on a tripod. Works well, but if there is low light you better use a different lens

If you are not sure if you should go this route and invest in this set up and you have more questions, please feel free to contact me, I will be glad to help.