Tuesday, 8 April 2014

JVC joins MFT, and launches large sensor 4K video

The big news this week is that JVC (JVC Kenwood) is joining the Micro Four Thirds format. So far, they have announced two 4K video cameras. The GY-LSX2 is a camcorder style video camera, while the GW-SPLS1 is a modular camera unit:

JVC GY-LSX2JVC GW-SPLS1
(Image from dpreview.com)(Image from dpreview.com)

These cameras have a Micro Four Thirds mount, of the "active" type. This means that you can use autofocus, you can set the aperture from the camera, and operate OIS.

Larger sensor!


However, in one way, they are very different from Micro Four Thirds cameras: The sensor is larger. The cameras will use the Altasens AL41410C sensor. Just like the Lumix GH4, it can record 4K video in 3840x2160 (Quad HD) and 4096x2160 (Cinema 4K).




It is different, though, in the sense that the 4K area of the sensor is 21mm x 11mm, with an image circle of 23.7mm. This is larger than the 21.6mm image circle of the Four Thirds sensor.

Do you need new lenses?


So does this mean that you need to buy new lenses to use this camera? Probably not. Many Micro Four Thirds lenses already cover a larger area than the 17.3mm x 13mm Four Thirds sensor.

Obvious examples are the Sigma lenses (19mm f/2.8, 30mm f/2.8, 60mm f/2.8). Since these lenses have optical designs for covering the APS-C sensor format, they readily cover the sensor area of the new JVC 4K video cameras as well.

But that is not all. Using an adapter, I mounted some M4/3 lenses on an APS-C sized sensor camera. I had a hard time finding lenses that did not cover almost the entire APS-C sensor size. Here are some examples (click to enlarge):

Lumix G 14-42mm @ 18mmOlympus 45mm f/1.8
Lumix G 14mm f/2.5Lumix G 20mm f/1.7

Note that the image is a not centred perfectly in these examples. This is due to the crudeness of the adapter. This also explains why the focus is bad.

Also, you'll see that some of the images have a bit of barrel distortion. This is because the geometric distortion correction is not done. I'm sure the JVC cameras will do this distortion correction inside the camera, eliminating this problem.

Apart from these oddities, you'll note that in most cases, the image circle is sufficient to fill out the Super 35 sensor of the new JVC cameras. So the good news is: Most of your lenses are probably going to work quite well on the JVC camera.

On the other hand, even if the image circle does cover the Super 35 sensor area, it could be that the quality of the image in the corners may be unsatisfactory. But I am sure that a lot of tests will pop up, saying which lenses you can trust, and which you cannot trust.

Conclusion


JVC joining Micro Four Thirds is very good news, and interesting. They are going to bring a lot of pro videographers to the Micro Four Thirds system. And another good news is: Your lenses are most likely going to be useful for the new system, even if the sensor requires an image circle larger than Four Thirds.

Another thing to note is that using a bigger sensor means that your lenses will become wider, effectively. Using the image circle diameter as the scaling parameter, there is a crop factor of 1.8. This means that a 14mm lens will become equivalent to 26mm for a traditional film format!

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