PLx1.4 Mark II optical improvements include the ability to shoot at wider apertures on your lens without losing sharpness or contrast. For example, you can shoot at T1.9 without losing any quality, which allows for a very narrow depth of field. This enhances the creativity and versatility of the extender and allows for it to be used with faster lenses.
Extenders are most helpful on long primes when you need to get even longer, as well as on zooms when you need the long end to go further. I find them extremely useful on lightweight zooms, as I am typically handheld in these situations. They're especially useful when I need to have a longer focal length than the lens can provide natively, but without moving to a larger lens that requires more weight and set up. In this situation, I just add the PLx1.4 Mark II to my camera package for more versatility.
For my test, I first shot with an ALEXA Mini at 4KUHD, Apple ProRes 4444XQ, and an IB/E Optics Raptor 100mm lens. This lens is a T2.9, so I was able to capture all my macro shots at wide open with the new Mark II extender. This means I didn't have to sacrifice stop at all. With the 1.4x extender, the focal length becomes 140mm, allowing for extreme close ups. For the second portion of the footage, I used the RED EPIC DRAGON 6K, shot at 8:1 with a Canon 30-105mm T2.8 Zoom. This made the zoom a 42mm to 147mm, which was a great range for shooting B-roll of downtown Chicago. Due to the optical enhancements of the Mark II, I was able to keep the lens wide open and still keep my set up lightweight. I found the footage to be very pleasing, maintaining the sharpness and contrast of the lens, and I didn’t notice any focus shift in the footage, which is also something to look out for with extenders. Take a look for yourself in the video above.