Average sized Four Thirds (19 x 10 mm mm) sensor Even though Blackmagic Cinema 4K's sensor is significantly larger than a typical compact camera sensor, it is still hard to achieve that shallow depth of field and a blurry background for your portrait shots.
Very Low Resolution Sensor: 9.0MP Blackmagic Cinema 4K's 9.0MP sensor will not provide much room for cropping or large printing your portrait shots.
No Image Stabilization Lack of Image stabilization may result in blurry photos especially in long exposures and at long focal lengths