4K Ultra HD Video MicroscopySeptember 1st, 2015
Just as we were early adopters of 1080 HD video, we are now exploring 4K Ultra HD video for microscopy. So called “Full HD” 1080p HD format is 1920 x 1080 pixels which is the equivalent of about a 2MP still image output at live video speeds of 30 frames/ second(+/-). The new 4K Ultra HD is 3840 x 2160 pixels, or more like 8.3MP still images output at video frame rates.
As of fall 2015, we haven’t found a perfect solution: a camera that will output live 4K HD to a 4K display while simultaneously recording 4K video in-camera. Several 4K HD camcorders will record 4K or display 4K, but will not record and display at the same time. The camera we’ve selected as we enter into this market is the Sony Alpha a7S mirrorless, full-frame DLSR. It will output 4K HD at 30 fps via an HDMI cable to a 4K HDTV, and the fact that it has interchangeable lenses and a full frame sensor means that we can use our MM-SLR universal microscope adapter to mount this camera on virtually any microscope. However, this camera will not record 4K HD video internally. It can record 1080p HD, and it can be used with an Atomos Shogun 4K recorder if one wants to spend another $2,000.00. Despite this limitation, we find that this camera with our MM-SLR adapter does provide extremely high quality live video output to a 4K HDTV, and is eminently suitable for live classroom or conference room microscopy. Our MA7S basic package includes the camera body, MM-SLR adapter, AC adapter, and HDMI cable.
In our testing, the Sony Alpha a7S will produce an image on a matching 4K HDTV with so much detail that it can actually surpass the optical resolution of the microscope as seen through standard 10x eyepieces. This makes perfect sense when one considers the numerical aperture of the objective and other physical limits of light microscopy: for instance a 20x objective with an NA of 0.40 combined with 10x eyepieces provides 200x magnification to the eye. But because the NA is 0.40, the rule-of-thumb resolution limit is 400x, so there is more detail that could be seen by using 20x eyepieces. The 4K HD camera makes this additional resolution visible. In contrast to a 1080p display, one can get extremely close to the 4K HDTV display without seeing much, if any, pixelation, and without any visible noise. However, from maybe ten feet away, the fine detail naturally becomes lost, and at that point it’s harder to say that the 4K HD image is appreciably better than 1080p. But up close – wow! The images below are close-ups of actual HDTV screens taken with an iPhone: