October 27th, 2009 Comments off
The Prototype-4.x family of 3D-360s is based on a camera that we have been developing for over a year. While several areas of enhancement are still left to be implemented, the new camera is ready to be compared against the Canon 5D. Prototype-3 used eight Canon 5Ds, and the new camera in Prototype-4 needs to meet or exceed the 5D's performance. One significant difference between our camera and the Canon 5D is that the 5D (and all other color cameras) uses tiny color filters arranged in a Bayer pattern on top of the individual pixels inside of the camera. While the 5D has 12 million pixels, only 3 million are RED, 6 million are GREEN, and 3 million are BLUE. Our camera is arguably a 15 million pixel sensor because it cycles through three large filters with the 5 million pixel monochrome sensor to produce 5 million RED pixels, 5 million GREEN pixels, and 5 million BLUE pixels. Our camera is immune to color artifacts caused by the Bayer patterns, but taking a picture takes three times longer because the filters must be rotated into place between shots. Fortunately our system automatically changes between filters in less than one second. In the future we may want to add filters for other parts of the spectrum including infrared (IR) and ultra violet. The purpose of this test is to compare the color reproduction, noise, and Bayer pattern artifacts between the two cameras. The 5D has a 14mm Canon lens, and the FOV is similar to our custom lens. Here is the test procedure: 1) Take a picture with each camera in RAW mode 2) Use minimal automatic processing on each image. For the 3D-360 Photoshop was used for color balance and sharpening. For the Canon 5D the image was processed with DxO 3) Compare the cropped images at actual size and zoomed to 600% Here are the results: Above is the shot from the Prototype-4 camera, And below is the shot from the Canon 5D. The two shots show that our camera compares well to the Canon 5D. A slight BLUE halo is visible to the left of some objects, but this may be caused by a dirty or warped Wratten filter. Below is a zoomed comparison of the areas the GREEN circles. Close inspection shows that the 3D-360 camera has less noise and fewer Bayer pattern artifacts, but the 5D seems a little sharper. The difference in sharpness could be related to the dynamic range of the two images. The raw 3D-360 image covers a linear range of 24 bits, but the 5D covers a smaller range of only 12 bits. We use a combination of linear and logarithmic curves to squeeze the 24 bits per pixel per color channel down to 16 bits per pixel per channel. To improve contrast we may reduce our range from 24 bits to 22 bits. I am pleased with this early test, and we are currently implementing upgrades that should make the difference even more dramatic.