Achromatic back

February 4, 2011

phase one achromatic plus

A couple of weeks ago Phase One announced the release of a new line of digital camera backs (the high-end model featuring a monstrous resolution of 80 megapixels). However, as I was browsing through their website, it was something else that drew my attention.

An achromatic back? Wait, could it be… Indeed: no Bayer array, no IR filter. 39 megapixels of pure unfiltered sensor.

The Bayer array is today’s standard in digital camera sensors. A colored filter is fixed over each and every pixel on the sensor, so that each pixel can only record red or green or blue. In fact 50% of pixels record green, 25% red and 25% blue. During raw conversion, an interpolation takes place and each pixel of the final image results in having all 3 values (R,G,B). It is through this function that the two missing values for each pixel (e.g. the blue and red value, if the pixel records just green) are calculated (guessed) based on the corresponding values of neighboring pixels. Depending on the interpolation algorithm, this does have a small impact on the overall picture quality and what is mainly affected is the image resolution.

In an achromatic (maybe monochromatic would be a better description) sensor, there is no need for color filters. Each pixel records light intensity in the same monochromatic scale. No Bayer array means no interpolation. This is the cleanest and sharpest a sensor can perform.

But this back was not designed to make black and white purists daydream. This kind of purity would cost someone something over $1000 per megapixel.

It is the lack of infrared filter that lays the ground to a plethora of scientific applications (aerial photography, medical photography, forensics, photogrammetry to name a few) — applications that traditionally used to rely on specialized film. This particular sensor’s spectral response ranges from about 350nm to 1050nm (ultraviolet to near infrared). By applying external filters, someone can selectively include (or exclude) wavelengths of interest (or not) and record only the desired spectrum.

(I wouldn’t mind getting one for my birthday.)

phase one achromatic plus

photo &#169


Leave a comment