Camera sensor modifications for Black and White photography
On today's photographic market, black and white digital cameras can be counted on the fingers of one hand.
The brands that have developed real black and white digital cameras are basically two: Leica and Phase One, both brands have manufactured two or three models in their entire product line, their digital black and white cameras are oriented to a niche market, wich insanely high prices (also due to the non mass scale production).
In the Year 2010 with a crazy idea, taken by a group of mad astrophoto amateurs on the net, I started converting my old EOS 300D first for infrared and then with many tribulations for black and white ... the results for those times were extraordinary.
Debayer means the removal process from the sensor surface of RGB color filter array matrix
What, how and why a sensor debayer:
The ccd / cmos sensors of today's digital cameras for shooting color images, are built with a reticle of RGB filters which varies according to the type / brand, but which basically consists of colored filters deposited directly on the chip.
This solution through the filtering of the Red, Green and Blue chromatic components, and the subsequent mathematical elaboration (interpolation) allows the reconstruction of the colors.
The color image with various methods can be transformed into gray tones, the classic black white filters cannot be used in front of the lens, the contrast must be corrected and the chromatic contributions that will be translated must be corrected in black and white from the color image. Obtaining an image congruous to luminance is always a problem, each photo are adapted from time to time.
BEFORE
During the removal, the filter array shown in the lower part of the image.
AFTER
At the end of the Debayer process each photosites is able to read the luminance without any filtration...
Back to the past
For black and white purists, using tools designed primarily for color photography has always been a limitation, the camera sensor free from the RGB matrix, however, is able to record the intensity of light like good old film.
For this reason in recent years a large number of photo amateurs have attempted the operation of removing the color filters matrix with the most disparate techniques some of which even unorthodox which ranged from grating the chips with vampire-killing wood to the blowtorch up to attempts to dissolve the sensor in the acid (medieval debayering)..
The ancient scraping method...
This method is consisting in scraping the CFA from the surface of the sensor using wood tools etc. Although this method is practicable, the success ratio is around 40%, very often the sensor is irreparably ruined, the edges of a scratched sensor are always inaccurate and only the center of the frame is usable.
On the left, one of the first medieval scraping kit, today no more available !
All these more or less approximate techniques have "allowed" with very low success rate, the appearance of "Monochrom" style cameras of different APS-C formats, full frame / reflex / mirrorless.
Although not perfect sensors, those who have used them have been able to appreciate the greater purity of the images, the increased resolution and a tonal range very similar to that obtained with the BW film.
These features are highly appreciated by astrophotography enthusiasts for whom, in many cases, a camera with a debayer sensor is needed, but also amateur and fine art photographer appreciate the feel and look of the images made with debayer cameras.
My method
With the study of sensor construction techniques, I have developed a special process that allows the sensors of the various cameras to be debayered with results of the highest quality.
I can't say more about my technique here, if interested please contact me!
Some example images made with my monochorme converted cameras
One debayered sensor mounted inside a Canon EOS 600D
An EOS 600D M Monochrome Modified
Debayerized sensor caracteristics and defects:
Although the sensor is perfectly clean to the naked eye, very small defects, dust and / or very small remnants of the RGB texture may be visible only after very careful analysis of the enlarged images, these micro imperfections do not affect the use of the camera, they can be corrected with photo retouching but in most cases this lite imperfection are not perceptible (even the film had micro imperfections).
Group of photographer durig a photoshoot in Turin
A black and white panorama using Infrared filter
RAW or JPG ?
Once our photo is taken, by setting the camera in black and white the JPG is immediately usable, for the photos that we consider worthy it is possible to proceed with the processing of the RAW.
The firmware of the debayed camera does not know that the sensor has lost the colors for which the programs interpolate the color filters (which in reality are no longer there) this produces an image with a Black/Magenta tones...
A magenta world
Raw images if not treated with specific programs have a Magenta intonation.
The videos and jpgs if you set up the camera with a black and white profile are immediately usable.
Off course we can use this images desaturating them but ...
For the correct management of debayer raw, I recommend the use of one of the softwares:
- RawTherapee
- Raw Photo Processor osx
- Darktable
- AccuRaw Monochrome OS X
- Dcraw
Transforming the debayer RAW image is the key to obtain the true black and white and benefit the advantage of the debayer sensor.
My preference
Normally I use DCRAW, it is freeware and is compiled for windows, linux and osx, no graphical interface...
Example of use: if by hypothesis I choose to transform the image called "IMG_6215.CR2" the command is like this:
dcraw -D -a -6 -T IMG_6215.CR2
The command parameters produce a conversion from RAW to TIFF in black and white at 16bit, with automatic adaptation of the brightness and above all without making any interpolation, each pixel represents the brightness, the image obtained has on average more than double the resolution of an interpolated image, an 18Megapixel aps-c camera will produce an image with a resolution comparable to that of a 45Megapixel camera.
The extra resolution is very well accepted for lovers of black and white and for astrophotography.
