I have a Sony A7Rii that I had converted to monochrome by removing the CFA and did some test shots in 2019 using the same subject and lens on a Sony A7Riii which has the same 42MP sensor. This illustrates the real world detail resolving difference between CFA and no CFA. The resolution improvement by removing the CFA, while barely visible, is somewhat underwhelming as is the slight improvement in sensitivity -- the main reason I did the conversion was to shoot IR.
Anyway, here are 100% crops from each camera -- the color images from the A7Riii were converted to black and white by extracting the luminance channel. There are minor differences in tonality due to the different spectral sensitivities.
its not apples to apples ,,,,, you had to use a special program like Monochrome 2 dg on the converted camera .... also thee can be " unknown unknowns " with regards to the software and electronics of a converted camera and a dedicated one
"Almost all digital cameras that are released today are color cameras. Several Leica and PhaseOne models are rare exceptions, but these cameras are even more of a niche product than the color cameras or digital backs made by those same companies. Nevertheless, there is demand for BW (Black and White) cameras (for reasons explained in detail below), and many photographers want BW cameras with the same lens mount as their main (color) camera, so that they can use the lenses they already own.
Since a color camera differs from a BW camera due to the existence of color filter array (CFA, Bayer mosaics) over the sensor, converting a color camera to BW is done by removing the CFA*.
After the CFA is removed, the demosaicking process that is done during RAW file processing becomes unnecessary. This, in turn, leads to higher resolution and a decrease in the number of processing artefacts (see the
Bayer Moiré article), which is, essentially, why people perform the conversions of color cameras to monochrome.
However, during such conversion, the firmware of the camera doesn’t change, and the camera doesn’t know that it’s become monochrome, which leads to the following:
- The monochrome file recorded by the camera cannot be told apart from a color shot without a complete analysis of of the RAW data – all of the metadata corresponds to the color file.
- In many cameras, sensor data is processed differently for different color channels before the RAW is recorded (for example, White Balance preconditioning for Nikon: the values of the red and blue pixels are multiplied by small coefficient). In the case of a camera converted to monochrome, equally exposed pixels that originally, before conversion, belonged to different channels, receive different RAW data numbers.
The first problem leads to most RAW processing programs continuing to think that they’re processing a color file and, accordingly, preform demosaicking, which leads to resolution decreases, moiré, and aliasing. " - Monochrome 2 dg
but I'm sure it was beneficial to some of the newbies on this forum. LOL!!! You guys are amazing.
