Converting DSLR/Digital Camera to Mono by removing filters.

AndyWest

AndyWest

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With the Leica Monochrome now released there was an article in AP about the Leica and also converting std digital cameras to mono by removing the filters in front of the sensor. This should result in sharper black and white only images. There is a company in the US who do the conversion. Does anyone know a company here in the UK that would do it. I know they do Infra red conversions so Mono conversions I would think would not be that difficult.

Anyone had this done?
 
Im not up on sensor builds or array patterns or even rgb layers but im aware that most rgb ccds are layers of red green and blue to make up the sensor wafer.
The leica uses every sensor site in mono, if you removed any of the sensor sites be it red green or blue from a colour ccd then surely you are only removing sensitivity to the removed channel but also reducing your pixel count by however many pixels are taken up by the channel you remove?
I don't think its as simple as yanking out some filters lol
 
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I think its something Leica dreamed up to cream more money off their followers. Whatever perceived sharpness difference you can see in their camera should be easily replicated in post production surely?
 
IR conversions are done by removing a big rectangular filter that's in front of the sensor. Mono conversions are done by removing microscopic filters that are on the sensor itself.

Different kettle of fish.
 
Ahh so not so easy then! I think I will do more research.
 
Dont see how leica can make it any sharper without physically altering the sensor or removing the high pass.
Normally an IR conversion is done by removing the high pass filter (blocks almost all the IR wavelengths and allows visible light) and replacing it with a filter that blocks visible light light and allows IR.
You can use filters that stop light below 720nm and that gives near infrared as well as deep ir, thats where the red cast comes from on IR pics.
Or use something like an 820nm that stops near IR but allows deep IR that looks more like a black and white pic.
However an IR B&W is not the same as a normal picture converted to B&W, they have different info and a lot of objects behave differently, grass, vegetation, skin eyes etc
 
HMansfield said:
With no need for Beyer interpolation, there's no anti-aliasing filter.
Click to expand...

So they are basically removing the colour info from all the data coming off the sensor? Will have to look up the specs behind it and see what they're doing.
 
funky_sam said:
So they are basically removing the colour info from all the data coming off the sensor?
Click to expand...

[assuming you're talking about the Leica M9 Monochrom]

No, there's no colour information going into the sensor in the first place. It has no Colour Filter Array in front of the sensor.
 
essexash said:
I think its something Leica dreamed up to cream more money off their followers. Whatever perceived sharpness difference you can see in their camera should be easily replicated in post production surely?
Click to expand...

No.

With a Bayer sensor, the Colour Filter Array (CFA) means that you have to interpolate (guess) the luminance/chroma values of individual photosites from those surrounding them.

Bayer Array

RG
GB​

So, you're measuring the Red value in the Red photosite, but you have no information about the level of Blue or Green light at that point. Similarly, you only measure the amount of blue light at the Blue photosite and have no information about what the levels of Green and Red light are at that point, etc.

With a panchromatic sensor (no CFA) you're measuring the luminance level, across the whole spectrum, at every point on the sensor, so no interpolation is required.

A Bayer array has two Green photosites for every one of Red and Blue, since that is where a larger proportion of the luminance data for human vision comes from. This is also why you get more noise in the red and blue channel when you examine an image from a Bayer array camera in Photoshop - the green channel started out with twice as much information as the others.

Moreover, since you're filtering out two thirds of the light spectrum at every point you're measuring it in order to gather colour information with Bayer, you're losing that much sensitivity in your sensor compared with a naked (panchromatic) photosite - put another way, it's noisier.

Practical example

http://diglloyd.com/blog/2007/20070727_1-Monochrome_vs_Color.html

One downside of a monochrome sensor is that you lose any latitude for over exposure. Once a photosite is maxed out, it's blown. With Bayer (and others with a CFA) there may be some residual information from the other colour channels with which to reconstruct a partial image, even if one or two of the colour channels are blown.
 
funky_sam said:
So they are basically removing the colour info from all the data coming off the sensor? Will have to look up the specs behind it and see what they're doing.
Click to expand...
Camera sensors are essentially black and white to start with, and they have teeny tiny red, green or blue filters stuck in front of them to make them sensitive to that colour. The camera mixes the values of red, green and blue and makes all the other shades out of them.

This camera has no coloured filters so only ever worries about shades of grey. There's more than fifty of them, despite what your missus might be telling you.

When a colour camera is converted to a mono camera, they remove the coloured filters by essentially grinding them off, hence not a lot of places are willing to do it.
 
essexash said:
I think its something Leica dreamed up to cream more money off their followers. Whatever perceived sharpness difference you can see in their camera should be easily replicated in post production surely?
Click to expand...

I would have thought so. I'd also suggest that starting with a colour image has many advantages too, as it lets you have more control over tonal separations.
 
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