It depends on the scanning software. Some, like Vuescan, allows the user to choose which rgb channel is used to make the grayscale channel.
Message
Re: [Digital BW] Re: B+W Scans from RGB Scanners
2009-01-05 by Peter De Smidt
Yahoo Groups archive
Message
2009-01-05 by Peter De Smidt
It depends on the scanning software. Some, like Vuescan, allows the user to choose which rgb channel is used to make the grayscale channel.