With some papers, printers set to black and white can crunch up shadows and show other signs of non-linearity.
Keith looks at using a free test image with a basic scanner, so as to create a simple adjustment curve to correct some of the printer non-linearity.
There is a much more detailed article going into the details of the process at: https://www.northlight-images.co.uk/fine-tuning-black-and-white-photo-printing/
It looks at the basic process [in the video] using a scanner - it also has links to alternative approaches if you have any of the more advanced measuring devices mentioned in the video.
The test image is available via:
https://www.northlight-images.co.uk/test-image-for-black-and-white-printing/
Se also Keith's short video guide [https://youtu.be/X3K3y7R7IMI ] to using the Black and White printer test images available for free download on the Northlight Images web site.
The site has a wide variety of freely available colour and B&W test images, along with articles detailing more advanced uses. http://www.northlight-images.co.uk/printer-test-images/
Keith has produced nearly 200 articles, reviews and videos related to black and white photography and printing on the Northlight site at:
https://www.northlight-images.co.uk/digital-black-and-white-photography/
There is also a B&W play-list for this channel