Scanning

Having inked in the comic book pages on the bristol board the next stage was to scan them.

1. Scanning at 1200dpi as Black and White worked. That gives a bitmap image, which means the image is just one level of colour, which is pure black on white. Since this is the lowest level of colour information you can be greedy and scan at a very high resolution and still have a small file size. My scanner has a maximum of 1200dpi but 2400 would not be uncommon for black line illustrations. The pixels on a bitmap image will always be stepped (jagged) since there are no intermediate greys to smooth out the curved lines (called anti-aliasing). This makes it very important to scan at the highest possible resolution so the pixel steps are so small they do not appear jagged.

The blue construction lines disappeared since the scanner in the above mode will deem them to be too light to be black and so will treat them as white.

2. Scanning in greyscale didn't work. In this mode the scanner treats the image as a range of greys. The black ink line will be black but the blue pencil will be light grey. Trying to then use Levels and Contrast in Photoshop to get rid of these light grey lines whilst retaining the black is not so straightforward. It can be done, but the final lines left behind were no better than the top method, and may have started to break up a bit with application of high contrast.

Scanning in Greyscale at 1200dpi gives a much bigger file size (more levels of shades in the file), so takes ages. Scan at a lower res, say 600dpi works, but then the lines loose in sharpness what they might gain with the 'antialiasing' smoothing.

3. Scanning in colour works. Quite interesting. With this number of colour levels 1200dpi is out of the question, but 600dpi was manageable. With the colour file in Photoshop you will have real black line and blue pencil lines. So all you have to do is to eliminate the blue. For some odd reason in RGB  the blue channel didn't seem to represent the blue! Convert to CMYK mode in Photoshop solved this. 

(Note in Photoshop there are 'channels' for each primary colour which mix to make the full spectrum of colours. They are Cyan, Magenta, Yellow and Black)

Now the light blue pencils I use are in fact Cyan (light blue) and so all appear only in the Cyan channel. Brilliant, just delete all of this channel and the pencils are gone leaving just the black.
Well actually not quite. Maybe it just my basic desktop scanner, but the black ink line doesn't appear only in the Black channel, they also appear in the Cyan. So once the pencil lines had been removed by lightening up or deleting the Cyan channel then the black line became lighter, ie grey. The final image contrast now had to be  to get the lines back to black. I thought affected the line quality and certainly wasn't any better than the above two methods. Shame, I think better scanners would separate the black and blue better since I believe this is the normal method used by artists.

So I used method one at 1200dpi. Then for colouring up I made a duplicate changed the mode to greyscale and reduced the file to 300dpi. This way I get the advantage of pin sharp 1200dpi initial scan, and then by converting to greyscale I have the benefit of antialiasing when the image scales down.

It has to be scaled down in order to have a manageable file size for colour, and my Mac couldn't cope with 600dpi and lots of layers.

Next the file is changed into CMYK mode, ready for colouring in Photoshop.