Getting rid of discoloured paper

[GordonM]

I am a complete newbie on the use of Affinity Photo. I have scanned a number of line drawings from a 120 year old book. I have found the most detailed scan on the Epson Perfection V39 is obtained by setting the image type at 24 bit colour. That seems to give me a nice line picture (at 300 dpi). However I want to get rid of the yellowish colour of the paper as it appears outside the image as well as between the fine lines - with the result that I have a line drawing which, surprisingly does mot appear as clear as on the original slightly yellowed paper. I have also sharpened the image 4 times using the filter/unsharp mask (Radius 2px, Factor 4 and Threshold 100%},  I attach the file which I am busy working on. I would be most grateful if someone would help me to get over the problem of the yellowish colour as described above. 

img099ax42pxF4Th100.afphoto

[GarryP]

Adding a Black and White Adjustment (adjust levels to suit) and a Levels Adjustment (bring the White Level down to around 88%) will do most of what you want. You can then use the Erase Brush or the Paint Brush to get rid of the little ‘flecks’ that are left over.

[John Rostron]

It may also be worth adding a Threshold Adjustment (Layer > New Adjustment Layer >Threshold, right at the bottom). I usually find a value of 75 works well.

John

[GordonM]

Thanks GaryP and John Rostron. My goodness, what a difference. Now I will be able to soar ahead. In a previous thread I was shown how to flatten my pdf and now with this as well . . . what can I say?

Zikomo Kwambiri! - very many thanks, as we say in Malawi (Chichewa)

[GarryP]

You're welcome.

[captainpat]

Thanks Gary and John, using your suggestions I was able to restore an old sketch my Uncle created about fifty years ago.  Thanks so much.