Cleaning up Microfilm

[Jim Slade]

I have a large number of microfilm images like the attached that I need to clean up for print.

 

I would like to know what sequence of cleanup would get rid of the noise in the background here.

[John Rostron]

You could try the Threshold Adjustment. Choose a threshold that will separate your dark grey from the lighter greys of the background.  There is no guarantee that this will work,  but if it does, it is probably be more efficient than other methods.

John

[NotMyFault]

If possible, try to get better images. The example you uploaded shows strong jpeg compression artifacts. This makes it 10x harder to achieve good results. The overall contrast is extremely low. 
 

These 2 issues alone will cost you so much time.

Any chance to scan the microfilm again?
Any chance to get non compressed images (no jpeg, use tiff or png with lossless compression).

[Jim Slade]

This is what we have to work with. The microfilm is marked "Poor Original Copies."  The originals were destroyed some time after 2000. The last printed copies are sitting in the hold of a ship that is waiting to be scrapped.

[NotMyFault]

Below my try with focus on making fine details like test visible and boost overall contrast.

1. blur 0.1px Gaussian to remove compression artifscts
2. a level adjustment to equalize histogram (blacks, and gamma)
3. select huge rectangle on left side, copy as pixel layer
   1. add motion blur
   2. set blend mode of pixel layer do divide
   3. stretch via move tool to cover full area
   4. this helps to remove overall horizontal color pattern, better contrast 
   5. i duplicated the layer and reduced opacity to increase effect
4. Add highways filter to boost details
5. add unsharp mask to bist details. Both will increase background noise, but the text become readable. If you have time, apply sharpening via mask selectively to fine details

image

[thomaso]

Another approach (without pixel selection / mask / brush). Since dark gray in background & drawing are partially identical it appears impossible to remove the grain only without affecting the drawing. (… unless you add motive related masks, which I assume you want to avoid)

[firstdefence]

Another method, quite a quick method with minimal work, ultimately it's how you would like the microfilm to end up looking.

• Duplicate the background layer and change the duplicate layer to Blend Mode: Reflect
  
• Right Click on the duplicate layer and select Merge Visible
   
• Paint over the remaining marks white a white brush.
  

Took me less than 3 mins to do, yup I timed myself lol!