How to normalize brightness and contrast levels for Grayscale pictures

[discoversci]

How to normalize brightness and contrast levels for all Grayscale pictures

Hallo friends. Don't know much about Photoshop (know only elementary functionalities). After printing some of the pictures with characters (grayscale picture), I've noticed that some pages are more bright than others, i.e. individual grayscale characters seem to have higher brightness than others. Is there a way, to be able to somehow normalize all pictures (all characters for that matter) into the same level of luminosity. Preferably with a batch job. I guess some sort of luminosity should be normalized across all the pictures, right ? Help/suggestions needed. Thank you.

 

[thebestcpu]

Hi @discoversci
You might want to check out the "auto" commands in this link as a starting point:
https://helpx.adobe.com/photoshop/using/making-quick-tonal-adjustments.html

It is hard to be precise with your description. For more focused help, providing a couple example images where you want the tone to match would be helpful
John Wheeler

 

[discoversci]

Hi @discoversci
You might want to check out the "auto" commands in this link as a starting point:
https://helpx.adobe.com/photoshop/using/making-quick-tonal-adjustments.html

It is hard to be precise with your description. For more focused help, providing a couple example images where you want the tone to match would be helpful
John Wheeler

Hello. Thank you for your reply. I have attached 3 pictures. Characters in one of the picture are brighter than in the other ones (noticed especially when printed with my printer). For instance, if I change the brightness in picture 3, I can get close to characters on picture 2 (namely, the characters here are more black, than on the picture 3). The goal is to normalize all the pictures in terms of characters having the same "blackness" - thickness so to speak. I hope these pictures help to demonstrate the problem.

 

[thebestcpu]

Hi @discoversci
No pictures were attached to view.
John Wheeler

 

[discoversci]

Hello. Correct. That was my mistake. I have completely overlooked that pictures were too large for upload. Now it should work. Thank you.

 

[thebestcpu]

Hi @discoversci
There are a few things going to that make a difference/contrast/weight/brightness of the lettering.

- One major factor is that the text that was digitized were all in different fonts. Font types can appear heavier / darker from just a basic font difference and some fonts have a bold option as well. To fix those types of difference in batch mode would be a bit more difficult than the other factors I will mention

- Another factor is if the black point and white point are set correctly. Along with that some of the characters in one of the images have some very light pixels within the character itself. To do this in batch mode one has to guess where to set an adjustment that might be better on a case by case basis. Yet if I needed to do batch mode here is the setting I would use using a Levels adjustment Layer or an Curves adjustment Layer could be used:

Here is the Levels adjustment that I would use in a Batch Operation:



Or here is the Curves Adjustment Layer I would use in a Batch siutation (same effect as the Levels Adjustment Layer above:




To automatically adjust for different font size would be quite a bit more difficult in Batch mode and beyond any simple approach.

One other factor that would clean up the images is not to save in JPEG (compression artifacts) and rather use PNG instead. If that is not an option, when opening in Photoshop, if you have a recent version I would use the Filter > Neural Filter > JPEG Artifacts Removal
This will remove some of the bit artifacts surrounding each of the characters.

Note that when one prints on a printer or a big box printer when not done by yourself, there may be some automatic adjustments that might alter the desired intent of your print (e.g. averaging or weighting the total dark vs white pixels.

That may not be needed by you as it gets into having a color managed work flow from editing to monitor to printer.

I would bet that is a minor issue compared to the ones already mentioned above.
Hope this gives you a starting point to help with your project and you can always ask additional questions if you have them
John Wheeler

 

[discoversci]

Hello. Thank you for the proposed options. I'll try and dive in and report back, if I make any progress