Shadows in the crease from scans.

[Starbase1]

I'm having problems cleaning up scans - and the scans are not by me, so I can't just do them again properly.

My problem is that I find myself often working with scans where the are near the fold in the book is distinctly darker. And while adjusting the levels helps, there are also grey images on the pages, which lose subtlety with a contrast stretch.

Now, I can generally get to good enough, by mucking about with lots of selections, but I'm wondering if there's a better way. The shading is very regular, so I think there may be a way...

I attach an example, which may help clarify.

Thanks, Nick

 

 

[v_kyr]

1 hour ago, Starbase1 said:

My problem is that I find myself often working with scans where the are near the fold in the book is distinctly darker. And while adjusting the levels helps, there are also grey images on the pages, which lose subtlety with a contrast stretch.

Now, I can generally get to good enough, by mucking about with lots of selections, but I'm wondering if there's a better way. The shading is very regular, so I think there may be a way...

Well as those are bitmap/pixel based images and the greylevel shading of the fold part (certain greylevel pixel values in there) can also be found in the main rocket image shading parts, any filtering on the whole image doc will also affect the main drawing. You can perform a "Select Sampled Color..." in order to see that certain fold part greylevel color pixels are also part of the main rocket drawing here.

So the whole is difficult to overall repair/handle without any area selections or maskings here, since then the whole image (all pixels inside) is always taken into account. Thus you have to make some sort of "selection" or "area wise masking" in order to limit the area which should be only altered/affected here. - Other than that one can also Dodge the shadows/midtones near the fold in order to lighten them up.

 

[walt.farrell]

41 minutes ago, v_kyr said:

You can perform a "Select Sampled Color..." in order to see that certain fold part greylevel color pixels are also part of the main rocket drawing here.

Or perhaps a Flood Selection, with a low tolerance and Contiguous turned off?

[thomaso]

2 hours ago, Starbase1 said:

scans where the are near the fold in the book is distinctly darker.

These shadows are mostly in a rectangular area. Accordingly, a rectangular vector mask can be an easy way with flexible scaling, stretching and rotation options for the adjustment, regardless of the adjustment type and setting. – Just a quick example for the principle (here in APub V1):

[David in Яuislip]

I've added a curves layer to sort of sort out the dirt then a nested rectangle with a gradient fading from 100% to 0 opacity to clip the effect

You can copy the adjustments and paste them onto your next scan, adjust rectangle size & curve value as required
You can also use it on a left hand page ie where the shadow is on the right. Paste as before then right align the adjustments, note the width in this case 316px
Drag the right handle to the left until it's about right then enter 316 into the W box, the gradient is automagically reversed

It ain't perfect but it's quick

RLA120.zip