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yellow stain removal from negatives

Forum|Forum|8 years ago
July 21, 2017
9 respuestas
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Hi there. I've tried looking at answers on the forum but nothing just seems to fit.

I work for an aerial photographic company photographing ships, and we have a huge library of images. Unfortunately some of the negs have been stored with neg bags where the glue used is not a neutral ph and is leaving this nice yellow/red staining.

At the moment we have found 100's of negs like this. When one of these shots is needed we use a combination of lasso to start removing the cast by hue/saturation, colour balance basically any tool that helps, and gradually over many lasso attempts get to a point where we can make a viable print. The majority of prints are 6"x 4" and 10"x 8". What gets REALLY tricky is when they ask for a 36"x 24"!! Depending on where the ship is in the shot we can sometimes just clone over the sky and sea but most are like the one in the attached picture.

So in desperation i have turned to the real Photoshop experts in the hope that there is a magic wand to make this problem disappear.

Yours in hope,

John.

Este tema ha sido cerrado para respuestas.

Mejor respuesta de davescm

Hi

If you take this in steps.

We started here:

The first step is to address that yellow color. I add a new layer and in the layers panel set blending mode to color. This means that the color will be used but the luminosity (i.e. the "brightness") will use the layer below so will not be changed.

I then use a soft brush and use Alt-click to pick up color from other parts of the image which I then brush on.

You don't even have to be exact as the detail is taken from the unchanged original layer.

On it's own my color layer looks like this:

But when combined with the layer below it looks like this:

The next step is to address the brightness. So I add another layer this time with blending mode set to screen. This will lighten any areas I brush with a lighter color. I have set the opacity very low and brushed very lightly onto the grey stain, using a brush again Alt clicking on nearby areas. The idea is to lighten just enough to blend the stain.

I have shown the brushing at 100% opacity and normal blend below:

But when set to screen - opacity down 10 11% and blended with the layers below it looks like this:

Finally another new layer and the clone stamp tool used just to put some detail in the sky and address the last smudge mark.

On it's own own that clone layer looks like this:

but with opacity reduced to 39% and the other layers back on - it looks like this

I hope that helps you.

Dave

Terri Stevens

Legend

Lots of good ideas here from everyone, but it is inevitably correcting 100s' of stained images will to be very time consuming. I tend to agree with that for best results Frequency Separation is the way to go and then it is just a matter of sampling colors on the low frequency layer and painting over the stain with a brush using 'color' mode for the brush-not the layer.

D

dotslash

Inspiring

i'm a noob. care to expound on how "Frequency Separation" is done?

thanks.

davescm

Community Expert

Hi

I took a similar approach to the others .

A layer set to color - and just picked up color from other parts of the image and brushed it on. This was very quick.

A second layer set to screen and used to balance some of the harsh luminance differences.

Some light cloning on the sky.

Finally a crop to straighten that horizon - which was bugging the life out of me

Dave

J

jc62Autor

Participant

Hi Dave.

I really like the simplicity of your fix. However, I should of said that in photoshop terms i am what you might term an advanced beginner.

Yes i have messed around with layers, blend modes etc, over the years. But i have spent ages trying to replicate your result with no success. If you could possibly run through it step by step in more detail and treat me like an idiot i would be forever grateful.

I know what you mean about the horizon but it was just a full neg scan from a 6x7, and to be honest i wasn't expecting this many replies so quickly.

John

davescm

Respuesta

Community Expert

Hi

If you take this in steps.

We started here:

The first step is to address that yellow color. I add a new layer and in the layers panel set blending mode to color. This means that the color will be used but the luminosity (i.e. the "brightness") will use the layer below so will not be changed.

I then use a soft brush and use Alt-click to pick up color from other parts of the image which I then brush on.

You don't even have to be exact as the detail is taken from the unchanged original layer.

On it's own my color layer looks like this:

But when combined with the layer below it looks like this:

The next step is to address the brightness. So I add another layer this time with blending mode set to screen. This will lighten any areas I brush with a lighter color. I have set the opacity very low and brushed very lightly onto the grey stain, using a brush again Alt clicking on nearby areas. The idea is to lighten just enough to blend the stain.

I have shown the brushing at 100% opacity and normal blend below:

But when set to screen - opacity down 10 11% and blended with the layers below it looks like this:

Finally another new layer and the clone stamp tool used just to put some detail in the sky and address the last smudge mark.

On it's own own that clone layer looks like this:

but with opacity reduced to 39% and the other layers back on - it looks like this

I hope that helps you.

Dave

Semaphoric

Community Expert

Is the stain visible on the surface of the negatives? Like when viewed obliquely? If so, you could possibly photograph the negs, maybe with a polarizer, and transform the images to the same orientation as the original, and use that to help create a mask for adjustments..

barbara_a7746676

Community Expert

It would be fairly easy to create a mask in LAB. Duplicate the b channel and increase contrast. Then clean up the mask with the Brush.

E

edgrimley

Participating Frequently

I didn't spend much time on this so it could be better but... I used cloning for the sky and water beneath it. For the main ocean part I used a blue brush on a new layer set to color mode. A second color mode layer to clean up the ship area a bit.

Stephen Marsh

Community Expert

You can create an action using the following methods to get 80-90% of the image corrected using a simple apply image step using no selections etc. After the apply image step, you may then need to mask, clone or paint in color blend etc.

I duplicated the original image to a new layer, targeted the blue channel and turned on the full RGB composite preview while only using the apply image step to the blue channel.

RGB Apply Image:

Yes, important parts of the vessel have changed colour, however they are quick and easy to restore using masks, or history brush etc.

Here is the same sort of Apply Image move applied in Lab colour mode, which I prefer:

As I said, not 100% fixed, but around 80-90% recovered without using any selections, manual edits etc. Put into an action or batch, this starting point can be applied in seconds.

After the start point, in 1-2 minutes you can have something like this:

I have only been addressing the colour issues in this quick demo, I did not address the minor tonal variations.

Anyway, I’m confident that you can significantly improve your correction times and output quality by using a similar process.

Good luck!

Myra Ferguson

Community Expert

You might want to try a technique known as frequency separation. The technique is often used by photographers to smooth out blemishes, but it can also be used to remove color casts. Here's a tutorial on how to do that, and it includes an action that you can download to make the separations. https://www.slrlounge.com/removing-tricky-colour-casts-free-frequency-separation-action/

barbara_a7746676

Community Expert

I don't have any magic bullets, and it will take time no matter what, but here's a technique you could try.

Make a duplicate of the image (always a good idea for safety).

Convert the duplicate to LAB mode (instead of RGB)

LAB separates light and dark values from color values, which will let you concentrate on changing the color without changing the texture.

You'll see that most of the problem is in the 'b' channel, which contains the yellow to blue color information. 'a' contains the red to green information, and Lightness contains only the light and dark values.

Now I would target the b channel, but because I like to see the overall picture, the other channels are visible.

Use the Clone Stamp tool with a feathered brush (so that the transitions aren't too harsh) to clone from a good color area onto the bad color area.

Now I have this. I didn't try to change the boat itself. There's a little redness.

To fix that, target the a channel, and Clone Stamp in that channel. So now I have this:

Fixing the ship you'll need a smaller brush for the Clone Stamp, but same technique.

For some of the more delicate areas of the ship. I targeted the composite LAB channel and used Color mode (instead of normal) to touch up.

In the sky there's a noticeable dark area which could be blended in with the Dodge tool on the Lightness channel.

Ended up with this. I'd spend a bit more time on it if it was a 'real' project for me, but I think you get the idea.

J

jdanek

Inspiring

The only way I can think of is to use the Red channel and isolate the ship ( select only the ship ) then invert the selection so you then are only working on the water and sky. You could try using a Layer Copy and adjusting the curves / levels to match the surrounding water / sky on the Green and Blue channels. The Red channel virtually has no stains. Then, invert your selection again and adjust the ship's Green and Blue channels.

michelew83603738

Community Expert

Have you tried adding a blank layer on top, setting it to color blend mode and sampling the colors surrounding it often to try and get ti out? I tried it on your image and this is the result with a quick attempt. If you sample more often and play with brush size I am sure the results would be much more accurate.

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