Transfer the shadow of an object on white paper to ruled paper

Question

I have taken two photographs:

1. a hand holding a pen and writing on a white paper
2. a sheet of paper with lines

Both photographs have been taken from the same camera angle (using a tripod), with the ruled paper placed in the same position as the white paper.

I now want to copy the two images into each other, making it appear as if the hand had written on the ruled paper. The end result should look something like this:

My photographs are completely sharp, so it is easy to cut out the pen, the hand, and the written text from the background of the white paper and overlay it on top of the ruled paper. The problem is the shadow of the pen and hand.

How do I need to set layer effects, or what else do I need to do, to make the white paper transparent and have the shadow appear on the ruled paper?

I'm working in Photoshop CS 5 on a Mac, if that matters.

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I've tried the method described in the accepted answer to this related question, but this results in a light grey blur overlaying the lines. Using the technique in the linked answer, it seems as if the lines disappear in the shadow. Or in other words: the shadow darkens the paper, but not the light blue lines.

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No, I cannot write on the ruled paper and photograph that. Don't ask why.

Answer 1

An old question seemed to raised on top by the system. Maybe one answer still is needed. Here it is.

Obviously the questioner has compatible images. That means:

• both have the wanted final resolution or more
• the papers can be put to fit geometrically with minimal distorting jobs
• the ruled paper has no own shadows
• both have good exposure and acceptable white balance (the ruled paper can be black and white)

Here are two shots that are compatible:

At first there were 2 background removals. The ruled paper and hand with the pen are needed separately. The plausibility of this fraud is lost totally, if the hand and the pen aren't separated surgically. I used the quick selection tool + fixed the edges with the polygonal lasso. As well I could have made a clipping path - so inaccurate are all automatic methods.

At the bottom there's the Writing on the white paper layer. It has a dedicated curves adjustment layer. The purpose is to lift the paper as white as possible without losing the writing nor the shadows.

The next layer is the ruled paper (in my case the squared paper). The blending mode = multiply. The idea is to darken the writing layer with the squares. Multiply does not make anything brighter, only darker. So there's added also a dedicated (=pointed to single layer) curves layer to keep the paper white, but the squares dark enough.

On top there is the separated hand with the pen.

Here's the result until this:

If we temporarily disable the contrast boost of the writing layer, the shadows get lost under the squares:

So, we keep the contrast, but it's not ready. Altough the squared paper was dragged to optimal position, the edges do not fit.

The easiest fix is to clip all to straight and clone the background or white paper to fill the holes. The squared paper is quite straight and larger than the white paper, so that was done. Here's the result:

Another fix is to warp the paper edges to fit. I tested it. In the following screenshot the warping is done to save the bended edge.

Actually the squared paper is warped, the white paper was expanded by cloning and partly clipped off + replaced with cloned table.

Answer 2

Make a mask of the pen only (not shadow), and apply this mask to the ruled paper image. Set the ruled paper image layer above the pen+writing image layer. Set the ruled paper image layer blend mode to "darken."

Basically, overlay the rule onto the image, not the other way around.

To tweak, you can:

• make the ruled paper layer greyscale (desaturate);
• adjust the levels of the ruled paper so you eliminate the paper texture;
• adjust transparency of ruled paper layer;

Answer 3

If I understand you correctly, it seems that the answer might be fairly simple. Put the layer with the shadow above the ruled paper layer and set it to Multiply. Then mask off anything from the shadow layer that you do not wish to see.

Two original photos:

Shadow layer set to multiply:

Position and mask out unwanted portion:

Adjust hue and saturation for complete composite:

Answer 4

I'd make a separate layer.

Take the picture of the shadow on white (remove the pen itself from this copied layer) and turn that in to a fairly high contrast monochrome image. Use that high contrast image as the layer mask for a new layer. Fill the layer mask with a decent shadow color and/or set it to a subtractive blending mode (multiply, burn, etc)

This way you can later easily still change the shadow opacity, color, and (using curves blur and sharpen on the mask) falloff.