How to make realistic shadows in composites?

Question

Currently I'm practising doing compositing combining different photos to make them look like taken as a single picture. I find it quite difficult. Especially making realistic shadow. What do you think about the shadow in the attached picture? Any tips how to make it believable? Please also share your feedback what do you think about this composite in general, I'm open for constructive criticism :)

Update: Thank you for all the wonderful feedback. I tried to improve the shadow making it shorter and different direction. To keep it simple I also flipped the rocks to match more the central lightning. Still doesn't feel right, maybe longer shadow? Let me know what you think :)

Here is longer shadow, slightly different direction. Should the shadow expand the further it goes from the subject?

Answer 1

If the glare is supposed to represent the sun, then the shadow of the figure is pointing in the wrong direction. Look at this. It shows a rough idea how shadows fall for a distant light source like the sun.

Also in your example the shadows and highlights on the rocks are not in the right direction. Notice how the highlights and shadows fall on the poles in the above image in relation to the position of the sun, the same would happen with the rocks.

To help you get the directions right, it might be worthwhile drawing up a perspective grid with a vanishing point directly below the sun.

For example

Answer 2

I don't wish to come across too harshly...

Lighting in photo composites is the hardest, most difficult aspect of any composite. You need to ensure all lighting is seen as coming from the same direction(s). ANY variation on that immediately ruins all "realistic" impressions you may be trying to convey.

You've got multiple light sources in the image, all varying. And that is disregarding the huge "radial blur flare + vignette" in the center of the image. To be frank, the only thing that flare appears to be lighting is the center of the image and the edges.. nothing internally at all. It looks "slapped on" last minute.

The yellow circles/lines show where primary lighting seems to be. Note that it is different for the rocks and the girl. It's clearly not the same light source.

• The hard shadows on the rocks indicate the light is high in the sky because there are little to no cast shadows.
• The bright arm/face/shoulder of the woman indicates the light is above and to the left of her face.

The magenta circles/lines indicate secondary light sources -- Lighting which is not a bright but clearly casting shadows. This is often due to ambient lighting as opposed to direct lighting.

• The shadow on the woman's dress and left arm would indicate a lower, less bright light source somewhat behind her.
• The shadow being cast by the woman indicates a wildly different light source far away from her and low in the sky. The higher the light source the shorter cast shadows are.

Painting light is a difficult task. It takes a lot of practice to get good with it. And in photo composites it means you often need to remove existing lighting in order to render similar lighting. Again, very difficult and takes a great deal of practice to get good at it.

The methods to paint proper lighting would be far too much to go into detail here, but you can search the web for "How to Paint Lighting" and you'll get some good resources that way [1],[2].

Answer 3

Like this, probably have to clean some of the rocks up too.

It's like magic...

It also good to tie shadows together, so here I tie her shadow to the shadow at the lower right corner, it directs your attention around the image and makes if feel more anchored.

The three big rocks on the left should be shaded on the opposite side they are now, and a few other minor tone issues (like the bright spot on the big rock in the lower right), that I will leave for you.

I think the biggest problem you have right now, besides the direction, is the falloff. Think like a beam of light, it doesn't get more dense the further from the light source, it radiates out and weakens as an inverse square, double the distance quarter the power (like gravity too). This is because it's spherical and the surface of a sphere is 4πr^2, basically inverse square happens because of the relation to volume and area of a sphere. But shadows are a phenomenon of light (or lack of light) so much like the light they tend to widen and dissipate over distances. I mention this because to do light effects (realistically) you have to know how light works.

There is a lot of geometry in light and shadow, I mean the Greeks basically calculated the circumference of earth just using shadows and geometry.

So with the one you have it seems to get narrower and maintains it's darkness even wen moving away from the source. The one I did is sort of like a cone with the point cut off at her feet. So there is some falloff to the sides, it doesn't lighten so much as it moves away, but this is because it blends into the shadows at the corner.

Just for reference

The rocks are a bit harder to fix, if I had the original of them without the vignette adding shading, I would vertically mirror the ones on the left and then patch the seam, that way their shadows would be on the left and not the right. But with that extra shading by the vignette effect, it would take more time then I care to spend.

Also the lettering looks a bit to "Fuzzy" for my taste...

Hope that helps.

Answer 4

The girl looks pretty good but the rocks weren't adjusted to match. Like the rock dead center should really have almost no shadow. Then the rocks on the left side should all have their shadows on the left side -- probably easier to just flip the rocks.

It might help to create a more defined sphere to give scale and position to light you have. It's a bit hard to tell if its right next to her or if she's a little in front of it. Likewise I took it as floating directly over that rock in the middle of the image but it's really not clear if that's the case or not.