One of the simlest method is... working with orginal image.
- Copy orignale boots into new layer (CTRL+J)
- Use CTRL +T and then press command kay to use distort option and transform your boots as you need
- Use Layer panel and FX option - Color Overlay - use balck 100% opacity
- Use some blur - GFilter >Gaussian Blur
- Use some Opacity to add realistic look
- Use blend Mode - Multiply - go to Layer palette and choose Multiply form Blen Mode menu
- Drag yur shadow below original image
- If you wish use Layer mask to adjust direction and fade of this layer
How about: On a separate, transparent layer, sketch a rough idea of where the shadow ought to be. Then use the Pen tool to trace a path along the bottom edge of the sole. You could then use the Direct Selection tool and Transform Path repeatedly to "Unwrap" the path from the sole, and position it along the sketch line you drew earlier. You would start by selecting the points in front of the insole, and transform with the pivot point aligned with the point where the path joins the unselected portion. With each iteration, you would deselect some more points from the left.
Once you have the path along the sketch line, you (we hope) have the shape and spacing of the lugs maintained, and you can use it toset up your fake shadow, in the manner Pawel described.
There are so many ways to add a shadow... I tried this as a test to see how it would look
1. Make a silhouette using the Quick Selection tool
2. With the boot selected create a new layer ? CMD J
3. With the Pen tool trace the bottom of the boot and save the path
4. Create 2 separate layers below the boot
5. Stroke the Path on the layer directly below the boot with a soft round brush (size 150) to make a shadow
6. Fill the layer below the stroked path with white
7. Position the Shadow correctly making sure that it is going in the right direction and change the opacity to 50%
8. Use the eraser brush to finesse the shape
This might not be a practical technique for 150 boots... it was quick to do though.
I do this kind of work all the time. Here’s my method.
1. Duplicate the product layer.
2. draw an outline path around the product, and use the path to create a layer mask on the top layer.
3. Rename the bottom layer to “shadow”
4. Use a hue/saturation adjustment on the shadow layer to remove all of the color (even if it doesn’t look colored)
5. Use a levels adjustment on the shadow layer to take the lightest areas all the way to white. Do this by moving the right most triangle in Levels to the left until you get white.
6. Paint out any remaining grey areas that aren’t part of the shadow. In this case it would be the background wall.
7. Change the blend mode of the shadow layer to multiply.
If you are also the photographer you can make sure your white background extends beyond the cast shadow. In this case the shadow on the left edge hits the side of the frame. You will need to paint this to smooth it out.
First of all: start with a properly exposed image - one that could actually have a white background! Like this:
Next, a realistic shadow isn't uniform. It's very dense and sharp where the object hits the ground - much lighter and more diffused as the distance increases. So you need to build up using several layers with different brushes and opacities. This was actually done in five minutes:
BTW a lot of product photography is done with full backlight to eliminate shadows altogether - and save you a ton of masking time in Photoshop... But often it works well on its own. This is just a detail (can't show the whole thing here):
It's actually fairly easy to set up, using a portable flash unit and a translucent white sheet of perspex or similar.
All in all, this kind of work can be incredibly time-consuming if you rely entirely on Photoshop. Yes, it can be done, and it's very comfortable to just sit in front of a screen and do everything there - but a little care in the actual shooting can cut the total time spent to a tenth or less. It doesn't really take all that much. Just smooth out that wrinkle, remove that speck of dust, shield that reflection - that sort of thing.