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Replacing backgrounds - how to do shadows?

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alan_potter

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I'm trying to convince myself I can understand the process for removing a subject from one background and placing it in another, but I'm having trouble with shadows.

So I understand that one masks the original subject and paints it in at 100% white (on the mask). That means that the subject is selected, and can be placed on a new background. I also understand that there are a few techniques for reducing any "halo-ing" round the subject. So far so good.

Now let's look at shadows. If we just mask them in as before, then any texture or detail that is in the shadow will be copied over... which we probably do not want. We don't want to have the detail of the shadow, we just want to darken whatever is in that area of our new background.

So is this achieved through a different blending mode? Do we put the mask for the shadows onto a different layer from the subject so that we can merge them in different ways?

I think that these are really newbie questions, but I'm having trouble with them!

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
Google "photoshop add shadow"

I get 1.9 million results, but there are many good ones on the first page.
 
Thank you. I was hoping to find information on retaining original shadows and re-using them on the new layered image, and have had very little luck at finding anything on that - but I'll keep looking

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
Do a search on this forum for Topaz Remask 2, Eric, one of the developers monitors the subject and may have a suggestion. I tend to reconstruct shadows with a low opacity brush myself, but the "magic brush" in Remask 2 may do the trick.
--
Alan
 
Thank you. I am using ReMask2 to help separate the subject from the background, but I have not tried doing it for shadow areas - I've had a look at the Topaz Labs forum and will give it a try.

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
Thanks for the help. Here's what I ended up doing... still room for improvement, but I think I'm reasonably happy.

Here's the original (note that these are all stored on Flickr at http://www.flickr.com/photos/atp/sets/72157622842994405/ )



So, obvious problems. Firstly, I used Topaz ReMask2 to isolate the girls from the background, then I created a gradient layer to give a nicer background. But the girls looked "disconnected" from the gradient. That was where the shadows came in.

So, I
  • selected the area of the original background where the shadows were and jumped that into a new layer.
  • duplicated that to a new image
  • used TopazRemask2 on the new image to remove the legs
  • converted the new image to black and white
  • adjusted the levels until I had pure white for the non-shadowed areas and the shadows looked reasonable
  • (this is where I think things started to go a little awry) went to the channels palette in that new image, and duplicated this channel back into the original image
  • copied that new channel into a new image layer on the original image, and put that above the gradient layer
  • set its blend mode to multiply
And the result was



Any thoughts? I'm sure I'm doing a lot more messing around in that duplicating / copying phase than I need to.

I've been using Photoshop Elements for a long time but am not sure I've got to grips with the full-blown product and the use of layer masks yet, so any C+C would be much appreciated :)

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
I think you're making the mistake of seeking a verbal solution to a visual problem. You'd learn more by working with an image than by searching for tutorials. Why don't you post what you're trying to do?
--
~ Peano
http://www.radiantpics.com
 
Lovely conversion!

I did try the Photoshop Mama tutorial, but for some reason I couldn't get the density mask to work... the selection and and "filling in" parts just didn't seem to go into the right places.

But based on what you've done here, maybe I should try again!

thanks again,

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
One method is to use whatever selection tool you prefer (I use the polygonal lasso) and outline the existing shadow. Then create a new layer and fill the selection with black. Set the blend mode to multiply and adjust opacity to taste. Then use selective blurring on the shadow so that it is more blurred the further away from what is casting it. Finally, use a layer mask to fade the shadow in or out as necessary. It's easiest to handle each shadow on a separate layer so they can be modified individually.

This method is more useful for photos not shot on seamless, because as you've found out it's fairly easy to use the existing shadow in the knocked-out composite. But I'd thought I'd mention it in case you ever need to retain a shadow in a photo shot on grass, concrete, etc.
 
Ah, I've tried Photoshop Mama's process again... when I was creating the density mask and filling it in with black, I think I got too hung up on where the marching ants were. If I just ignored them and carried on, the shadows looked great :-)

Thanks again,

regards,
alan

--
http://www.flickr.com/photos/atp
My stage photography (more a hobby than a company!): http://www.stagepics.co.uk
 
Great! Glad you stuck with it. It is not easy stuff to explain which is why I think P-mama did a fantastic job with the video.

Ronny
 
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