I know that my question will look odd, but here is my problem :
I will make a stop motion movie with hard shadows. But i want to have one element in my scene to have only soft/diffuse shadows. This is a part of my story telling.
I don't want to record this element separately with a green background and composite it because i will have camera moves, and that will be too complex to manage.
So my first call will be to put a "tulle" just behind the character ( where the shadow will be ) to create a more soft shadow ( and maybe the tulle will not be visible ... )
I could have a special light source for this element, but the problem is that my entire movie will be in a forest. So i will have a lot of elements close together. And i need to have the shadows of the trees cast in my character but no shadows going from it. ( that's an other reason to not film twice my scene with green screen )
i don't want a small blur ( that i could create after in photoshop or other software ) i really want a big soft shadow ( almost like there were no shadow at all>> this is actually my goal : to make the shadow disappear )
Every king of help, tricks could be very helpfull
I have never done anything like this before, so I probably don't know what I am talking about, but I really like the idea of the problem so I thought I would throw in a suggestion.
Would you consider using two exposures? So for every frame you take two pictures that you combine later on. If you took the first picture with the object in scene and then the second without, you have both an image with the object and one without a shaddow. If you combine the images together with 50/50 intensity you would get a 'ghost' like effect. With additional effort you could paint the object into the image without it avoiding copying the shaddow in. This would require moving the object a lot so you would need a good mounting point so that you can always get it back in the same place.
I think a lot of this comes down to what the object is. If it is quite simple you probably have more options than if the object will cast reasonably complicated shaddows.
Ok, after sleeping on this I woke up with a decent idea. Originally I was coming up with things that would be too difficult or impossible and probably not work anyway, but this one is simple and elegant.
All you really need is one or 2 small reflectors down by his feet angled up toward him. They can be as simple as a small piece of paper folded to form its own stand. I often have envelopes or bits of paper towel just off camera with spotlights aimed at them reflecting back up onto my puppets to fill in some shadow. These reflectors can move with the puppet and be hidden by trees or shrubs or possibly erased digitally if they peek out and become visible. You can probably get away with just one reflector positioned on his shadow side - let your hard lighting fall on the puppet just like on everything else, but then the reflector will fill in the shadows and give him a very different look - soft lighting with no shadows.
The key is you need 1 or 2 tiny spotlights with shaped beams like this: Solux framing art light
It has a series of lenses inside it that allow you to focus the beam as well as internal shutters you use to shape the beam precisely. This means you can cast only a small tight square or rectangle of light with no spill shaped to fit only onto the reflector itself and not cast any light onto the set itself (except for some of the reflected light back-cast beyond the puppet a little bit, if there is any). The nice thing about small reflectors like this is the reflected light doesn't go very far - about far enough to light the puppet and then it fades out, if you carefully filter the amount of light (which you can de with neutral density gels inserted in front of the light source itself).
Here's a post from my blog showing what this little baby can do: http://darkmattr.blogspot.com/2007/08/ridin-lightwave.html
(For info on how I rigged the Solux to not be a track light and to work on my set): http://darkmattr.blogspot.com/search/label/light%20bashing
Alternatively you could use an old slide projector and make a slide to shape your beam. Black tape on a piece of glass can work, but be careful you don't set fire to your set! Here's info on using a slide projector for this: http://darkmattr.blogspot.com/2007/07/lightmatters-or-hobo-in-studi...
In fact you might not even need the shaped beam spotlight - it's possible yu can just position your reflector to catch the light already being projected by your hard light sources and reflect some of it back up onto the puppet - reflected light is very soft and diffused. Just set up something for a test and play around - a single hard light source and a small pice of folded paper as a reflector with something to stand in for your puppet. With just a little playing around you should be able to get some really good results.
I tried to check your photos or videos to see what kind of lighting you've had experience with, but you haven't got any photos or videos uploaded. Have you already got some experience in photography working with hard and soft light? A little experience with each would help, though I suppose if you're brand new to it you can still do this.
Ok, I just re-read your original post and it sounds like maybe what you want is a little different from what I just described.
Do you want hard shadows from the trees to fall on the puppet but the puppet to cast a soft shadow onto the background?
If so, that's tricky. I mean, it would be essentially the same technique, but instead of having hidden reflectors to fill in shadows on the puppet you'd want reflectors to diffuse shadows on the set behind the puppet. I think it would be a lot harder to hide reflectors there, unless they could be hidden behind the trees and you could move around your shaped beam light(s) as needed.
Possibly you cloud use the puppets back as a reflector. This might not work at all - his back might be too small or have a color you don't want cast into the background (though you could make just his back white or grey or silver). Then you'd need to use a shaped beam light carefully aimed and shaped to fall only on part of his back where it doesn't show as edge light on his shoulder or anything. Of course this would result in a weird effect behind him - it wouldn't be totally consistent, it would look like his back is dimly glowing and as he walks around the shading behind him would change as he moves.
The problem of course is that soft diffused light is hard to control - hard light can be shaped and blocked effectively because it's a collection of straight rays all going the same direction, but with diffused light the rays are all going different directions so you can't effectively shape or block it where you want.