I am doing an indoor shoot tomorrow of my friend and a dog. We have to do it mid afternoon and inside. There is a large window shining into the room but because of the time of day I'm worried we won't have enough light. I have a flash gun which I can experiment with. Also I have a fast lens but I need larger DOF in some shots. I can take 2 studio flash lights but I can't figure out if this is going to work without a backdrop. I haven't been able to check location out. If I light up subject with studio flash lights in a large room then the background will be dark unless I slow down shutter speed right?....I'm really confusing myself. Any advice please? Some shots I need about 20-30cm DOF and other shots up to a metre. The idea is to capture a canine therapist working within a home environment so a backdrop isn't going to help achieve this.