I would definitely play around with it. Your not going to want to go too wide with 4 because odds are they will move around a bit and you’ll end up with some soft faces. Some key things to remember would be try to keep their faces all on the same plane of focus, that will allow you to shoot a little wider. Generally with 4 kids I would aim to shoot around f/4 but certainly play around. At that aperture you may want to consider moving them further away from the background. Keep in mind the closer you are to them and the further away from the background they are the more bokeh you will get!
You can channel our cavemen ancestry with Custom Photo Prop’s Faux Fur Mat, safe in the knowledge that no animals were harmed in their making. These synthetic mats are PETA-approved, machine-washable and hypoallergenic. They can be ordered as a basket stuffer in a 20 x 32-inch size. It’s sold as a 15 x 15-inch layer or in 3 x 5-foot and 5 x 6-foot sizes. They’re super comfortable on baby’s skin as well.
The fabric has a slight odor similar to vinegar and evaporated milk but airs out if you leave it unfolded a few days. The fabric, as expected, is lightweight but decent quality cotton. By definition Muslin is lightweight cotton cloth and, yep, it's thin so a backing layer is necessary if used against a bright light or window (e.g., my uploaded image). It ... full review
Football season is nearly upon us and Backdrop Express’s sports and stadium-themed printed backdrops are a great way to capitalize on the bone crunching. They’re available in poly paper or vinyl in either 4 x 5-foot or 5 x 6-foot sizes, or a fabric with sizes ranging from 5 x 6.5 feet up to 10 x 10 feet in a choice of light or heavyweight. The poly paper version is water resistant and has a matte finish. If you opt for vinyl, you’ll get a more durable backdrop that’s also water resistant and has a matte finish. The heavyweight fabric is a polyester/cotton knot that’s washable and wrinkle resistant with a sewn-in rod pocket. The lightweight fabric is a 100 percent polyester weave that Backdrop Express likens to a tablecloth. It, too, is wrinkle resistant, though less than the heavyweight fabric. On the plus side, Backdrop Express says the printed design is “slightly clearer” on the lightweight version. Decisions, decisions.
What this tells us is that the further away the light source is from the subject and backdrop, the more likely we are to get an equal exposure from one to the other. The quality of the light source can also change with distance. You will notice that as the light gets further away it becomes a harder light with less transitional values. Also, if the subject appears to be further away from the backdrop in the last image, it's due to me needing to use a shorter focal length (zoom out) to avoid getting the softbox in the shot. The shorter focal length exaggerates perspective.
Again, if you are starting out or having trouble I would recommend getting the light a little further back (somewhere between 4 to 8 feet if using a similar sized light source). You will also notice that the right side of my backdrop is actually not 100 percent white, it fades to a light gray shade. I could increase my fill or correct this in post-processing, but the slight shift is intentional in this image.
If you do many in-studio portrait sessions, you probably have a lot of space set aside for background materials, props, and supports. Add to your stash with canvas backdrops for photography, and selections made of durable, low-maintenance materials, such as cotton and wrinkle-resistant polyester. Several backgrounds come on rolls so you can mount them to autopoles and smoothly swap out designs between poses. Seamless paper works particularly well for everyday needs, as you can roll sheets out to the desired length and then reuse or trim away pieces for easy recycling. Muslin photo and video backdrops feature non-reflective surfaces that diffuse light more naturally, which can help keep the focus on your subject. If you prefer materials that allow for fast and efficient cleanup, vinyl and PVC backgrounds are a solid choice, especially when you use them in potentially messy situations involving pets, babies, and toddlers.