Viewfinders are another thing to take into consideration, particularly if you’re switching from a DSLR or other type of camera that has an optical TTL (through-the-lens) viewfinder. A TTL viewfinder means that what you are seeing is exactly (or very close to) what the lens is seeing. Since, by design, there is no mirror to direct the view of the lens to the viewfinder, many mirrorless cameras utilize an electronic viewfinder, or EVF.