Digital medium format cameras started as digital camera backs which could be fitted to many different medium format film cameras. These digital backs have electronic sensors in to convert them. They can shoot up to twice the size of a 35mm film frame, they deliver more pixels than other cameras and have lower noise. The digital backs started in 1992 by Leaf Systems Inc. Mounted on Sinar studio cameras, the camera back wwas later moved to medium format camera. By the late 1990s a few companies had created digital backs. Hasselblad merged with Imacon and partnered with Fuji to create a line of digital medium format cameras, the H-Series. Mamiya created the Mamiya ZD back, and also partnered with Phase One.