The primary difference between 135 and 35mm film is the size of the frame that they use. 135 film, also known as 35mm or full-frame film, utilizes a 24x36 mm negative for each image. 35mm film uses a smaller 10x14 mm negative per image. This means that 135 has more detail and resolution than 35mm since it fits in more area on the same amount of surface area. Additionally, because of its larger size and higher resolution, 135 can be blown up to produce bigger prints with greater clarity than those from 35mm negatives. Finally, most modern digital SLR cameras have an APS-C sensor which is about half the size of a full-frame sensor found on professional cameras so using135 instead of35 gives you much better results when shooting with these types of cameras