645 Cameras 645 cameras also known as ideal format are smaller in size and handle much like a 35mm. They are very popular as their rectangular frame corresponds to standard printing paper sizes such as 8X10 or 16X20. This is the only medium format in which autofocus models are available. 6X6 cameras 6X6 format also known as the square format produces 3X larger transparencies and negatives than 35 mm. Photographers moving up to this format may find it difficult to compose their pictures in square format as they are used to seeing and photographing in rectangular proportions, while long time 6X6 users see nothing unusual about it.
Square formats gives cropping options which many photographers and photo buyers prefer.
You must pay attention when composing within a square viewfinder as the final image must be cropped. This is a draw back to some photographers. Tightly composed pictures will be cut off so make sure to allow room for cropping. Below is a list of models that are available. 6X7 cameras 6X7 format is also considered ideal format as it also corresponds to the standard printing paper sizes.