Medium Format Cameras
In most good digital still cameras which cost less than about $5,000- the lens projects the image onto a digital sensor which is much smaller than even a 35mm film negative (which back in the bad old days we thought of as fairly small). Typically these digital CCD or CMOS sensors are around a size of 23.6 mm x 15.7 mm (0.929 inches x 0.618 inches). This equals an area of 0.57 square inches. 
A 35mm film negative is 36mm x 24mm (1.417 inches x 0.945 inches) so the area is 1.34 square inches. Call a 35mm film negative about 2.3 times larger in size than most digital sensors.
Now compare this to an 8 x 10 inch picture (roughly A4 size) which has an area of 80 square inches. So a 35mm film negative is enlarged 60 times to print an 8 x 10 picture, and the image captured by the sensor in a typical digital camera must be enlarged 140 times to make an 8 x 10.
Professionals like Ansel Adams shot with large format film negatives which were much bigger. Many times these were 4 x 5 inches or even 8 x 10 inch negatives! It becomes readily apparent that if one wants to crop much at 
all, or make high resolution big enlargements like 8 x 10 inches (A4) or 11 x 14 inches (A3) it is most helpful to have as large a film negative or a digital sensor as possible.
I own several Nikon 35mm film SLR cameras, and I also have one medium format SLR film camera made by Mamiya. It shoots onto a negative the size of 60mm x 45 mm (2.363 inches x 1.772 inches) or an area of 4.19 square inches. This is about 3.1 times larger than a 35mm film negative, and roughly 7.4 times larger than a typical digital camera sensor.
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This medium format camera is the main one I am using in trying to roughly duplicate Ansel Adams’ famous 1947 picture of El Capitan in the Guadalupe Mountains of West Texas.
I bought a fun camera today via the internet. It is an Ensign brand camera made in 1931, the model Pocket Twenty. At one time this company was the largest maker of film cameras in Great Britain.
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The seller alleges that this camera still actually works (we shall see). It uses the same size of fim as my medium format film SLR, so it should be interesting to play with.
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