Shooting for Print Size
Among the decisions that one has to make when shooting film is what print size you are aiming for. This is because smaller cameras are more versatile, while a larger cameras provide the possibility of more detail.
Experience seems to confirm that film can be reasonably magnified up to a factor of 10. This means that a 35mm frame (36x24mm) can be used to generate a 11x14 print, or more realistically 8x10, which works out to a magnification of about 7x.
To see how the negative (or positive) area relates to a print size I use a spreadsheet. The following table shows the magnification required to match the print dimensions I typically use:
From this we can start to work out what format is required for a given print area. The other factor is the fact that many if not most photographs can be improved with judicious cropping. Smaller cameras give you agility and the freedom to take a many more exposures, but they also provide much less margin for error in the way a scene is framed.
The amount of light you need to collect is proportional to the image circle the lens has to project. This is one reason lenses with a wider field of view become very valuable on larger formats.
Capturing more detail does indeed provide additional flexibility, but better skill in framing is still a better answer. The following was an image I thought had promise, but when I printed it I realized that my daughters were lost in the scene
Print area from Ilford fp125+ negative (Mamiya 645 Pro, with 55mm lens at f8)
The crop I chose helped in bringing them forward, but the visible area left is less than 45% of the original negative. I could have taken nearly the same photograph using a 35mm camera.
An even better solution would have been to get the composition right. If I had moved forward the subjects would have rapidly have begin to fill the frame and the surrounding scene would fall off more dramatically. Swing and a miss.