This is my first Medium Format film post, it was shot on Fuji Colour Pro 400 and scanned at 2400ppi at 100%. The TIFF file is 115 meg, at 1200 it's around 50-60 meg which is good enough for large prints. Low light with a long lens closed down the image is quite good. It is a bit of a bother to use film but I find that I'm forced to think a bit more about the shot. Mirror Lock Up (it can be handy) was not introduced in the Pentax 645 until the 645 NII the 645 N was the first auto focus model but no MLU. You can get into medium format film for a fraction of the cost now. My 645 with four lenses (150 mm 3.5, 120 mm 4.0 macro, 75 mm 2.8 and 75 mm 2.8 leaf) as well as two film inserts (both are 120) was less then $500.
The 645 negative is 6*4.5 cm. Other formats on the 120 film are 6*6, 6*7 & 6*9 to name the more popular. Other medium format film cameras such as Hasselblat (older ones 500 C), Mamiya and Yashica are inexpensive to buy. Hasselblat lenses are still expensive.
Note. Medium format digital is becoming popular, well for those who can afford it. Cost, $7000 to $35,000 body only (who else but Hasselblat).