Sometimes I crop to focus attention or remove unwanted items in a picture. Often a change in the aspect ratio of an image can change the whole look or feel.
The aspect ratios dictated by film or sensor are a starting point but I don’t feel bound by them, in fact whilst I would rather have the correct lens, I don’t have a problem with the practice of cropping at all.
Maybe because I began with 35mm film, the 36mm x 24mm 3:2 ratio feels comfortable, I often print at 12” x 8”. I used medium format briefly and enjoyed square 6cm x 6cm format on 120 film but was never completely taken with the 645 on my Bronica ETRSi. Funny that the square format which is over eighty years old now, far predating 35mm film, has now regained such popularity, thanks in no small part to Instagram.
When I was using film I always wanted a Hasselblad X-Pan but never got my hands on one. I am now experimenting with some more extreme panoramic style crops. In cinema 1.85:1 and 2.39:1 are common and with the right starting image, can dramatically change the look and assist in creating a cinematic feel.
4:3 was the original aspect ratio of 35mm movie film and while cinema has gone wide screen, the two newest photographic systems have adopted this ratio. Micro four thirds systems and the iPhone use the 4:3 aspect ratio. It is interesting that MFT is very popular in video despite the trends towards wider aspect ratios in cinema. Personally I find this a bit too tall on my Panasonic GM1 and Olympus E-M1 and find myself cropping down to 3:2 frequently and loosing pixels.
Native sensor size will effect final pixel count in the cropped image, Micro four thirds looses the most pixels on letterbox crops while 35mm looses more proportional on square images.
1:1 - Typical of medium format 6cm x 6cm 120 film classics, Rolleiflex TLRs and Hasselblad 500 series
1:1.25 / 6x7 - Less popular 6cm x 7cm (approximate) medium format, although responsible for the standard 8” x 10” print size.
1:1.33 / 4:3 - Original movie format dating from the first silent films, returned with medium format ‘645’ camera and again more recently on the iPhone and micro four thirds system
1:1.5 / 3:2 - Popularised by 35mm film, full frame digital and APS-C digital cameras have now standardised on this aspect ratio
1:1.85 - 1:2.39 - Widescreen cinema formats