"nospam" wrote in message
...
This means that if you take a
photo on 120 film and on 35 mm, with appropriate focal lengths of the two
lenses to give the same field of view of the subject in both cases, and
use
the same aperture, the DOF will be less on the 120 photo than the 35 mm
photo.

nope. it will be identical for the same image quality.

So as long as film grain isn't the limiting issue, you should be able to
take a photo on 120 film with a lens that gives a certain field of view, and
then on 35 mm with a different lens that gives the same field of view, and
if you use the same aperture on both lenses, you shouldn't see a shallower
DOF on a print from the larger format negative?

That goes against everything I've ever learned about photography, and the
fringe benefit of using larger film (the main one being finer level of
detail for the same type of film).

I'll have to try taking comparison photos on my SLR and compact cameras, to
test it.

As I thought, the SLR photo has a shallower DOF than the compact, for same
aperture and comparable lens focal lengths to give same field of view in
both photos.

Nikon D90, 18-200 mm lens, set to 150 mm, 35 mm equivalent=225mm, f5.6,
image size 4288 x 2848 pixels

https://s22.postimg.cc/phiylnsnl/DSC_0151.jpg


Canon Powershot SX260HS, 4.5-90 mm lens, set to 34 mm, no 35 mm equivalent
stated, f5.6, image size 4000 x 2664

https://s22.postimg.cc/k6420pe81/IMG_1316.jpg

Both these are full frame, both focussed on the pins of the mains adaptor in
the centre of the picture. Both pictures taken from same position (ie same
distance to subject in foreground). Very similar image resolution.