I post too Much on Here!!
- Jan 29, 2011
That simply isn't true. If the subject is framed the same size, which is the whole point of long lenses, the aperture number gives consistent DOF. So a 700mm f8 from further away to give the same subject size on the sensor has greater DOF than a 400mm f4 shot from closer, if you shoot from the same place and crop the 400mm f4 shot to give you the same framing as the 700mm shot you get even less DOF.That's not really true though. At f8 700mm, your depth of field will be shallower than a 400mm lens at f4. Focul length has a much greater affect on DoF than aperture.