mojo43
Well-known member
If what you wrote was not a typo, and you want the same depth of field but with a wider field of view, then you have to use the same lens, but go even wider aperture (divide by 1.5) when you're using the FF camera (for example: 35mm f/2.1 on APS-C has the same DoF of 35mm f/1.4 on full frame). http://www.similaar.com/foto/dof/dof.php?f_x=1.5&f_r=1.77&f_mm=35&f_f=2.1&f_d=2 http://www.similaar.com/foto/dof/dof.php?f_x=1&f_r=1.77&f_mm=35&f_f=1.4&f_d=2 The advantage of full frame is that, if you wanted to take that same second shot with an APS-C camera (i.e. wider FoV and just-as-shallow DoF) you'd need a 24mm f/0.95!!! ------------ But you're bound to be disappointed in any case: DoF is only half of the equation, perspective is the other half. If you take a picture of a face, the size of stuff on your background will change dramatically if you go from 17mm to 180mm. And that affects bokeh big time: at 17mm, you'll see a whole building behind your subject, and it will be out of focus but you'll know it's a building, and recognize its features; at 180mm lens, with the background at the same distance, all you see behind your subject is a small patch of wall, so it will not be just out of focus, it will be blurred beyond recognition. If you take both shots at the same aperture, and the subject has the same size in both pictures (i.e. you back up when you switch to the longer lens), then depth of field is the same, but the background will be a lot softer on longer lenses. Example here: http://www.similaar.com/foto/tuten/320.html
Thanks so much for taking the time to explain that. It makes sense to me now. Can you tell me what far focus is on that web page? Is that the point at which every thing becomes in focus (approaching infinity focus)? Sorry also to derail the topic. Last question, i promise...