----- Original Message ----- From: "Chris Brogden" Subject: RE: The flood gates open....
> On Thu, 27 Feb 2003, J. C. O'Connell wrote: > > > > Not true. Using a film camera, take a picture of a person with a > > > telephoto lens so that all you can see is their head and shoulders. Then > > > put a wide angle lens on, and walk closer to the subject until you can see > > > just their head and shoulders. Now your subject is the same size as it > > > was with the telephoto lens, but you have much more DOF. > > > > This is false. If the reproduction ratio remains the same like > > youre describing above the DOF is also the same for > > a given f-stop, regardless of focal length... > > ...only if the photographer stays in the same place. If you stand in the > same place and take shots with different focal lengths, the DOF is the > same (you're essentially just cropping). But if you *change position* > (like I said above) to keep the subject size the same while using a > different focal length, then your DOF will change, too. DOF depends on > focal length and aperture, as you say, but also on subject distance. > Chris, reproduction ratio is reproduction ratio. Period. How you get there is optional. William Robb
