----- Original Message ----- From: "Antonio" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, August 08, 2004 1:42 AM Subject: Re: first question
> Now that starts to make more sense. Not what you said originally though. Why > not be honest and just admit you got it wrong first time round? > > Antonio > It's exactly what he said first time around. I got it. A few others got it. Not his fault you are too goddamned stupid to actually read and assimilate a post before spewing forth your email vomit. You've done the same thing to me. Normally I just ignore it, and you. I refuse to talk baby talk just for your benefit. Most of us have pretty good comprehension. You should try it sometime (comprehension that is). I'll go back to ignoring you now. Regards William Robb > > On 8/8/04 5:20 am, "graywolf" <[EMAIL PROTECTED]> wrote: > > > OK, Keith, I apologize for misunderstanding. > > > > What both Bill Robb and I were saying is that if you take a photo from the > > same > > position with both the 24mm and the 100mm it will have the same perspective. > > Then if you blow up the photo from the 24mm so the subject is the same size in > > it as in the one from the 100mm and crop it so both are say 4x6 inch prints > > the > > images will be the same except the grain in the 24mm shot will be far more > > obvious. (Obviously that is not cropping in camera) > > > > I also said for the DOF to be exactly the same in those 4x6's you need to use > > the same aperture (f-stop is focal-length/aperture, so focal-length/f-stop is > > aperture). For instance f/2.0 with the 24mm is approximately a 1/2 inch > > aperture, so is f/8.0 with the 100mm. > > > > ONLY that is WRONG (muddy thinking on my part), because of the blowup of the > > 24mm shot, you have to factor the extra magnification into the equation. In > > this > > case it is 4x (100/24). Because of that magnification factor you would need > > the > > same f-stop. (DOF is determined by aperture and magnification) > > > > To recap, if you take the photos from the same position, with the same f-stop, > > and enlarge, and crop the photo taken with the shorter lens. The photos will > > be > > identical except for the problems caused by the higher magnification > > enlargement. > > > > However, if you took the photo with the 24mm from a distance where the subject > > appeared the same size as in the 100mm shot , say 5 feet and 20 feet (no extra > > magnification, or cropping) the apertures, not f-stops, would need to be the > > same for the same DOF. But then they would have different perspectives (as you > > said). > > > > Obviously, in this case you probably would not want to use a 24 in place of > > the > > 100. The quality cost would most likely be too high. But you might use your 50 > > as the loss would only be a 1/2x. If you, like I do, carry 24, 50, and 100mm > > lenses then the extra blowup of the enlargements can easily take the place of > > 35, 85, and 135mm lenses. Giving you the equivalent of 6 lenses with the > > weight > > and cost of only 3, as you still get to use about an APS size portion of the > > negative. > >
