I wonder about this. There is an increased apparent depth of field with the smaller sensor, or with smaller film for that matter (try using a 6x7 for macros!). I would think this translates to more latitude on focus accuracy and camera shake too. Regards, Bob S.
On 9/4/05, Jens Bladt <[EMAIL PROTECTED]> wrote: > I've thought about this too. > I believe that a 50mm will require at least 1/75 sec to obtain the same > amount of blurriness as 1/50 sec. om a 35mm camera, provided you enlarge the > DSLR picture MORE to obtain the same, final picture size. > > If a car moves at a certain speed, it will go from left to the right hand > side of the frame in lets say 1 second when using a 50mm lens on a 35mm > camera. That's 150mm/second on a 4x6" print. If the same car is photographed > by a DSLR using a 33mm lense, the same thing happens - the car will move > from left to right in 1 second. > > But, if you put the 50mm on the DSLR the car (driving at the sam actual > speed) will move across the frame in just 0,67 seconds, causing an even more > blurry picture. The car will travel at a speed of 225mm/second across the > 4x6" print. This should prove that you must mulitiply the denominater of the > usual "speed rule of thunb" by 1.5, when using an APS soize sensor. This > means 1/75sec. for a 50mm on the *ist D/DS. > > I never reallty minded, because I really don't like to use slow speeds. How > fast the speed should minimum be has something to do with how much > movement/blurryness is acceptable for normal enlargments. It's the same kind > of arguments that are used when we're talking about Circle of Confusion. > There's no absolute truth, just a rule of thumb - or a matter of taste, if > you like. > > Jens Bladt > Arkitekt MAA > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Juan Buhler [mailto:[EMAIL PROTECTED] > Sendt: 2. september 2005 12:22 > Til: [email protected] > Emne: Auto-selected shutter speed on istD/s--wrong? > > > I've been thinking about this for a while. > > Typically, in program modes with a FA lens, the camera will keep the > shutter speed high enough to avoid blurry pictures when handheld. On a > 35mm sized filmplane camera, this is roughly the inverse of the focal > length, as we all know. So if you have a 50mm lens, 1/60 is the > minimum the camera stays at (1/30 sometimes, but even that is > acceptable.) > > It seems as if Pentax didn't update that part of its programs for the > aps sized sensors. With a FA50mm on the istD, I keep getting 1/30s, > even if the aperture is not full open (for example, I will get 1/30 at > f:2.8 with the FA50/1.7, instead of the more acceptable 1/60 at f2). A > 50mm on the istD is equivalent to roughly 75mm, so shouldn't 1/60 or > 1/90 be the minimum speed the program chooses? > > Or am I very wrong? > > j > > -- > Juan Buhler > http://www.jbuhler.com > photoblog at http://photoblog.jbuhler.com > > >
