[SDK2003]

Originally Posted by TT Originally Posted by SDK2003 Originally Posted by Darkel BTW I've heard many people talking about those magic (and a bit less expensive than the equivalent IS models) 200/300mm f2.8 without IS, it's IMO not that great considering some usual situations when the car is far away and the light is crap, "whoaa f2.8 power" and they end up with 2mm of the front bumper sharp and the rest nicely blurred o_O For info, (Applies to 300D, 350D, 10D, 20D, 30D) Focal length of 200mm Aperture : F2.8 Subject distance : 30 meters Gives a total depth of field of : 2.4 meters (in total sharpness) This is enough for cars - the out of focus falls off gradually. Weird... with my 70-300 when I shoot between 70 and 100 mm and min F, ence 4.0 to 4.5 I usually end up with the rear of the car already blurry, so I really don't see how 2.8 could be good for such pics.. like here:

A few things could effect that.

1: Subject distance - If the subject is closer then you get less depth of field.
2: Focus/Depth of field - The standard rule for depth of field is 1/3 in front of the focus point and 2/3 behind. So focus toward the front of the subject and you should be ok.
3: Unless you need a wide aperture due to low light then you might as well use a higher one - F8 or above.