4/19/2023 0 Comments Back in focus 1.0.2![]() Lenses longer than “normal” deliver a magnified (telephoto) view. Lenses shorter than “normal” deliver a wide-angle view. For the DX (compact digital), this is about 30mm. For the FX (full frame) this is about 45mm (traditionally rounded up to 50mm). ![]() A camera delivers a “normal” view when the focal length of the lens is approximately equal to the diagonal measure of the format frame. A “normal” lens delivers a view that is about the equivalent of the perspective we see with our unaided eyes. The focal length is the fundamental measure of the power of the lens. The focal length engraved on the lens is the distance from lens to image this is usually stated in millimeters. The Pentax K-x (mid level), for example, offers a global adjustment and the Pentax K-5 (mid-upper level) offer a per lens adjustment. More entry levels (like my Nikon D3100) have no adjustment options. Which of these is an option, typically depends on the 'level' of camera you have. (Usually up to some reasonable number of lenses.) Your camera may have a per lens adjustment in which the camera will remember that this lens always needs a certain small adjustment that you provide in order to function properly. Your camera may have a global adjustment in which you can tell it to always adjust its autofocus front or backwards by a small adjustable amount. Send your camera and lens to the manufacturer to be 'fixed' or calibrated. Modern choices to fix it usually include one of three options that I'm aware of: There's a host of why, but most of them boil down to something being not quite calibrated, aligned, or working 'properly'. Your autofocus could be not properly functioning due to a software issue (this seems to be the case for the Pentax K-x camera with tungsten light sources.go figure).Things could be in an acceptable QA range, but your combination of camera and lenses could be at opposite ends of the acceptable range.Things may be out of spec from the factory, due to poor QA.In terms of why it would be this way for the equipment: You or your subject could have moved slightly after focusing and this would also cause front or back focus. It could be you or it could be your subject. ![]() it could be mis-aligned, mis-calibrated equipment. Your subject will look slightly out of focus and something in front of them will be razor sharp in focus.īack focus is correspondingly when something behind them is in focus, instead of your intended subject.Īs to why. Front focus is when the lens and camera focus in front of your intended focus point. ![]()
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