![]() ![]() By tilting a lens downward while the film plane remains level, one is able to use a larger aperture and still keep everything from foreground to distant background in focus. Such lenses allow one to tilt the lens downward from the film plane, or upward depending upon the effect one wants to achieve. Sometimes referred to as a tilt shift lens. ![]() And now Richard tells me that if I shoot at f/18, my images will not be as good as they could be if I shot at f/8. For example, I have found that I need to shoot at f/16, f/18, or even f/22 to get everything from foreground, to mountain range in the background, in focus. The problem with all this is that one normally needs a higher f-stop when doing landscape photography. I am grateful to Richard for interpreting the math for me, frankly I would have never fully understood this whole topic if he had not taken the time to explain it to me in plain English. Why? Because the softness produced by the defects (or the lack of resolution of the sensor) of the image making apparatus is far greater than the softness produced by diffraction alone.” “If you set the aperture larger than where the lens/camera combination becomes diffraction limited, you won’t see it. “Since no camera/lens combination will produce a perfectly sharp image, the question is, “How much image softening can we tolerate from diffraction?” “What you will see is a softer image (loss of detail) due to the diffraction of light through the aperture. This may be a blow to those who believe more pixels is better as an absolute. As sensor resolutions increase beyond a certain point, one is forced to use larger apertures to stay below the diffraction limit of the lens/camera combination. “ The amount of diffraction increases with decreasing apertures. A different camera using the same lens could become diffraction limited at a smaller (or larger) aperture than f/11. In other words, if I shoot with a perfect lens using the camera, an f-stop higher than f/11 will result in a photograph of lesser quality than one taken at say f/5.6 or f/8. My friend Richard did the math for my camera, the Canon 1Ds Mark II, and advised me that the diffraction limiting of the camera/lens combination is somewhere between f/8 and f/11. An excellent resource about this topic can be found here. Which takes me back to the subject of lens diffraction, being an optical effect, which limits the resolution of your photograph. The first is resolution, and the second is the aperture setting for high quality lenses, which Richard points out may include stopping a lens down beyond its diffraction limiting point to correct other more objectionable defects in the lens.īTW, I still don’t exactly understand what Richard did in his career, but his resume says he did stuff like this: “Circuit designer involved with the acquisition, conditioning, and digitization of analog signals from remote sensors for data logging and computer controlled processes.” In sum, after all my reading, and after several discussions with my friend Richard Nowak, a retired engineer with an incredible list of experiences and credentials in photography, embedded microprocessor circuit designs and microchip test solutions in the electronics industry, I discovered that there are two significant factors which make one image better than another. I won’t bore you with all the reading I did, but I will reference several websites at the end of this post that you may examine if you are interested. The forum thread discussion at Naturescapes prompted another thought and that thought lead to five intensive days of investigation. – are all factors that can affect the quality of a photograph. Exposure, depth of field, using a remote shutter release, etc. But, when I am using a good solid tripod for both shots, I still see a difference. For years I thought it is because I was using a tripod in one shot and not another. There are numerous, probably an infinite number of reasons why this is. Same camera, same lens, but one image is distinctly better than another. ![]() Simply stated, “Why do some of my photographs appear better than others?” The thread proved to be the stimulus for an investigation of something that has trouble me for years. Recently I read a forum thread at Naturescapes about lens diffraction. Improving My Photography, An Inquiry Into Lens Diffraction (Bill Lockhart) ![]()
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