Notice that the top of the knife is very straight, and in this image it is rendered very sharply. I also adjusted the contrast on this image in Photoshop to further highlight this effect. I took this image in a completely dark room where the only source of illumination was my flash. I used a photo of a pocketknife to demonstrate the effects of diffraction on a straight line. Notice the the difference in sharpness between top of the actual blade and the shadow it casts. You may notice that even though the object has a sharp edge, the edges of the shadow are always fuzzy. Look closely, however, at the edges of that shadow. The mass of the object blocks the light, creating a shadow. Think of an opaque object placed in front of a light source.
The tiny aperture hole of a lens, or more specifically the aperture blades, has the effect of bending parallel light rays. This means that the light passing through the aperture creates new waves of light. Huygens' Principle states that "every point of a wave front may be considered the source of secondary wavelets that spread out in all directions with a speed equal to the speed of propagation of the waves." So all the properties which can be identified in other waves such as sound or water ripples can also be identified in light.
#Small f stop iso
Knowing the limits of your lenses is very important to avoid this phenomenon, as well as mitigating the high ISO or long exposure times required for using unnecessarily small apertures.Īlthough it may not appear so, light actually travels as a wave. This is counterintuitive to the purpose of using small apertures in the first place, which is capturing sharp detail. Although a smaller aperture will provide a larger depth of field, the effects of diffraction will become increasingly noticeable at extremely small apertures, reducing the overall sharpness of the image. It's easy to get carried away and stop down too much "just to be safe" in trying to to create a depth of field which is large enough.īe careful while doing this though. This is done by making your aperture smaller.
When taking landscape or architecture photos, it's natural to try to maximize detail by increasing the depth of field. But there is a point of diminishing return, and the reason for that is diffraction. Most photographers understand depth-of-field and how aperture affects sharpness. Diffraction is when the regular pattern of waves we see as light gets disrupted and behaves erratically.
0 kommentar(er)
