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But how does this impact your everyday photography? In fact, a similar experiment (with two slits rather than one) played a major role in proving that light can behave as a wave – one of the most important discoveries in scientific history. Diffraction in PhotographyĬlearly, diffraction is an important concept in physics. At its most basic, a small opening causes waves to bend and interfere with one another this, in turn, spreads out their signal. This is why light, which has a tiny wavelength, will not diffract significantly if it passes through a ten-foot wide opening – even though the ocean does.Ĭongratulations! You now understand the physics of diffraction. In fact, the opening only causes diffraction when it is similar in size to the wavelength that passes through it. (This is a slight simplification for more technical information, I recommend reading the Wikipedia page on the Huygens principle.)įinally, note that a “small” opening is relative. Smaller openings, though, affect a wave more significantly, causing it to bend at harsher angles. Since the waves are not particularly disturbed, they follow a relatively straight path towards the edge of the pool. Essentially, larger openings allow the waves to pass without much interference. These waves spread out in concentric circles, just like the image below:Īlthough it may initially seem unusual that a small opening leads to a larger spread of waves, the illustrations above should show that it makes logical sense. If you drop a rock into a perfectly still lake, you will cause a ripple of small waves to form. To make this easy to visualize, consider waves of water. In fact, every time that waves pass through a slit, they will interfere. That said, this section is meant to be understandable even if you are not a physicist we recommend reading it, since it will provide a more solid foundation for your understanding of diffraction.Īt its most basic, diffraction is the concept that waves – including light waves – can interfere with one another. Most photographers are interested in day-to-day knowledge rather than comprehensive background information, but it is impossible to talk about diffraction without describing how it works at a fundamental level. In explaining diffraction, it can be difficult to straddle the line between avoiding and embracing references to optical physics.