Content

• Steps
• Tips
• Warnings

An aperture, or aperture, is a hole that controls the amount of light that enters the camera's sensor (or film in film cameras). Aperture is one of three key elements when adjusting exposure (ISO, shutter speed, aperture).

Changing the value or division of the aperture not only allows you to control the amount of "collected" light, but also affects the final image, which you need to understand. Depth of field (depth of field) is most important, but optical distortion or changes are also possible. You need to know how the lens aperture works to make informed decisions about other exposure settings, create creative effects, avoid mistakes, and understand the effect of adjustments on the image.

Steps

1. 1 Become familiar with basic concepts and terms. This information will help you better understand the article.
   • Diaphragm is an adjustable hole in the lens through which light passes and hits the film (or digital matrix). Like a pinhole in a pinhole camera, it blocks light rays except for those that, even without a lens, could form an inverted image when passing through the center point to the corresponding point in the opposite direction on the film. Whereas with a lens, the aperture also blocks light rays that travel far from the center, where the lens of the lens less accurately reproduces (usually with different simple to implement spherical surfaces) geometric shapes without clear focusing (usually much more complex aspherical surfaces), resulting in aberrations.
     • Since each camera has an aperture that is usually adjustable (and if not, at least has the edges of the lens that act as aperture), it is the size of the aperture opening that is usually called “aperture”.
   • Aperture division or just diaphragm is the ratio of the focal length of the lens to the aperture value. This measurement is used because a certain f-number provides the same image brightness, so the same specific shutter speed is required for a certain ISO value (film sensitivity or equivalent matrix light amplification) regardless of the focal length.
   • Iris diaphragm is a device that is used in most cameras to shape and adjust the iris. It consists of a series of overlapping thin metal tabs that can pivot towards the center of the hole inside the flat metal ring. It forms a central hole, perfectly flat in the case of a fully open aperture, when the petals move to the sides, and is compressed by the displacement of the petals towards the center of the hole, resulting in a smaller polyhedral hole (which may also have curved edges).
     • If your camera supports interchangeable lenses or is “pseudo-mirror”, then the lenses are equipped with an adjustable iris diaphragm. If you have a compact model or a "soap dish" (especially in the budget segment), instead of an iris diaphragm, the device is probably equipped with a "ND filter". If your camera's mode switch has M, Tv and Av modes, then it is almost certain that the device has a real iris diaphragm (even in the case of small compact models). If the mode dial does not have these settings, the camera may be equipped with both an iris and a ND filter. The only way to find the exact answer is to read the specifications in the user manual or a detailed professional review (search for reviews of your camera model on search engines and read the available materials). If a ND filter is used, the ability to “fine-tune” settings, depth of field, or bokeh will be limited by the unit's fixed aperture. PLEASE NOTE to the mode switch: “M” stands for “Manual”, which allows you to set shutter speed and aperture values. "Tv" - shutter priority mode: the shutter speed is set manually, after which the camera itself selects the appropriate aperture value. “Av” is aperture priority mode: it is set manually (usually to control the desired depth of field), after which the camera selects the appropriate shutter speed.
     • Most single-lens reflex cameras close the iris, after which it can be seen from the front of the lens only when the exposure or depth-of-field preview is enabled.
   • Cover up or darken aperture means using a smaller or (depending on the context) relatively small aperture value (high f-number).
   • Open aperture means using a larger or (depending on the context) a relatively large aperture value (small f-number).
   • Open aperture is the largest aperture (smallest f-number).
   • Depth of field of the imaged area is a specific front or back portion of the frame, or (depending on the context) the amount of front or back portion that looks sharp enough. Decreasing the aperture increases the depth of field and decreases the amount of blurring of objects outside the sharp area. The exact value of depth of field is somewhat subjective, as sharpness gradually decreases from the most accurate focal length, and the perceived blur of the image depends on factors such as the type of object, other sources of lack of sharpness and viewing conditions.
     • The relatively large depth of field is called large, and relatively small - small depth of field.
   • Aberrations - these are flaws in the ability of the lens to sharply focus light. In general terms, inexpensive and exotic lenses (such as ultra-wide angle) will have more noticeable aberrations.
     • Aperture does not affect linear distortion (straight lines appear curved), but they often disappear closer to the center of the zoom range of a zoom lens. You can compose your shot so as not to draw attention to distortion (for example, not to place explicit straight lines such as buildings or the horizon close to the edges of the frame), or automatically correct a flaw in the camera or in subsequent computer processing.
   • Diffraction - This is a basic aspect of the behavior of waves that travel through small apertures, which limits the maximum sharpness of all lenses at small apertures. It becomes more noticeable after f / 11, with the result that an excellent camera and lens can produce quite mediocre results (although sometimes they are great for specific tasks such as very large depths of field or slow shutter speeds where low sensitivities or a ND filter cannot be used. ).
2. 2 Depth of field in the imaged area. Formally, depth of field is the range of distances to an object within which objects in the image have acceptable sharpness... There is only one distance at which objects will be in ideal focus, but the sharpness decreases gradually before and after that distance. At shorter distances in each direction, the blurring of objects will be so slight that the size of the film or sensor will not allow blurring to be detected. Even larger distances will not affect the "sufficient" clarity of the final image too much. Depth-of-field markings for specific aperture values ​​next to the lens focusing ring allow you to estimate this value.
   • About a third of the depth of field is before the focal length, and another two-thirds is behind (unless extending to infinity, as this refers to the value at which rays of light reflected from an object must bend to converge at the focal point, and rays that pass through long distances, strive for parallelism).
   • The depth of field decreases gradually. With a small aperture, the background and foreground will appear a little fuzzy or even sharp, while with a wide aperture, they will be very blurry or completely unrecognizable. If the foreground and background are important, then they should remain in focus. With a slight blur, the general context is preserved, and it is better to blur the distracting background as much as possible.
     • If you want to blur the background, but the depth of field is not enough for your subject, then focus on the element that will attract the main attention (often the eyes).
   • As a rule, in addition to the aperture, the depth of field also depends on the focal length (the greater the focal length, the smaller the DOF), the frame size (the smaller the film or sensor format, the greater the DOF if the angle of view or equivalent focal length remains the same) and the distance to subject (much smaller at short focal lengths).
     
     If you need to get a shallow depth of field, you can buy a super fast lens (expensive) or zoom in on the object (free) and open the aperture as much as possible, even with an inexpensive, low aperture lens.
   • In terms of artistic value, depth of field is used to sharpen the entire image, or to “de-focus” and blur the foreground or background that distracts from the central subject.
   • From a practical point of view, the depth of field allows you to set a small aperture and set the "super focal length" (the closest distance,in which the depth of field extends to infinity from a specific distance; refer to the appropriate table or the depth of field markings on the lens for aperture selection) or the estimated distance to quickly take pictures with manual focus or photograph a subject that moves too fast or unpredictably for autofocus to work correctly (which also requires a fast shutter speed).
   • It should be remembered that usually all changes in depth of field are hardly noticeable in the viewfinder or external screen when building a composition.... Modern cameras measure parameters at the maximum aperture of the lens and cover the aperture to the selected value already at the moment of exposure of the frame. Depth-of-field preview is usually only an approximate and inaccurate result (ignore strange patterns on the screen when focusing, as they will not appear in the final image). What's more, viewfinders on modern DSLRs and other autofocus cameras do not even show the true open-aperture depth of field when using lenses above f / 2.8 (it will be even shallower than it looks; rely on autofocus if possible, not on subject). The best option for a digital camera is to simply take a photo, view and zoom in on the LCD screen, and determine if you are happy with the sharpness (or degree of blur) of the background.
3. 3 Interaction of the diaphragm with pulsed light (flash). The flash usually fires so quickly that only the aperture affects the flash component of the exposure (film and digital cameras almost always have a maximum flash-compatible shutter speed for "sync"; at a faster shutter speed, only part of the frame is exposed, due to the peculiarity of the "curtain" shutter ; special high-speed flash sync modes use short-term firing of weak flashes, each of which exposes a different part of the frame; this significantly reduces the flash range, so this option is rarely used). The wide aperture increases the flash range. It also expands the effective range of fill-flash by increasing proportional flash exposure and shortening ambient light penetration time. The small aperture prevents overexposure in close-ups due to the lowest power below which it is impossible to dampen the flash (bounce flash, which is not as effective, will be useful in this situation). Many cameras support adjusting the balance of flash and ambient light through the "flash exposure compensation" function. For challenging flash photography, digital cameras are best, as the results of brief flashes of light are not obvious on their own, even though some studio flash models have “modeling flash” and functional portable flashes offer similar preview modes. with modeling backlight.
4. 4 Find out the optimum sharpness for your lenses. Different lenses differ from each other, and for optimal results you need to shoot at different apertures. Take photos of subjects with lots of fine details at different apertures and compare shots to see how lenses perform at different apertures. It is recommended to place the entire subject at “infinity” (10 meters or more for wide-angle lenses and several tens of meters for telephoto lenses; distant forest stands are usually suitable) so as not to confuse the lack of sharpness with aberrations. Here are some tips:
   • Nearly all lenses have poor contrast and reduced sharpness at their widest apertures, especially at the corners of the image... This is especially true for digital "point-and-shoot" or inexpensive lenses.Therefore, if you need to provide high detail in the corners of the image, it is better to use a smaller aperture value. Typically f / 8 provides the best sharpness for flat subjects. If objects are at different distances, then an even smaller aperture will provide a deeper depth of field.
   • Nearly all lenses result in noticeable vignetting at open apertures... In this case, the edges of the image appear darker than the center of the frame. This effect can be useful for many photographs, especially portraits; he focuses on the central part of the image, which is why many add this effect in post-processing. But it's always best to know what the original shot will look like. Typically above f / 8, vignetting disappears.
   • Zoom lenses differ in their focal lengths. Perform the indicated checks with different optical zoom levels.
   • The phenomenon of diffraction leads to the fact that pictures with almost any lens become less sharp at f / 16 or less, and especially at f / 22 or less.
   • All these aspects allow you to get an optimal picture in terms of clarity, if the best composition is already built for it, including depth of field, and if it will not be spoiled by camera shake when the shutter speed is not fast enough, or subject blur or noise with excessive "light sensitivity" (gain).
   • There is no need to waste film on such experiments. Check lenses on digital cameras, read reviews, and in a pinch, rely on the fact that more expensive fixed focal length lenses (no zoom) produce better images at f / 8, less expensive and bundled lenses perform better at f / 11. and cheap or exotic lenses such as ultra-wide-angle specimens and models with a wide-angle or telescopic extension lens should be used with an aperture of f / 16 (for extension lenses on digital soap dishes, set the minimum aperture aperture or use the aperture priority mode in the menu).
5. 5 Special effects associated with the diaphragm.
   • Japanese word bokeh is often used to describe the appearance of areas of an image that are out of focus, especially highlights as they look like drops of light. There is a lot of material out there about these light drops, which can be brighter in the center, sometimes brighter around the edges like donuts, or a combination of both, but usually they only pay attention to this in articles about the bokeh effect. It is important to remember that such blur spots are:
     • Will be larger and more diffuse with a wider aperture.
     • Will have soft edges at the widest aperture due to the perfectly circular lens hole (lens edges, not iris petals).
     • Depends on the shape of the opening of the diaphragm when it is not fully open. This effect is most noticeable when the aperture is wide open due to the size of the opening. Bokeh can be considered unattractive in lenses with an imperfectly circular aperture (for example, inexpensive 5- or 6-blade aperture lenses).
     • May be crescent-shaped instead of a circle around the edges of the image when the aperture is particularly wide (this may be because one of the lens elements is not large enough to fully illuminate all parts of the image at this aperture, or such light circles expand in a strange way due to "asymmetric aberration ”at a very wide aperture, which usually becomes a problem only when shooting flashlights at night).
     • They are predominantly in the form of rings and bagels in telephoto SLR lenses due to the presence of central interference.
   • Diffractive rays form asterisks... Very bright areas of the image, such as light bulbs at night or small specular reflections of sunlight, will be surrounded by "diffractive rays" that form "stars" at a small aperture (the effect is due to increased diffraction at the vertices of the polyhedral aperture formed by the aperture blades). The number of vertices or rays corresponds to the number of aperture blades (with an even number) due to the overlap of opposite rays, or twice their number (with an odd number of blades). Beams are weaker and less pronounced on lenses with very many blades (usually older lenses like older Leica models).
6. 6 Do snapshots. The most important thing (at least in the context of aperture) is to control the depth of field. It's simple: the smaller the aperture, the greater the depth of field; the larger the aperture, the shallower the depth of field. Also, a wider aperture blurs the background more. Here are some examples:
   • Cover the aperture for a greater depth of field.
   • Depth of field decreases as you get closer to your subject... So, for macro photography, you can cover the aperture more than for landscape photography. Insects are often photographed at f / 16 or less and illuminate the subject with plenty of artificial light.
   • Open the aperture for shallow depth of field... This method is suitable for portraits (much better than the awkward automatic modes). Open the aperture fully, fix the focus on the eyes, adjust the composition: a blurred background will distract less attention from the main subject.
     
     Remember to use a faster shutter speed for a wide aperture. In bright daylight, make sure the camera is not trying to go beyond the fastest shutter speed (typically 1/4000 for DSLRs). To do this, you need to lower the ISO value.
7. 7 Take pictures with unusual effects. If you are photographing light sources in the dark with a suitable camera and want to get stars, then close the aperture. In the case of large and round bokeh drops (although not always full), use an open aperture.
8. 8 Use fill flash. Set a relatively wide aperture and fast shutter speed if you need to combine flash and daylight so that the flash does not block out all the shadows in the picture.
9. 9 Take pictures with optimal quality. If depth of field is not critical (objects are far enough from the lens and will still be in focus), the shutter speed is long enough not to blur the image with camera shake, the ISO is low enough to avoid noise or other quality loss (typical daytime conditions). lighting) and you don't have to trick your aperture, and your flash is powerful enough to work properly in daylight, then set the aperture to get the most detail for your lens.
10. 10 Choose your desired aperture value and start getting the most out of it with aperture priority mode.

Tips

• No wonder they say f / 8 and no questions asked... Typically an f / 8 aperture allows for depth of field that is suitable for most stationary subjects. and provides better (or nearly better) sharpness on film and digital cameras. Feel free to use this aperture or program mode (leave the camera in this mode for sudden unexpected shots) for moving subjects that won't wait for you to change camera settings.
• Sometimes you have to find a compromise between aperture, shutter speed and sensitivity (ISO). You can also shoot in automatic mode and leave the settings at the mercy of the camera.
• A fuzzy image due to diffraction and (to a lesser extent) focus miss (which, in addition to being blurry, creates strange patterns) can sometimes be corrected using functions such as “unsharp masking” when processing on a PC. Examples include GIMP and Photoshop. The function will allow you to sharpen the boundaries, although it will not be able to create small details that did not fall into the picture (if applied too much, the transitions will be too sharp and inaccurate).
• If aperture size is important to your shot and you are using an automatic camera, then Aperture Priority or Program Shift (pre-set aperture and shutter speed pairs for correct exposure in different conditions) will suit you.
• All lenses have certain distortions: “ideal” lenses cannot be found even among professional models costing tens of thousands of rubles. The good news is that renowned optics manufacturers like Nikon, Canon, Pentax, Zeiss, Leica, Sony / Minolta and Olympus often create “distortion correction” profiles that can be downloaded from the Internet and applied during image processing (for example, in Adobe Photoshop and Adobe Camera RAW). By using good lens software and profiles, you can get shots without barrel or pincushion distortion, which are more pleasing to the eye. In this example with a wide-angle panoramic landscape shot, the problem is that "perspective distortion" and "barrel distortion" bends the trees at the corners of the image toward the center of the image. It is quite obvious that this is lens distortion and it is unlikely that trees would be rounded this way.
  • Now take a look at the shot after applying the lens profile and vertical distortion correction in Adobe Camera RAW. The trees have become completely vertical both in the center and at the edges of the image due to the easy framing of the image. The photo has become pleasing to the eye, and the slope of the trees does not distract attention.

Warnings

• Make stars with bright points of light, like street lamps, that are less bright than the sun.
  • Do not point a telephoto lens, especially a super aperture lens or an ultra long focus lens, directly at the sun for stars or any other reason, as there is a risk of damaging your eyesight, shutter, or camera sensor.
  • Do not point cameras without a shutter mirror like the Leica towards the sun (only briefly when shooting handheld and with a small aperture), so as not to burn a hole in the shutter, otherwise repairs will cost you a lump sum.