How to make sure that the sharpness is always there, and the photos are clear?

I have to answer this question a little more extensively than I wanted.

1) About exposure

IMG 7248
The object is deliberately static, excerpt everyone is normal

So, first, let's talk about the exposure. Not the one that provides your endless enthusiasm, but the one that you control on the camera. These are the same curtains that dose light when taking pictures on the matrix or film of your camera. So that's it. If the curtains are open longer than necessary (long excerpt), then most likely both the subject and the surrounding area will be blurred. The object - from the movement, the world around him - from the shaking of the camera.

However, there should not be so much light that the camera is blinded. You, for example, on a sunny day cannot look against the sun with your eyes wide open? So the camera can't. Do not torment him, but set the shutter speed shorter. Close the curtains exactly as much as is required for normal lighting of the future frame. How to determine it by eye?

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Exposure is clearly not enough to fix objects. But what an atmosphere ...)

It is worth shooting a couple of thousand frames to immediately begin to understand the approximate ratio of speed shutter to the environment (no). The camera usually tells you what shutter speed would be correct in the conditions in which the picture is being taken. You've got plenty of practice, I'm sure. Simple Tips:

  • slow shutter speeds are used in conjunction with burst shooting. Then the chance of shaking from the hands is reduced. Albeit insignificantly. Usually the shutter speed is slowed down in low light conditions. But more on that another time.
  • a fast shutter speed should be used in sufficient lighting and to freeze moving objects. As an example - a child running on a playground on the street. Then try to keep track of it for a start. An excellent training object, by the way.
  • do not shoot against the sun, as the shutter speed will have to be reduced so that the object you are shooting is clearly distinguishable .... unless, of course, you do it on purpose. Otherwise, you will get an almost black contoured spot, and a detailed background.
  • if there is a lack of lighting, for example, in a room (apartment), the camera will not have enough light from the lamps, and you will have to choose between increasing shutter speed with blurring the moving parts of the model, or freezing the model to the detriment of image quality. With a short shutter speed, we get darker frames, because there is little light, so we also let it pass less to the camera matrix.
  • The minimum shutter speed at which you are guaranteed not to blur the frame is 1 / focal length lens... This number is printed on the lens. For example, the whale lens Canon - these values ​​​​range from conditional 1/18 to 1/55 (18-55mm is drawn on the case). Of course, such values ​​\uXNUMXb\uXNUMXbcannot be set, but approximate ones can be selected.
  • Short exposure 1/4000s <——1/125s ———> 1s Long excerpt

2) Let the camera do everything by itself, I paid so much money for it

But he won't. Only a person can determine exactly what he wants from the instrument. The tool does not matter, it will lie on the shelf well. Switch the camera to shutter priority mode (Tv, Sv) and play with the settings.

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Shutter priority mode on Canon cameras

The camera works in automatic modes according to the program set in it at the factory, and often these programs are actually so-so, because there are no ideal shooting conditions) Do you feel this divine power? Now you can dictate your will to the instrument, and not vice versa. There are not many nuances, in fact. I'll tell them all, I have nothing to hide from you. Free, without registration and SMS. :)

tv scr

Try to determine which excerpt set in the settings in this screenshot, short, or long. And if this is clear, let's move on.

3) About the stir and tremor

Another, but not the last thing that affects the sharpness of the frame is the shake. Yes, a slight tremor is present not only in inveterate alcoholics, or in the morning after those very outpourings, but also simply from the fact that you are a living being. If you hold the camera haphazardly and do not focus while shooting, especially in low light and at low shutter speeds, we run the risk of blurring the image. Holding the camera firmly and preferably not breathing while shooting (saying 22 to yourself while pressing the shutter button) are great assistants in shooting in low light. Well, you don’t have to press the shutter button with all your might - it is sensitive enough to light pressure. And it is best to hold the camera with two hands, and even better if we find some kind of support for ourselves with the body or hands.

4) How and what the camera sees during focusing

Pay attention to the picture below. This is a conditional image of how focusing occurs.

focusirovka

At the same time, it turns out that there is a difference where to point the camera. Which of the pictures correctly and incorrectly focused on the face? In any case, we see it like this:

camera focus

The sensor responsible for focusing is small and sits at the very bottom of the camera behind the lenses.

camera focus. focus sensors

He sees it like this:

lens focus

lens focus. correct and incorrect focusing

Sensors of old types in DSLRs sit in the same place, but they see worse:

lens focus

There are several types of sensors themselves. Horizontal, vertical, cross. And the more powerful this sensor, the better it sees sharpness.

D Datchik AF D

But even in the case of the most advanced in this example, the cross sensor, the visibility in the case of an incorrect focus point for the sensor will be near zero. In general, the sensors are shown too schematically. Each sensor module has a light-collecting cell:

Horizontal datchik

For them, the so-called "contrast transition" is important. Camera sensors see everything a little differently than we do, and that's where we aim, usually there should be a drop. Difference of light, colors - contrast transition. It is along the boundaries of the squares that the camera can easily focus on sharpness. But if we try to focus on a point that has a flat surface, then the camera will not see anything.

camera focus

camera focusing correct focusing

Focusing the camera through the viewfinder of a SLR camera has a clear advantage in speed, but it does not always work accurately. Especially when focusing (and most often it is) occurs at an open aperture in autofocus mode. At this moment, the following things work, on which the accuracy of focusing depends no less than on our hands. There is such a thing in this photographic world as an acceptable circle of sharpness, once in which, the camera will always think that everything is OK, and you - not always.
This spot has certain tolerances precisely in order to capture the approximate sharpness as quickly as possible, and give confirmation to the rest of the electronics, so that the camera reports that it is ready to take a picture. And everything would be fine if not for a few buts that usually affect the accuracy of this process.

5) Focusing on our own

If focusing is given to the camera, then we may not achieve an adequate result at all. According to his logic, he will definitely find something to cling to, as he executes the instruction, according to which there should be sharpness in a point or group of points and this sharpness should have a certain level. Therefore, the first thing to do is to manually determine the focus area for the camera.

camera focus. focus point selection

A good example for the first time is focusing the lens in the center using a group of points, or the center focus point of the camera. This way we know exactly where the camera is trying to focus, and we know exactly where to look to check focus after shooting. In addition, many cameras support several modes for setting the position of points for portrait and landscape photography.

camera focus. focus mode

Since we explicitly told the camera which point to focus on, now we can try to shoot something using this point. If we chose a portrait, then let's focus on the eyes. We focus on the eye closest to us, and take a picture.

6) Phase and contrast autofocus

SLRs and cameras that use phase sensors for focusing have such a thing as “permissible blur spot”. Relatively speaking, this is the range, having fallen into which, the camera will consider the focusing of the lens to be completed. At the same time, the picture on the display will be sharp, and then when viewed on the monitor, it will turn out that it is sharp where we do not need it. And it's terrible. Of course, this is also superimposed on the gaps in the focusing mechanism of the lens and camera. And on a similar device, this can occur more often than on a new one. How to prevent this disease? Very simple - we take several shots with refocusing at the same point. Usually this helps to get 10 frames from a series, 5-7 pieces are acceptable sharp for our eyes.

This disease does not affect the camera of a smartphone and a camera that uses a contrast or hybrid phase-contrast focusing method. In DSLRs, it turns on in LiveView mode, and in mirrorless cameras and smartphones it is used by default. This method is more accurate but slower. Although in modern cameras it has already caught up with phase focusing in terms of speed. In general, in both cases, the camera will focus on the contrast at the point / focus area.

In fact, usually with DSLRs, the central focus point of the camera is the most sensitive, and allows you to focus even in poor lighting.

autofocus sensors

The side dots are sensitive, but not as good. Therefore, I recommend working with the center point. Then you can try others, or combinations.

It is recommended to use the entire group of points when it is necessary to enable object tracking. In this case, it is more important for us to get some kind of sharp image than not to get it at all. Although, some cameras do this in a completely unpredictable way, focusing as if on high on anything but what is needed.

At the same time, in the viewfinder of a SLR camera, in addition to confirming the focus of the lens, you can tense up and see the depth of field. Mirrorless cameras, on the other hand, have such things as focus peaking, including which we can see sharpness both in the viewfinder and on the display. Focus-peaking emphasizes the sharp contours of objects with additional color so that it is clear without magnifying the picture where we are focused. A very useful thing when focusing both manually and in auto mode with fine-tuning by hand.

FP3

Now let's get to the more difficult part of the question. Which is more dependent not on us, but on physics, and how the developers are trying to defeat this physics.

7) Lens auto focus drive design

There are more precise mechanisms, such as the USM in Canon, there are less accurate ones, such as (now considered archaic), a traditional gear drive, which rolls the glass around the insides. In the case of using such an old mechanism, the accuracy depends on the size of the drive gears, as well as its wear. Typical problematic lenses in this regard:

And other junk of the ultra-lower price segment. In the case of increased wear, the camera can, of course, get into focus, and even give confirmation, but the backlash in the mechanism, even half a millimeter at the output, gives jokes on the spread of the lens focus.

TRADICIONNYJ MEHANIZM AVTOFOKUSIROVKI
Either shortfall or flight. Of course, it always worked like this before the advent of hybrids in focusing systems, although it was not so noticeable on fresh native lenses. You can try pressing the shutter button with refocusing at one point, and then see how it works on the results. There will be overshoot, undershoot, and hitting the target. But this takes time, and time, as you know, if not money, then at least not a waste of it.
The moments with overshoots and undershoots are especially obvious and infuriate when we shoot (especially after zooms) on lenses with a fixed focal length and wide apertures like f1.8. On the open, and so the depth of field is small, and then there are all sorts of features. In general, now, of course, the circumstances with this matter are much better than before, in cameras with a hybrid focusing system, however, in order to save money, some manufacturers are still in no hurry to bring the bottoms up to the level of top lenses.
Cameras of the lower price segment always gave a spread on open apertures, even if zooms were used, in which, constructively, in principle, the depth of field should allow you to shoot from the hip, without particularly bothering. In general, if everything is in order with the hands, this feature of the systems must also be taken into account.

But that's not all.

8) Sensor dimensions

As it turns out, the accuracy of AF when focusing still depends on the size of the sensors (we are considering DSLRs) that are responsible for the accuracy of focusing. And the path of light to these sensors lies not only through the lens, but also through the path of the camera, in which there is usually an additional mirror behind the main mirror, which sends part of the light to these sensors.

pentaprizma

The sensors are not only different (cross, diagonal, and horizontal / vertical) but it turns out that their size is important. So, for example, on cameras with large matrices, there is a place to be the area of ​​​​the sensors, which is significantly increased compared to cameras in the lower price segment. The accuracy of AF may also depend on the wear and tear of the drive mechanisms of this very mirror. Additional play, even a fraction of a millimeter, and that's it, the output is a ton of marriage. Fotik will say that everything is OK, and it doesn’t matter to him whether he hit or not, in fact, he did his job according to the instructions.

But that's not all. It turns out that sharpness may not depend on the camera, even on old manual mechanical cameras. Oh, is it. Yes Yes. Physics is like that.

9) Dependence on lens scheme

And the joke is that when designing optics, engineers are faced with tasks that require compromises, depending on what you want to get as an output. There is such a thing as "spherical lens error and its correction." This is when you kind of unscrewed it, as expected, got sharpness on the open, and then closed the aperture before shooting, iiii, at the exit there was a marriage. So, in optics, focusing accuracy also depends on whether this very spherical lens error is corrected or not. And correcting a lot of image errors is usually long, expensive and without a guarantee. Let's put this jamb of optics on the rest of the dependencies, and we get .... That at a certain moment, focusing, as you don’t adjust the camera and the lens, does not appear immediately after pressing the button.
Granit 11 80 200 4.5 shema bol
Lens schemes usually consist of several (tens) elements. In the 60s, such a concept as “floating elements” was introduced in order to maximally correct possible jambs of the resulting image. Lenses have a converging part and a diverging part. These parts are combined with each other using different types of glasses with different refractions. Why is it necessary to correct? Because, the collecting part gives a terrible quality at the input, and what lens usually collects? That's right, curved out. She obviously collects more than necessary, and the rest of the scheme is trying to compensate for what the front end has collected, and not always successfully. Have you seen the photos from the monocle? Well, a true monocle is a converging lens, and that's it. Not a very high quality picture.
monokl photo aleksandr roschin. nikon d700
The spherical error of the lens is corrected more or less successfully by always pressing the aperture. From, for example, to improve focusing accuracy when using modern hybrid phase contrast sensors, mirrorless cameras register an image and focus on the active aperture. Modern DSLRs, although their path has not been long, are trying to do the same.

10) Dependence on ambient temperature

But this is not all yet) the accuracy of the autofocus and focus mechanisms, in principle, is affected by the ambient temperature. There are gaps in the mechanisms, and these gaps vary in varying degrees from the natural change in the state of aggregation of the substance - the expansion of the gaps reduces and increases the accuracy in theory, and the additional compression (in the cold) increases the gaps. Thanks to progress for the fact that now you almost don’t have to think about it, but it’s worth keeping in mind, for a general understanding.

11) Focus issues

Maybe a service? Good idea, and it often visits those whose focus spread narrows to a constant inconsistency of the image with the intended zone of sharpness. A constant undershoot or overshoot can occur both due to a malfunction that has crept into the mechanisms that ensure the delivery of the image to the focus sensor, and individual errors of individual nodes, such as:

  • camera focus confirmation node
  • a mirror that sends a portion of the image to the AF sensors
  • distortion of any planes in the mechanisms of the lens or camera
  • malfunction of additional focusing sensors in the lens itself, if any
  • malfunctions associated with damage to the camera or lens after an unsuccessful or successful fall

As a rule, the backlash of the mechanisms, which has increased as a result of the operation, anyway, one way or another, using the method of re-focusing at one point, will give at least 30 percent of normal frames. If the camera constantly smears in one direction, then most likely “something is broken”.

To adjust to the individual characteristics of lenses, some manufacturers on some camera models provide software correction for overshoot or undershoot by autofocus, directly from the menu.

MENJu DLYa ZUMOV FIKSOV

And such tricks like Sigma, for some models of lenses, they released a special docking station, using which (naturally, for an additional fee) you can adjust the position of the AF lens, at home on your knee.

I deliberately do not indicate all the subtleties associated with firmware, cables and other electronics, because the sheet turned out to be rather big.

Сonclusion

  • When shooting portraits, it is better to aim at the closest eye of the model, and when shooting group portraits - at the person closest to us. The sharpness can be improved if you shoot with a closed aperture (a stop or two is enough). At the same time, a DSLR, for example, will beat all the same as if it were high, within its tolerances, but the increased depth of field will compensate for this.
  • Cropping can be done after focusing the camera. For example, when we do not need the central composition in the frame, we can fix the focus area by half-pressing the shutter button, and then, without opening our finger from the button, reframe the image. This is often done by photographers so as not to constantly switch focus points. The camera stops the lens where the lens was focused and waits for the command to release. Well, it really is faster and more convenient.
  • In low-light conditions and low-contrast scenes, you can use additional lighting, or a camera flash with autofocus assist. Usually, if the backlight is enabled, then the flash with an additional flashlight projects a grid, or highlights objects when focusing. Also, at some points, a strobe may fire (the flash blinks several times for the camera during focusing). A very handy item.
  • And of course, we control exposure)

Play around with the modes, capturing the dynamics - cars passing by, dogs running, skaters, or just people. Practice understanding the focusing process to get sharp shots.

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