And so, the lens can miss and the result can be a lot of reasons, both the camera itself and the photographer's mistakes!
Read the article to the end, very useful conclusions at the end!
Reasons for autofocus misses!
First cause - Autofocus Modes! Fotikov has different focusing methods, for example, there is a tracking autofocus! That is, when you choose this focusing method ( Canon - AI FOCUS / AI-SERVO; Nikon and Sony - AF-C / AF-A) as long as your finger is holding the shutter button half-pressed, the camera will track a moving object that falls on your chosen focus point! THOSE. keep an eye on the object, and sometimes when you need not, the camera can refocus - without asking your permission! And the focus will be completely not where you wanted! Therefore, it is better to select the "Once pressed - Once focused!" ( Canon - ONE SHOT; Nikon and Sony - AF S) - when, when you press the shutter button halfway, the camera focuses where you want it and locks autofocus exactly where you need it! She won't refocus anymore!
From the first reason it follows second - In the mode "Once pressed - Once focused!" ( Canon - ONE SHOT; Nikon and Sony - AF S) when you have focused and the camera has locked autofocus where you indicated. With a half pressed finger and locked autofocus, you begin to move back / forth, respectively, shifting the focus itself. Those. focused on the human eye and hwe stepped forward, and responsibly focus will go forward in the ear of a man! THIS IS THE MOST COMMON mistake of all novice (and not only) photographers. More often than not, your mistakes are precisely because of this! Or the opposite situation, you focused, and the model stepped back a little, and the focus remained in front of her! You will never notice this in the viewfinder of a DSLR! YES and it is not always noticeable on the screen, therefore CHECK THE SHARPNESS FREQUENTLY - increasing the image on the screen of your camera at the time of shooting, so that you can re-take a picture later!
The third the reason is AF point selection... If worth AUTO choice, the camera itself will determine exactly where to focus, by itself choosing the desired focus point. The problem is, the camera doesn't know what exactly you are shooting! Her logic is simple - FOCUSING ON WHAT IS CLOSER AND HIGHER CONTRAST! And if in the foreground you have a car hood with a headlight, and a little further a model, then the headlight will be sharp!
Therefore, it is better to choose the focus point yourself! For the camera itself does not know, what exactly you need to be sharp in the frame, and cannot distinguish a person from a cactus. This is especially true for SLR cameras! But mirrorless cameras CAN, as well as in your phone, they have auto face detection! That is, having seen a face, the camera will focus on it! But if there are many faces, the camera will not know which face you need (Although in SONY cameras you can register the face of your model and the camera will only react to this face!) But still, it's better to choose the focus point yourself!
And here we come to the focus points themselves and this fourth reason! If your SLR camera costs less than 60-80 thousand rubles. The focus points are not all the same there. As a rule, the most accurate and sensitive is center point. We will not go into details, the important thing is that it has a cruciform shape and works on any diaphragmx and clings to any lines, both vertical and horizontal, and the rest of the points do not! Therefore, we work like this - directing center point focusing on the subject, press the shutter button to the middle, (to keep the focus on the object) and then without releasing your finger from the shutter button, we position the frame as we need it (placing the object anywhere in the frame) and only after that we press the shutter button to the end and get the frame!
Remember, autofocus needs contrasting detail to focus! He will not be able to do this on a clean white wall for example! If you photograph a person - always focus on your model's eye - it is there that the most contrasting point! And for example, sony cameras even have such a function, the camera follows the model's eyes! And even in video mode !!!!
And so, the problem of different focus points does not apply to mirrorless cameras, all focus points are the same, and everything works well. This is due to the fact that the focus points of the mirrorless are located on the sensor itself, that is, some pixels partially fulfill the role "Phase focus sensors". What does this mean? Roughly speaking, the autofocus sensor for mirrorless cameras is itself matrix!
But for DSLRs, the autofocus system is a separate module that is located under the mirror below. And for it to work, the mirror must be lowered, at this time you see in the viewfinder the reflection of the picture from lens from this mirror. And count the focusing points - separate micro sensors stuck tightly in this module, and they, as we found out above, are not all the same!
So the types of autofocus are different and this fifth reason! And not all of them work well! The types of autofocus are - contrast, phase, laser, ultrasonic, etc. All of these methods are widely used in modern smartphones. But in cameras, two are mainly used - contrast and phase!
The contrast method appeared a long time ago (1981), but it began to be massively used only in the digital era, and was used in digital soap dishes and the first more or less smartphones like Iphone 4! It works like this - The camera takes a picture moves lens, takes a picture again, if the picture turned out more contrasting, again moves lens if even more contrasting, still moves lens if contrast got worsethen returns the lens back a little and stops the search - READY! everything is focused! Read for a LONG time? So it focuses for a very long time! The method is the simplest and cheapest, but it requires a lot of calculations, so the speed of such focusing is ooooooooooooooooooooooooooooooooooooooooooooooooooooooo, so the first mirrorless ones didn’t focus very quickly! Not yet invented a phase method of focusing on the matrix!
In contrast to the contrast method - PHASE very fast! It works like this. Light from different angles of the lens, through special. The prism will hit the special sensors that are nearby, the lens moves and the images from different angles are placed in different ways, and as soon as the picture coincides on both sensors, it means we are focused! This method is very fast and all DSLRs use it!
So that's why when you turn on Live View ( focusing on the screen, as in video mode) in her DSLR, it starts to slow down wildly and focuses very slowly! After all, the mirror is raised and the phase sensors no longer work! And the SLR switches to the matrix, and there only slow - contrast focusing method!
Why then don't mirrorless cameras slow down, but focus just as quickly like DSLRs and do it on the screen?! Everything is very simple with mirrorless cameras matrix - this is the focusing module, the phase sensors are located on the matrix along with the pixels, and they work as fast as the module that is in the DSLRs under the mirror!
I must say, not all DSLRs are hopeless, for example, in some DSLRs Canon the system is used DUAL Pixel for example Canon 80D or 5D mark IV and this is an analogue of phase focusing, and everything focuses very quickly on the screen! But then the question is - why is there a mirror and why are they so heavy and healthy! ??
In general - while you buy these healthy DSLRs, clumsy industry mastodons Canon and Nikon will rivet these outdated healthy DSLRs and will not develop the industry! After all, why waste money and time on development, you already buy a healthy black box to look through the periscope like 110 (one hundred and ten) years ago !!!
Then why do we need so many focusing points if we always use one?
And then what is it for at all auto focus point selection? Basically, it is needed for tracking autofocus, where a moving object quickly changes its position in your frame, for example, a running athlete or a racing car, in general, where it is difficult to quickly select a focus point yourself.
But this function works well only in expensive cameras like Nikon D7200 or Canon 5D mark IV. And also in mirrorless cameras such as Sony A6300. In the entry-level cameras, budget and mid-budget (up to 60 thousand rubles), it is there for show and works extremely poorly!
And finally - sixth reason! This is the front / back focus of your lens! Only SLR cameras have this problem, there is no mirrorless! This is a problem with the phase detection autofocus module. Motor impulses lens do not coincide with the frequencies of the autofocus module and because of this, the motor stops either earlier or later than necessary, and as a result, autofocus jumps or does not reach the target. As a result, by focusing on the eye, you will get either on the model's ear or on the tip of the nose!
And this is completely does not meanwhat is your camera or lens NOT FIXED! It's just that their impulses do not coincide, you can take them to the service for adjustment, but this often ends up with the other lenses beginning to smear. Therefore, it follows immediately when choosing lens, it doesn't matter NEW or BU - always check your DSLR with a specific lens for mistakes! After all, if you find this at home, they will not change the lens for you, firstly it is a technically complex product, and secondly it is completely working, and this does not meanthat with other cameras it will miss!
How to check the lens - the method is described at the link below!
But with mirrorless cameras, you can not be afraid of this, this does not happen there, you can safely order lenses even on the Internet, there will be no misses!
Let's summarize briefly!
- If you have an inexpensive camera (up to 60 thousand rubles) then DO NOT USE follower autofocus!
- Don't move back / forth when focused on the subject!
- Disconnect automatic point selection focus, choose the desired point yourself!
- If you have an inexpensive camera (up to 60 thousand rubles), use center point only focusing, as described above!
- If you DSLR do not use during focusing by Live view (on the screen), the only exceptions are mirrorless cameras and some Canon models with Dual Pixel.
- Required check out your lens on front / back focus!