A slight pressure on the shutter button and immediately you feel a slight movement of the lens barrel, emphasized by the hum of the motor slaved to the autofocus system, after a brief moment the focus is reached, the shutter completes its run and you hear the shutter sound dry, we have made our photo.
By now we are so used to the fact that our camera delivers in a fully automatic your subject is perfectly in focus, which is hard to believe that there are situations where it is preferable to disable the autofocus and use a manual focus. Current systems are able to adapt both to the still shots taken with a (AF-S, Single AF), and for those on the move (AF-C, continuous autofocus), based on an increasing number of measurement points can control a wide area of \u200b\u200bthe frame and cover effectively a high percentage of situations. Nevertheless there are still good reasons why in certain shooting situations it is useful to set the switch on our lens / camera in the manual position, let us see what can be:
1) Photo Macro and Close-up: photos at close range requires high precision in the treatment of focus because of the extremely shallow depth of field (in the macro is often played on few mm.), the autofocus is not always able to return the desired result and / or is being misled by the presence of objects in the field of view, in all cases to get the best in this kind of picture we have to be a decide which parts of the subject should be sharply focused or not.
3) Click through the barriers: windows, fences, nets metal, vegetation, etc.. and in these cases, the autofocus system can be brought to focus on the obstacle instead of the main subject as it is the first object it detects.
4) Action Photos: when you have to take pictures of bicycles, motorcycles, cars, even if the autofocus systems allow for continuous adjustment to track moving objects, it is often desirable to adjust the focus on a point where they must pass the subject and take not just enter the target area.
5) Close-Up: when doing close-ups to people or animals a general rule to follow is to hit precisely the focus on the eyes, but also wanting to disregard this rule, with manual adjustment we would have more control over which part should be in sharp focus.
6) photograph subjects at a distance: regardless of the size of the main subject and its possible movement, agree to get in and make manual adjustments to the infinity, preventing the autofocus can be fooled by any other object in the frame.
7) Creativity may extend up to cover the possibility of wanting to blur all or part of the subject, and possible operation under control only with the photographer to adjust the focus manually.
8) Overview: if we make a series of photos to be joined to get an overview, it is good that the photos all have the same setting, not only as a diaphragm as well as focus, so that we can see the difference once they are stacked is therefore preferable to exclude the autofocus setting fire on a fixed distance.
9) All fire, or use the hyperfocal distance: how to behave when we want the focus extends from one subject in the foreground to infinity?
In these cases, to be sure to get the desired result, we must make use of hyperfocal distance: is the distance at which adjust the focus because, from the middle to infinity appears to be all fire . The autofocus would try to focus on the first object of appropriate size who is not too far from the center of the frame, and the hyperfocal distance likely to match that, then it becomes essential manually adjust the lens.
The hyperfocal distance depends on lens focal length, the aperture used and the diameter of the circle of confusion (it differently depending on the sensor in our camera), the formula is:
where:
F is the focal
D is the aperture used
C is the circle of confusion
(dimensions in mm.) - to get the hyperfocal distance in meters simply divide the result by 1000.
1) Photo Macro and Close-up: photos at close range requires high precision in the treatment of focus because of the extremely shallow depth of field (in the macro is often played on few mm.), the autofocus is not always able to return the desired result and / or is being misled by the presence of objects in the field of view, in all cases to get the best in this kind of picture we have to be a decide which parts of the subject should be sharply focused or not.
manual focus.
The map of clover on the left may have misled the autofocus that much to the snout of the lizard is not in focus.
2) When there is little light all autofocus systems suffer more or less the situation in which the ambient light is very low as the brightness will become very slow and when it falls below a certain threshold, they can go in leteralmente cream continuing to move back and forth the objective lenses without being able to strike a correct focus.
The interior of the church of San Domenico in Cagliari, dimly lit .
An example of a view through the arches of the old steel bridge avenue Pula - Cagliari.
With the manual focus stems of this vegetazionene between the camera and the subject does not interfere with the outcome.
Mass Manual focus has prevented the autofocus could be deceived by the glass that protects the opening to the outside.
4) Action Photos: when you have to take pictures of bicycles, motorcycles, cars, even if the autofocus systems allow for continuous adjustment to track moving objects, it is often desirable to adjust the focus on a point where they must pass the subject and take not just enter the target area.
Panning, where the subject should be in focus despite being on the move.
5) Close-Up: when doing close-ups to people or animals a general rule to follow is to hit precisely the focus on the eyes, but also wanting to disregard this rule, with manual adjustment we would have more control over which part should be in sharp focus.
Halloween Night - 2010
Cody, one of our two cats.
6) photograph subjects at a distance: regardless of the size of the main subject and its possible movement, agree to get in and make manual adjustments to the infinity, preventing the autofocus can be fooled by any other object in the frame.
Sunset - Cagliari-Villasimius coast road .
Rainbow Boulevard from Europe - Cagliari.
7) Creativity may extend up to cover the possibility of wanting to blur all or part of the subject, and possible operation under control only with the photographer to adjust the focus manually.
The arc that connects via Portoscalas via Hospital - Cagliari.
Cala Sinzias.
Bari Sardo - Torre di Bari
9) All fire, or use the hyperfocal distance: how to behave when we want the focus extends from one subject in the foreground to infinity?
In these cases, to be sure to get the desired result, we must make use of hyperfocal distance: is the distance at which adjust the focus because, from the middle to infinity appears to be all fire . The autofocus would try to focus on the first object of appropriate size who is not too far from the center of the frame, and the hyperfocal distance likely to match that, then it becomes essential manually adjust the lens.
everything in focus from 60 cm. infinity with 18mm focal length. and f16 aperture.
hyperfocal distance = (F x F) / (D x C) + F
where:
F is the focal
D is the aperture used
C is the circle of confusion
(dimensions in mm.) - to get the hyperfocal distance in meters simply divide the result by 1000.
See also the post: Objectives and their characteristics - 3rd Party , where they are also referred to two sites where you can find the tables for the APS-C sensors and full-frame and a few small programs for free Hyperfocal distance calculation.
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