Auto Focus

[peeperita]

i generally use the auto focus.....except....

when the light is so low the auto can't lock in.....or.....when the camera insists on a focus point that is not my subject and the old "lock and swing" falls short of the mark......

peeper

[Elmo]

Coming from a time before Auto Focus, even before Auto Exposure. I say not always. But let’s look at the situation from a teacher’s point of view. I suspect this is an entry level class. Who are the average students? From experience teaching both basic and advanced classes I say he is correct in his statement. The reason; most of the folks in the class are only interested in improving their snapshots not doing artsi-fartsy stuff.

From the point of view as a working professional (retired) photographer, starting before anything was automatic, automatic features are features are great. When available I did and still do shoot 90 percent in an automatic mode. The key is to learn to use the auto mode features. For example look at NASCAR do pit crews use single handle lug wrenches to change tires? Not a chance, they use the proper tool for the job. Sometimes manual is the right tool but the majority of the time proper use of automatic functions is a better choice.

Let me clarify I am not referring to the A setting for exposure. But using the M setting is a waste of time especially when you are using the cameras meter to get basic exposure. M could be equated to Monkey Wrench. Would you hire a mechanic who only had a monkey wrench? Sometimes a monkey wrench is the only tool that works but most times other tools do a better job. Learn to use your tools and use the right tool for the job.

[wulf]

Even for an entry level class, assuming that was the case, I think "always" overstates the case for autofocus. Not least, it sets people up for a fall when they get overheard passing on their "wisdom" by someone who adheres to a different "always".

If I were teaching a beginners class and found myself asked if people should always use autofocus, I would aim for a much less partisan statement, such as "you will probably find you get a higher percentage of decent snaps by using automatic settings when you don't have time to carefully set things up". For myself, I revel in doing things manually and experimenting with the available options.

Wulf

[KodiakStar]

Depends on your gear.

If you can get crisp, in focus images doing M, then do it.

If you have a tiny ass viewfinder, like me, and can't focus no matter what with it... then Auto is the way to go, until you can afford the E-3

[daft_biker]

Using auto focus for macro can waste as much as half of the little DoF that is available. Auto focus will usually focus on the nearest point of a subject but because a significant amount of DoF is in front of the point of focus that's not where you want it to make use of all the available DoF.

Like with hyperfocal distances it's about shooting at the optimum setting for the sharpest possible shot. I think it's one of the many enjoyable challenges of photography if you chose to take it. I find manual focus is well suited for the times I use a tripod.

Auto focus has it's uses but then so do other techniques such pre-focussing. However, even with auto focus there are different setting that can be used...how the AF points are selected, how many AF points are active, what kind of AF points, if and how moving subjects will be tracked...

Using the same settings and technique for every shot is bad advice in my book.

[RexK_Cozumel]

Heck no. If I let autofocus try to do everything for me I would be sitting there trying to take a macro shot for days. Or when I am shooting with models it will focus on the tip of their nose instead of their eye. Autofocus is fine for some applications but if you ALWAYS use autofocus you will have a lot of mis focused shots.

[kencaleno]

First Step:

Set your Focus icons - detach lens, (so you are adjusting focus on focus point, not image) - adjust dioptre (next to viewfinder) so focus points are sharply in focus. (easier against a white, or light background) Re-attach lens.

Focus

Is the measure of the degree of sharpness in our images.
All modern cameras have Auto-focusing, which works very well, but there are times when you need to focus manually. For auto-focus to work properly it requires a certain amount of contrast, if the contrast isn’t adequate you will need to focus manually.[ NOTE: In your camera’s viewfinder, depending on camera-flagship models generally have many focusing spots, and lesser, entry-level dslr’s will have around 5 focusing spots. With lens wide open, any of these spots can be used for selecting where to auto focus-But, depending on maximum aperture of lens in use, the ones you are able to use get fewer. Top-of-the-line cameras will only have the centre spot usable at F8,and entry level cameras at F5.6, and less than that, even these single spots aren’t reliable.]
Actually it is more beneficial to set auto focus by the centre spot, then re-compose, rather than use the peripheral spots-The reason being that only the centre spot has vertical and horizontal pixel rows. This means that if you use the peripheral spots (top and bottom spots have horizontal pixels only and right and left spots have vertical pixels only) To focus, you must have a part of the scene crossing a line of pixels at 90 degrees, and the centre spot gives you a more accurate reading ,having both vertical and horizontal pixels) It will pay you to manually focus most of the time, for full control of the situation. For instance, if an unnoticed reed encroaches into your image, when your are shooting a swan at the lake, for instance, your lens may auto-focus on that reed, rendering your actual subject out of focus.

Concerning Auto focus

There are times, you will find when auto focus will fail to respond favourably-although auto focus is able to lock on to any subject, there are certain conditions where it may not be possible ,even when the indicator lights are on, and the shutter releases.

Subjects with low contrast
Solution: Focus on something the same distance as the subject you want to make an image of, then aim at that subject
Subjects that do not contain vertical lines
Solution: Hold camera vertically, lock focus, then switch to horizontal
Subjects in excessively bright light
Solution: Focus on something the same distance as the subject you want to make an image of, then aim at that subject
Two subjects at differing distances
Solution: Focus on something the same distance as the subject you want to make an image of, then aim at that subject, and re-compose
Subjects with repetitive patterns
Solution: Focus on something the same distance as the subject you want to make an image of, then aim at that subject, and recompose
High speed subjects at close range
Solution: focus on another subject at the same distance-to-subject distance first, then re-compose your frame

To ensure you are in focus, there, in the viewfinder, is the electronic rangefinder icon, that comes on when you are in focus. NOTE: Each lens has its “sweet-spot”, that is when the aperture and zoom length combine to give optimum sharpness- 18-55 mm zooms usually have this “sweet-spot” at the 35mm distance setting and 2 stops back from wide open. On a 70-300mm zoom the “sweet-spot” would be around 185-200mm aperture 2 stops back from widest.
Auto focus is good for situations where you cannot focus fast enough, manually, such as sports and wildlife photography.
Depth of field appears to be the most confusing of focus elements. Depth of field is a range of acceptable sharpness in an image, from near to far. Three factors control Depth of field: Aperture: The wider the aperture, the shallower the depth of field. Focal length of lens, The longer the focal length of the lens, the shallower the depth of field will be. and Distance from subject, Landscape images have great depth of field, whereas Macro (extreme close-up) images have very shallow depth of field. Concerning depth of field, Hyperfocal distance seems to be even more confusing -Hyperfocal distance is a point of focus where at a certain aperture, Half the distance from that point to Infinity, (which starts at 30 feet, and extends to as far as you are able to see)) will be in acceptable focus, The best lenses for hyperfocal distance are 80mm or wider ; telephoto lenses, because of their relative short depth of field, are rarely used. (Prime lenses have a scale on them for this, zooms do not) Using a 18mm setting on your zoom lens at f11, Hyperfocal distance is somewhere around 5 feet (1500mm), so depth of field at this aperture would be from 2 1/2 feet ( 750mm) to infinity, when focused at 5 feet. A good guideline for great depth of field for landscapes is to use the bottom focusing marker in your DSLR viewfinder, (either horizontal, or vertical) as this will focus 1/3 of the way into the distance, (It is on the lower third imaginary “Rule of Thirds” gridline!) ,as is usually recommended. [ NOTE: Unless your camera has depth of field preview, looking through the viewfinder all will not be in focus, because your lens, until you press the shutter button to make the shot, will be open at full aperture.]


Ken

[Ottaviano]

There is no right or wrong here. I think you should use your auto-focus and become comfortable with it. Especially getting comfortable in moving the focus points around without taking the camera away from your eye. However there are situations, like when you are working with a narrow depth of field where a manual focus and actively thinking about where you focus lands is the best way to go.

[Gonzo13]

Most of the time I use auto focus but I set the focus point for what I am photographing so I am kind of in control. While shooting macro and in not well lit areas I use manual focus. For alot of things in life the word "always" doesn't usually work.

[Atomic_13]

NO! Although I usually uses autofocus for fast moving subjects or people, DONT use it when you're taking a macro photo or some static subject.