Most Digital (and film) cameras today offer a nice feature called Manual Focus. This has not always been the case. The older more experienced folks remember that in the good old film days there was a big excitement when auto focus was introduced as a new feature.
There are many reasons to use Auto Focus - it is fast, accurate, and let you, the photographer concentrate on composition, lighting, framing and other technical and artistic factor of your picture.
However, there are still many situations when Manual focus can give better results than auto focus. [image cc by dalantech]
1. Macro
When taking a macro picture the lens is usually very close to the subject. In some cases less then an Inch. Depth of Field (DOF) can be as shallow as two or three millimeters. The Auto-focus mechanism can not always detect what is most important to you in a macro shot - if it is not the center, you are better off making the decision yourself.
This is true event if you go to your highest possible depth of field, say f/22 or f/32.one way of dealing with the needed accuracy is to use special railing that make it easy to move the camera one or two milliliters forward or backwards. [image CC by markop]
2. Action
The more expensive your camera body is the faster is the AF sensor it has. If you have a fast lens, your autofocus will be even faster. But even the fastest focus engine can not always compete with fast action shots.
Whether you are shooting your kid on a water slide, or a fast formula one race, if you know when the subject will be at the critical moment, set your focus there in advance and keep in on manual. When the subject enters the frame is positioned right, click the shutter release. [image CC by kiwêhowin]
3. Old lenses
Sometime auto focus is not really an option at all. if you want to benefit some of the fine old lenses, you may find that they do not have auto focus capability at all or that they are not compatible with your SLR autofocus system.
For example, if you want to use the razor Nikkor 28mm f/2.8 lens you have no choice - you must go manual.
Ken Rockwell has a great compatibility chart for Nikon (and Nikonians have one too). It is easier for Canon users, any non EOS lens will not work with any new EOS camera - AF or no AF. [image cc by redandwhite]
4. Low light
It is hard for the autofocus sensor to focus in low light. Even fast lenses with wide apertures can have a hard time in a dark room like a church or a cave.
If you shoot still life, you can use the auto assist bean, it is a beam that throes some light in front of the lens and helps the auto focus sensor. If you're photographing people, it can be harder - using the AF assist beam can be annoying to some, break the feel of the moment it draws attention to you and ruin a shot. [image cc by nickwheeleroz]
5. Blurring a shot
Sometimes you want to have some artistic control over in a particular picture and create a blur effect for artistic reasons.
You may want to have the entire picture out of focus or have a negligible, almost off the frame object, in focus. In either case, moat auto focus mechanism will not allow you to perform the first and will give you a hard time achieving the second.
DPS has a nice tutorial on taking out of focus images. [image CC by kubina]
6. Going Hyper Focal
Have you ever wondered how the take those stunning nature shots that have both the nice rocks at the close front and the water fall at the far back sharp. Hyper Focal Distance is a photography term used to note the point that if you set your focus to it, you will gain the most Depth of Field front to back.
Jeff from has a great Hyper Focal Distance tutorial, which is recommended both for the technical enthusiastic and starting nature photographer.
Alex Wise (site) is one of my favorite photographers who makes it a habit to post lots of vertical hyper focal landscape images. [image CC by night86mare]
7. Shooting Fireworks / Stars
In light of the fact that we have just celebrated the forth of July we had a ton of great shooting fireworks tutorials (those are six of my favs). What's common to taking pictures of both fireworks and stars it that you want to set your camera to manual focus and focus on infinity (that's the weird "8" that's laying on the side). Honest! Look at all those tutorials - they all say it. [image cc by sacharules]
8. Panning
When taking a panning picture, you have to follow a moving subject. One way to deal with the movement is to set your focus mode to AF-C (continuous auto focus), another is to rapidly half-press the shutter release.
I would like to suggest a third way. If you know the route of your subject, you can set the focus to a pre-known location that your subject will go through. Now you know that your subject will be focused in the critical section of the pan. [image cc by mactiste]
9. Lens Babies
Lensbabies are lots of fun. they give a nice shallow focus effect.
Lensbabies do that by having a flexible mount which imitates tilt/shift lens.
Just like old lenses, Lensbabies are manual focus only. On the other hand, this is just what you'd expect from a lens baby - you make the artistic call, including setting the focus point.
from : www.diyphotography.net
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