Most modern day lenses for digital SLR cameras have auto focus technology built in to them. Technological advancements are good and, on the whole, this is the case with auto focus technology especially for those who are starting out in the world of digital photography. However, lenses containing auto focus technology do have their problems and there are times when it is best to turn the technology off and revert back to manual focussing when taking digital images.
There are times when the auto focus feature of the lens will struggle to find the desired point and get a positive lock. Instead, the lens will hunt around and move erratically whilst trying to focus. This situation is most likely to occur in low light conditions therefore it is a common problem for shooting at twilight and in to the hours of darkness. A hunting auto focus is annoying and during these circumstances there is only one course of action, and that is to turn the auto focus feature off and focus manually.
Another situation is on still life assignments. When taking photographs of still life subjects the overriding primary objective is to ensure the subject is pin sharp and everything is in focus. The whole frame should be tack sharp from front to back. Fortunately, the photographer has time to achieve this, and this is one situation where using manual focus produces far better results than using auto focus. Focusing manually allows you to fine tune the focus and if combined with the live view feature it allows you to zoom in and ensure that the subject is sharp in the frame.
Macro photography is a further discipline where focusing manually produces better results than auto focus. The performance of the auto focus feature in all macro lenses will deteriorate as you get closer to the subject, which is mainly due to the reduction in light. As you get closer to the subject the auto focus will hunt around more trying to get a positive lock, and when a positive lock is achieved it is often on the wrong part of the subject. In order to get a pin sharp focal point on the correct part of the subject manual focussing is essential.
Many people starting out in the world of digital photography have a reluctance to focus manually and rely far too heavily on their lens’ auto focus feature. Many are of the opinion that manual focussing is hard and takes a long time to master. However, focussing manually is not as difficult as it may first appear and whilst it may be a bit slow and cumbersome at first, if you practice you will find that it becomes much easier and quicker. Manual focussing is something that all photographers should be able to do.
So, how does a photographer go about focusing manually? First, turn the autofocus feature off, which is achieved by sliding the focus button from ‘AF’ to ‘MF’. If using a digital SLR camera the focus button will be located somewhere along the barrel of the lens. If using a point a point and shoot camera you will need to consult your manual because all makes and models are slightly different.
With the lens set to MF mode it is a case of pointing the lens at the subject and then turning the focusing ring clockwise, whilst looking through the viewfinder, until the subject becomes sharp in the frame.
If you reach the end of the focus ring’s range and the subject never becomes sharp turn it the other way until the subject becomes sharp. It is common practice to go beyond the point of sharpness and when this happen turn the focus ring the other way to get the subject back in focus.
If your camera supports live view mode then turn it on. Zoom right in on the subject, to the maximum which is usually 10x, and move the cursor around the subject making sure that everything you want sharp is sharp. If the sharpness is not right, turn the focusing ring until it is right. Once you find the sweet spot take the image.
There are times when the final bit of focusing, i.e. that last little bit to get the image absolutely tack sharp, is best done by moving the whole camera backwards or forwards as necessary. The movement required will be very slight and is best achieved by slightly pushing your whole body backwards or forwards. This technique is favoured by many macro photographers when taking extreme close up images.
Whilst there are many benefits and advantages of using your lens’ manual focus there are situations when it is best to use auto focus. A prime example of this is when taking images of moving subjects. Many photographers are more than capable of using manual focus when taking images of slow moving subjects, such as a snail sliding across a leaf or a grey heron stalking some fish in a lake, however anything constantly moving creates a few more problems and using auto focus will overcome these. As a general rule it is best to always use auto focus when taking images of moving subjects, regardless of how fast or slow they move or how good and fast your manual focusing skills are as it will ensure you get some decent photographs.