Focus - Auto and Manual - Notes

Auto Focus and Manual Focus notes

Sometimes pictures are taken with focus points on different objects. Here is one example.

• In the first picture below, I had the shorter candle  in focus (front focus) to get a sharp image of the shorter candle .The longer candle behind  was out of focus and hence blurred.
• In the second picture below, I changed the focus (back focus) to the longer candle to get a sharp image of the longer candle .This time the shorter candle was out of focus and  hence blurred .

shorter candle in focus and longer candle is blurred(front focus)

longer candle in focus and shorter candle is blurred.(back focus)

• This is achieved by setting the focus using  AF or MF modes in the camera and telling the camera which object is in focus.
• Setting to Auto Focus or Manual Focus is straightforward.The button for AF and MF is on the top of the camera and sliding the switch to AF or MF puts the camera in auto or manual focus modes respectively.There is also the "+" button (in Canon),on clicking which, many focus points appear in an elliptical pattern  on the view finder .One can select one of the points by moving the cursor and this tells the camera which object is in focus.
• Clicking on one of the points half way through in AF mode produces a red light on the focus point and that is set as focus after which one can fully click and capture the image.
•  The AF (auto focus) sensor in the camera  uses light and contrast to detect distinct features and focuses based on that. Sometimes  it cannot distinguish  the distinct features ,either due to  wet and misty or foggy conditions .Manual focus comes to the rescue in such cases . A crisp and sharp image can be obtained using this option.
• Manual focus is also used for taking pictures when there is an obstruction , for example taking a picture of a monument  from behind the bars of a gate, where the  bars are the obstruction or say taking a picture of an animal in a cage .If the manual focus is set to a certain point, then the focus is only on the subject ,the obstruction is not in focus.In the auto focus  mode ,the lens can not interpret what image has to be taken as the sensor sees the obstruction (gate or cage bars) first ,in this example.Using manual focus one can tell the camera to focus on the right subject.
• Manual Focus is also used when shooting fast moving objects like cars .One would then focus on an arrival point before the car speeds and then shoot ,as soon as it reaches that point.This is also true for taking shots of a squirrel moving ,a bird perching after a flight or even kids in a playground playing a sport.These shots can also be taken in auto focus modes (continuous autofocus )it all depends on user's preference.
• There are many options in the auto focus modes itself (link from bullet 1 below) that one can achieve the focus and  the use of manual focus may not be required unless really required (see link from bullet2 ).

I found these very useful links listed below which explains some of the facts of auto and manual focus in depth, still learning by the way and much more to learn 🙂 Happy Clicking!

1.  DSLR auto focus modes
2. Auto Focus vs Manual Focus
3. How to get sharp photos with focus techniques