Depth of Field Pt. 2
In depth of field pt1 where we used a shot or wide lens and showed you how short focal lengths have a large depth of field. Now let's look at it through a long lens. As you increase your focal length or zoom your depth of field gets less and less. This is because long lenses always have a shallower depth of field than short ones.
This makes long lenses great for making a soft fuzzy background. You have to understand how to combine depth of field with where to focus if you want to control image sharpness.
Aperture size is the main depth of field control - but focal length and how far away you are from the spot you've locked your auto focus onto also makes a difference.
We're still using our bit of red tape in this exercise just as we did in part 1. Take a look at these images. The top image was taken with a wide aperture of about f5.6 and the bottom one at a much smaller f45. Both are focused on the red tape and you can clearly see the change in depth of field.
However even at the smallest aperture which gives you the most depth of field it's obviously not sharp all the way to the hedge on the other side of the garden. Go out and practise this for yourself - it doesn't matter what your practise pictures look like but it's important you understand how to do it.