Photography Tip Thursday #3 ~ Depth of Field

Hi everyone and welcome back to my Photography Tip Thursday. I know I'm getting this out late but believe me when I say it was busy today at 21 Rosemary Lane. Now here we are so lets get down to this week's lesson.

As you may remember last week we talked about the three exposure modes photography that determine your photographs final outcome. They are...

Shutter Speed

I also discussed a little bit about something called depth of field. Simply stated depth of field is the area of the photograph, front to back, which is in focus. For example last week I used a picture of fruit to demonstrate the meaning of depth of field.

There is deep depth of field which will look like this...

Every part of the photograph is in focus, both the apple and the fruit lying behind it.

A photograph with shallow depth of field will look like this...

The apple is in perfect focus while the grapes and lemon look fuzzy in the background.

There are 3 factors which will affect the depth of field in your photographs and they are...

1. The size of the aperture or the setting of the f-stop
2. The distance from the camera to the subject
3. The focal length of the lens

So let me talk about focal length of the lens or we can say short (wide angle lens) versus long (zoom or telephoto lens). How does length focal lens affect your pictures? Well when using a short lens you will take in more or the scene you are shooting and the smaller it will make each object in the picture. Conversely when you use a long lens you will see less of the surrounding elements and the main object you are shooting will seem closer. My text book had a great way to clarify the difference between the two types of lenses. Take your forefinger and your thumb and create a circle with them. Hold your fingers close to your eye, or lens. You could probably view most of your surroundings with your fingers close to your eye. Pick out an object to focus on with your fingers still close to your eye...now slowly move your fingers away from  you and what happens...the surrounding aspects of the scene begin to move to the outside of the circle, and the object you have focused on begins to look larger in size. This is exactly what happens when you change from a short to long lens.

Now that you have this concept the next question is how does lens length affect depth of field? When using a short lens to shoot an object you are capturing more of the scene and with more scene in the photo you have a better idea of the distance between objects in the foreground verses objects in the background. Let me see if I can give you an illustration.

There's our doggy Buster lying on the couch where he is so not suppose to be, but for the sake of this tutorial I will let it go. We can see the plant the the coffee table in front of Buster, this is a deep depth of field. In this field you can get a pretty good idea of the distance between Buster and the plant, but look at what happens to that relationship when I zoom in on the plant...

As you can see it is actually difficult to tell how far apart the dog and the plant are because the depth of field has been made shallow by using a longer lens.

Here is the exercise we did in class to demonstrate depth of view. Trying to keep the roll of paper towels fairly close in size in each picture, we shot the photo on the left close and using our wide angle focus. Then we were asked to back up and zoom in on the paper towels. You can see as we lengthened our focus the depth perception of how close the paper towels are to the door behind it has changed. The paper towels in the photo on the right actually looks closer to the door.

The next factor affecting depth of field is the proximity of the camera to the subject. The closer the camera is to the subject the larger the subject will appear in comparison to the objects in the background. This creates a bit of distortion but also can be used as a creative tool.
Below a photo of a baby's foot. Notice the size of the foot in comparison to the rest of the baby's leg. Also the background is a bit blurred out. This short lens created a shallow depth of field due to its proximity to the main subject.

stock photo : Close up of baby foot. Shallow depth of field.

The third way of controlling depth of field is aperture or F-stop setting.The smaller you go with your F-stop setting say from f2 - f16 the greater is your depth of field. So as the aperture becomes smaller less light is allowed in and the sharper the image will be. Let's go back again to my fruit pictures. The first shot below has a an aperture setting which is large say f-2.8 (remember the size of the opening of the aperture has an inverse relationship with the f-stop number.) thus creating a shallow depth of field.

This next photo has a tight or small aperture setting thus creating a deep depth of field with all components of the picture in focus.

Remember what I said last week was that the only way to really wrap your brain around depth of field is to get out there with your camera and start experimenting. And that is exactly half of what my first photography assignment is! I need to produce two photos showing a change in depth of field. I need also to consider the 7 C's of creative image making which was covered in lesson one of this series. So you may want to give it a whirl yourself. Play with the aperture setting, focal length and proximity to subject so to get a working handle on these concepts. Practice practice practice!

And have a great week!!!

Linking up to these parties this week...

Chic on a Shoestring Decorating

1 comment:

  1. Hi Barbar I am Andi from the Wednesday Baker. I am following along with you also. I am interested in your photo talk. I have a nikon coolpix L120 and know about nothing. Was going to take a adult ed class this winter and nothing was offered. So I play. I will be back to read and hopefully learn. Thanks for visiting my blog and nice to meet you andi


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