Filmmaking Basics/Camera Lenses/Depth of field

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Table of contents for All about camera lenses:

This school is: Narrative Film Production

This course is:: Fundamentals of filmmaking
This lesson is:: All about camera lenses

The pages of this lesson are:

Camera lenses - The impact of camera lenses

Pop Quiz #1 - Is there a difference? - 2 points

Lesson page - The basic moods of lenses

Pop Quiz #2 - "Oh, dear! What should I do?" - 2 points

Lesson page - Positioning the camera

Lesson page - Depth of field

Over-the-shoulder shots

Can you see the difference?

Depth of field means the distance where the picture is in focus (and not a blur.) Depth of field is measure by how close and by how far in image is in focus.

Below are shots with (on the right) and without (on the left) a limited depth of field.

Another way to say this is the shots on the left have unlimited depth of field and the shots on the right do not.

These are shots from Mok without and with depth of field

Unlimited depth of field

A extreme wide-angle lens

This is a 14mm lens for 35mm motion pictures, That is a very wide-angle lens. This lens can see 74 degrees of scenery (measured horizontally.)

A wide angle lens has a huge depth of field. Even with a normal wide angle lens on a video camera, the depth of field is almost infinite. On a video camera with a super wide-angle adapter, the picture above is exactly what you would see. The glass on a video camera is so narrow, it acts like a pin hole camera which has an infinite depth of field.

Therefore, on most video cameras, you cannot use depth of field to isolate one actor from the others.

Limited depth of field

2.8 f-stop

A wide-angle lens has little control over the depth of field. Yet, because a wide-angle lens accentuates distances so much, the effect of limited depth of field is larger that you might think.

That is why you must always look through the actual lens to see the depth of field. It is too hard to predict just by using tables, etc.

Unlimited depth of field

A slight wide-angle lens

This is a 29mm lens for 35mm motion pictures which has a 40 degree view horizontal.

Remember that the focal length (such as 29mm) is a function of the size of the film frame. Movie cameras, still film cameras, video cameras all have different frame sizes so you cannot compare focal lengths directly.

Even the angle of view is measured differently. Still cameras measure the angle of sight across the diagonal, not the horizontal.

Limited depth of field

2.8 f-stop

A slight wide angle lens brings the people closer together than a super wide angle lens.

Therefore, limiting the depth of field by using an f2.8 f-stop helps isolate the girl from the other actors.

As you can see, this is a much more interesting picture than the picture on the left.

Unlimited depth of field

A mild telephoto lens

This is a 50mm lens for 35mm motion pictures which has a 24 degree view horizontal.

Now that the actors are brought closer together, this shot looks crowded.

Limited depth of field

2.8 f-stop

See how much better this shot looks which you limit the depth of field. You get this limited depth of field by opening up the lens to f2.8.

Remember that a video camera has a small aperture so you will see an unlimited depth of field like the picture on the left. A typical video camera cannot give you the picture above.

Unlimited depth of field

A portrait telephoto lens

This is a 85mm lens for 35mm motion pictures which has a 14 degree view horizontal.

This is the lens used for serious portraits. Old time portraits did not use such a powerful lens but now this is concidered normal for a portrait.

Limited depth of field

2.8 f-stop

As with the previous set of pictures, this scene looks crowded. You need to limit the depth of field to get a better picture.

With a video camera which has a small aperture, you will see an unlimited depth of field like the picture on the left.

Unlimited depth of field

A strong telephoto lens

This is a 135 mm lens for 35mm motion pictures which has a 9 degree view.

Limited depth of field

2.8 f-stop

With a video camera which has a small aperture, you will see an unlimited depth of field like the picture on the left.

Unlimited depth of field

A extreme telephoto lens

This is a 180 mm lens for 35mm motion pictures which has a 7 degree view.

Now the camera lens is so powerful, it clearly separates the actors without limiting the depth of field.

What is not obvious is the camera has been more far away from the actors when you have a telephoto lens. Also any bounce in the camera will be magnified and look awful.

Limited depth of field

2.8 f-stop

Because a telephoto lens compresses the image so much, the depth of field is smaller than you might think.

Therefore, measuring the exact depth of field become difficult and critical. This is much harder for the focus puller to control. But it does make a beautiful picture.

Let's take a quick quiz