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Chapter 5

Depth of Field

Depth of field is the distance in front of and behind the subject that can be considered sharply focused. This distance, or range, varies. Factors that affect depth of field are:

    1. How far away the subject is.

    2. The focal length of the lens you are using. Lenses of short focal length produce more depth of field than longer lenses.

    3. The f-stop. Large f-numbers (f8, f11, f16, etc.) generate greater depth of field than do smaller f-numbers (1.8, f2, f4).

Perhaps the best example of the use of this is a picture where the background is blurred while the foreground is rendered perfectly sharp. This would be made with the aperture set at f2. With shallow depth of field only the focused subject is sharp.

Another excellent example is the photo that is perfectly sharp from ten or twelve inches to infinity. This is accomplished by setting the aperture to f16, or f32.

The depth of field on a wide angle lens at this aperture can be from one foot to infinity.

Here are some photos taken with a 35mm Nikon camera fitted with a 150mm Zeiss lens made for the Hasselblad Camera and attracted to the Nikon with a Spiratone adapter.

Remember, what we are talking here about a zone of acceptable sharpness. That's important. The camera lens is always focused on the subject, in front of and behind the subject the focus becomes less sharp. This loss of sharpness is gradual, fading into blur.

Can you see depth of field before taking the picture? Yes you can.

To actually see the depth of field change as you look through the camera you need to stop down the lens. To do this use the depth of field preview button.

The depth of field preview button exists because the camera is designed to keep the aperture wide open until the picture is taken. In this way you always have a bright viewfinder to focus and frame the subject. To actually see the depth of field you must stop the lens down to the aperture that you will make the exposure at. Hence, the depth of field button preview button.

NOTE: When you Press the depth of field preview button the image in the viewfinder will become dark at small apertures. that is normal because you restrict the light into the camera at small apertures.

You may have trouble seeing the depth of field at small apertures initially. With practice you will do just fine.

This is a skill well worth the time it takes you to master. So, take you time and get this skill in your bag of tricks. It will take your photography to new heights.

Soon, you will use this technique when you begin creating pictures before you take them.w

Go take pictures. Use Depth of Field, see it, understand it. Make it part of your photographic toolbox. You will never be sorry. Know this short chapter and the camera becomes an extension of your mind, of your intellect. Of you.

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