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COM60203 - Focus/Depth of Field

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Wai Leong

on 17 September 2014

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Transcript of COM60203 - Focus/Depth of Field

Known as One-Shot AF (Canon) and Single-servo AF (Nikon), use this when you’re shooting static subjects.
It’s the default mode, as it won’t let you take a picture until the camera gets something in focus.
Single shot AF is perfect for most shooting situations, unless you move closer or further away from the subject after locking focus.

When to use single shot AF

Capture the water splashing effect.
2 snapshot

Depth of Field – Reflection 3

Focal length refers to the amount of magnification that a lens has.
A wide-angle lens- great depth of field for deep focus and A telephoto lens- shallow depth of field for less range of focus in the picture.

Focal Length

Can be found in mostly inexpensive and older cameras feature.

Zone Focus

Sometimes advertised as Focus-free lenses, are designed to keep everything in focus from a minimum distance of 3,4, or 5 feet (0.9, 1.2 or 1.5 meter) to infinity.
As long as you are no closer to your subject than the minimum distance indicated in the camera’s instructions, everything you see in the viewfinder will be in focus.

Fixed Focus

No focusing adjustments can be made.

Fixed Focus

But why would you want to stop autofocus? If you’re tracking a moving subject and for some reason it becomes obscured, you can temporarily switch off autofocus to preven the lens from refocusing.

When to use AF lock

Manual focus (MF) requires you to manually focus the lens by twisting its focus ring. It’s useful in low light photography, when the camera’s autofocus system can struggle, or when subtle focus adjustments are required, such as in close-up and still life photography.

When to use manual AF

AI Focus AF (Canon) and Auto Select AF (Nikon) are ‘intelligent’ modes that switch from single shot to continuous autofocus when the camera detects a moving subject, and vice versa.
It’s a good choice when you’re photographing unpredictable subjects – if taking portraits of a bird that might take off, for example.

When to use auto select AF

AI Servo AF (Canon) and Continuous-servo AF (Nikon) adjusts the focus as long as you press the shutter release.
It’s the best mode to use when shooting moving
The focus position is never locked, and the camera will let you fully press the shutter to take a picture even if the subject isn’t in focus.

When to use continuous shot AF

Just aim main subject within the focusing frame in the center of the view finder and press the shutter release button.

AutoFocus (AF)

The basic rule: Focus on the most important part of
your picture.
With portraits, for instance, focus should be on the eyes of your subject.


As you can see from the image, a wide angle lens(having small focal length) has widest range while the reverse is true for telephoto lens.

Focussing For Depth of Field - The Effect With Different Lenses

Depends on several factors:
Focal length
F/stop used
The distance at which the lens is focused.

Depth of Field

After focusing on your main subject and making an exposure meter reading to determine the f/stop and shutter speed settings for a proper exposure, check the lens depth of field scale.

Depth of Field

The scale consists of matched pairs of numbers that correspond to f/stops.
Located on either side of the point of focus indicator on the lens.
The scales vary according to the lens (wide-angles, telephoto)

Depth of Field

Landscapes, for example, where everything is in focus have good or deep DOF and a macro shot where only a small part of the image is in focus has poor or shallow DOF.

Depth of field is the term used to describe the amount of your image that is in focus.
Larger apertures giving shallow depth (not much in focus) and vice versa.

Focussing for Depth of Field

Instead of exact focusing distances, three symbols are marked on the lens focusing ring, the photographer manually adjusts the focus according to whether his subject are very close, nearby, or at a distance.

Zone Focus

You can usually customise the operation of both of these buttons, such as removing the autofocus from the shutter release altogether or enabling the rear AF button to stop autofocus instead.

All digital cameras let you activate the autofocus system by lightly pressing the shutter-release button, but many also feature an AF button that does the same thing.

When to use AF lock

The greater the distance, the fewer or meter designation given.
The point or distance at which everything beyond will be in focus, INFINITY, is indicated by elongated eight on its side, ∞ or INF.

Manual Focusing

The focusing ring on all SLR lenses is engraved with a “Distance scale” to indicate the point of focus (feet/meters).

Manual Focusing

Automatic modes (A)
Single shot (S)
Continuous Focus (C )

AutoFocus (AF)

To autofocus an SLR, aim the camera so that the subject is at least partially located within the “Focus Detection Area” marked by a circle or brackets in the view finder, the micromotor will be activated once the shutter release pressed.

AutoFocus (AF)

Is common to most 35mm compact cameras, APS cameras.
Permanently mount lenses and cannot focus manually.

AutoFocus (AF)

Most convenient is the DoF scale because it is engraved on the lens barrel and available for quick reference.

Depth of Field

Lecturer & Tutorial :
Ms. Leong Wai Kit

Semester 4, Year 2
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