Digital Photography Jargon

c

Digital photography C is for ........

Camera Shake

Camera shake describes the cause of blur as a result of unintentional movement of the camera during exposure.

Cure the problem by

• Holding the camera correctly – tuck your elbows firmly against the side of your body, left foot half a pace in front and shoulder width stance.
• Smoothly depress the shutter button – don't jab it
• If its windy – try and stand in a sheltered spot
• If available use the built in image stabilisation system of the camera or lens
• If you know the 35mm focal length equivalent for your lens – use a shutter speed of faster than the reciprocal of the focal length (e.g. if the 35mm focal length equivalent is 200mm - you will need shutter speed of 1/200th second or faster.) If necessary raise the ISO sensitivity to allow this.
• Use a tripod or other stable base and activate the shutter via remote control or the self timer. (Some image stabilisation systems should be switched OFF when using tripods.
• On Dslr use the mirror lockup facility to avoid the small shock as the mirror moves when you press the shutter.

Circles of confusion

Your lens will focus only subjects exactly on the focal plane to precise points ( and therefore sharp images) on the camera sensor.

Light coming from subjects either in front of or behind the focal plane will be converging or diverging cones of light dissected by the image sensor – and thus are recorded as fuzzy blurred circles. These are called circles of confusion.

When the recorded image is enlarged for display on a print or screen, the circles of confusion also become enlarged.

Depth of field limits are defined by when, after enlargement, the detrimental effects of circles of confusion upon sharpness are evident.

compact camera

A Compact Camera is defined by having non interchangeable lens and an electronic viewfinder.

Pros

• Being small and light they are convenient to carry
• They are more discreet
• Typically are lower cost (than Dslr)

Cons

• Image quality is typically lower than is possible with a Dslr due to smaller sensor size and lower quality optical components.
• Smaller image sensors also limit creative control – particularly when shallow depth of field or high ISO sensitivity is desired (with low light, non flash photography for example)

Summary – Despite the limitations to image quality and creative control, GREAT photos can still be achieved with compact cameras.

See the article top ten tips for taking digital photographs for more advice.

Composition

Composition describes the arrangement of everything included in the final image (so composition can be determined to an extent by cropping during post processing)

There are no absolute rules for composition, but there are some general guidelines to consider.

• Check carefully all that is framed in your viewfinder (or if you have time to repeat the shot – review the image on your camera's lcd screen). It is all too easy to fail to spot distracting objects that detract from the image you want to capture.
• Decide which part of the image is most important – this is called the focal point – and consider placing this on one of the “thirds” - one of the four intersecting points of an imaginary grid that divides the frame into thirds, vertically and horizontally. (Many cameras give you the option to display a rule of thirds grid on the viewfinder to aid composition)
• If your focal point is a moving object, or a person (who is NOT looking directly at the camera) allow some extra space to the side in the direction of the movement or the gaze of the person – this avoids the sense of “crowding” in the image.
• Try and give some balance to the image by including more or less equal space to light and dark areas.

Remember – all photos primarily boil down to just two things COMPosition and ExpOSURE – think of having good COMPOSURE and you won't go far wrong.

See also

Digital photography basics

Digital photography exposure explained

crop factor

Crop Factor is the ratio between the diagonal dimension of an image sensor and that of a 36mm x 24 mm full frame sensor.

It describes the amount of the image circle that is recorded on a smaller sensor compared to a full frame sensor for a given focal length.

Small sensors have high crop factors.

The higher the crop factor, the shorter the focal length to achieve the same field of view and magnification. As short focal lengths mean smaller aperture diameters – this limits the ability to create shallow depth of field with small sensors.

When using a lens designed for a full frame sensor on an a Dslr with a smaller sensor – multiplying the focal length by the crop factor gives the effective focal length/angle of view/magnification.

Eg a 200mm lens mounted on a Dslr with a crop factor of 2.0 – will give the same magnification as a 400mm lens mounted on a full frame camera.

see also

focal length angle of view and crop factor

useful links from digital photography jargon c

Ten top tips for taking digital photography

Digital photography basics

Digital photography exposure explained

Focal length angle of view and crop factors

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