digital photography jargon


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Digital Photography Jargon T thro' Z is for....

  • TIFF
  • Viewfinder
  • Zoom

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digital photography jargon

T to Z is for.....

TIFF

Tiff is an acronym standing for Tagged Image File Format.

The Tiff digital image format is readable and editable in a wide range of display and editing software.

Tiff versus JPEG

Unlike JPEG, Tiff images can be stored in 16bit as well as 8 bit format. This gives a far greater range of tonality when image editing, with 4056 levels of tone per colour channel versus 256 for JPEG (66billion colours versus 16million for JPEG)

Tiff files can also be saved with editable “layers” intact (whereas JPEG images have to be “flat”)

Tiff files can be compressed or uncompressed – but the compression system is “lossless” meaning no image data is discarded during the compression process.

That said, the file size, even of compressed 8 bit JPEG is significantly higher than the highest quality JPEG of equivalent pixel resolution.

This means Tiffs take up more digital storage space and take longer to open and edit.

When to use Tiff

Some photographers choose to use Tiff format for archival storage of their images as (unlike JPEG) subsequent editing and re-saving does not result in image quality loss. There are however other lossless archival formats such as camera RAW and DNG that have smaller file sizes.

Tiff formats are most widely used in the commercial printing sector.


Viewfinder

The viewfinder is the cameras device to enable you to “see” the image (or a close approximation of it) as it will be recorded on the image sensor.

In digital photography there are four main types of viewfinder – some cameras will have more than one type fitted.

Non reflex optical type

This type of eye level optical viewfinder will give an approximate idea of how the image will be recorded, but due to a parallax effect – especially significant when the subject is close to the lens – may not give an accurate view.

(Parallax is the result of the viewfinder and the image sensor experiencing slightly differing fields of view. You can understand the effect by holding a finger at arms length and viewing it with just one and then the other eye – the finger will appear to move but only very slightly. Now repeat the exercise with the finger held very close in front of one eye – now when you view it through each eye it will appear to be in two completely separate positions)

This type of simple optical viewfinder has a fixed angle of view and will not reflect any “zooming” in on the subject – these viewfinders are therefore typically only found on entry level fixed focal length point and shoot style cameras.

Electronic viewfinder (E.V.F)

E.V.Fs are also mounted at eye level.

The image in the viewfinder is a digitised version of what will be captured during exposure by the image sensor.

E.V.Fs have the advantage of being viewable in low and bright ambient lighting conditions.

The disadvantage of E.V.Fs is that image resolution tends to be low making it difficult to be certain of accurate subject focus, and the image is momentarily “frozen” as it refreshes during each exposure making it difficult to track fast moving subjects during high speed “burst” mode.

L.C.D screen “Live View”

Most modern digital cameras – including Dslrs – now enable the image playback L.C.D screen, to also be used as a real-time “viewfinder”.

Screen resolution tends to be significantly higher than for E.V.Fs making it easier to assess image focus.

Live view viewfinders often have several other features and benefits, such as being articulated and rotatable making it easier to compose from high or lower than eye-level positions or for self portraits. They also may enable variable size and position of autofocus area and increased magnification of the focus area to assist with fine tuning manual focus.

The downside however is that L.C.D screens can be difficult to see clearly in bright ambient light conditions and they consume a lot of battery power.

Optical viewfinder on single lens reflex cameras

As found on DSLRs, this type of eye-level optical viewfinder receives the same light rays that are passing through the lens and is therefore bright, of the same effective resolution as normal eyesight, does not suffer from any parallax effects and will also display any change in the angle of view, or focusing by the lens.

However the image is “as seen” by the lens “wide open” and so depth of field at the exposure aperture can only be viewed if the camera has a “depth of field” preview function – the image in the viewfinder will then be significantly dimmed when small apertures are selected.

On some DSLRS the image in the optical viewfinder may give slightly smaller coverage than by the actual image sensor, but normally not less than around 95%.


zoom

Zoom refers to changing the magnification of an image by adjusting the angle of view.

Optical Zoom is the result of varying the focal length of the lens.

Digital Zoom simply displays fewer pixels from a more central part of the image sensor and is therefore more or less the same effect as cropping the full resolution image in post processing.

Any lens with variable focal length can be described as a zoom lens.

Zoom lenses are available across all categories of field of view, from super wide angle to super telephoto.

Compact digital cameras tend to use the magnification factor to describe zoom range whereas interchangeable dslr lenses quote minimum to maximum focal length.

e.g. A standard 18mm to 55mm lens has 3X optical zoom.


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