Icon

A thing or symbol which represents something else.  In computing it is a pictogram or ideogram which is a small image displayed as a link or route to an object or function.  This is not to be confused with a thumbnail, which is small version of an image used to represent it.

Image

This word has many uses and meanings, so you need to be careful with it.  For example it can be a verb or a noun.  In optics an image is formed by a lens or mirror and has precise properties.  In photography we normally mean a photograph which may be a print, negative or slide and in digital an image file which can be projected or viewed on a monitor.

To illustrate some of the difficulties consider a photographer who takes two photographs from the same viewpoint with the same settings, are these the same or different images.  If he makes a copy of the file, is that a different image?  How about two different photographers using the same tripod holes?  Answers on a postcard.

Image file types

The normal method of naming files in most operating systms, including Windows, Mac-OS and Linux is a filname and file extension.  There are several different image formats and to distinguish them they are given different file extensions.  The most important are:-

image stabilisation

This is a technique used in DSLRs where the lens or camera includes electronics to compensate for movement of the camera (hand shake) during the exposure.  Different manufacturers use different names for this so you may find it as VR for vibration reduction.  At the present time this is an evolving technology and newer models give better performance than older ones; price may be a factor too.  The effect is that it lowers the limiting shutter speed at which you can hand hold a shot, before needing a tripod.

The role of thumb for hand held shots is the reciprocal of the focal length used, so a 50mm lens can be hand held at 1/50th of a second.  This is only a rule of thumb, some people are better than others at this.  However IS will improve this by a number of f-stops.  If you have an IS lens you should experiment to find what your limits are with and without IS.  IS is designed to eliminate hand shake, if you are using a tripod it will not improve focus and can even make it worse through hunting, so the recommendation is to turn off IS when using a tripod.  However I would think it might help in strong winds if you get vibration unless you have a very sturdy tripod.  c.f. wikipedia.

Interlace

A video and TV technique of sending odd scan lines on one frame and even scan lines on the next.  This has the effect of doubling the apparent frame rate without increasing the bandwidth requirements.  Not used with 1080p or 720p and not normally used in still photograpy.

intrinsic

belonging naturally, essential, of its own nature.

ISO (International Standards Organisation)

So what has that got to with Photography?  They have their finger in every pie.  Let me tell you a story.

When we had film cameras, we had films to put in them, and you could buy different films for different things; monochrome for Black and White photography, colour film for colour prints, transparency film for slides.  These were usually described by makers numbers, for example Ilford's FP4 (tears of nostalgia to the eyes).  However you could also get fast films and slow films and so that people knew what they were buying these were standardised by the American Standards Association (who also standardised lots of other things) and given ASA numbers.  So when you bought your 100ASA film you could use your exposure meter and work out how to set your camera.

Things move on and now we have digital cameras instead of film cameras and we have the ISO (in Geneva) who look after things on a world wide basis, but it is more or less the same.  The ISO setting equates to film speed; the higher the number the faster, i.e. more sensitive.  Of course it is not the same as film, when you change your ISO setting it is not like using a different film, the sensor is not exchanged for a faster one.  You still use the same sensor, but so that it can record a bigger number the signal is amplified and amplification brings noise which is the downside of using too high an ISO setting.