Sunday 8 January 2017

Camera Terminology Explained Series, Part 4 (I-J)


Image Resolution

Image resolution is the detail an image holds.  The higher the resolution, the sharper and clearer the image becomes.  For cameras, image resolution is measured in pixels, with the more pixels giving a better image.  The amount of pixels is particularly important if you want to print out your photos and enlarge them.  Generally speaking, the higher the amount of pixels in your image, the larger print-out you can have that will still look sharp.

Cameras are described in ratings by megapixels.  The higher the megapixel, the sharper and clearer the image will be.  However, you need to bear in mind that the higher the megapixel, the more space each image will take up on your memory card.


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Image Stabilisation (IS)

Image Stabilisation is a system built into a camera or lens that helps to reduce the effects of camera shake or movement, which is particularly useful when using longer focal lengths or slower shutter speeds.

Image Stabilisation won’t work for every situation.  It may struggle with fast moving subjects, but will produce good results correcting slight camera shakes.  Image Stabilisation helps to prevent the effects of blurred images which is particularly more pronounced when using a long zoom lens or using a slow shutter speed for low light conditions.

There are 3 different types of Image Stabilisation, utilizing either hardware or software inside the camera or lens:  Optical IS, Digital IS, and Dual IS.

Optical IS uses hardware to correct the effects of camera shake.  This type of Image Stabilisation typically uses a built in gyro-sensor that measures any movement which it passes through a stabilisation microchip to the charge-coupled device, which shifts slightly to compensate for the movement.

Digital IS basically increases the ISO sensitivity, so that the camera can create an image from lower light and therefore shoot at a faster shutter speed, which helps to prevent camera shake in the first place.  However, increasing the ISO sensitivity can introduce more noise into the image which will lower the quality and sharpness of the image.

Some cameras use built-in software to edit the image after the picture has been taken to try to reduce camera blur.  Some manufacturers also refer to this technology as Digital IS.

Dual IS uses a combination of Optical IS and Digital IS, i.e. it uses hardware/gyro-sensor together with increasing the ISO sensitivity.

Some manufacturers also refer to Dual IS when they have image stabilisation built into both the body of the camera and in its lens(es).


ISO & ISO Noise

ISO is the measurement of the camera’s sensitivity to light.  ISO is rated by numbers, e.g. 100 ISO, 200 ISO, 400 ISO and so on.  The higher the ISO number, the more sensitive to light the camera is.  Therefore, a higher ISO number will allow you to shoot in lower light conditions.  However, bear in mind that the higher the ISO speed is, the more ISO noise you will introduce into your images, i.e. the grainier your images will become.


JPEG/JPG

Often viewed as the .jpg extension, JPEG is an image file format that is compressed for digital images.  Because it is compressed to save space, some loss of image quality is experienced with JPEG.  The more compressed the image is, the smaller the file will be, but the lower the quality of the image will end up being.  Some cameras allow you to adjust the degree of compression giving you a choice of the best combination of storage size and image quality.


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Further reading/articles in the Camera Terminology Explained Series:

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