explain about iso?

Answer 1

Higher numbers are for darker lighting conditions, but might give you some visible artifact in the image. Higher ISO lets you use faster shutter speeds in regular lighting conditions, also, and this is helpful if your subject is moving, such as at a sports event.

Lower numbers are for better lighting conditions (more light) and will give better detail.

If you have no other reason to change the ISO, try to stick to 100 or 200 and you will like your pictures better. 400 is still usually pretty good, but if you have 800 and use it, you will start to see some little flecks in the images, especially in the darker portions.

Answer 2

ISO is a measure of sensitivity to light. Basically, how long does my camera sensor (film) need to be exposed to the scene to absorb enough light for my photo to appear.

Generally you should use a low ISO number, below 200. Depending on the type of camera you have, beware that any ISO setting above 200 may give you very grainy (lots of tiny coloured dots) photos so experimentation will be necessary.

A low ISO, eg 50, 80 or 100 means very insensitive to light, therefore it takes longer for the photo to be exposed.

A high ISO, eg 800 or 1600 means it's very sensitive to light, therefore it takes less time for the photo to be exposed.

Photos taken at low ISO are smoother and have less noise and dotting than photos taken at high ISO. That's just the camera gods' way of preventing us from using high ISOs - because then life would be too easy for us photogs.

If that explanation doesn't quite work, consider the analogy that taking a photo is like filling a bucket of water using a hose.

LIGHT is the WATER

APERTURE is the diameter of the HOSE
(big hose fill fast, little hole fill small)

SHUTTER is how long the HOSE is left OPEN
(more water the longer it's open)

Then ISO is the size of the BUCKET you're filling.
(low ISO big bucket, high ISO small bucket)

Now that should either make it all crystal clear, or totally confuse you. ;)

Either way, may I recommend Bryan Peterson's simply excellent book "Understanding Exposure" that explains the triumvirate of APERTURE, SHUTTER, ISO.

Answer 3

ISO refers to the "speed" or sensitivity of film. ISO 25 would be very slow film, and 800 would be faster film. Each doubling of the ISO number reduces by half the amount of light needed to obtain the same exposure. ISO 50 is twice as fast as 25, 100 is twice as fast as 50, etc.

This speed comes at a cost. In films, higher speed film is usually grainier. A close look will usually reveal that pictures taken with high speed film will have a speckled look. That's the grain.

In digital cameras, the ISO number still refers to the speed or sensitivity, but since there's no film, it's the camera's light receptor. Digital cameras usually select the ISO speed automatically, but many models let you select the speed manually for various lighting situations.

Like film, higher ISO speeds in digital cameras usually result in grainy looking pictures, but in digital cameras it's refered to as digital noise. Look for mottled looking sections of the pictures, usually in shadows, or look at solid colored objects, especially those which aren't well lit. Digital cameras can employ electronics, to analyse the pictures to reduce the effects of digital noise.

Answer 4

iso is international organisation for standardisation. there are 9000 rules to be followed to get that iso certificate.a company which owns iso certificate only can export it's products.

Answer 5

An ISO image (.iso) is an informal term for a disk image of an ISO 9660 file system. More loosely, it refers to any optical disk image, even a UDF image.

As is typical for disk images, in addition to the data files that are contained in the ISO image, it also contains all the filesystem metadata (boot code, structures, and attributes). All of this information is contained in a single file. These properties make it an attractive alternative to physical media for the distribution of software that requires this additional information as it is simple to retrieve over the Internet.

Some of the common uses include the distribution of operating systems, such as Linux or BSD systems, and LiveCDs.

Most CD/DVD authoring utilities can deal with ISO images: Producing them either by copying the data from existing media or generating new ones from existing files, or using them to create a copy on physical media.

Most operating systems (including Mac OS, BSD, Linux, and Windows with Microsoft Virtual CD-ROM panel) allow these images to be mounted as if they were physical disks, making them somewhat useful as a universal archive format.

Console emulators, such as ePSXe, and many other emulators that read from CD/DVD, are able to run ISO/BIN (and other similar formats) instead of running directly from the CD drive. Better performance is achieved by running an ISO since there is no waiting for the drive to be ready and the hard drive I/O speed is many times faster than the CD/DVD drive.

A copy of CD contents, stored as an .iso file, is made this way: the ripper searches for the sectors of the CD that have been used, say 251,000 for instance (there are 330,000 sectors on a 74 min CD and 360,000 sectors on an 80 min CD). Each sector is copied to the .ISO file, one by one. For CDs each sector is 2048 bytes, the .ISO file should then be of size 251,000 x 2048 = 514,408,000 bytes.

Answer 6

An ISO image is an informal term for a disk image of an ISO 9660 file system.