A questions about ISO?

I'm not sure how much you know about photogtaphy so i'll try to explain this as best as i can.

ISO is film speed. With digital it controls the speed of which your photos are taken. If its darker outside you would set your ISO to something like 800 or 1600. This will lessen the quality of your photos and you will see more grain. If you are photographing in bright sunlight its ok to shoot at ISO 100. Your images will look better when you are using a lower ISO. A pretty standard ISO is 400.

If you were outside in the evening you could change your ISO to 800 and still take hand held photos. If you set it on 100 you would not. Your camera determines the fstop and shutter speed depending on what ISO you are using.

Say you're shooting at 100 in the evening. Your shutter speed might be something like 1/8 of a second- u cannot shoot this handheld, you would get camera shake. Then if you change to 800 your shutter speed might be something like 1/100 of a second which you can shoot with camera in hand.

Hope this helps

If I remember correctly it stands for International Standards Organization- a body that sets standards on products for manufactures and consumers.

In terms of photography, it directly relates to all film/digital cameras. As stated by others, by selecting the ISO speed you tell the camera how sensitive to set the exposure meter. The higher the ISO, the more sensitive to light and vice versa. A slow speed such as 25, 50, or 64 yields smaller grain or noise patterns. This allows a larger picture before the grain/noise becomes a problem. Medium speed is the 100 to 200 range. And 400 and above is considered fast.

No one ISO is perfect. It comes down to what you are shooting and what the end result you want is. Most people do just fine with medium speed film and the first high speed one of 400.

Shutter speed is how long the shutter stays open to let the light come in Aperture is how wide the opening is. (Low F number means wide opening) ISO is how sensible the sensor is to light. (High ISO means high sensitivity)

Should you always take pics at ISO 80 ?

A short answer would be yes, but in fact there is more to it. Basically your goal is to take the pictures with the lowest ISO possible. That isn't always possible tho, that's why you can boost the ISO. For your night shot, if you have a tripod, try taking the picture at ISO 80(using slow shutter speed), if your scene is too dark, boost the ISO. Better even, if you can, take a picture at each ISO your camera allows and see for yourself on your computer, but keep in mind you'll most likely have to adjust the shutter speed in order not to overexpose the scene... Actually if your 1st shot at ISO 80 isn't underexposed, you'll have to change it for each raise in ISO.

Everything being constant, every time you double the ISO, the shutter speed should be divided in half. At ISO 100 a shutter speed of 8 seconds will be 4 at ISO 200 and 2 at ISO 400.

My recommendation is simple, use the smallest ISO number possible in order to keep noise at acceptable level.

The higher the rating of ISO, the more sensitive the film.

Ina darkened room a high ISO film will capture more of the available light thereby enabling a faster shutter speed which will help prevent blurry photos.

The opposite applies with lower ratings of ISO.

Basically high ISO film is better where available light is poor.

A low ISO rating is better for bright sunlight.