What is ISO speed? Is it good to have higher ISO Speed?

Question

for example, my camera has ISO speeds of:

AUTO

50

100

200

400

I would also like to know the difference between Superfine and fine pictures.

Answer 1

ISO is a definition of how quickly your camera absorbs light. The higher the number, the faster it absorbs light.

Now, one would think: "higher ISO equals brighter, faster, better shots" right? Not entirely the case. The higher your ISO, the more "noise" you encounter. Noise is little marks of discolouration in solid areas of colour. So for example, it a large area of black or grey, you'll see flecks of red, blue, green, yellow, etcetera as you look at it. The higher your ISO, the more pronounced these flecks will be.

Most current digital cameras try to combat this, however point & shoot digital cameras cannot combat it overly well. Better than they used to, but still not all that well.

The difference between "Superfine" and "Fine" is as follows. When your camera takes a picture, it converts it into a JPeg image. In doing so, it has to compress and chop off a bit of information. These "fine-ness" settings tell the camera to keep from removing a certain amount of information. Superfine will remove less information and produce larger files than Fine, just as Fine will remove less information and produce larger files than Normal.

Hope that has helped you some.

Answer 2

ISO is the measurement of the sensitivity to light of a light sensitive surface, whether film or digital sensor. The lower the ISO the less sensitive the light sensitive surface. The higher the ISO the more sensitive. The lower the ISO the better the image quality. At higher ISO settings the image begins to lose quality.

To achieve a proper exposure requires that the aperture (f-stop) and shutter speed be set properly based on the available light and the ISO set.

Lets look at some hypothetical examples to show the ISO-aperture-shutter speed interaction. We'll be shooting on a clear, sunny day.

ISO 50

f2 @ 1/250

f2.8 @ 1/125

f4 @ 1/60

f5.6 @ 1/30

f8 @ 1/15

f11 @ 1/8

f16 @ 1/4

ISO 100

f2 @ 1/500

f2.8 @ 1/250

f4 @ 1/125

f5.6 @ 1/60

f8 @ 1/30

f11 @ 1/15

f16 @ 1/8

ISO 200

f2 @ 1/1000

f2.8 @ 1/50

f4 @ 1/250

f5.6 @ 1/125

f8 @ 1/60

f11 @ 1/30

f16 @ 1/15

ISO 400

f2 @ 1/2000

f2.8 @ 1/1000

f4 @ 1/500

f5.6 @ 1/250

f8 @ 1/125

f11 @ 1/60

f16 @ 1/30

Although the example used may never be duplicated in real life, the relationship holds. As less light is admitted by the lens at each successive f-stop (f2.8 admits 1/2 as much light as f2; f4 admits 1/2 as much light as f2.8, etc.) our shutter speed decreases since the light must expose the light sensitive surface longer.

If you want to prove the relationship, mount your camera on a tripod, place it in Aperture Preferred (so you can set the f-stop and let the camera set the shutter speed), set the ISO to 50 and your lens at its widest aperture (f2, f2.8, f3.5 - whatever it is) and focus on an evenly illuminated white wall. Look at the shutter speed and record it. Do this with each f-stop and all 4 ISO settings on your camera. This experiment will prove to you that the example I used is a valid representation of the ISO-aperture-shutter speed relationship.

Answer 3

The higher the iso number the less light the camera needs to operate.

A high iso will let you shoot in lower light, or allow a smaller aperture or faster shutter, should the occassion demand it.

This will be at the sacrifice of some image quality, the higher the iso, generally the less vibrant the colour, the less fine the detail, and at extreme ISO settings, there can be a grittiness to the pictures.

Superfine and fine refers to the compression system in JPEG mode, superfine is less compressed and gives a better image, but means you will fit less images on the memory card.

JPEG is a fairly lossy compression system, so I would opt for SUPERFINE, expecially if used in tandem with a high ISO number.