ISO

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Animal

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Hi
Is there anywhere a guide on this forum about ISO's etc

I have slowly worked out all the rest of the stuff but for some reason cannot get my head around the ISO's...

Am I just being thick or is there a easy answer to what they are and do?

thanks
 
Hi there, ISO is just like the old film speeds. The higher the ISO the quicker the shutter speed you can use. So if you had 1/500th shutter speed at ISO 100 if you set ISO 200 the shutter speed would go up to 1/1000 and vica versa. However the higher the ISO the more "grain" shows up in your photo's.
 
Basically its just how sensitive to light the sensor or film is - a low number ie 100 needs a Longer exposure time than a high number 800 would to produce a image exposed the same, so a increase in the ISO will also allow you to increase either the shutter speed or decrease the aperture and still get a correctly exposed image.


Too llate type faster.
 
did you read Robc's thread in this section on- Appature, Shutter and ISO-
helped me get my head round it more
 
fabs said:
ISO increases light sensitivity. In other words, the higher the iso, the more light is let in.......
Click to expand...

That is incorrect. ISO changes how sensitive the sensor is to the light that it receives.

Aperture and shutter speed control how much light is let in; aperture by varying the size of the hole in the lens that the light comes through, and shutter by varying the length of time that the light is let in for.
 
Scarecrow said:
That is incorrect. ISO changes how sensitive the sensor is to the light that it receives.

Aperture and shutter speed control how much light is let in; aperture by varying the size of the hole in the lens that the light comes through, and shutter by varying the length of time that the light is let in for.
Click to expand...
Quite an important distinction there I think! :clap:
 
Scarecrow said:
That is incorrect. ISO changes how sensitive the sensor is to the light that it receives.

Aperture and shutter speed control how much light is let in; aperture by varying the size of the hole in the lens that the light comes through, and shutter by varying the length of time that the light is let in for.
Click to expand...

Correct - the ISO dial is pretty much a volume control for the amplification circuit that takes the signal from the sensor and passes it to the processor. So, the lower the ISO number, the lower the gain, and the lower the noise. As you increase the gain, the noise increases - just like the background hiss on a Hi-fi setup. This manifests itself in the image becoming speckled or "noisy"
 
I always think of a tap, hose pipe and bucket of water analogy.

A correctly exposed photo will have the bucket nicely filled 3/4 (for example).

The shutter speed is how long you leave the tap open.

The aperture is the diameter of the hose; the larger the hose, the quicker you bucket will fill up.

ISO is how much you open the tap / water pressure: if you need to fill your bucket in a given amount of time and you're already using the biggest hose you can get, then you need to pump the water faster to compensate for your hose pipe diameter. Problem is, the more pressure, the more splashes and noise you make :D
 
tfboy said:
I always think of a tap, hose pipe and bucket of water analogy.

A correctly exposed photo will have the bucket nicely filled 3/4 (for example).

The shutter speed is how long you leave the tap open.

The aperture is the diameter of the hose; the larger the hose, the quicker you bucket will fill up.

ISO is how much you open the tap / water pressure: if you need to fill your bucket in a given amount of time and you're already using the biggest hose you can get, then you need to pump the water faster to compensate for your hose pipe diameter. Problem is, the more pressure, the more splashes and noise you make :D
Click to expand...

That's a cool definitition:lol:
 
In basic terms the higher the iso, e.g.1600 the grainier the picture is, but you can use it in lower light conditions.

The lower the iso eg 100, the image is less grainy.

Best thing to do is take a couple of picture on a tripod of the same thing, using different isos, so you can see how it all changes.
 
so what would people recommend as all the info etc says stick to 100
 
Animal said:
so what would people recommend as all the info etc says stick to 100
Click to expand...

If possible but there will be many occasions when it's not possible to stick to it and you have to compromise. For example, if you are shooting people, in lowlight, handheld, you need to stick to a minimum shutter speed (1/60 ish) to avoid camera shake or movement blur, you have the aperture wide open (what value depends on the lens but say f4) and still the cameras meter tells you it'll be under exposed... what can you do? Up the ISO.
 
brill thanks - so it's down to knowledge and the good old fashion - PLAY!
 
that is really helpful - thank you - will add that to my favs
 
Animal said:
so what would people recommend as all the info etc says stick to 100
Click to expand...

Can I ask what info?

It probably says to stay at your lowest ISO to keep the digital noise at a low level. But what if you can't get the shot because the shutter speed is so low that you end up with a blurry picture? Either due to subject movement or camera shake. Then what do you do, give up, get a tripod or use a stable surface? But then, the slow shutter speed will blur out any moving subjects. If you really need to get that shot then increase your ISO. I want the shot and don't worry about the noise.

So don't fret about ISO. Jump all over it, only when you have to though. I do. No need for a high ISO shot in good light, that is not the point. ;)

Learn about the amount of noise your camera produces by taking shots at higher ISO in the appropriate circumstance, i.e. low light. See which ones you can correct successfully and more importantly look good in print NOT on the screen. 100% pixel peeping is bad for moral! :D

Oh, and always shoot RAW and look at getting Noiseware, there is a free version available.
 
Tim, what camera do you have? Chances are it has an auto ISO feature which can be quite useful; it will adjust the ISO for you when your current settings for aperture and shutter speed aren't good enough. But I don't want to confuse you any more :)
 
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