ISO?

[tevo]

So I am confused. In a normal composure, I would adjust my Shutter, Aperture, and White Balance. However, I do not usually change my ISO. What would ISO change in an image?

I am confused D:, any help appreciated

 

[Opher]

ISO is your "film speed" or sensor sensitivity. A higher one will need less light to create a good exposure but will result in more noise/grain. The opposite is also true. Generaly if you can get your iso low then do it

 

[Overread]

ISO mostly equals to the ASA value that was on film - the only difference being that with digital you can now change the ISO as you shoot without having to add/remove anything from the camera (whilst back in the film days you needed to have interchangable backs and stuff to change between different film speeds).

This comes at a cost though - the higher the ISO the more digital noise you will see in a shot and different camera bodies produce different levels of noise - higher tier bodies do better and in general the larger "fullframe" sensors to better than the crop sensor digitals (though even though the fullframe to better the crop sensor can still get some impressive results)

 

[tevo]

Oh, so a higher ISO in low light increases the sensitivity, and vice versa?

 

[Overread]

Exactly - though it should also be noted that with digital if you underexpose a shot (or have darker areas) the noise will show up more than in a correctly exposed photo. However you can somewhat deal with noise in editing using noise removal tools - so its not all lost - and in general if you need more shutter speed raising your ISO is preferable to motion blur (which can't be corrected)

Also note that higher ISOs contract the camera sensors dynamic range. I'm not sure of the values but it does occur and will of course be more noticable at the extreme ends of high and low.

 

[tevo]

Alright cool. Something I have been doing is "pre"-composing my shot in Auto and looking what the camera thinks is a good ISO.. Then I take this value and set it in my "M" or "A" mode.

Im learning ^^

 

[fokker]

How to expose a photo:

1. Figure out the end goal of the photo and what you are trying to convey - if you are trying to convey motion you'd use the Tv (shutter priority) mode. You might use a slow shutter speed to show motion blur or you may want to freeze an action shot with a fast shutter speed. The other facet you can easily control is the depth of field in the shot by using the Av mode (aperture priority). You may want to have a person's face in focus with a blurred background so you'd choose a wide aperture, or you may want a landscape photo with everything in focus so you use a small aperture.

2. After choosing your main point of exposure control (aperture or shutter speed) and selecting an appropriate value, you will have to adjust the other one - so if you want a fast shutter speed you will need a wide aperture for more light or vice versa. Up until this point you shouldn't worry about ISO, always assume it stays at 100 or 200. The only reason to ever raise it is if you can't possibly get a fast enough shutter speed to take the shot you need (factors such as subject motion or camera shake).