Some Newbie Questions.

[Glasticart]

Hi, Im a forum newbie and am looking into starting photography, Im getting my first ever SLR camera in afew weeks so iv been doing quite alot of research and studying photography in my spare time. Here are some really stupid newbie questions I need answered.


What happens if you dont use the correct ISO when capturing an image ?
How do know how much to bring the ISO up or down, I know you use a higher ISO if your in dull light and the use a low ISO in bright light but how do you know how much to bring it up or down (Same goes for aperture) ?



Thanks In Advance :hugs:

 

[JimmyO]

Let me google that for you :hug::

 

[SrBiscuit]

[ame=http://www.amazon.com/Understanding-Exposure-Photographs-Digital-Updated/dp/0817463003]Amazon.com: Understanding Exposure: How to Shoot Great Photographs with a Film or Digital Camera (Updated Edition) (9780817463007): Bryan Peterson: Books[/ame]

 

[bazooka]

+1 for Jimmy. A little reading goes a long way.

Each of the three variables that determine exposure have a creative aspect to them. Apterture controls depth of field. Shutter speed controls motion. ISO controls grain. Most will recommend shooting the lowest ISO possible while maintaining correct exposure to minimize grain. But if you want grain, set ISO first. Or you can try to balance all three however you like. A tripod, image stabilization, and ND filters all work in some way to give you more creative control when working with available light.

 

[Dao]

Before you jump into ISO, you may want to learn more about exposure.

Exposure (photography) - Wikipedia, the free encyclopedia


To make it short, it is the amount of light allow to expose a medium such as film or light sensor. And you control the amount by how much light per a given time (aperture) and how long you allow the light to pass through in one shot (shutter speed).

However, to have the correct exposure, we also need to know the sensitivity of the medium (film or sensor). And ISO (or ASA) represents the sensitivity. The higher the ISO value, the more light sensitive medium. (in other words, the medium use less light to have the correct exposure).

The draw back on higher ISO is more noise on digital sensor or grains on film. So in general photographers choose the lower ISO setting or lower ISO/ASA film to get the correct exposure.

Example:

Full moon photo: Exposure Value (EV) 15
Aperture: F/11
Shutter Speed: 1/250
ISO: 100

So if you like to take the photo at F/11 aperture but with a faster shutter speed, you can double the ISO value. Then the settings are ..

Aperture: F/11
Shutter Speed: 1/500
ISO: 200

So I double the ISO value so it is twice more sensitive. In order to make the same exposure, I can double the shutter speed to 1/500 (less exposure time).