Workshop 4: ISO

ISO/ ISO equivalent

ISO (equivalent) speed on a digital camera gives an indication of the sensitivity of the image sensor.

Some uses

If by adjusting the shutter speed / aperture combinations you cannot obtain a correctly exposed picture (usually in low-light situations), then you may want to select the next higher ISO.

Noise

ISO usually results in noisy images because of the high sensitivity.

ISO speed and image sensor size

The size of the image sensor determines the ISO speed range that a digital camera can use without suffering from undue noise. Image sensor (of same resolution) that is smaller will exhibit more noise at higher ISOs than the larger one.

S2IS has ½.5” sensor size

Notes:

1. You obtain the best image quality by using the lowest ISO possible on your digital camera. If you want to ensure your digital camera always uses the lowest ISO setting, switch the ISO setting from the default "Auto ISO" (this setting is usually found in the Menu) to the lowest possible on the camera, say ISO 50.

Here's another good one that I got from A-mountain in Tempe.

References:

http://www.photoxels.com/tutorial_iso.html

Workshop3: Shutter speed and Aperture settings

There are plenty of references on the web for this topic. I do not want to repeat the explanation. I’m listing down some really useful references here which will explain the concept. Well, I worked a lot on this! My album doesn't really reflect that coz I keep deleting the photos that I am not satisfied with.

My notes:

1. Use as small shutter speed as possible and compensate exposure by aperture; bigger the shutter speed, more the blurry effect.

2. Always think of what depth of field you want to use:
- Wider the aperture (or smaller F-# like F2.8) smaller the DOF (refer previous post also)
- Using Reciprocity to Compose Your Image:

You can adjust the aperture setting and shutter speed to create several different correctly exposed images. The relationship between the aperture and shutter is known as reciprocity. Reciprocity gives the photographer control over the depth of field of the image, which controls the area of the image that remains in focus. This is the easiest way to control what part of the image you want the viewer to pay attention to.

3. Technically what exactly is f-stop?

An f-stop is a ratio of the focal length of the lens to the diameter of the opening of the aperture. For example, a 50 mm lens with an aperture opened up to a diameter of 12.5 mm results in an f-stop of f4 (50 ÷ 12.5 = 4). Therefore, the larger the numerical value of the f-stop, the smaller the opening of the aperture.

4. You can eliminate camera shake by using a tripod or by increasing the shutter speed to a value higher than the focal length. For example, if you’re shooting at a focal length equivalent to 100 mm, you should set your shutter speed to 1/100 of a second or faster. The digital image sensor will capture the image before the movement of the lens has time to register additional light information on the sensor.

As per my understanding till now, ‘Exposure’ is a result of three settings:

- Shutter speed

- Aperture

- ISO

A very useful and extensive documentation of various exposure settings: http://www.fredparker.com/ultexp1.htm - This may not make much sense until we study ISO too!

And, btw... what role does white-balance play in all this? Hmm, will add it to 'yet-to-do' list!

Other References:

http://www.photonhead.com/beginners/shutterandaperture.php