Wednesday, May 21, 2008

My blunder.

So, for those of you that don't know, there is a setting on most decent digital cameras that sets the ISO level of the camera.

For digital cameras, ISO is shorthand for the ISO 12232:1998 specification maintained by the International Organization for Standardization.

This standard specifies signal to noise ratio and brightness requirements (or saturation for cameras that are limited by well capacity) for a camera to earn a certain ISO rating. These ratings are intended to be similar to those of ISO 5800:1987, which specifies ratings for film. Thus, at a given f/stop, shutter speed, and ISO, both film and digital exposures should produce roughly the same brightness as output. Note that in practice this isn't always the case due to many factors including interpretation of the standard, different tone curves, rounding, and marketing considerations.

As with traditional film ISO ratings, increasing the ISO corresponds to an increase in sensitivity. For example, in moving from ISO 100 to ISO 200, while keeping the f/stop constant, you will achieve the same exposure by using a shutter speed twice as fast.

In practice a single camera can achieve multiple different ISO ratings by applying some form of amplification to the signal coming off the sensor. This can be done by applying analog amplification to the signal before it hits the A/D converter, or by bit shifting the results after they have gone through the A/D converter. Cameras may apply a combination of these approaches, depending upon the desired ISO. Which is best will depend upon whether amplifier noise or A/D converter noise is larger.

I had my camera set to have a ISO of 1600 that means more noise for about the last 1200 shots.

Luckily I found a great plugin for Photoshop called DeFine. It removes noise better then any other program I've used.

1 comment:

Pamela said...

you kill me with your wit.