The February 2012 League City Photography Group’s monthly meeting took place on 02/02/12. Below are my notes.

Announcements

Upcoming Posted Events

Feb 17 Fri 5:00 PM | Photo Submission for The Arts Alliance Exhibit

Other events

FotoFest 2012 Biennial | Mar 16 – Apr 29
Galveston Featherfest | Apr 12-15

Topic – White Balance

Mike Fisher gave a detailed talk titled “Raw Files and White Balance or …Do you trust your histogram”.

Summary ::

A gray card reflects all the light falling on it in equal amounts.

Your camera’s light meter essentially sees the world as a gray card and will try to set the exposure so that the average brightness of all the things in the image is the same as the brightness of a gray card.

Most digital sensors use a Bayer filter to record an image.

Your camera’s sensor records a set of three numbers at each pixel site – one for the brightness of the red light falling on it, one for the brightness of the green light, and one for the brightness of the blue light.

Differences between JPEG and Raw

JPEG uses eight bits to record a brightness level. That means each value can range from 0-255.
Raw files, depending on the camera, use twelve or fourteen bits to record a brightness level. Using twelve bits means the values can range from 0-4095. Using fourteen bits allows the values to run from 0-16383.

Color Spaces: Most cameras will allow you to set a color space, usually sRGB or AdobeRGB. The camera usually defaults to sRGB. Raw files themselves don’t have a color space.

Histogram: Even when you shoot raw, you still get a JPEG. That’s because the camera develops a JPEG using the white balance and camera profile information you set. The histogram the camera displays is based on that JPEG, not on the raw file.For that reason, the histogram may not correctly show the light levels actually recorded by the sensor.

Link to Mike’s presentation slides: Raw Files and White Balance or …Do you trust your histogram

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