metering-29apr10-150dpi-med

metering-29apr10-150dpi-med - Exposure metering(AE Marc...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Exposure metering (AE) Marc Levoy Computer Science Department Stanford University CS 178, Spring 2010 I added two recap slides after the lecture. You are responsible for metering on the midterm, but not HDR imaging. I also adjusted the midterm review slides to reduce coverage of gamma correction, since I didn’t fully cover it during this lecture. Good luck on your midterm! ! Marc Levoy Outline: metering ! What makes metering hard? • the meter doesn’t know what you’re looking at • the dynamic range problem ! background topics • Ansel Adams’ zone system • gamma and gamma correction ! metering technologies ! metering modes (center, evaluative,...) ! shooting modes (Av, Tv, P, M) ! exposure compensation, etc. ! high dynamic range (HDR) imaging 2 ! Marc Levoy What makes metering hard? ! light meters don’t know what you’re looking at • so they assume the scene is mid-gray (18% refective) ! the world is Full oF hard metering problems... 3 (London) (http://fotocommunity.de ) ! Marc Levoy Ansel Adams’s zone system ! roughly 1 f/stop per zone • X = “maximum white of the paper base” • IX = “slight tonality, but no texture: Fat snow in sunlight” • VIII = “textured snow, lightest wood at right” ..... • V = 18% gray card ..... • 0 = “maximum black that photographic paper can produce” ! lesson for the digital age • plan the tones you want in your image for each part of the scene 5 X IX VIII VII VI V IV III II I (London) ! Marc Levoy The dynamic range problem ! even if meters were omniscient, the dynamic range of the world is higher than the dynamic range of a camera ! the real world 800,000:1 surface illuminated by sun vrs by moon, (20 f/stops, or 1/1000 sec vrs 13 minutes) 100:1 diffuse white surface versus black surface 80,000,000:1 total dynamic range 6 ! Marc Levoy Illuminated by sun versus by moon ! total difference in shooting settings = 256,000:1 ! luminance of snow pixels (in RAW Fle) differ by another ~2 " 7 1/500s, f/6.3, ISO 100 8s, f/1.7, ISO 400 ! Marc Levoy Illuminated by sun versus by moon ! total difference in shooting settings = 256,000:1 ! luminance of snow pixels (in RAW Fle) differ by another ~2 " ! JPEG value = (RAW value / 65536) 1/ ! " 255, where ! = 2.2 8 1/500s, f/6.3, ISO 100 8s, f/1.7, ISO 400 RAW fle RAW fle ! Marc Levoy Illuminated by sun versus by moon 9 1/500s, f/6.3, ISO 100 8s, f/1.7, ISO 400 JPEG fle JPEG fle ! total difference in shooting settings = 256,000:1 ! luminance of snow pixels (in RAW Fle) differ by another ~2 " ! JPEG value = (RAW value / 65536) 1/ ! " 255, where ! = 2.2 ! Marc Levoy ADC must output more bits than JPEG stores (contents of whiteboard) !...
View Full Document

{[ snackBarMessage ]}

Page1 / 62

metering-29apr10-150dpi-med - Exposure metering(AE Marc...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online