08.12.2012 Views

Imatest Documentation

Imatest Documentation

Imatest Documentation

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

<strong>Imatest</strong> <strong>Documentation</strong><br />

3D Plot for MTF50 (one of many available results).<br />

3D plots have a great many display options;<br />

they can be rotated freely or viewed from the top.<br />

The SFRplus test chart<br />

The standard SFRplus test chart is illustrated below.<br />

Lens-type MTF plot<br />

(similar to MTF plots from the<br />

Canon, Nikon, and Zeiss websites.<br />

Standard SFRplus test chart: 5x9 grid, 10:1 and 2:1 contrasts,<br />

20-step 4x5 stepchart (0.1 density increment), and focus star.<br />

Sharpness is derived from light-to-dark slanted edges at the boundaries of the squares, as described in Sharpness: What is it<br />

and how is it measured? The new chart enables SFRplus can handle a wide range of camera aspect ratios; the left and right<br />

sides of the chat can extend beyond the frame or be inside the frame.<br />

The essential features of the SFRplus chart are<br />

Bars at the top and bottom used for measuring distortion and facilitating edge detection.<br />

A grid of slanted squares with contrasts no greater than 10:1. 4x7, 5x7, 5x9 and 7x11 (row x columns) are the available grid sizes.<br />

The square orientation facilitates measurement of Lateral Chromatic Aberration using vertical edges (which are<br />

near-tangential) near the corners. This orientation also helps with the Lens-style MTF plots, which are similar to MTF<br />

displays on the Canon, Nikon, and Zeiss websites.<br />

The squares above and below the middle square are reserved for non-spatial measurements. In the standard chart, the square<br />

below the middle is a 4x5 stepchart with density steps of 0.1 used to measure tonal response and gamma, and the square above<br />

the middle square contains either a fine star pattern (used as a focusing aid; not for analysis) or a 4x5 color pattern for measuring<br />

color accuracy.<br />

A small number of low contrast (typically 2:1) squares for measuring the effects of nonlinear signal processing. Charts may<br />

optionally have squares of a single contrast. This is helpful for 3D plots that map the performance over the image surface.<br />

Grid of squares 5x9<br />

SFRplus chart options (can be selected when ordering)<br />

Standard Options & notes<br />

4x7, 5x7, and 7x11 are also available. 5x9 is best suited for HTDV (16:9 aspect ratio) and<br />

DSLRs (3:2 aspect ratio). 5x7 is best suited for compact digital cameras and cameraphones<br />

(4:3 aspect ratio).<br />

Main contrast level 10:1 from 40:1 to 1.1:1, Greater than 10:1 not recommended.<br />

Secondary<br />

contrast level<br />

2:1 Same as main level or as low as 1.1:1. Shows effects of nonlinear processing.<br />

Stepchart Included (below center) Omitted in chrome on opal or glass charts<br />

Color chart Omitted Included (above center). L*a*b* values will be sent in a file.<br />

Focus star Inluded (above center) May be omitted. Used as a focus aid (not for analysis). Omitted if color chart is included<br />

Advantages of the SFRplus chart over the ISO 12233 chart<br />

159 of 451

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!