Which chart to buy or print depends on what you need to measure, how much of the field of view you need to cover, and how much room the test stand has. This article is a starting point; the module documentation for the version you are running has the detail.
Start from the measurement
| You want to measure | Look at |
|---|---|
| Sharpness across the frame, plus tonal response and color in one shot | SFRplus, eSFR ISO |
| Sharpness only, with a chart that tolerates being photographed at an angle | SFRreg |
| Sharpness with the densest set of edges for a given chart area | Checkerboard |
| Color accuracy and tonal response on their own | Colorchecker 24, or a step chart |
| Distortion and field of view | A dot pattern or a grid |
SFRplus and eSFR ISO both measure several image quality factors from one capture, which is usually what makes a test efficient: one exposure, one analysis, several numbers.
Then check it fits
A chart has to fill enough of the frame for the features to be resolved, and it has to be lit evenly. Two practical limits decide most choices:
- Distance. A wide-angle lens at close range needs a large chart, or the chart occupies too little of the frame. SFRreg exists partly for this case: its registration marks let separate small targets be placed across the field instead of one large chart.
- Lighting uniformity. The larger the chart, the harder it is to light evenly, and uniformity errors show up in tonal and color measurements before they show up in sharpness.
Printed or transmissive
A printed reflective chart is cheaper and easier to light, and its contrast is limited by the paper: enough for sharpness and color, not enough for dynamic range. A transmissive chart on a light box reaches much higher contrast, which is what dynamic range measurements need.