3NH分辨率测试卡

ISO 12233 RESOLUTION TEST CHART FOR ELECTRONIC STILL CAMERAS
ISO 12233标准分辨率测试卡——电子静态数码相机专用
INSTRUCTION PAPER FOR PHOTOGRAPHERS摄像师专用说明书
3nh chart is precise aid, designed for image quality determining and for judgement of resolution limits of digital cameras.
The chart is designed for photographic cameras up to 2000 addressable pixels in picture high (cca 6Mpix camera). When
testing cameras with higher resolution (up to 24Mpix cameras), place your camera to double distance from the chart. The
test image will cover only 50% of active pixels in image high and concurrently multiply all values on the chart by two.
3nh 测试卡是一种精密辅助工具，用于测定图像的质量和判断数码相机的分辨率限制。这种测试卡专为摄影照相机在高分辨率图像（600
万像素）中达到像高内2000 可寻址像素所设计。在测试更高分辨率（2400 万像素以上）的数码相机时，需将相机放在离测试卡两倍距
离远的地方。测试图像仅覆盖像高内50%的活跃像素，并且会同时将测试卡上所有的值放大两倍。
The chart is made in various versions (on Photographic Paperr, Chrome on Glass, Chrome on Opal,), in various contrasts
(15:1 to 30 000:1)) and in various sizes (20x36 mm to 800x1422 mm).
For complete analytical test of your camera, we recommend you to shoot one more test image, composite of:
18% grey card (GC18) + colour chart (BST4 or BST11) + grey step wedge (OW20).
本测试卡有多种版本（照相纸、玻璃、欧泊），多种比例（15:1 到30000:1），并且还有多种尺寸（20x36 mm 到800x1422 mm）
若要对数码相机进行全面分析测试，我们建议您拍摄多个测试图像，综合以下测试方法：
18%灰度卡(GC18)+颜色测试卡(BST4 or BST11)+灰色梯尺(OW20)。
THE CHART CONTAINS 测试卡包含以下内容：
· Black frame “F” and central focusing element “C” – for basic setup of the camera.
· Hyperbolic resolution elements “H” (6 elements in 3 directions in central part) and “H′” (4 composite patterns in corners)
– for visual resolution determination (on monitor).
·Swept frequency wedges “S” – for limiting resolution and visual “sharpness” measurements (according to the loss of
modulation at higher frequencies).
· Isolated lines “G” – useful to study quality of image details and software sharpening.
· Wheel “M” – for scanning linearity observations.
· Chessboard “N” – for compression artefacts study.
· Slanted lines “E” (bold lines with 1.5° inclination) – to judge stair stepping.
· Bursts “O” (horizontal and vertical belts with 5° inclined lines) – for aliasing ratio measurement.
· Other elements (L, T, T′ ) are used for SFR measurements. Special software is required for this application.
· 黑色外框“F” 和中心对焦元素“C” —— 用于相机的基本设定
· 双曲线分辨率元素“H”（中心部分3 个方向上的6 种元素）和“H′ ”（角落中4 种组合模式）—— 用于视觉分辨率的测定（针对显示器）
· 扫频楔“S” —— 用于极限分辨率和视觉“清晰度”测量（通过更高频率上的调制损耗）。
· 间隔线“G” —— 用于研究图像细节质量和软件锐化。
· 旋轮状“M” —— 用于扫描线性观测。
· 棋盘“N” —— 用于压缩假象研究。
· 斜线“E”（1.5°倾斜的粗线）—— 用于梯级判断。
· 脉冲“O”（5°倾斜的水平和垂直线带）—— 用于图像折叠失真定比测量
· 其他元素（L, T, T′）用于SFR（空间频率响应）测量，这种应用程序需要特定的软件。
2
INSTRUCTION PAPER IS FOCUSED ON
· Visual resolution determination
· Limiting resolution and visual sharpness measurements
· Quality of image details study
· Aliasing ratio determination
本说明书主要针对：
· 视觉分辨率测定
· 极限分辨率和视觉清晰度测量
· 图像细节质量研究
· 图像折叠失真定比测量
Resolution power judgement is based on some terms:
· Visual resolution – indicated in numbers of visible pixels (lines) per image high (= lph).
· Limiting resolution (in lph) – measured by decrease of amplitude (= difference between black and white levels), to
selected X% level (relatively to low frequency amplitude). Samples: Visual resolution corresponds to such frequency,
where amplitude falls to 50% value of 50 lph amplitude.
· Amplitude response of camera and its dependence on relative input spatial frequency, called SFR (spatial frequency
response). SFR is described by curve – dependence of measured amplitude on input spatial frequency. The curve is
calculated from digital levels corresponding to “S” frequency wedges (see picture), using linearized ESF (edge spread
function = signal progression on theoretical limiting sharp edge). Whole computation necessitates special software and
skills. It is applied only in specialized laboratories.
· Aliasing = “artefacts in image of sampled system with significant energy” are created by combination of regular
structure of camera sampling. Aliasing has significant effect at frequencies higher than Nyquist frequency (fn= double of
sampling frequency). It is indicated by moiré (for f<fn) and by irregular stair stepping at edge transition.
分辨率判断基于以下术语：
· 视觉分辨率：指每像高若干视觉像素（=单位图像高度内的清晰度线条数）
· 极限分辨率(在每单位图像高度内的清晰度线条数中)：通过减小振幅（振幅是指黑电平与白电平之间的差异），选择X%的级数（相对低
频振幅）来测定。例如：当振幅减小到50 lph 振幅值的50%时，视觉分辨率就对应此种频率。
· 数码相机的振幅响应及其对相对输入空间频率的依赖称为SFR（空间频率响应）。SFR 用曲线描述，与输入空间响应的测定振幅相关。
此曲线利用线性化ESF（边缘扩展函数=在理论极限锐边的信号进程），计算了从数字层面到与之相应的“S”频率楔形（如图）。整个计算
需要特定的软件和技巧，它仅用于实验室。
· 图像折叠失真：是指“图像采样系统中具有显著能量的假象”，它由取样相机的常规结构组合而形成。在频率高于奈奎斯特频率（ fn=两
倍取样频率）时，图像折叠失真有明显的效果，它通过叠纹（f<fn）和在边缘过渡的不规则梯级呈现。
All resolution values on the chart (1 to 20) are indicated in hundreds of lph. For mensuration in horizontal direction (lines
oriented to width of image), it is used the same metrics, because high to width ratio of image varies according to the
camera type (3:2, 4:3, 16:9). Sample: all back lines with “10” marking have thickness of 1/1000 of image high. Overall
resolution (number of distinguishable pixels on image area) can be computed as a product of “lph” values in both
directions, multiplied by sides ratio (mostly 4/3 or 3/2).
The chart complies ISO 12233 norm (Resolution measurements of electronic still-picture cameras). Precise normative
camera evaluation requires measurement and calculation of SFR (sometimes called MTF=modulation transfer function).
For the SFR measurement, you should have (besides the chart) special evaluation software, metrology knowledge and
signal evaluation skills.
测试卡（1 到20）上所有分辨率值显示了数以百计的单位图像高度内清晰度线条数。在测量水平方向（清晰度线条倾向于图像宽度）时，
也使用同样的度量，因为图像的高与宽的比率会随着相机型号(3:2, 4:3, 16:9)的不同而不同。例如：所有标记为“10”的黑线厚度为像高
3
的千分之一。总的来说，分辨率（像区内若干可辨像素）能够作为“单位图像高度内清晰度线条数”数值的结果进行双向计算，并双向放大
比率（通常放大4/3 or 3/2）。
本测试卡符合ISO 12233 标准（电子静态画面数码相机分辨率测量）。精确评估标准相机需要进行SFR 测量和计算（有时候称为MTF=
调制转换函数）。在进行SFR 测量时，除了测试卡之外，您还需要有特定评估软件、计量知识和信号评估技巧。
We recommend you 4 evaluation programs, which are available free on web:
我们推荐您使用网上四种免费评估程序：
1) ImageJ graphic program (http://rsb.info.nih.gov/ij/download.html). Its “plot” function converts digital levels of pixels
(0 to 255) into graphic form. It is possible to create a curve of amplitude response to spatial frequencies, using frequency
wedges “S”. Relative decrease of amplitudes at higher fre