3NH分辨率測試卡

ISO 12233 RESOLUTION TEST CHART FOR ELECTRONIC STILL CAMERAS
ISO 12233標準分辨率測試卡——電子靜態(tài)數(shù)碼相機專用
INSTRUCTION PAPER FOR PHOTOGRAPHERS攝像師專用說明書
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 測試卡是一種精密輔助工具，用于測定圖像的質量和判斷數(shù)碼相機的分辨率限制。這種測試卡專為攝影照相機在高分辨率圖像（600
萬像素）中達到像高內2000 可尋址像素所設計。在測試更高分辨率（2400 萬像素以上）的數(shù)碼相機時，需將相機放在離測試卡兩倍距
離遠的地方。測試圖像僅覆蓋像高內50%的活躍像素，并且會同時將測試卡上所有的值放大兩倍。
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).
本測試卡有多種版本（照相紙、玻璃、歐泊），多種比例（15:1 到30000:1），并且還有多種尺寸（20x36 mm 到800x1422 mm）
若要對數(shù)碼相機進行全面分析測試，我們建議您拍攝多個測試圖像，綜合以下測試方法：
18%灰度卡(GC18)+顏色測試卡(BST4 or BST11)+灰色梯尺(OW20)。
THE CHART CONTAINS 測試卡包含以下內容：
· 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” 和中心對焦元素“C” —— 用于相機的基本設定
· 雙曲線分辨率元素“H”（中心部分3 個方向上的6 種元素）和“H′ ”（角落中4 種組合模式）—— 用于視覺分辨率的測定（針對顯示器）
· 掃頻楔“S” —— 用于極限分辨率和視覺“清晰度”測量（通過更高頻率上的調制損耗）。
· 間隔線“G” —— 用于研究圖像細節(jié)質量和軟件銳化。
· 旋輪狀“M” —— 用于掃描線性觀測。
· 棋盤“N” —— 用于壓縮假象研究。
· 斜線“E”（1.5°傾斜的粗線）—— 用于梯級判斷。
· 脈沖“O”（5°傾斜的水平和垂直線帶）—— 用于圖像折疊失真定比測量
· 其他元素（L, T, T′）用于SFR（空間頻率響應）測量，這種應用程序需要特定的軟件。
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INSTRUCTION PAPER IS FOCUSED ON
· Visual resolution determination
· Limiting resolution and visual sharpness measurements
· Quality of image details study
· Aliasing ratio determination
本說明書主要針對：
· 視覺分辨率測定
· 極限分辨率和視覺清晰度測量
· 圖像細節(jié)質量研究
· 圖像折疊失真定比測量
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.
分辨率判斷基于以下術語：
· 視覺分辨率：指每像高若干視覺像素（=單位圖像高度內的清晰度線條數(shù)）
· 極限分辨率(在每單位圖像高度內的清晰度線條數(shù)中)：通過減小振幅（振幅是指黑電平與白電平之間的差異），選擇X%的級數(shù)（相對低
頻振幅）來測定。例如：當振幅減小到50 lph 振幅值的50%時，視覺分辨率就對應此種頻率。
· 數(shù)碼相機的振幅響應及其對相對輸入空間頻率的依賴稱為SFR（空間頻率響應）。SFR 用曲線描述，與輸入空間響應的測定振幅相關。
此曲線利用線性化ESF（邊緣擴展函數(shù)=在理論極限銳邊的信號進程），計算了從數(shù)字層面到與之相應的“S”頻率楔形（如圖）。整個計算
需要特定的軟件和技巧，它僅用于實驗室。
· 圖像折疊失真：是指“圖像采樣系統(tǒng)中具有顯著能量的假象”，它由取樣相機的常規(guī)結構組合而形成。在頻率高于奈奎斯特頻率（ fn=兩
倍取樣頻率）時，圖像折疊失真有明顯的效果，它通過疊紋（f<fn）和在邊緣過渡的不規(guī)則梯級呈現(xiàn)。
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 “l(fā)ph” 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.
測試卡（1 到20）上所有分辨率值顯示了數(shù)以百計的單位圖像高度內清晰度線條數(shù)。在測量水平方向（清晰度線條傾向于圖像寬度）時，
也使用同樣的度量，因為圖像的高與寬的比率會隨著相機型號(3:2, 4:3, 16:9)的不同而不同。例如：所有標記為“10”的黑線厚度為像高
3
的千分之一?？偟膩碚f，分辨率（像區(qū)內若干可辨像素）能夠作為“單位圖像高度內清晰度線條數(shù)”數(shù)值的結果進行雙向計算，并雙向放大
比率（通常放大4/3 or 3/2）。
本測試卡符合ISO 12233 標準（電子靜態(tài)畫面數(shù)碼相機分辨率測量）。精確評估標準相機需要進行SFR 測量和計算（有時候稱為MTF=
調制轉換函數(shù)）。在進行SFR 測量時，除了測試卡之外，您還需要有特定評估軟件、計量知識和信號評估技巧。
We recommend you 4 evaluation programs, which are available free on web:
我們推薦您使用網上四種免費評估程序：
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