Imatest Documentation

Recommendations

Info

Imatest Documentation The upper plot displays the sine and bar patterns: original and after blurring by the lens. The middle plot displays the luminance of the bar pattern after blurring by the lens (the red curve). Contrast decreases at high spatial frequencies. The lower plot displays the corresponding MTF (SFR) curve (the blue curve). By definition, the low frequency MTF limit is always 1 (100%). For this lens, MTF is 50% at 61 lp/mm and 10% at 183 lp/mm. Both frequency and MTF are displayed on logarithmic scales with exponential notation (10 0 = 1; 10 1 = 10; 10 2 = 100, etc.). Amplitude is displayed on a linear scale. The beauty of using MTF (Spatial Frequency Response) is that the MTF of a complete imaging system is the product of the the MTF of its individual components. MTF is related to edge response by a mathematical operation known as the Fourier transform. MTF is the Fourier transform of the impulse response— the response to a narrow line, which is the derivative (d/dx) of the edge response. Fortunately, you don't need to understand Fourier transforms or calculus to understand MTF. Green is for geeks. Do you get excited by a good equation? Were you passionate about your college math classes? Then you're probably a math geek— a member of a misunderstood but highly elite fellowship. The text in green is for you. If you're normal or mathematically challenged, you may skip these sections. You'll never know what you missed. Traditional "resolution" measurements involve observing an image of a bar pattern (usually the USAF 1951 chart) on film, and looking for the highest spatial frequency (in lp/mm) where a pattern is visible. This corresponds to an MTF of about 5-10%. Because this is the spatial frequency where image information disappears— where it isn't visible, it is not a good indicator of image sharpness. Experience has shown that the best indicators of image sharpness are the spatial frequencies where MTF is 50% of its low frequency value (MTF50) or 50% of its peak value (MTF50P). MTF50 or MTF50P are ideal parameters for comparing the sharpness of different cameras for several reasons: (1) Image contrast is half its low frequency or peak values, hence detail is still quite visible. (2) The eye is relatively insensitive to detail at spatial frequencies where MTF is low: 10% or less. (3) The response of virtually all cameras falls off rapidly in the vicinity of MTF50 and MTF50P. MTF50P may better for oversharpened cameras that have peaks in their MTF response. Although MTF can be estimated directly from images of sine patterns (see Rescharts Log Frequency, Log F-Contrast, and Star Chart), a sophisticated technique, based on the ISO 12233 standard, "Photography - Electronic still picture cameras - Resolution measurements," provides more accurate and repeatable results. A slanted-edge image, described below, is photographed, then analyzed by Imatest SFR or Rescharts Slanted-edge SFR. (SFR stands for Spatial Frequency Response.) Origins of Imatest SFR The algorithms for calculating MTF/SFR were adapted from a Matlab program, sfrmat, written by Peter Burns ( ) to implement the ISO 12233 standard. Imatest SFR incorporates numerous improvements, including improved edge detection, better handling of lens distortion, a nicer interface, and far more detailed output. The original Matlab code is available on the I3A ISO tools download page by clicking on ISO 12233 Slant Edge Analysis Tool sfrmat 2.0. In comparing sfrmat 2.0 results with Imatest, note that if no OECF (tonal response curve) file is entered into sfrmat, it assumes that there is no tonal response curve, i.e., gamma = 1. In Imatest, gamma is set to a default value of 0.5, which is typical of digital cameras. To obtain good agreement with sfrmat, you must set gamma to 1. The slanted-edge test for Spatial Frequency Response Slanted-edge test charts can be created with Imatest Test Charts (SVG charts are especially recommended) or downloaded from How to test lenses with Imatest. The bitmap chart has horizontal and vertical edges for best print quality. It should be 6 of 451
Imatest Documentation tilted (about 2-8 degrees) before it is photographed. Imatest SFR can also take advantage of portions of the ISO 12233 test chart, shown on the right, or a derivative like the Applied Image QA-77, or as a less expensive alternative from Danes-Picta in the Czech Republic (the DCR3 chart on their Digital Imaging page)). Two such portions are indicated by the red and blue arrows. ISO 12233 charts are used in imaging-resource.com and dpreview.com digital camera reviews. A printable vector-graphics version of the ISO chart is available courtesy of Stephen H. Westin of the Cornell University Computer Graphics Department. It should be printed as large as possible (24 inches high if possible) so edge sharpness is not limited by the printer itself. (There may be some jaggedness in the slanted edges; not a problem with the recommended printable target.) A typical portion is shown on the right: a crop of a vertical edge (slanted about 5.6 degrees), used to calculate horizontal MTF response. An advantage of the slanted edge test is that the camera-to-target distance isn't critical. It doesn't enter into the equation that converts the image into MTF response. Imatest Master can calculate MTF for edges of virtually any angle, though exact vertical, horizontal, and 45° can have numerical problems. Slanted edge algorithm (calculation details) The MTF calculation is derived from ISO standard 12233. Some details are contained in Peter Burns' SFRMAT 2.0 User's Guide, which can be downloaded from the I3A ISO tools download page by clicking on Slant Edge Analysis Tool sfrmat 2.0. The Imatest calculation contains a number of refinements and enhancements, including more accurate edge detection and compensation for lens distortion (which could affect MTF measurements). The original ISO calculation is performed when the ISO standard SFR checkbox in the SFR input dialog box is checked. It is normally left unchecked. The cropped image is linearized, i.e., the pixel levels are adjusted to remove the gamma encoding applied by the camera. (Gamma is adjustable with a default of 0.5). The edge locations for the Red, Green, Blue, and luminance channels (Y = 0.3*Red + 0.59*Green + 0.11*Blue) are determined for each scan line (horizontal lines in the above image). A second order fit to the edge is calculated for each channel using polynomial regression. The second order fit removes the effects of lens distortion. In the above image, the equation would have the form, x = a0 + a1 y + a2 y 2 . Depending on the value of the fractional part fp = xi - int(xi ) of the second order fit at each scan line, the shifted edge is added to one of four bins (bin 1 if 0 ≤ fp < 0.25; bin 2 if 0.25 ≤ fp < 0.5; bin 3 if 0.5 ≤ fp < 0.75; bin 4 if 0.75 ≤ fp < 1. (Correction 11/22/05: the bin does not depend on the detected edge location.) The four bins are combined to calculate an averaged 4x oversampled edge. This allows analysis of spatial frequencies beyond the normal Nyquist frequency. The derivative (d/dx) of the averaged 4x oversampled edge is calculated. A windowing function is applied to force the derivative to zero at its limits. MTF is the absolute value of the Fourier transform (FFT) of the windowed derivative. Additional details of the calculation can be found in Appendix C, Video Acquisition Measurement Methods (especially pp. 102-103), of the Public Safety SoR (Statement of Requirements) volume II v 1.0 (6 MB download), released by SAFECOM, prepared by ITS (a division of NTIA, U.S. Department of Commerce). Imatest SFR results 35mm camera lens tests use line pairs per millimeter (lp/mm) as the units of spatial frequency. This works fine for comparing lenses because all 35mm cameras have the same 24x36 mm picture size. But digital sensor digital varies widely, from under 6 mm diagonal in ultra-compact models to 43 mm diagonal for full-frame DSLRs— even larger for medium format backs. The number of pixels also varies. For this reason, spatial frequency should be measured in units that indicate the response over the total sensor height rather than the response per distance. 7 of 451
Page 1 and 2: Imatest Documentation © 2009 Imate
Page 3 and 4: Imatest Documentation Using SFRplus
Page 5: Imatest Documentation Image Quality
Page 9 and 10: Imatest Documentation MTF50 in Line
Page 11 and 12: Imatest Documentation SQF Subjectiv
Page 13 and 14: Imatest Documentation RAW converter
Page 15 and 16: Imatest Documentation cm (4 inch) h
Page 17 and 18: Imatest Documentation CSF( f ) = 2.
Page 19 and 20: Imatest Documentation correlate wit
Page 21 and 22: Imatest Documentation Unlike the ab
Page 23 and 24: Imatest Documentation Since luminan
Page 25 and 26: Imatest Documentation committee" (I
Page 27 and 28: Imatest Documentation The formula f
Page 29 and 30: Imatest Documentation The image to
Page 31 and 32: Imatest Documentation Sharpness com
Page 33 and 34: Imatest Documentation (DPR) Canon E
Page 35 and 36: Imatest Documentation but their noi
Page 37 and 38: Imatest Documentation The average t
Page 39 and 40: Imatest Documentation Chromatic abe
Page 41 and 42: Imatest Documentation Veiling glare
Page 43 and 44: Imatest Documentation A Kodak Q-13
Page 45 and 46: Imatest Documentation with UV filte
Page 47 and 48: Imatest Documentation Czajkowski' r
Page 49 and 50: Imatest Documentation P_Rm = O_Rm*A
Page 51 and 52: Imatest Documentation Split view, s
Page 53 and 54: Imatest Documentation ISO Sensitivi
Page 55 and 56: Imatest Documentation Multicharts T
Page 57 and 58:
Imatest Documentation Shoulders are
Page 59 and 60:
Imatest Documentation Related docum
Page 61 and 62:
Imatest Documentation between image
Page 63 and 64:
Imatest Documentation We display va
Page 65 and 66:
Imatest Documentation Blur units, M
Page 67 and 68:
Imatest Documentation σ 2 = Σ (ti
Page 69 and 70:
Imatest Documentation Drill holes l
Page 71 and 72:
Imatest Documentation rummaging thr
Page 73 and 74:
Imatest Documentation Target size C
Page 75 and 76:
Imatest Documentation Level the tar
Page 77 and 78:
Imatest Documentation Kodak Q-14 St
Page 79 and 80:
Imatest Documentation Imatest Instr
Page 81 and 82:
Imatest Documentation in the Imates
Page 83 and 84:
Imatest Documentation samples (fold
Page 85 and 86:
Imatest Documentation Using Imatest
Page 87 and 88:
Imatest Documentation About RAW fil
Page 89 and 90:
Imatest Documentation Options I for
Page 91 and 92:
Imatest Documentation Special user
Page 93 and 94:
Imatest Documentation CSV files- Ex
Page 95 and 96:
Imatest Documentation RAW files RAW
Page 97 and 98:
Imatest Documentation dcraw The ori
Page 99 and 100:
Imatest Documentation The Rawview w
Page 101 and 102:
Imatest Documentation identical (th
Page 103 and 104:
Imatest Documentation The Imatest T
Page 105 and 106:
Imatest Documentation Tripod and ac
Page 107 and 108:
Imatest Documentation Targets Chart
Page 109 and 110:
Imatest Documentation Left of cente
Page 111 and 112:
Imatest Documentation Rope trick (f
Page 113 and 114:
Imatest Documentation Distortion ta
Page 115 and 116:
Imatest Documentation If you fail t
Page 117 and 118:
Imatest Documentation Diagnostics r
Page 119 and 120:
Imatest Documentation A horizontal
Page 121 and 122:
Imatest Documentation the edges pri
Page 123 and 124:
Imatest Documentation The camera mu
Page 125 and 126:
Imatest Documentation Epson 2200 Pr
Page 127 and 128:
Imatest Documentation Using SFR Par
Page 129 and 130:
Imatest Documentation ROI fine adju
Page 131 and 132:
Imatest Documentation Pixel size ha
Page 133 and 134:
Imatest Documentation contrast in h
Page 135 and 136:
Imatest Documentation Two precautio
Page 137 and 138:
Imatest Documentation The PNG files
Page 139 and 140:
Imatest Documentation nroi = 9 nwid
Page 141 and 142:
Imatest Documentation An optional .
Page 143 and 144:
Imatest Documentation SFR results:
Page 145 and 146:
Imatest Documentation Right column
Page 147 and 148:
Imatest Documentation Right: Input
Page 149 and 150:
Imatest Documentation Below the plo
Page 151 and 152:
Imatest Documentation Multi-ROI 2D
Page 153 and 154:
Imatest Documentation The Legend at
Page 155 and 156:
Imatest Documentation MTF50 (Cy/Pxl
Page 157 and 158:
Imatest Documentation Summary plot
Page 159 and 160:
Imatest Documentation 3D Plot for M
Page 161 and 162:
Imatest Documentation The standard
Page 163 and 164:
Imatest Documentation degrees are i
Page 165 and 166:
Imatest Documentation Using SFRplus
Page 167 and 168:
Imatest Documentation SFRplus setup
Page 169 and 170:
Imatest Documentation SFRplus setti
Page 171 and 172:
Imatest Documentation Gamma Gamma i
Page 173 and 174:
Imatest Documentation Using SFRplus
Page 175 and 176:
Imatest Documentation Weighted MTF5
Page 177 and 178:
Imatest Documentation This display
Page 179 and 180:
Imatest Documentation space of the
Page 181 and 182:
Imatest Documentation window, shown
Page 183 and 184:
Imatest Documentation It's easy to
Page 185 and 186:
Imatest Documentation Using Reschar
Page 187 and 188:
Imatest Documentation Select an ima
Page 189 and 190:
Imatest Documentation MTF contours
Page 191 and 192:
Imatest Documentation SFRplus SFR H
Page 193 and 194:
Imatest Documentation Log F-Contras
Page 195 and 196:
Imatest Documentation Log Frequency
Page 197 and 198:
Imatest Documentation Color moiré
Page 199 and 200:
Imatest Documentation The display o
Page 201 and 202:
Imatest Documentation phase) is twi
Page 203 and 204:
Imatest Documentation Downloadable
Page 205 and 206:
Imatest Documentation If Express mo
Page 207 and 208:
Imatest Documentation The display o
Page 209 and 210:
Imatest Documentation The differenc
Page 211 and 212:
Imatest Documentation Star Chart An
Page 213 and 214:
Imatest Documentation ROI fine adju
Page 215 and 216:
Imatest Documentation MTF (linear f
Page 217 and 218:
Imatest Documentation The plot on t
Page 219 and 220:
Imatest Documentation MTF Compare C
Page 221 and 222:
Imatest Documentation MTF Compare r
Page 223 and 224:
Imatest Documentation Comparison of
Page 225 and 226:
Imatest Documentation Batchview Pos
Page 227 and 228:
Imatest Documentation Rescharts SFR
Page 229 and 230:
Imatest Documentation Running Batch
Page 231 and 232:
Imatest Documentation Center mean O
Page 233 and 234:
Imatest Documentation standard mono
Page 235 and 236:
Imatest Documentation Lighting Inte
Page 237 and 238:
Imatest Documentation Run Imatest S
Page 239 and 240:
Imatest Documentation SFRplus setup
Page 241 and 242:
Imatest Documentation SFRplus setti
Page 243 and 244:
Imatest Documentation Additional pa
Page 245 and 246:
Imatest Documentation Output files
Page 247 and 248:
Imatest Documentation Lens-style MT
Page 249 and 250:
Imatest Documentation File formats
Page 251 and 252:
Imatest Documentation Purchase or d
Page 253 and 254:
Imatest Documentation Sharpness tar
Page 255 and 256:
Imatest Documentation Proper exposu
Page 257 and 258:
Imatest Documentation If you answer
Page 259 and 260:
Imatest Documentation SFR input dia
Page 261 and 262:
Imatest Documentation Figures (.PNG
Page 263 and 264:
Imatest Documentation contrast imag
Page 265 and 266:
Imatest Documentation Chromatic Abe
Page 267 and 268:
Imatest Documentation QA-61 ISO-160
Page 269 and 270:
Imatest Documentation Stepchart inp
Page 271 and 272:
Imatest Documentation First Figure:
Page 273 and 274:
Imatest Documentation Third Figure:
Page 275 and 276:
Imatest Documentation A camera's (o
Page 277 and 278:
Imatest Documentation The total dyn
Page 279 and 280:
Imatest Documentation Gamc is typic
Page 281 and 282:
Imatest Documentation ISO-15739 Noi
Page 283 and 284:
Imatest Documentation You can enter
Page 285 and 286:
Imatest Documentation Results If RA
Page 287 and 288:
Imatest Documentation Dynamic range
Page 289 and 290:
Imatest Documentation Using Colorch
Page 291 and 292:
Imatest Documentation horizontal fi
Page 293 and 294:
Imatest Documentation Colorcheck in
Page 295 and 296:
Imatest Documentation The first fig
Page 297 and 298:
Imatest Documentation The backgroun
Page 299 and 300:
Imatest Documentation saturated gre
Page 301 and 302:
Imatest Documentation (blank line)
Page 303 and 304:
Imatest Documentation CMC An early
Page 305 and 306:
Imatest Documentation The the equat
Page 307 and 308:
Imatest Documentation Multicharts o
Page 309 and 310:
Imatest Documentation If you select
Page 311 and 312:
Imatest Documentation The Zoom chec
Page 313 and 314:
Imatest Documentation + b* Pseudoco
Page 315 and 316:
Imatest Documentation Shows the gra
Page 317 and 318:
Imatest Documentation Multicharts S
Page 319 and 320:
Imatest Documentation Read from a 5
Page 321 and 322:
Imatest Documentation Use these ord
Page 323 and 324:
Imatest Documentation Color correct
Page 325 and 326:
Imatest Documentation Options: Colo
Page 327 and 328:
Imatest Documentation Exif and Colo
Page 329 and 330:
Imatest Documentation The Labsphere
Page 331 and 332:
Imatest Documentation Scaling butto
Page 333 and 334:
Imatest Documentation F-stop contou
Page 335 and 336:
Imatest Documentation Uniformity (L
Page 337 and 338:
Imatest Documentation density— vi
Page 339 and 340:
Imatest Documentation the Corner an
Page 341 and 342:
Imatest Documentation The local noi
Page 343 and 344:
Imatest Documentation Local nonunif
Page 345 and 346:
Imatest Documentation Image with sp
Page 347 and 348:
Imatest Documentation Using Distort
Page 349 and 350:
Imatest Documentation Set exposure
Page 351 and 352:
Imatest Documentation Plot distorti
Page 353 and 354:
Imatest Documentation Imatest will
Page 355 and 356:
Imatest Documentation MTF (sharpnes
Page 357 and 358:
Imatest Documentation Intersection
Page 359 and 360:
Imatest Documentation function of r
Page 361 and 362:
Imatest Documentation Imatest Instr
Page 363 and 364:
Imatest Documentation Horizontal di
Page 365 and 366:
Imatest Documentation Zone plates (
Page 367 and 368:
Imatest Documentation Along with ch
Page 369 and 370:
Imatest Documentation Preview image
Page 371 and 372:
Imatest Documentation Light Falloff
Page 373 and 374:
Imatest Documentation Monitor Calib
Page 375 and 376:
Imatest Documentation Black level (
Page 377 and 378:
Imatest Documentation Reset pattern
Page 379 and 380:
Imatest Documentation SVG Test Char
Page 381 and 382:
Imatest Documentation SVG SFR chart
Page 383 and 384:
Imatest Documentation To run Test C
Page 385 and 386:
Imatest Documentation Invert light/
Page 387 and 388:
Imatest Documentation Contrast (alt
Page 389 and 390:
Imatest Documentation window. Print
Page 391 and 392:
Imatest Documentation files. Quick
Page 393 and 394:
Imatest Documentation File selectio
Page 395 and 396:
Imatest Documentation Imatest IT/EX
Page 397 and 398:
Imatest Documentation cyclesper_val
Page 399 and 400:
Imatest Documentation optional. The
Page 401 and 402:
Imatest Documentation Change to the
Page 403 and 404:
Imatest Documentation Detailed inst
Page 405 and 406:
Imatest Documentation Scanner profi
Page 407 and 408:
Imatest Documentation Although this
Page 409 and 410:
Imatest Documentation Gamut is exce
Page 411 and 412:
Imatest Documentation S=1 HSL Hue p
Page 413 and 414:
Imatest Documentation An additional
Page 415 and 416:
Imatest Documentation Instructions
Page 417 and 418:
Imatest Documentation 7. 8. Mask im
Page 419 and 420:
Imatest Documentation 9. Corr Image
Page 421 and 422:
Imatest Documentation Appendix Cros
Page 423 and 424:
Imatest Documentation Sorted by tes
Page 425 and 426:
Imatest Documentation Distortion Un
Page 427 and 428:
Imatest Documentation Create Scalab
Page 429 and 430:
Imatest Documentation f-stop . Gamm
Page 431 and 432:
Imatest Documentation Glosario en E
Page 433 and 434:
Imatest Documentation Troubleshooti
Page 435 and 436:
Imatest Documentation You can selec
Page 437 and 438:
Imatest Documentation Imatest Chang
Page 439 and 440:
Imatest Documentation below, next t
Page 441 and 442:
Imatest Documentation Jan. 6, 2007
Page 443 and 444:
Imatest Documentation Nov. 6, 2005
Page 445 and 446:
Imatest Documentation Sept. 11, 200
Page 447 and 448:
Imatest Documentation XML Changes N
Page 449 and 450:
Imatest Documentation License The I
Page 451:
Imatest Documentation 11. GENERAL T
show all

Imatest Documentation

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?