1pfshdrcalibrate(1) General Commands Manual pfshdrcalibrate(1)
2
6 pfshdrcalibrate - Create an HDR image or calibrate a response curve
7 from a set of differently exposed images supplied in PFS stream.
8
11 pfshdrcalibrate [--response <type>] [--calibration <type>] [--gauss
12 <val>] [--response-file <filename.m>] [--save-response <filename.m>]
13 [--multiplier <val>] [--bpp <val>] [--luminance] [--samples <val>]
14 [--help] [--verbose]
15
18 Create an HDR image or calibrate a response curve from a set of differ‐
19 ently exposed images supplied in PFS stream.
20 When used with 8bit images, luminance in the output HDR image corre‐
22 sponds to real world values in [cd/m^2] provided that hdrgen script
23 contained correct information on exposure time, aperture and iso speed.
24 Note that sometimes ISO speed indicated by camera does not correspond
25 to standard (ISO-100 is in fact ISO-125).
26 The accuracy of absolute calibration has not been thoroughly tested
28 with different camera models, however one can expect the relative mea‐
29 surement error below 8%. Use pfsabsolute in case of systematic error.
30
33 --response <type>, -r <type>
34 Allows one to choose from predefined response curves. This can
36 be used either to apply this response or use it as an initial‐
37 ization for automatic self-calibration. Predefined response
38 curves are: "linear", "gamma", "log". Default is "linear". This
39 option can be used only with Robertson method.
40 --calibration <type>, -c <type>
43 Type of automatic self-calibration method used for recovery of
45 the response curve and/or type of method used for HDR merging.
46 Accepted types include: "robertson", "mitsunaga". "robertson" is
47 the default and recommended algorithm (see commends in the Bugs
48 section below). More infomation on the algorithms can be found
49 in:
50 M.A. Robertson, S. Borman and R.L. Stevenson
52 Dynamic range improvement through multiple exposures
53 In: Proc. of International Conference on Image Processing 1999
54 (ICIP 99), pp 159-163 vol.3
55 and
57 T. Mitsunaga and S. K. Nayar
59 Radiometric Self Calibration
60 In: Proc on IEEE Conf. on Computer Vision and Pattern Recogni‐
61 tion (CVPR'99). Volume 1, p. 1374
62 --gauss <val>, -g <val>
64 Sigma value for the Gaussian used as a weighting function (in
66 the range 0-1). Applies to Robertson02 algorithm. Default value:
67 0.2
68 --response-file <filename.m>, -f <filename.m>
71 Use response curve saved in the matlab format file. Turns off
73 automatic self-calibration. Uses Robertson02 or Mitsunaga99
74 model to apply the response curve (see -c option).
75 --save-response <filename.m>, -s <filename.m>
78 Saves the response curve calculated during automatic self-cali‐
80 bration stage in a matlab format file. Can be later reused for
81 set of images captured with given camera. Also works fine for
82 plotting with gnuplot.
83 --multiplier <val>, -m <val>
86 Input multiplier value. Can be used to manipulate the range of
88 source exposures. Default value for Robertson method is 256
89 since LDR images are by default scaled to 0..1. This value is
90 set to 1.0 for Mitsunaga method.
91 --bpp <val>, -b <val>
94 Number of bits per pixel in input data from the camera. Default
96 value is 8.
97 --samples <val>, -p <val>
100 Number of samples used during the self-calibration in Mitsunaga
102 algorithm. Default is 50000.
103 --deghosting, -d
106 EXPERIMENTAL. Try to use a simple rejection criterion to reduce
108 ghosting artifacts due to movement in dynamic scenes. This is
109 currently not well implemented to the results can be disappoint‐
110 ing.
111 --luminance, -Y
114 Recovery of response curve will be performed for luminance chan‐
116 nel only.
117 --verbose
120 Print additional information during program execution.
122 --help
124 Print list of command line options.
126
129 pfsinme *.JPG | pfshdrcalibrate -v -s response.m | pfsview
130 Recover the response curve from set of all JPEG files in the
132 current directory and save it to response.m file. To view the
133 response curve, use pfsplotresponse command.
134 pfsinme *.CR2 | pfssize --maxx 1200 | pfshdrcalibrate -r linear -v
136 --bpp 16 | pfsout result.exr
137 Read Camera RAW images (from Canon), resize them so that the
139 image width is equal or less 1200 pixels, merge them into an HDR
140 image using all 16 bits and save as an Open EXR image.
141 pfsinhdrgen sample.hdrgen | pfshdrcalibrate -x -f response.m | pfsview
143 Create an HDR image from exposures defined in sample.hdrgen
145 using the response curve "response.m" and view it. Fix the prob‐
146 lem with black values given to overexposed pixels.
147 pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
149 Create an HDR image from exposures defined in sample.hdrgen
151 using the default self-calibration method and view it.
152 pfsinhdrgen sample_dcraw.hdrgen | pfshdrcalibrate -b 16 -r linear -c
154 none | pfsview
155 Given that the script sample_dcraw.hdrgen refers to camera RAW
157 files (see pfsindcraw), this example will generate an HDR image
158 assuming a linear response.
159 pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
161 Create an HDR image from exposures defined in sample.hdrgen
163 using the default self-calibration method and view it.
164 pfsinhdrgen sample.hdrgen | pfshdrcalibrate -c mitsunaga -samples
166 100000 -s resp_mitsunaga.m >/dev/null
167 Create an HDR image from exposures defined in sample.hdrgen
169 using the mitsunaga self-calibration method with 100000 samples
170 and save it to "resp_mitsunaga.m".
171
173 pfsplotresponse(1) pfsinhdrgen(1) jpeg2hdrgen(1) pfsview(1) pfsind‐
174 craw(1) pfsabsolute(1) pfsglview(1)
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177 Currently Mitsunaga and Nayar's method does not produce reliable camera
178 response curves. Robertson's method should be used instead.
179 Robertson's method may banding or wrong colors in strongly over-satu‐
181 rated and under-saturated areas. For best results, there should be a
182 sufficient numbers of exposures in which no pixels is over- or under-
183 saturated in all the exposures. It is possible to fix these issues with
184 some heuristics (as most HDR merging software does), but it is cur‐
185 rently not done in this release. pfscalibration was meant to be used
186 for research purposes and getting accurate result is more important
187 than generating good looking images. The heuristics could hide the well
188 visible artifacts, but would also introduce error to the measurements.
189 For any other issues please report bugs and comments on implementation
191 to the discussion group http://groups.google.com/group/pfstools
192 pfshdrcalibrate(1)