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 --fix-saturated, -x
106 Use this option if you see black pixels in overexposed / satu‐
108 rated areas. The black pixels are visible if all exposures con‐
109 tain pixel values that are outside reliable range (are under- or
110 over-exposed). This flag gives non-zero weight for the brightest
111 and the darkest pixels, thus avoiding zero-weighted pixels. Note
112 that the calculated luminance values for these pixels are not
113 reliable.
114 --luminance, -Y
117 Recovery of response curve will be performed for luminance chan‐
119 nel only.
120 --verbose
123 Print additional information during program execution.
125 --help
127 Print list of command line options.
129
132 pfsinme *.JPG | pfshdrcalibrate -v -s response.m | pfsview
133 Recover the response curve from set of all JPEG files in the
135 current directory and save it to response.m file. To view the
136 response curve, use pfsplotresponse command.
137 pfsinme *.CR2 | pfssize --maxx 1200 | pfshdrcalibrate -r linear -v
139 --bpp 16 | pfsout result.exr
140 Read Camera RAW images (from Canon), resize them so that the
142 image width is equal or less 1200 pixels, merge them into an HDR
143 image using all 16 bits and save as an Open EXR image.
144 pfsinhdrgen sample.hdrgen | pfshdrcalibrate -x -f response.m | pfsview
146 Create an HDR image from exposures defined in sample.hdrgen
148 using the response curve "response.m" and view it. Fix the prob‐
149 lem with black values given to overexposed pixels.
150 pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
152 Create an HDR image from exposures defined in sample.hdrgen
154 using the default self-calibration method and view it.
155 pfsinhdrgen sample_dcraw.hdrgen | pfshdrcalibrate -b 16 -r linear -c
157 none | pfsview
158 Given that the script sample_dcraw.hdrgen refers to camera RAW
160 files (see pfsindcraw), this example will generate an HDR image
161 assuming a linear response.
162 pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
164 Create an HDR image from exposures defined in sample.hdrgen
166 using the default self-calibration method and view it.
167 pfsinhdrgen sample.hdrgen | pfshdrcalibrate -c mitsunaga -samples
169 100000 -s resp_mitsunaga.m >/dev/null
170 Create an HDR image from exposures defined in sample.hdrgen
172 using the mitsunaga self-calibration method with 100000 samples
173 and save it to "resp_mitsunaga.m".
174
176 pfsplotresponse(1) pfsinhdrgen(1) jpeg2hdrgen(1) pfsview(1) pfsind‐
177 craw(1) pfsabsolute(1) pfsglview(1)
178
180 Currently Mitsunaga and Nayar's method does not produce reliable camera
181 response curves. Robertson's method should be used instead.
182 Robertson's method may banding or wrong colors in strongly over-satu‐
184 rated and under-saturated areas. For best results, there should be a
185 sufficient numbers of exposures in which no pixels is over- or under-
186 saturated in all the exposures. It is possible to fix these issues with
187 some heuristics (as most HDR merging software does), but it is cur‐
188 rently not done in this release. pfscalibration was meant to be used
189 for research purposes and getting accurate result is more important
190 than generating good looking images. The heuristics could hide the well
191 visible artifacts, but would also introduce error to the measurements.
192 For any other issues please report bugs and comments on implementation
194 to the discussion group http://groups.google.com/group/pfstools
195 pfshdrcalibrate(1)