LiYuXie - Revision history

imported>Projects221: /* Conclusions */

2014-03-22T08:54:16Z

Conclusions

← Older revision		Revision as of 08:54, 22 March 2014
Line 280:		Line 280:
	=Conclusions=		=Conclusions=

	'''Luminance'''--For all these three kinds of images, we can see from the displayed image that with the increase of light level, image quality in terms of noise is getting better, which ~~is coincident~~ with what is shown in the vSNR plot. With the increase of light level, the overall image quality is getting better. Thus, we could conclude that this camera image quality metric can effectively reflect the noise level and overall image quality in terms of light level.		'''Luminance'''--For all these three kinds of images, we can see from the displayed image that with the increase of light level, image quality in terms of noise is getting better, which matches with what is shown in the vSNR plot. With the increase of light level, the overall image quality is getting better. Thus, we could conclude that this camera image quality metric can effectively reflect the noise level and overall image quality in terms of light level.


	'''Pixel Size'''--For all these three kinds of images, we can see from the displayed image that with the increase of pixel size, image quality in terms of noise is getting better, which is also indicated in the vSNR plots. However, the overall image quality from human observation might not be the best at the largest pixel size. Due to the influence of resolution factor, human eyes may sense the best overall image quality at a specific pixel size. Thus, we could conclude that this camera image quality metric can effectively reflect the noise level of the images in terms of pixel size, but it does not coincide with human feelings, because of the influence of resolution.		'''Pixel Size'''--For all these three kinds of images, we can see from the displayed image that with the increase of pixel size, image quality in terms of noise is getting better, which is also indicated in the vSNR plots. However, the overall image quality from human observation might not be the best at the largest pixel size. Due to the influence of resolution factor, human eyes may sense the best overall image quality at a specific pixel size. Thus, we could conclude that this camera image quality metric can effectively reflect the noise level of the images in terms of pixel size, but it does not coincide with human feelings, because of the influence of resolution.

			'''Exposure Time'''--From the image displayed, we could see that image quality in terms of noise is better when exposure time is increasing, meanwhile the image quality if getting better. This can be related to luminance, since longer exposure time gives more photon cast on the scene, thus reduces the photon noise. VSNR can reflect the noise level of image as well as the observed image quality.

imported>Projects221: /* F-number */

2014-03-22T07:50:43Z

F-number

← Older revision		Revision as of 07:50, 22 March 2014
Line 228:		Line 228:
	'''Human Face'''		'''Human Face'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		exposureTime=0.03, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): fnumber = [3, 5, 8] <br>		Vertically (from top to bottom): fnumber = [3, 5, 8] <br>
Line 245:		Line 245:
	'''Text'''		'''Text'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		exposureTime=0.03, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): fnumber = [3, 5, 8] <br>		Vertically (from top to bottom): fnumber = [3, 5, 8] <br>
Line 264:		Line 264:
	'''Landscape'''		'''Landscape'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		exposureTime=0.03, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): fnumber = [3, 5, 8] <br>		Vertically (from top to bottom): fnumber = [3, 5, 8] <br>

imported>Projects221: /* Exposure Time */

2014-03-22T07:48:06Z

Exposure Time

← Older revision		Revision as of 07:48, 22 March 2014
Line 173:		Line 173:
	'''Human Face'''		'''Human Face'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		f#=5, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>		Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>
Line 190:		Line 190:
	'''Text'''		'''Text'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		f#=5, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>		Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>
Line 209:		Line 209:
	'''Landscape'''		'''Landscape'''

	~~Fov~~=5, viewD=0.2, pixel = 1 <br>		f#=5, viewD=0.2, pixel = 1 <br>
	Horizontally (from left to right): lightLevels = [50,100,200] <br>		Horizontally (from left to right): lightLevels = [50,100,200] <br>
	Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>		Vertically (from top to bottom): exposure time = [0.01, 0.03, 0.3] <br>
Line 222:		Line 222:
	<br>		<br>
	From the above plots we could see that vSNR is higher when exposure time getting longer. Thus, we could conclude that vSNR can effectively reflect the noise level and overall image quality of human face image, in terms of exposure time.		From the above plots we could see that vSNR is higher when exposure time getting longer. Thus, we could conclude that vSNR can effectively reflect the noise level and overall image quality of human face image, in terms of exposure time.


	== F-number ==		== F-number ==

imported>Projects221: /* Pixel Size */

2014-03-22T07:47:08Z

Pixel Size

← Older revision		Revision as of 07:47, 22 March 2014
Line 128:		Line 128:
	'''Human Face'''		'''Human Face'''

	~~Fov~~=5, f#=5, viewD=0.2 <br>		exposureTime=0.03, f#=5, viewD=0.2 <br>
	Horizontally (from left to right): lightLevels = [5,10,100,200] <br>		Horizontally (from left to right): lightLevels = [5,10,100,200] <br>
	Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>		Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>
Line 143:		Line 143:
	'''Text'''		'''Text'''

	~~Fov~~=5, f#=5, viewD=0.2 <br>		exposureTime=0.03, f#=5, viewD=0.2 <br>
	Horizontally (from left to right): lightLevels = [5,10,100,200] <br>		Horizontally (from left to right): lightLevels = [5,10,100,200] <br>
	Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>		Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>
Line 157:		Line 157:
	'''Landscape'''		'''Landscape'''

	~~Fov~~=5, f#=5, viewD=0.2 <br>		exposureTime=0.03, f#=5, viewD=0.2 <br>
	Horizontally (from left to right): lightLevels = [5,10,100,200] <br>		Horizontally (from left to right): lightLevels = [5,10,100,200] <br>
	Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>		Vertically (from top to bottom): pixel = [0.5,1,2,4] <br>

imported>Projects221: /* Background */

2014-03-22T07:46:03Z

Background

← Older revision		Revision as of 07:46, 22 March 2014
Line 5:		Line 5:

	=Background=		=Background=
	~~== Image Quality Metrics ==~~
	Nowadays, a lot of metrics are used to evaluate image quality, such as ISO 15739 visual noise, S-CIELAB and vSNR, which can be found in the paper ''Development of the I3A CPIQ spatial metrics''[1]. Their goals are to predict the visible differences between a pair of images. These metrics are commonly used to measure the important aspects of image quality such as sharpness, noise, contrast and so on.
	~~== visible SNR ==~~
	Signal-to-noise ratio(SNR)is a measure that compares the level of a signal to the level of background noise. It is defined as the ratio of signal power to the noise power. The SNR used in imaging is a physical measure of the sensitivity of a imaging system.

	The vSNR is the inverse of the standard deviation of the SCIELAB representation of a uniform field; its units are 1/ΔE[2].The vSNR metric can be used in simulations to predict how imaging system components affect noise visibility[2].		Nowadays, a lot of metrics are used to evaluate image quality, such as ISO 15739 visual noise, S-CIELAB and vSNR, which can be found in the paper ''Development of the I3A CPIQ spatial metrics''[1]. Their goals are to predict the visible differences between a pair of images. These metrics are commonly used to measure the important aspects of image quality such as sharpness, noise, contrast and so on. However, the optical non-uniformities prevalent in cell phone cameras and the potentially higher noise level lead to challenges to the ISO 15739 protocal.
			Thus we would like to introduce vSNR as our main metrics here. Signal-to-noise ratio(SNR) evaluates the level of a signal to the level of background noise. It is defined as the ratio of signal power to the noise power. The SNR used in imaging is a physical measure of the sensitivity of a imaging system. For visual noise evaluation, vSNR is the inverse of the standard deviation of the SCIELAB representation of a uniform field; its units are 1/ΔE[2].The vSNR metric can be used in simulations to predict how imaging system components affect noise visibility[2]. From technology side, PRNU and DSNU can be minimized, but photon noise cannot. VSNR probably is a good metric to measure noise, specifically photon noise here, but the its effectiveness in reflecting human subjective observations is yet to be checked. It is quite important to identify whether it could correlate the human observation and physical measurement, or we are supposed to find better metrics.

	=Methods=		=Methods=

imported>Projects221: /* Appendix I */

2014-03-22T07:43:10Z

Appendix I

← Older revision		Revision as of 07:43, 22 March 2014
Line 308:		Line 308:
	s_Psych221_winter2014_vSNR.m		s_Psych221_winter2014_vSNR.m
	[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]		[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]
	<br>		<br><br>
	To change light level, pixel size, fnumber, edit in:		To change light level, pixel size, fnumber, edit in:
	cameraVSNR.m -- "Tuning the camera parameters" part. <br>		cameraVSNR.m -- "Tuning the camera parameters" part. <br>

imported>Projects221: /* Appendix I */

2014-03-22T07:42:57Z

Appendix I

← Older revision		Revision as of 07:42, 22 March 2014
Line 309:		Line 309:
	[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]		[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]
	<br>		<br>
	To change light level, pixel size, fnumber, edit ~~the parameters~~ in cameraVSNR.m -- "Tuning the camera parameters" part. <br>		To change light level, pixel size, fnumber, edit in:
			cameraVSNR.m -- "Tuning the camera parameters" part. <br>
	To change exposure time, edit in both these two files: <br>		To change exposure time, edit in both these two files: <br>
	cameraVSNR.m -- "Tuning the camera parameters" part. <br>		cameraVSNR.m -- "Tuning the camera parameters" part. <br>

imported>Projects221: /* Algorithms */

2014-03-22T07:39:44Z

Algorithms

← Older revision		Revision as of 07:39, 22 March 2014
Line 18:		Line 18:

	== Algorithms ==		== Algorithms ==
	To evaluate the effectiveness of vSNR for measuring image quality, we investigate vSNR effectiveness with different parameters for processing different type of scenes. We use ISET to calculate metrics for different parameters (e.g. luminance, pixel size, F-number). We also use ISET to simulate how camera captures and processes different type of scenes (e.g. faces, text and landscapes). For each condition, we compare the metrics with the appearance of these images as they are rendered on a display. We use control variate method to measure and compare the influence of each variable.		To evaluate the effectiveness of vSNR for measuring image quality, we investigate vSNR effectiveness with different parameters for processing different type of scenes. We use ISET to calculate metrics for different parameters (e.g. luminance, pixel size, exposure time, F-number). We also use ISET to simulate how camera captures and processes different type of scenes (e.g. faces, text and landscapes). For each condition, we compare the metrics with the appearance of these images as they are rendered on a display. We use control variate method to measure and compare the influence of each variable.

	== Experimental Procedure ==		== Experimental Procedure ==

imported>Projects221: /* Experimental Procedure */

2014-03-22T07:38:38Z

Experimental Procedure

← Older revision		Revision as of 07:38, 22 March 2014
Line 44:		Line 44:
	(iii) For landscape, <br>		(iii) For landscape, <br>
	Control light level = [5,10,100,200], Exposure Time=0.03, f-number=5, viewD=0.2. Change pixel = [0.5, 1, 2, 4].<br>		Control light level = [5,10,100,200], Exposure Time=0.03, f-number=5, viewD=0.2. Change pixel = [0.5, 1, 2, 4].<br>


	(3) Exposure Time <br>		(3) Exposure Time <br>
Line 60:		Line 61:
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.03.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.03.<br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.3.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.3.<br>


	(4) F-number <br>		(4) F-number <br>

imported>Projects221 at 07:36, 22 March 2014

2014-03-22T07:36:30Z

← Older revision		Revision as of 07:36, 22 March 2014
Line 52:		Line 52:

	(ii) For text, <br>		(ii) For text, <br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 3.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.01.<br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 5.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.03.<br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 8.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.3.<br>

	(iii) For landscape, <br>		(iii) For landscape, <br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 3.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.01.<br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 5.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.03.<br>
	Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change ~~f-number~~ = 8.<br>		Control Exposure Time=0.03, viewD=0.2, light level = [50, 100, 200]. Change Exposure Time=0.3.<br>

	(4) F-number <br>		(4) F-number <br>
Line 300:		Line 300:
	[2] J. Farrell et al., ”Using visible SNR (vSNR) to compare the image quality of pixel binning and digital resizing”, Proc SPIE 7537, 75370C (2010).		[2] J. Farrell et al., ”Using visible SNR (vSNR) to compare the image quality of pixel binning and digital resizing”, Proc SPIE 7537, 75370C (2010).

	We appreciate guidance and help from Professor Farrell.		'''We appreciate guidance and help from Professor Farrell.'''

	=Appendix I=		=Appendix I=

	s_Psych221_winter2014_vSNR.m		s_Psych221_winter2014_vSNR.m
	[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]		[https://www.dropbox.com/s/u9paxmu4mc2r8oy/s_Psych221_winter2014_vSNR.m]
	~~<br>~~<br>		<br>
	To change light level, pixel size, fnumber, edit in:		To change light level, pixel size, fnumber, edit the parameters in cameraVSNR.m -- "Tuning the camera parameters" part. <br>
	cameraVSNR.m -- "Tuning the camera parameters" part. <br>
	To change exposure time, edit in both these two files: <br>		To change exposure time, edit in both these two files: <br>
	cameraVSNR.m -- "Tuning the camera parameters" part. <br>		cameraVSNR.m -- "Tuning the camera parameters" part. <br>