TCG Challenge #1
CALCULATING CAMERA SNR
Agenda
•SNR definition
•Calculation Method
•Visual Results
•Results
•Conclusions
Definition
Traditionally, SNR has been defined as the ratio of the average signal value to the standard
deviation of the background.
However, when presented with a high-contrast scene, many imaging systems clamp the
background to uniform black, forcing to zero, artificially making the SNR infinite.
In this case a better definition of SNR is the ratio of the average signal value to the standard
deviation of the signal.
Method
Following the definition we calculate the “average of the signal” defining each pixel along the
samples as a signal and using the arithmetic mean.
Arithmetic Mean (Mn)
= (𝐼1 +𝐼2 +𝐼3 + ..... +𝐼𝑛 )/𝑛
In order to be able to calculate the standard deviation from each signal we then need to
calculate the true value of each signal/pixel to conform the “True Image” we determine each
pixel of this image using the arithmetic mean, the median and mode as average to determine
which one yields better results.
Median (Md)
= 𝐼𝑛/2 𝑓𝑜𝑟 𝑠𝑜𝑟𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝐼
Mode (Mo)
= the most repeated value
Standard Deviation (SDi) = ((𝐼1 −𝐼𝑟 )2 + (𝐼2 −𝐼𝑟 )2 + … (𝐼𝑛 −𝐼𝑟 )2 )/2
Visual Results “True Image”
ORIGINAL IMAGE
“TRUE IMAGE” BASED ON MEAN
Visual Results “True Image”
ORIGINAL IMAGE
“TRUE IMAGE” BASED ON MEDIAN
Visual Results “True Image”
ORIGINAL IMAGE
“TRUE IMAGE” BASED ON MODE
Median vs Mean vs Mode
Results
20 log10 𝑆𝑁𝑅
40
35
30
25
20
15
10
5
0
Djalma
Jonatas
Victor
mean
median
Graziele
mode
Renato
Conclusion