Simple math:
log2 (x) = logy (x) / logy (2)
where y can be anything, which for standard log functions is either 10 or e.
Answer from Adam Crume on Stack OverflowReddit
reddit.com › r/canon › c-log 3 vs c-log 2
r/canon on Reddit: C-log 3 vs C-log 2
February 4, 2023 -
Hi I’m new to the whole high end camera thing. When I first got into shooting videos all the YouTubers were talking about C-log 3 when reviewing canon cameras. I recently for the first time heard about C-log 2. Is the difference that noticeable? What would be the differences?
Top answer 1 of 3
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According to Canon, C-Log 2 gives more dynamic range in shadows, but is slightly noisier as a result. C-Log 3 preserves less shadow detail but has a cleaner noise floor, meaning it's less likely noise reduction is needed in post. The reality is very few Canon cameras carry C-Log 2, and C-Log 3 in theory provides more than enough dynamic range for most canon camera's, apart from those with dual gain output (C70). That being said, C-Log 2 does preserve more information in the shadows, and does permit better shadow recovery!
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R cameras only have Clog3 or Clog1. Dynamic range goes; Clog1 lowest, Clog 3, Clog2 highest. The r5 does not max out the dynamic range of Clog3. I assume it is similar story for the rest of the R line. So Clog2 would have only negative impact if it was used. R5 is not a great sensor, 10.3 clean stops with 8k raw in the R5. 11.9 in H2s. 12.3 in C70 Even beat by the tiny sensor in the GH6 at 11 https://www.cined.com/canon-eos-r5-lab-test-to-film-in-raw-or-not/ https://www.cined.com/fujifilm-x-h2s-lab-test-rolling-shutter-dynamic-range-and-exposure-latitude/ https://www.cined.com/canon-eos-c70-lab-test-with-the-raw-update-rolling-shutter-dynamic-range-and-latitude/ https://www.cined.com/panasonic-lumix-gh6-lab-test-rolling-shutter-dynamic-range-and-latitude/
W3Schools
w3schools.com › c › ref_math_log2.php
C Math log2() Function
The log2() function returns the base 2 logarithm of a number. The log2() function is defined in the <math.h> header file. One of the following: log2(double number); ❮ Math Functions · C Functions Tutorial · C Math Functions Tutorial · ★ ...
Videos
When to use Clog2 vs Clog3 | C70 Comparison
Le C-LOG2 sur le CANON EOS R5 Mark II et étalonnage ...
34:05
C-Log Color Grading - Easy Techniques (Including FREE) - Premiere ...
08:27
How to expose Canon C70 Clog 2 - YouTube
04:35
EXPOSER LE C-LOG2 ET C-LOG3 FACILEMENT ( très facilement ) - YouTube
08:26
YES! You CAN capture CLog2 on the CANON R5 - YouTube
What is the difference between Canon Log, Canon Log 2 and Canon Log 3?
The original Canon Log delivers a dynamic range of approximately 12 stops, Canon Log 2 up to 16 stops, and Canon Log 3 up to 14 stops. Canon Log 2 retains more detail in darker areas than Canon Log 3 but also features an elevated noise floor. Canon Log 3 is easier to grade thanks to producing a cleaner image and retains the same amount of highlight information as Canon Log 2.
canon-europe.com
canon-europe.com › professional photography & video › stories
Enhance your filmmaking with Canon Log - Canon Europe
What is Canon Log used for?
Canon Log is used to capture video footage that has a wider dynamic range and exposure latitude than standard video. The Canon Log tone curve is applied at the point of capture to retain more details in the highlights and shadows compared to standard video.
canon-europe.com
canon-europe.com › professional photography & video › stories
Enhance your filmmaking with Canon Log - Canon Europe
How does Canon Log help with colour grading in post-production?
Canon Log helps with colour grading as it is recorded at 10-bit colour depth and provides a flat image with low saturation that is an excellent foundation for colour adjustments and HDR workflows. It is easier to match footage shot on different cameras that have been set to Canon Log, enabling clips from Cinema EOS and EOS mirrorless cameras to be combined and colour matched to give a consistent look on a multi-cam shoot.
canon-europe.com
canon-europe.com › professional photography & video › stories
Enhance your filmmaking with Canon Log - Canon Europe
Cppreference
en.cppreference.com › w › c › numeric › math › log2
log2, log2f, log2l - cppreference.com
February 15, 2022 - #include <stdio.h> #include <math.h> #include <float.h> #include <errno.h> #include <fenv.h> // #pragma STDC FENV_ACCESS ON int main(void) { printf("log2(65536) = %f\n", log2(65536)); printf("log2(0.125) = %f\n", log2(0.125)); printf("log2(0x020f) = %f (highest set bit is in position 9)\n", log2(0x020f)); printf("base-5 logarithm of 125 = %f\n", log2(125)/log2(5)); // special values printf("log2(1) = %f\n", log2(1)); printf("log2(+Inf) = %f\n", log2(INFINITY)); //error handling errno = 0; feclearexcept(FE_ALL_EXCEPT); printf("log2(0) = %f\n", log2(0)); if(errno == ERANGE) perror(" errno == ERANGE"); if(fetestexcept(FE_DIVBYZERO)) puts(" FE_DIVBYZERO raised"); }
Canon Community
community.usa.canon.com › t5 › Professional-Video › ICYMI-Canon-dropped-the-C-Log-2-3-to-Canon-709-LUT › td-p › 563580
ICYMI: Canon dropped the C-Log 2/3 to Canon 709 LU... - Canon Community
January 13, 2026 - ICYMI: Canon dropped the C-Log 2/3 to Canon 709 LU...
Cplusplus
cplusplus.com › reference › cmath › log2
Cplusplus
Returns the binary (base-2) logarithm of x. Header <tgmath.h> provides a type-generic macro version of this function. Additional overloads are provided in this header (<cmath>) for the integral types: These overloads effectively cast x to a double before calculations (defined for T being any ...
Educative
educative.io › answers › what-is-log2-in-c
What is log2 in C?
The log2 function returns the binary logarithm of the number given as a parameter. The returned number is of datatype double. ... Copyright ©2025 Educative, Inc.
Canon Asia
snapshot.canon-asia.com › article › eng › videography-faq-what-is-canon-log
Videography FAQ: What is Canon Log? - SNAPSHOT
September 15, 2023 - There are three different Canon Log modes: the original Canon Log, Canon Log 2, and Canon Log 3.
Canon Europe
canon-europe.com › professional photography & video › stories
Enhance your filmmaking with Canon Log - Canon Europe
Technology has rapidly developed since then, with today's cutting-edge 12-bit DGO and BSI sensors delivering up to 16-stops of dynamic range. Being able to capture this extra 4-stops of latitude led to the introduction of Canon Log 2 and Canon Log 3, with the original Canon Log no longer being required in current models.
Danielhaggett
danielhaggett.com › home › blog › canon c300 mkii log log2 or log3 which is best?
Canon C300 mkii Log Log2 or Log3 which is best?
If you are looking solely for high dynamic range, then LOG2 is the curve for you. For high contrast bright outdoor scenes the LOG 2 curve works really well. I always shoot the LOG2 Cine Gamut preset if using this LOG, as the Cine Gamut gives the greatest colour spectrum for grading.
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61
From here:
Prototype: double log2(double anumber);
Header File: math.h (C) or cmath (C++)
Alternatively emulate it like here
#include <math.h>
...
// Calculates log2 of number.
double Log2( double n )
{
// log(n)/log(2) is log2.
return log( n ) / log( 2 );
}
Unfortunately Microsoft does not provide it.
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log2() is only defined in the C99 standard, not the C90 standard. Microsoft Visual C++ is not fully C99 compliant (heck, there isn't a single fully C99 compliant compiler in existence, I believe -- not even GCC fully supports it), so it's not required to provide log2().
Microsoft Learn
learn.microsoft.com › en-us › cpp › c-runtime-library › reference › log2-log2f-log2l
log2, log2f, log2l | Microsoft Learn
July 9, 2025 - double log2( double x ); float log2( float x ); //C++ only long double log2( long double x ); //C++ only float log2f( float x ); long double log2l( long double x ); #define log2(X) // Requires C11 or later ...
GeeksforGeeks
geeksforgeeks.org › c language › log2-log2f-log2l-functions-in-c
log2, log2f, log2l Functions in C - GeeksforGeeks
April 12, 2022 - log2, log2f, and log2l are functions in C that compute the logarithmic of base 2 of a given number.
Pozo Production
pozoproduction.com › blog › unleashing-the-power-of-c-log-2-on-the-canon-r5-mark-ii
Unleashing the Power of C-Log 2 on the Canon R5 Mark II — Pozo Production
January 1, 2025 - C-Log 2 is designed to unlock the full potential of your Canon R5 Mark II by maximizing dynamic range and offering a smoother, more natural image quality.
Top answer 1 of 2
5
#include <stdio.h>
#include <math.h>
int main() {
double x = 42.0;
printf( "log( %f ) = %f\n", x, log2(x) );
return 0;
}
OUTPUT
% ./a.out
log( 42.000000 ) = 5.392317
%
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3
You can also create a helper function which converts to any log base you wish:
Something like this:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
double
my_log(double x, int base) {
return log(x) / log(base);
}
int
main(void) {
double x = 42.0;
printf("log(%f) = %f\n", x, my_log(x, 2));
return 0;
}
Compiled with:
gcc -Wall -o logprog logprog.c -lm
Output:
log(42.000000) = 5.392317
KooR
koor.fr › C › cmath › log2.wp
KooR.fr - Fonctions log2, log2f et log2l - Langage C
Ces trois fonctions permettent de calculer le logarithme, en base 2, de la valeur passée en paramètre.
GeeksforGeeks
geeksforgeeks.org › c++ › log2-function-in-c-with-examples
log2() function in C++ with Examples - GeeksforGeeks
July 12, 2025 - // C++ program to illustrate log2() function #include <bits/stdc++.h> using namespace std; // Driver Code int main() { long b = 16; float c = 2.5; double d = 10.35; long double e = 25.5; // Logarithmic value of long datatype cout << log2(b) << "\n"; // Logarithmic value of float datatype cout << log2(c) << "\n"; // Logarithmic value of double datatype cout << log2(d) << "\n"; // Logarithmic value of long double datatype cout << log2(e) << "\n"; return 0; }
Quora
quora.com › What-is-the-implementation-of-the-C-log2-built-in-function
What is the implementation of the C++ log2() built-in function? - Quora
The first one stands for Floating-point Y times Log2 X and the second is Floating-point Y times Log2 (X Plus 1). Interestingly, the second instruction is faster than the first because it operates on a smaller domain (|x| <= 1 - sqrt(2)/2). If ...