V-Log/V-Gamut
REFERENCE MANUAL

November 28, 2014

V-Log/V-Gamut REFERENCE MANUAL

Revision history
RevisionDateExplanation

Rev.1.0

November 28, 2014

First Edition

Table of Contents
1. Introduction
2. Curve Characteristics
3. V-Log Formula
4. Colorimetric Information
5. Appendix

1

V-Log/V-Gamut REFERENCE MANUAL

1. Introduction
This document describes technical information on the log curve and gamut used in Panasonic’s“Varicam” for utilization in recording and workflow composition.
V-Log has characteristics similar to a log curve of a scan from negative film and is highly compatible
with conventional firm workflow. Light information collected via a lens is converted to electronic
information by sensors. In other words, light information and electronic information have a proportional
relation. Log curve characteristics show the relationship between the linear domain video signal andexposure measured in stops, and a change in each stop of exposure increases or decreases the signal byalmost the same amount.

2. Curve Characteristics
Fig. 2.1 shows the characteristics of V-Log. This graph is defined as the x axis being exposure and they axis being 10bit code values. Fig. 2.2 shows reflection and code assignment. Gray output code withreflection of 18% is defined as 433, black output code with reflection of 0% as 128, and white output codewith reflection of 90% as 602. Varicam also supports 12bitV-Log output, and a value four times that of
10bit code is the output code with 12bit code.

Fig.2.1 V-Log characteristics

2V-Log/V-Gamut REFERENCE MANUAL
Input reflection [%]V-Log
IRE [%]

10bit Code Value

12bit Code Value

07.3

128512

184243317329061602

2408

Fig.2.2 V-Log Code Value

3. V-Log Formula
3.1 Scene Linear Reflection to V-Log
The function for converting from linear signal to V-Log data is as follows. With linear reflection as “in”and V-Log data as “out”,
out =5.6*in+0.125(in < cut1 )out = c*log10(in+b)+d(in >= cut1 )cut1 = 0.01, b=0.00873, c=0.241514, d=0.598206
However, 0<=out<=1
3.2 V-Log to Scene Linear Reflection
The function for reverting compressed V-Log data to linear refection is as follows. With V-Log data as“in” and linear reflection as “out”,out = (in - 0.125) / 5.6(in < cut2 )out = pow(10.0, ((in - d) / c)) – b(in >= cut2 )cut2 = 0.181However, 0<=in<=13.3 V-Log 10bit code to Scene Linear Reflection
This shows an example of converting 10bit code value V-Log data to linear reflection using theabove-mentioned inverse function. However, V-Log 10bit code value is IN10BIT.
in = IN10BIT/1023
out = (in - 0.125) / 5.6(in < cut2 )out = pow(10.0, ((in - d) / c)) – b(in >= cut2 )3

V-Log/V-Gamut REFERENCE MANUAL

4. Colorimetric Information
4.1 V-Gamut
Super35mm Sensors in the Varicam 35 achieve wide color gamut V-Gamut by optimizing the on-chipfilter characteristics for splitting light into RGB. V-Gamut is therefore the optimum color space as a masterarchive, and video production with high color reproducibility is possible by converting to P3DCI color
space and ITU-R BT.709 color space in post-processing. V-Gamut can also enable operation ofsubsequent stage color conversion in a common conversion matrix through chromatic adaptation
processing.
The following is wide gamut RGB primary, and White point is defined in the D65 color space.

Fig.4.1 V-GamutxyR

0.730

0.280

G0.165

0.840

B

0.100

-0.030White(D65)

0.31270.3290

Fig.4.2 V-Gamut RGB primary
4V-Log/V-Gamut REFERENCE MANUAL
4.2 Gamut Conversion Matrix
The V-Gamut RGB to CIE 1931 XYZ conversion matrix is shown below.
0.679644

0.152211

0.118600

0.260686

0.774894-0.035580-0.009310-0.004612

1.102980

The CIE 1931 XYZ to V-Gamut RGB conversion matrix is shown below.
1.589012-0.313204-0.180965-0.534053

1.396011

0.102458

0.011179

0.0031940.905535

The V-Gamut RGB to ITU-R BT.709 RGB conversion matrix is shown below.
1.806576-0.695697-0.110879-0.170090

1.305955-0.135865-0.025206-0.154468

1.179674

The V-Gamut RGB to ACES RGB conversion matrix is defined as a matrix including chromatic adaptationand is shown below.
0.724383

0.166748

0.108497

0.021354

0.985138-0.006319-0.009234-0.001043

1.0102735V-Log/V-Gamut REFERENCE MANUAL

5. Appendix
Here, the clip level of Varicam 35 (model number AU-V35C1G/AU-VREC1G) and Varicam HS (modelnumber AU-V23HS1G/AU-VREC1G) is expressed in 10bit code. Firmware version is shown individually.
Varicam 35 (Firmware version1.15 or higher)
ISO

Clipping Level
10bit code

800

911

1000

911

1250

911

1600

911

2000

911

2500

911

3200

911

4000

911

5000

911

6400

911

8000

911

10000

911

12800

911

Varicam HS (Firmware version1.15 or higher)
ISO

Clipping Level
10bit code

2500

896

3200

896

4000

896

5000

896

6400

896

8000

896

10000

896

12800

896

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