All Things Color for Film and Digital Cinema
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Posts Tagged ‘color calibration’

Color Share – Overview

colorshare124

ColorShare for Android

https://play.google.com/store/apps/details?id=com.research.glgrade

 

COLOR | COLLABORATE | INTENT

Color Share is a powerful Non-Destructive Image and Photo editing and color enhancement tool.
Easy to use, start with the numerous presets or craft and save your own color adjustments from scratch. All color adjustment and image manipulation functions are constantly live.

Use Color Share’s unique meta share to share creative color intent between creatives such as cinematographers, colourists, and your DIT. Share Color Grading looks to Digital Grading Systems such as Baselight, Resolve and Mistika.
KEY FEATURES:

COLOR GRADING CONTROLS
• Lift Gamma Gain – Saturation ( Shadows Mid-tones Highlights )
• RGB/CMY “Printer Light” Exposure
• 3 Way Color Correction ( Lift Gamma Gain Color Wheels )

3D LOOKUP TABLES ( 3DLUT’s )
• Arri Alexa – Log2Rec709
• RED Log Film
• Sony SLog
• BMD Log
• User Defined

IMAGE EFFECTS
• Color Vignettes
• Textures
• Frames
• Color Maps ( Lomo – Push Process – ect.. )

BASIC DISPLAY COLOR MANAGEMENT:
• RGB Gamma
• Saturation
• RGB Brightness

EXPORT
• Edited Image as PNG ( Render Size is GL Device dependant – average 2048 x 2048 )
• Original Image
• Color Share Metadata
• ASC-CDL (color decision list) Color Metadata Information to your Digital Color Grading System
• Baselight CDL + .BLG.exr
• Davinci CDL
• Nucoda CDL
• Mistika CDL
• Photoshop ACV (coming soon)

PREFERENCES:
• ASC-CDL mode ( limits adjustments to ASC CDL compliant functions )
Slope Offset Power – Saturation
• BackGround Color
• Basic Color Management ( Display color management )
• Project Name
• Shoot Day
• User Luts
• Hide Show Prompts

nexus

colorshare124

Color Share is ADD FREE.

 

 


Color Share – Instructions

startup

 

open OPEN | SAVE | PREFERENCES

 

OPEN IMAGE :  openimage

    • Open an image from the SD-Card using your favourite Gallery. Make sure you select the image from a Gallery else currently the app will crash.
    • Choosing an image from “Recent Items” for example will crash the system.
    • Opens Dialog to choose either “Open As Is” or “Open and Crop”.

 

SAVE IMAGE:    save

    • Images are saved in the following directory on the SDCard

SDCard/colorShare/Save/yourProjectName/YourShootDay/

Project Name” and “Project Day” are set in Preferences

      • Save Options:
        • Image  -  Renders the current image as a JPEG
        • CDL  -  Saves the CDL file. (Use the CDL to replicate the grade in another system such as Baselight or Resolve) 
        • Original  -  Copies the Original image to the same location as the rendered version. (For use when sharing the ColorShare CDL)
        • Baselight BLG  -  Renders a Baselight BLG “grade”
        • Folder – Render all the above in a folder named the same as the input “filename”.

Example Filepath- input still is called A012_BR5E_A002.jpeg

SDCard/colorShare/Save/myProject/ShootDay_001/A012_BR5E_A002/

A012_BR5E_A002_colorshare.jpeg

A012_BR5E_A002.cdl

A012_BR5E_A002.blg

 

 PREFERENCES :  settings

    •           ASC-CDL Mode ON/ OFF

When ASC CDL Mode is On only Primary Color Correction and 3DLUTS are Active. Frames , Textures and Vignettes are Disabled.

    • User Name
    • User Email
    • Project Name

Keep files organised and create a new job Folder per Project

    • Project Shoot Day

If working on a film Shoot create a new “Shoot Day” Folder per day to keep files organised

    • BackGround Color

Black Grey White

    • Screen Calibration On/Off
    • Setup Screen Calibration
    • Show Hide Help Prompts
    • User Lut  File Path  1 – 2 – 3

Select and Set File Paths to User 3DLUTS.  (See below description under LUT menu for more info)

select_lut_off COLOR MENU

Lift Gamma Gain :  levels2

RGB Exposure :  exposure2

3Way Color Wheels :  three_way2

fx_on FX MENU

Vignette :  b_vignette

Texture : b_texture

Frames / Borders :  b_frame

ColorMap :  b_colormap

lut_on_z LUT MENU

  • Here You can select Preset LUTs or add your own.
  • There are three ‘USER’ slots for loading your own LUTs that must be in a flattened .png Format.
  • The User LUTS are loaded in the Preferences menu. Click on the button for each one to save the new path for each one.
  • Downloadable Null LUT Here.
    • IdentityLUT    Film Curves Example
    • identity    No Adjustment Example
    • Load the image above into your favourite color-corrector, apply the grade over the top and save with the same dimensions and in a png format.
    • Then import the resultant image into the LUT folder.

 

bypass_off  BYPASS MENU

 

save_off  PRESETS MENU

    • SELECT PRESET     b_openpreset

Opens PopUp Window with List of Presets in the database.

    • SAVE PRESET          b_save

Opens the Presets Manager where you can Save a new Preset or Overwrite an existing Preset in the Database.

Save / Delete Rename and Overwrite Presets.

    • OPEN PRESET FROM DISK    b_openxml

Open Preset from the options below:

        • Open standard ASC-CDL
        • Open ColorShare CDL with extended metadata.
        • Open ColorShare CDL with associated/linked image.

 

    • SHARE

Future

TIPS

    • Reset Color Parameters

In the color grading Menus “long hold” the top left text icon of the current page to reset the parameters.

    • Adjusting Parameters

When adjusting parameters  pull your finger down to the bottom of the screen while adjusting. The input values will still track and the screen will be clear of the value sliders.

 


Coming Soon for Android – 2014 – Cinematography Color Grading Assistant application

Screen Grabs from my new Color Grading Application for Android.

2014_02_19_16.02.38

Color Grading Modes

  • Collaborate, Share and Manage OnSet “Looks” between DP, Colorist and OnSet DIT.
  • 3D Lut Support
  • Grading Modes – Levels – RGB Exposure ” Printer Lights” – 3 Way Color Correction
  • Database support for “look” tracking and management.
  • Includes effects for additional image treatment. (NB: THESE FUNCTIONS ARE NOT ASC CDL ‘AWARE’ )
    • Textures
    • Vignettes
    • Frames
  • All operations are “Live” and not compounded operations as in many other Android image processing apps.
  • or simply use as a professional Color Grading app for your Phone Stills (Lite Version) saving as PNG or JPEG.
2014_02_19_15.47.43

3 Way Color Correction

2014_02_17_21.33.07

Effect Modes – Vignette | Texture | Frames | Color Map

2014_02_19_15.41.16

All parameters are Live – No pre-rendering required between modes

Application includes:

  • 3d LUT support:
  • ASC SOP color Grading
  • Additional Image Effects
  • Android Screen Color Calibration
  • Export of ASC CDL grade files for Import into any color Grading Application.
  • Internal Database for managing grades:
    • Project Name
      • Shoot Day
        • Clip Name
  • Export Options:
    • “Extended Metadata” ASC CDL .cc file
    • Graded Reference Still
    • Original Ungraded Still
  • Preferences:
    • Help functions On / Off
    • User Name | Project Name | Shoot Day
    • Background Color
    • Load User Luts
    • Screen Calibration

2014_02_17_17.54.48

Adrian

 


DCI P3 White Point and color primaries – Measurement Reference – 6300k

Projecting a set of white and color primary  test images from your DCP player or software/Hardware solution should give the following readings when properly projected through a calibrated system and measured with an accurate  color meter.

Measuring and calibrating a projectors DCI white point should not only be performed with the projectors internal test patches. I personally argue to test calibration with both the projectors internal test patterns as well as external test patterns because depending on the image interface to the projector from the DCP player or SDI hardware output, experience tells me some of these interfaces/modules can and do add additional adjustments to the color gamut and levels.

Luminance 14 Ft Lamberts

Gamma: 2.6

White:  x 0.314   y 0.351

Red:      x 0.680   y 0.320

Green:  x 0.265   y 0.690

Blue:     x 0.150  y 0.060

 

 


Protected: DCI – Digital Cinema Projection Reference

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Video Waveform Visualization and Creation

As an addition to the prior post on waveforms here we examine a more visually descriptive way of showing how a video waveform is created and therefor how it can be interpreted.

Fig:1 Waveform and Live Image

Above we can see a standard Live Video Feed and its represented waveform.

Below I have created a 3Dimentional Luminance map of the same live feed. In this representation every pixel on the image is represented on the z-axis as a luminance value bw 0 and 1023 video code values. The ‘lighter’ or more intense the pixel value the higher it appears on the z-axis.

Fig: 2 Luminance Relief Map  Face On

As I rotate this image in 3D space, around the y-axis, you can see the luminance values more clearly represented as a Height map in the 3 Dimensional space.

Fig: 3 Luminance Relief Map Rotated 45 Degrees

When finally rotated a full 90 Degrees we end up with the Waveform interpretation.

Fig: 4 Luminance Relief Map Rotated 90 Degrees

Adrian Hauser


Waveform Vs Histogram interpretation in Digital Cinema Cameras

Understanding how to read Histograms present on many new digital cinema cameras can be tricky and are easily misenterpreted.

For analysis, I will use the below still from the film Daybreakers as reference.

Ethan Hawke in "Daybreakers" (2010)

The following snapshots have been taken using DpxRead available on the Panavision website.

Immediately we can see that there is a massive difference in the way these two images are represented in each of the graphical/statistical graphs.

Histograms represent the volume/percentage of light levels exposed within a particular image. The resulting graph shows the distribution/intensity plot of those levels.

Histogram Exposure

The above image reference image  is quite ‘moody’. The histogram shows us this quite literally but surprisingly shows nothing of where the midtones sit. This is because Histograms work with percentages and Ratios of light. If for the most part an image is dark, say 60% of the overall area , then the rest of the histogram has to be interpreted with the remaining 40 percent of image area. For that reason the intensity represented by the histogram for the remaining light values is visually a lot lower than the Dark spike shown in our reference.

To better show the way a histogram graphs an images lightness values I have put the below gradient into the scopes.

Linear Grayscale Ramp

We can see that because there is an even amount of each light level within the gradient image the Histogram shows an even intensity/distribution of each ‘level’.

Video Waveforms on the other hand give us a lot more visual information with which to evaluate your exposure and contrast ratio. As well as showing us the distribution of light values the graph is also plotted across the horizontal plane of the image. With this additional ‘axis’ one can easily determine where within the frame a particular item sits in its digital exposure value. This makes it easy to find for example the exposure of someones skin tone in relation to the background subject matter.

Histograms are Cheap and Easy to display from a programmers POV but in my opinion are quite useless in representing photographic content and should not be used for indepth exposure analysis.

Adrian


iRiS – Photochemical Color Timing Reference Image

Here is a color reference image I generated for quickly visualising Color Density Readings. You should ask your lab to write down their density readings of the LAD / 445 CV grey patch at the head of each Roll on each Box/Can of print film you receive. With this information you can immediately determine if the print is a “little magenta” or a “little dark” and pre warn clients before a screening that the neg is OK but this particular print out of that particular days processing bath is a biased in that direction.  

Click the LINK HERE for a downloadable version.

 

iRiS - Lab timing reference

iRiS - Photochemical Lab Timing Reference Image

 

 

The printer light settings on the rotary dials are arbitary 25-25-25 settings. More than likely each lab changes these settings each day after calibrating themselves to the processing bath using a sensitometric wedge. I have personally found it is better to talk to your Lab consultant in terms of printer point changes      IE +1 red -2 Green +1 Blue      rather than actual printer lights, 26 23 26, as this can cause confusion. 

For example if your print had a LAD density reading of 1.03 1.06 1.03 you could deduct that the print was a little Red and a bit lighter. IF though the print LAD was “on AIM” ie 1.09 1.06 1.03 but you still thought the print was a little red you could ask in subsequent prints for a trim of -1 Cyan (the complimentary opposite of RED) which would result in a print that was less red and a fraction darker. The numbering seems a little counter intuitive but referencing the numerics on the RGB rotary wheels you can see that subtracting one point on the red ‘wheel’ you would be pushing it up (making 25 become 24) which in turn is letting less red light through. This in turn makes the Green and Blue ‘lights’ more visually dominant, hence Cyan. 

 

 Coming very soon is my visualization Application for MacOSX that is pretty much the above user interface but provides realtime color feedback to the image of your selection with adjusted printer lights using your preferred input 3DLUT. Very useful for dealing with your film LAB of Choice when making and timing Answer Prints.

If you would like to know any more about this application please feel free to email me.

 

 

 

 

Adrian Hauser


The film scanner as a densitometer

 

The Spirit 4k Datacine

The Spirit 4k Datacine

Why all these posts on Densitometry?

 

Because for me to understand the nature of how a scanner accurately scans and represents the filmed dynamic values and colors of a scene I delved in to the science of  the sensitometry of film. 

The color film scanner functions very much like a densitometer. A light is passed through the film, detected and its optical density read by a sensor. In digital imaging, color needs to be defined by three components Red, Green and Blue. Each pixel on the array of the scanner reads the Color density of the section of the image hitting its photosite and converts the results into data values which are then read into a file for each frame. 

The understanding of things like densitometry and the sensitometry of film has helped me in being able to deliver the best most accurate scans that deliver the creative intent and the pure colorimetry of a scene. To come later will be posts on color cross talk and purity.

Adrian


Protected: Densitometry Pt2 “the 21 step test strip”

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Protected: From neg to print via digits – DI – the round trip

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Densitometry for Lookup Tables Pt.1

A densitometer is a device that measures the optical density of an image on any printed medium, be that celluloid print film, paper, photographic film negative or any other medium. If the image is printed on paper we could read its optical reflectance, if printed on 35mm print film we would be reading its optical transmission qualities.

As human vision is measured in logarithmic values so too are the results of the densitometer. When taking readings of a Motion Picture print over a densitomter we are reading the prints transmissive qualities of light. In Status A densitometry (more on that in the next post) the lighter the patch the more it transmits light. The denser the image the less transmission of light. Density is defined as  

Optical Density = log10(1/transmittance)

I have a X-Rite310 densitometer which is common to most Film Labs around the world. It reads, for any given reference, the Red, Green and Blue optical transmission values which is imperative in creating RGB Color profiles or 3D lookup tables (3D LUT’s) for film.

Fig:A a 4x4x4 example target

Fig:A 4x4x4 example unity target or Identity LUT

 

Printing a set of specific color and grey scale patches to the desired medium, like the ones in figure A, an operator can read and translate the optical transmission characteristics of each individual patch and create a ‘lookup table’ . This profile can then be used to visualize on a monitor what the image will look like when printed to film. It is also profiling the characteristics of the imaging device which recorded the patch to film. In our case an Arri Laser film recorder. The more colors sampled the more accurate the representation will be. (The example used is extremely ‘low res’ and is only used for demonstration purposes.) To achieve an accurate representation we tend to use a ‘matrix’ of 4096 color patches!

 Lets look at those color patches from Fig:A mapped into an RGB cube to see just how these work. (See Fig:B)

Fig:B Representation of the 4x4x4 Color Cube

Fig:B Representation of the 4x4x4 Color Cube

 

If you compare the image in Fig:A and the Color Lattice to the left you can see each of the 64 patches are represented in a 3 dimensional cube which we can call the RGB Color Cube. The extreme corners represent %100 code values for all the primary colors of the cube, and Black. If you were to only look at the points down the diagonal axis from Black to White you would be looking at a grey scale.   From this would could create an identity LUT which would read something like Fig:C in ASCII text. Being an identity LUt it would have no optical effect to the original image.

 

 

 

ASCII 3DLut 4x4x4 identity matrix

ASCII LUT

         Starting at Black and reading the 4 points across to red expressing them as RGB Triplets. (I am assuming a an 8 bit scale which doesnt divide very well in 3 from 256 code values so excuse the rounded math)

 

        We then move up one row towards Green and read out the next row of 4 points.

 

 

         Until we read the top at which point we move in one row towards Blue and then begin reading the rows on that plane in the same way. Eventually after 64 entries of RGB triplets we have successfully mapped the cube.

 

 

 

In the photographic desktop publishing world images like the one in FIg.D are used. These are called Targets. The most used one is the Kodak IT8 Target.

kodak_IT8_target

Fig:D Kodak IT8 Target

 

 

 

 

 

 

 

Fig:B 4x4x4 identity LUT

Fig:E 4x4x4 identity LUT

Due to the different optical characteristics of different papers, films and imaging devices the original image will never look the same when printed, unless, through software we mimic those qualities on the monitor we are referencing the digital image on.

When printed to the desired medium and each of the patches are measured on a densitometer we remake the cube and will notice that the points are slightly deformed taking on and showing us the optical properties of the medium.We then transpose those results to represent the films qualities in to a new ASCii LUT

Fig:C transformed LUT

Fig:F transformed LUT

 

We then transpose those results to represent the films optical qualities in to a new ASCii LUT that can be fed into the monitoring device.

 

 

What I have just described is the most rudimentary basics of color management and 3D color Lookup’s. The Following Posts will go deeper into real world color calibration also touching on, using Marcie,monitor characteristics, viewing environments, film projection characteristics, different recording and printing stocks.

 

Adrian.

 

Image References:

Nvidia.com – Graphics GPU technology examples

RPIImaging.com  - IT8 printing Targets.

cube-lattice


Photochemical Color Timing

 

Colormaster Color Analyzer for Photochemical Color Timing

Colormaster Color Analyzer for Photochemical Color Timing

 

When it come to the ‘dark arts’ photochemical color timing and film processing has to be up there in the TOP TEN. Understanding the film lab and its physical tolerances in achieving AIM Density is as critical as having your internal color management/LUT’s spot on. (you can have the most precise Print emulation LUT in the universe, but if you are unaware of your Film Labs characteristics you could still be in for a surprise. WYSIWYG should really be What You See Is Pretty Much What You Get in the perfect world. The colors and density may be great but both digital and Film projection technologies and their visual characteristics through different light sources in different cinemas are still very …… different. )

 

 Here is a link to a pdf file that shows the effect of printer light adjustments on a print.

Adrian Hauser