f900/3, f900R & f950

f23

CVP Gamma Curve Builder

After making payment, details on how to download the selected product will be sent via e-mail, so be sure to supply your e-mail address! This is done automatically during the payment procedure, but it would be helpful if you also send an e-mail to steve@digitalpraxis.net as soon as payment has been made.

Pre-Built CVP Gamma Curves
The selection of curves range from ones aimed to generate a pleasing image 'in-camera' without the need to perform too much post-production colour correction, through to curves that generate extremely low-contrast, high-dynamic range images that emulate the capture process of film negative, and require post-production manipulation (printing!) to generate a final usable image.

Such low-contrast curves are recommended only when capturing to D5, HDcam SR, or to disc, with the f900. With the f950 and f23 there are no such issues (although see note on f950 at the end of this page!)

As always, test and evaluate the curves prior to using them for real jobs. However, as said above, it is possible that the stretched nature of the high-dynamic range, low contrast curves may push the image data beyond the spatial resolution available with the 8bit capture system employed with HDcam, and therefore it is recommended that either a low compression vtr is used, or a disc recorder such as the S.two D.mag.

The curves are provided as a Zip file, and when extracted will show the necessary file structure format for the curves to be copied to a memory stick for camera use.

For additional information on these curves please contact steve@digitalpraxis.net.

You may be interested to know that the BBC requested a modified curve to meet their specific requirements for their new Block Buster series Planet Earth.

The pre-built Gamma Curves are based on the Kodak Cineon Log format; some with Rec 709 shadow detail for a 'nicer' in-camera image, while others have much lower contrast shadow detail, allowing for better grading in post-production - making the image very similar to a scanned film negative image.

709 Shadow detail

Cineon Shadow detail

The steeper the curve the more output change there will be for a given change of input. Hence the lower-contrast curves will generate lifted blacks, showing more shadow detail than the 709 based curves with their standard Rec 709 video shadow response.

The following images show the variation and help understand the benefit of a low contrast, high dynamic range image.

'Default' camera video settings

Log curve with 709 shadow detail

Full log curve

In the above images the difference is fairly obvious between the first image, which has no room for grading, with crushed shadows and clipped highlights, while the second two images show good shadow detail and highlights that are not clipped. These images can be graded to look exactly as required as all the detail throughout the whole dynamic range has been captured. The difference between the final two images is less, with the shadow detail and highlight being a little further extended in the second image.

Images curtesy of Geoff Boyle, CML, who is a great believer in the Digital Praxis Gamma Curves .

Any user feedback on these curves will be greatly appreciated, and any necessary adjustments made to improve their use. Obviously Digital Praxis can't guarantee the use of these curves, so individual tests must be carried out by the user prior to any real work being performed.

Contents of pre-built Gamma Curves
The following is a list of the various pre-built Digital Praxis Gamma Curves.

There are a maximum of 5 Gamma Curves allowed per memory card, and the f23 has two card's worth of files due to the extended dynamic range capabilities of this camera.

Please also note the actual curves supplied may be different due to changes made based on customer feedback!

f900/f950

• DP-709-100/600 - 709 shadow detail, with max output signal at 100% input (lowest contrast setting for best highlight/limited clipping)
• DP-709-108/600 - 709 shadow detail, with max output signal at 108% input (clipping a little earlier for better mid range contrast)
• DP-Log-100/600 - log shadow detail, with max output signal at 100% input (Has improved shadow detail but will require post-grading)
• DP-Log-108/600 - log shadow detail, with max output signal at 108% input (Has improved shadow detail, with lower highlight clip point)
• DP-Log-120/600 - log shadow detail, with max output signal at 120% input (Has improved shadow detail but will require post-grading, although clips a little earlier for improved mids)

f23 - card 1

• DP-709-100/1000 - 709 shadow detail, with max output signal at 100% input (lowest contrast setting for best highlight/limited clipping)
• DP-709-108/1000 - 709 shadow detail, with max output signal at 108% input (clipping a little earlier for better mid range contrast)
• DP-Log-100/1000 - log shadow detail, with max output signal at 100% input (Has improved shadow detail but will require post-grading)
• DP-Log-108/1000 - log shadow detail, with max output signal at 108% input (Has improved shadow detail, with lower highlight clip point)
• DP-VG-108/1000 - Variable Gamma with extended shadow and extended highlight (inverse D-LogE curve), with compressed mids

f23 - card 2

• DP-709-120/1000 - 709 shadow detail, with max output signal at 120% input (clipping a little earlier for better mid range contrast)
• DP-Log-120/1000 - log shadow detail, with max output signal at 120% input (Has improved shadow detail but will require post-grading, although clips a little earlier for improved mids)
• DP-MG-108/1000 - Mega Gamma extended mid detail, beyond the Log setting, with clipping at 108%
• DP-MG-120/1000 - Mega Gamma extended mid detail, beyond the Log setting, with clipping at 120%
• DP-VG-120/1000 - Variable Gamma, but with max output at 120% input

Curve Loading - Sony f900/3 & f900R; f23
The following is the procedure for loading the Gamma Curves into a Sony F900/3, or similar capable CineAlta camera. Once loaded the curves will disable some menu options, and it is best to set all other to off, or to their default. To check you have all the curves loaded connect the camera to a monitor and cycle through the curves; it will be obvious the curves are loaded by the various different looks you will see.

Please note that there is a serious bug with the Sony f950 CineAlta camera that makes using any CVP Gamma Curve curve an issue - due to date level differences between 4:2:2 YUV and 4:4:4 RGB HD the f950 image data gets re-mapped to 4:2:2 levels when a CVP Gamma Curve is applied. You have been warned!

f900/f950

• Un-zip the downloaded zip file directly to a Sony formatted memory stick
• Load memory stick into camera slot
• Top Menu FILE - Go to page 4 (user Gamma) and LOAD memory stick.
• Top Menu PAINT - Go to Page 3 (Gamma) - scroll down to Table - you see Standard and User options - select User - you will now see the files as a drop down option list - select curve and enjoy :o)
• Select each curve once to see your favored setting compared to the others.

f23

• Un-zip the downloaded zip file directly to a Sony formatted memory stick
• Load memory stick into camera slot
• Load the gamma table data via a memory stick using the (USER GAMMA) page of the FILE menu in Custom mode
• Position the menu pointer to READ (MS t CAM)
• push on the MENU SEL/ENTER dial
• Select USER on the first line of TABLE on the (GAMMA) page of the USER (PAINT) menu and display the desired user gamma

For additional information on Gamma Curves please contact steve@digitalpraxis.net.

You may also want to read this independent article written by Alfonso Parra, AEC, where he looks at the original Digital Praxis Gamma Curves, as well as his story on the shooting of The Bicycle, shot with Digital Praxis Gamma Curves.

CVP Gamma Builder

Note: v3.0.0 has been proven to work with PC/Windows. MAC operation is not recommended or fully supported by Digital Praxis.

Requires Excel 2003, or later.

However, the program is not easy to operate, lacks well thought-out and informative instruction, and can all too easily generate next to useless curves. Hence the Digital Praxis pre-built Gamma Curves above.

However, should you wish to make your own Gamma Curves, the Digital Praxis CVP Gamma Builder enables the making 0f Sony formatted Gamma Curves, ready for loading into Sony's CvpFileEditor software, a lot easier.

The software has 8 manipulation points, either numerical or directly via the graph (a larger graph is available for this) with the resultant curve shape shown immediately.

When the correct curve shape has been defined it can be exported to Sony's CVP software for formatting for use in Sony's f900/3, f900R, f950 or f23 CineAlta cameras.

Unfortunately you do still need the CVP program to make the 'Sony' format files to load into the camera, but the Digital Praxis Curve Builder does make it a lot easier to generate the curve data in the first place!

Therefore, you could make a low-contrast gamma curve for the camera via the CVP Gamma Curve Builder, and an inverse View LUT with the Digital Praxis View LUT Builder for monitoring on-set via HDlink or Cine-tal monitor, etc.