“Dynamic Range Capabilities of RED MX Digital Camera"

By Yuri Neyman, ASC  - Gamma and Density Co. and
Aaron Peak, colorist-researcher of Hollywood DI

 

A lot of questions have been asked about the claimed 11, 13, or 16 f-stop “capabilities” of certain digital cameras.

Using new 3D Gamma and Density chart, 3cP Software and Digital Intermediate Suite at Hollywood DI we conducted a test  which showed to us that while : Observable “Flat” Dynamic Range  of the most cameras is (including RED MX)  is 5.7 Fstops, the Extractable Dynamic Range of MX camera is 9.5 – 10 Fstops

We started from MX just because many of our clients wanted to know right away what its latitude is. In the nearest future we plan to conduct similar tests with other cameras.

Here is our methodology and point of view on this contentious subject. 

We’re really talking about two separate definitions: Observable “Flat” Dynamic Range and Extractable Dynamic Range.
Observable “Flat” Dynamic Range is what the human eye can see in "spotting” mode when observable field of vision is much brighter than the surrounding environment (like a film screen or computer/TV monitor in a darkened room). Observable “Flat” Dynamic Range  is what we can see on wave form monitor without any postproduction hardware/ software assistance.

Here is Observable “Flat” Dynamic Range of the ideal subject - Chart

Maximum Ideal Latitude –is 6.3 F-stops

Here is Observable “Flat” Dynamic Range  MX test

The range between point 2 (Darkest Visible Point) and point 3 (Brightest Visible Point) is 5.7 Fstops.
The test performed by very experienced Red and 3cP expert DIT Brook Willard confirms the same findings – roughly +2 / -3.5  Fstops  of useful Observable “Flat” Dynamic Range  for Red Camera

 

Bur our practical experience showed to us that it must be more to it – additional values are hidden when we observe only “Flat” Dynamic Range, but we can discover more with the help of post and thus establish the Extractable Dynamic Range.

We created a special chart - Gamma and Density’s experimental 3D-texture latitude Chart. It provides a real world test image to evaluate digital image exposure with extreme black and white 3D textures. This kind of chart will show better then flat chart in what degree the over exposed or under-exposed texture can be extracted from the file during post production

Test were done for tungsten and daylight conditions with two ISO camera ratings – 320 and 800.

Here are results:


The Testing Method

RED MX Camera Image Acquisition:
320 ISO - 5500K - Meter at 4.5 approx 12 f/c
800 ISO - 5500K - Meter at 5.6 approx 12 f/c

Gamma and Density’s experimental 3D-texture latitude Chart: provides a real world test image to evaluate digital image exposure.  The center grey card we are calling a 50% grey value when viewed on a waveform.  The other detailed dark and light areas are used to track the loss of image detail through the test exposure range.  The brightest detail points in the image are the white areas at the top left of the image between the napkin and edge of the twist-ties The darkest detail areas are located in the Velcro strip just to the right and below the grey card as well as in areas of the dark sand paper backing of the right side.

The Image Workflow:

For the left column:
'native' images .R3D Redcode RAW files were transcoded via redcine-x to 1920x1080 Prores444 files using a full 4K debayer with no changes made to the image settings.  Images were transcoded using the RedColor/RedGamma recommended color space and gamma settings.

For the center column:
'graded' images were color corrected and rendered from the .R3D Redcode RAW in a 16 bit space using Apple Color to 1920x1080 Prores4444 files using a full 4K debayer.  The 'KEY' neutral image was adjusted to have the grey card land at 350mv index, darkest black at 0mv and brightest white at 700mv.  All other under and over image exposures were then graded to match the 'KEY' exposure image, both via the waveform and visually.  The waveform image corresponds to the 'graded' images.

Results:

RED MX Useable Extractable Latitude (conservative)
800 @ F5.6:   -2 thru +1.5 = 9.5 Stops
320 @ F4:   -2.5 thru +1.5 = 10 Stops

RED MX Potentially Acceptable Extractable Latitude (generous)
800 @ F5.6:   -2.5 thru +2.5 = 11 Stops
320 @ F4:   -3 thru +2 = 11 Stops

Stop measurement, how we got the numbers:

The KEY image recorded at optimal exposure shows a visible dynamic range of 6 stops.  We then add a stop for each image recorded over and under exposure that can be graded successfully to match the KEY image.  For the over-exposed images the image is considered successful until either the highlight detail is lost or when the shadow detail begins to deteriorate during color grading. For the under-exposed images the image is considered successful until the noise created by extracting image range is objectionable. 

'Successful' is a subjective judgment and that is why it is important to evaluate the images specifically using your own judgment.