October 28, 2012

Easily Calculate Crop Factor, Focal Length, and Depth of Field with RED's Cinephotography Tools

To round out the good amount of RED-related news we've covered recently, Jarred Land has recently posted about something not directly related to their cameras or software. While not busy working on their new sensor or getting a bunch of SCARLETs ready for shipping (hopefully to you), RED has been working on a few online tools to calculate the inter-connected nature of sensor crop, focal length, and the field of view of your final shot -- among other things. Read on for more details.

Presently these tools exist only on RED's site, but Jarred says they're planning mobile app versions as well. Here's a screen-cap of the Crop Factor tool, the first on the list (image courtesy RED):

As you can see, the tool visualizes the field of view for any given combination of lens focal length (from 17-300mm) and the aspect ratio and crop factor dictated by the selected shooting mode -- the modes are standard Super35, widescreen, anamorphic, and 16:9 (for HD downscaling without having to crop), variously offered for 5K all the way down to 1K. This accounts for the 'windowing' that occurs at the sub-native resolutions generally necessitated by higher frame rate shooting. Each combination of input variables exists within a full-frame 35mm (still photography) context for comparison to that format -- which demonstrates what your FOV with, say, a 5D Mark III would be given a companion lens designed for full-frame. Along with generating the images, there's also the lower table which provides crop factor ratio and what effective focal length a full-frame 35mm system would need to be outfitted with to achieve the actual highlighted area of view. A similar tool designed by Stu Maschwitz has been available on his blog (also available for mobile platforms -- couldn't get a link due to lack of access to iCloud). AbelCine also offers something comparable.

RED has also implemented a nifty recording-time calculator, which tells RED shooters how much footage they'll be able to fit on the given amount of storage space, plus an estimate of what the average bit-rate would be. The tool does recommend that shooters confirm these figures with their own field testing, and bring a little extra storage just in case. Next is a tool which allows you to anticipate which frame rates and shutter-angles will (likely) result in images free of noticeable flicker due to artificial lighting sources (such as fluorescents, HMIs, neons, or LEDs) given the refresh rate of the power grid (60 Hz in North America and 50 Hz pretty much everywhere else).

The last of the new tools is the depth of field guide pictured above. Options for resolution are as comprehensive as the crop factor tool, going as far as including a Super 16mm option. Focal length (14-1200mm), aperture setting (f/1.4-64), and distance to subject (focus length -- in feet, inches, meters, and centimeters) are all variable. The chart spits out nearest and farthest acceptable-sharpness distances, and the total length of in-focus area. As well all know, of course, things like final resolution (assuming acquisition resolution isn't the same as projected/displayed), distance to display, detail in texture of the in-focus surfaces in question, and how bad your eyesight may be are all things that can affect the amount of play you have with acceptable focus, but the tool is certainly useful and a good guide with which to start.

Once again, if you'd like to have tools like these right in your pocket, RED is planning mobile app versions.

Do you guys think you'll be using some of these tools to help in your pre-visualization processes?

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4 Comments

abelcine also has a good DOF/sensor size comparator.

http://www.abelcine.com/fov/

October 28, 2012

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john jeffreys