Photography News 111 - Newsletter

Making movies

ProRes is ideal for Mac users and it now also works in Adobe Premiere Pro and DaVinci Resolve. When it comes to compression, we’re not just talking about individual frames, but compression between frames. All-Intra compression takes up more space than the Long GOP (Group of Pictures) format, but is better quality. There are often also progressive or interlaced options, usually used by TV companies for instant broadcast. But this is best avoided as it’s not the highest quality. Further options open to you may include H.264 and H.265, which are usually 8-bit or 10-bit respectively. Then you have bit rates to choose, and a choice of chroma subsampling, usually labelled as 4:4:4, 4:2:2 or 4:2:0. It’s easy to get confused, but the higher the bit-rate and the subsampling, the more colour information and hence quality you will get. But again, these take up more space and aren’t always offered in all resolution, frame rate and compression options. On top of all this, there’s the issue of how the camera records its images. Even a 4K video is only a succession of 8.3-megapixel images, which is much less than any modern stills camera is capable of. So, when capturing images 25 times a second or more, it makes what to do with the ‘extra’ megapixels a real issue. Oversampling is when the camera takes the image from the whole sensor and creates 4K, 8.3-megapixel moving images out of it, rather than just reading a crop of the sensor, or line skipping, which essentially leaves part of the images out. Raw deal for video If you are really serious about ultimate control and quality, then you may want to look at Raw files. Just as with stills photography, Raw really does use the raw data right off the camera’s sensor, which is then processed afterwards to allow you to decide on the white balance, noise

reduction and colour to achieve the perfect look and quality. But while all serious stills cameras offer Raw capture to your memory card, the majority don’t offer it for video – the file sizes are just too big. Some manufacturers offer their own version of Raw, which involves a degree of compression to make it smaller, as is the case with Nikon’s NRAW, Canon’s Cinema Raw Light and Blackmagic’s BRAW. But the majority of high-end cameras enable Raw output via the HDMI port, allowing it to be captured via an external recorder like an Atomos Ninja V or Blackmagic Video Assist. This output is stored on removable SSD drives and converted into editable files like Apple ProRes Raw. This allows for editing via most of the popular programs like DaVinci Resolve or Final Cut Pro, where you can play with the settings and create all sorts of cool grading effects. However, the file sizes are large and you have to work on every single piece of footage – that’s the price for ultimate control. Logging a certain look It seems the holy grail nowadays is dynamic range. To maximise it, many cameras allow you to shoot in various colour profiles such as flat or a Log option – like Sony S-Log or Panasonic V-Log. These record a very flat-looking, unsaturated image to retain as much shadow and highlight detail as possible. Getting back to a natural image involves post-processing, with the advantage of being able to grade the footage with a certain look. However, setting one of the Log gammas usually increases the minimum ISO significantly and removes noise reduction, so this also has to be adjusted in post. Having a much higher base ISO in turn often calls for ND filters to bring the exposure down, especially if you are shooting with a wider aperture for a shallow depth-of-field.

Using Log profiles is more work- intensive and is ideally for use on footage that has lots of colour information – shot in 10-bit 4:2:2 for example. If, alternatively, you use it on 8-bit 4:2:0 footage, then you are already removing even more colour information, so it’s not ideal. In short, Log options are not an easy fix-all that everyone should use all the time. Slow it right down Many cameras will offer frame rates such as 50, 60, 100, 120, 180, 200 or 240fps, as well as the more conventional 24, 25 and 30fps. These higher frame rates allow action to be played back as slow-motion footage. You also need to up your shutter speed accordingly, so using the double-the-frame-rate formula, you’d set a shutter speed of 1/250sec for 120fps, or 1/500sec for 240fps. If you have been shooting at 25fps for normal motion at 1/50sec shutter speed, then ramping this up to 240fps and 1/500sec means you have lost more than three stops of light. As a result, you may need to increase the ISO, reduce the strength of your ND filter or change the aperture – if you don’t mind a shallower depth-of-field. However, at high speeds, audio often isn’t recorded – and in some cases the AF doesn’t work either. Check your camera for the specifics. That said, often if the camera will let you select the frame rate via its regular menu, then it will record audio and retain AF operation. If the only way to set the fastest frame rates is via the S&Q menu, then this tends to be without audio and slows the captured footage down in the camera, so it’s already in slow motion. Super slow-motion can look cool but is best used sparingly. For example, a BMX rider undertaking TOOL TIPS An external monitor shows a waveform to gauge exposure, (above). Some cameras like the Lumix S1H (right) have this function built in

a jump that lasts no more than two seconds, will, at 240fps, last for almost 20 seconds – a very long time to keep viewers’ attention. The best practice here is to use a ‘speed ramp’ in post-production, enabling us to keep the peak of the action in super- slow motion, but speed up the rest to a more normal speed. Experiment with slow frame rates and you will get a dreamy, albeit blurry look, which can add a level of creativity when used sparingly. Get tooled up Although they won’t directly impact the quality of your films, your camera has a range of tools to help you get your footage right. The most obvious is focus peaking, which is an ideal aid when using manual lenses. When focusing, the part of the image that’s sharply focused has a brightly coloured outline imposed on it. You can change the peaking colour to see it clearly against the background. Some of the latest Sony cameras, like the A6700 and A7R IV, now have Focus Map, which is a new way of visualising depth-of-field. It functions in a similar way to peaking, with an overlay of the scene indicating which parts are in front of and behind the focus point. Other useful tools are zebra patterns, which show a striped pattern over the areas of the scene

that are overexposed. The zebra can be set to appear at a certain brightness level, from roughly 40% to 100%, which is pure white. Typically, a brightness threshold of 70-80% is good for skin tones, or a setting from 90-95% is ideal for overall screen exposure. Some filmmakers use the traditional histogram – as do many stills shooters. But a better option is waveforms, if your camera has this feature. A waveform shows the luminance values of the video signal vertically from 0 to 100. Unlike a histogram, the pixels are located in the same horizontal position as the original image, so you get a clearer idea of where the shot is either over or underexposed. Like a histogram, the image has more contrast if the signal is spread out vertically and less when it’s bunched together. One final exposure tool is false colour, which gives a bright visual display of the whole frame. By comparing the colours on your image to a false-colour chart, you can see if your skin tones are spot on. Green indicates middle grey, blue or purple means underexposure and yellow to red shows white clipping over an 80% brightness value. So, dig into those menus and experiment to see what works for you, and how advanced settings can lift the quality of your video.

“Experiment with slow frame rates and you will get a dreamy look”

NEW TECH The latest crop of Sony mirrorless cameras like this A6700 have a Focus Map system, which shows out-of-focus areas in bright colours

52 Photography News | Issue 111

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