Shooting Video For StillsJanuary 22, 2013
High resolution video has now surpassed the detail necessary for professional-sized prints. Techniques that make it easier to pull stills from video are therefore becoming increasingly important. In this article, we’ll take a closer look at the best practices and possibilities.
At 1080P, the largest print one could create was about 4×6 inches at 300 PPI. That was sometimes useful, but usually meant separate DSLR photography was needed for printed advertisements. The advent of 4K+ resolution has been a game-changer though; for the first time, more than enough detail gets captured for two-page magazine spreads or even billboards.
However, resolution isn’t the only enabler. Having a virtually continuous stream of stills from a subject makes results more predictable and consistent — because botched timing, framing and focus become less likely. One now has the ability to select just the right placement or expression; blinking during portraits, unintentional motion blur, and missed moments are all potentially things of the past.
If one plans for stills output from the start, several techniques can improve results. Each is described in the subsequent sections, and many also go beyond the standard practices used for capturing high-quality video.
MOTION BLUR & TIMING
Perhaps the biggest distinction is that while some motion blur is often desirable with video—to render smoother camera and subject movement—this is often undesirable with still images. One way to overcome this problem is to use a smaller shutter angle. For example, with 24 fps cinema the standard shutter angle is 180 degrees, which translates into a shutter speed of about 1/50 of a second. However, many stills scenarios, including sporting events and hand-held telephoto shots, typically need 1/250 of a second or faster.
Another way to achieve sharper stills is to use a higher frame rate (at the same shutter angle). This not only provides more frames to choose from, but also gives more control over subject placement, which can be critical with rapidly changing scenes. Shots where an athlete is about to catch a ball, make contact or cross a finish line can all improve. Higher frame rates also produce much smoother video – especially when fast shutter speeds have been used to minimize blur.
If subject blur is primarily due to camera shake instead of subject motion, one can use video as a form of image stabilization – by picking the frames with the least camera shake. This technique is especially helpful with hand-held telephoto shots, since these amplify the appearance of most camera movements. Video also makes it easier to hold a camera steady, since one no longer has to simultaneously press a shutter button, or anticipate holding still for a specific moment.
FOCUS & EXPOSURE BRACKETING
Misfocus and improper exposure can also cause still photographs to become unusable. As insurance, one can effectively bracket their stills by varying the lens aperture during the shoot, or by slowly rocking the focus with a razor-thin depth of field.
Alternatively, HDRX®; can provide extra-protection with high-contrast scenes, such as weddings, where subjects are wearing both light dresses and dark tuxedos. Since the regular and under-exposed versions are taken in rapid succession, one has the flexibility of either combining these or using one of the individual frames.
A side-benefit is that HDRx stores two versions of motion blur for each frame. One version could be the standard cinematic motion blur (180° shutter at 24 fps, giving 1/48 of a second shutter), whereas the second version could use a faster shutter to ensure sharper stills (such as 45° shutter at 24 fps, giving 1/192 of a second shutter). The greater the exposure protection used for HDRx, the greater the reduction in motion blur with the second frame. However, pushing the HDRx setting beyond 2-3 stops can also visibly increase image noise if the second frame is substantially brightened in post-production.
The advent of high resolution video has the potential to transform the visual arts, and is beginning to merge the roles of photographer and videographer. Artists are gaining the flexibility to output to multiple visual media, and since the skill sets are very similar, the transition between each often comes naturally.
All the fundamental exposure and sharpness trade-offs continue to apply as they did with stills photography. For example, one could achieve a more expansive depth of field by narrowing the lens aperture, but this comes at the expense of more image noise in low-light. Alternatively, one could compensate for this by using a slower shutter speed, but this comes at the expense of more blur with moving subjects. Shooting video for stills therefore closely parallels thinking about traditional photography – the results are just more flexible.
- For the opposite transition, see the Stills Photographer Intro to Video tutorial.
To learn more about minimizing motion blur, see the tutorials on Shutter Angles & Creative Control and High Frame Rate Playback.
To see the motion to stills workflow in practice, watch the REDCINE-X® Motion to Stills video tutorial.