Speed Up To Slow Down

Slo-Mo Video • What You Get Isn’t What You Got • False Magnification?

A rafting adventure on the Arkansas River is the perfect subject for slow-motion video. The fastest shutter speed on my Canon DSLR's video mode is 1⁄4000 sec.—plenty fast to stop the action in each frame of the video, which is captured at 60 frames per second, then rendered for viewing in slow motion.

Slo-Mo Video
Q I see videos on TV and YouTube that show the subject in slow motion. Are these photographers using special cameras and software, or can I do this with my DSLR's HD video? I'm especially interested in using this technique for flying birds and wildlife.
J. Crawford
Via the Internet

A I've always been fascinated by slow-motion films that allow us to see what the human eye and brain can't normally discern. So one of the best things about the newer DSLRs with high-definition video is that they offer us mere mortal photographers the opportunity to capture some great slow-motion footage. Here's how to get the best results.

First, it's best to capture the video with the camera set to 60 frames per second (fps) rather than the normal 30 fps. Depending upon your camera, this will probably mean a bit less resolution because, at the higher capture speed, most DSLRs shoot at 720p instead of 1080p. This isn't a big problem because 720p video still looks great on your computer screen or HDTV, but I'm sure that we'll see DSLR video with 1080p at 60 fps soon or maybe even 120 fps at 720p.

Second, set the video function on manual and choose a fast shutter speed for each frame of the video. When the video is slowed down, each frame needs to be sharp. The normal shutter frame rate for video is from 1⁄30 to 1⁄60 sec., but this isn't fast enough to stop action with a fast-moving subject, so every frame would be blurred. Keep in mind also that if the shutter speed is significantly faster than the frame capture rate, the action may not be smoothly portrayed when rendered in slow motion due to the blank time between each capture. Thus, your capture rate and shutter speed are variables you need to consider in the context of the subject's speed of movement and the ambient conditions. To attain faster shutter speeds in the video, the photographer can raise the ISO of the camera and possibly set a larger lens opening.

The third component is the rendering software where the viewing speed can be set for slow motion. I've been using Apple iMovie to render my video, but other programs, such as Adobe Premiere Elements and Apple Final Cut Pro X, have the same capability. If you want to take this to the next level, there are plug-ins for Final Cut Pro X that will smooth transitions in slower renderings.

So the answer is yes; you can produce great slow-motion video with a video-capable DSLR, especially those shooting at 60 fps, and basic video-rendering software. Now all you need is an action subject that lends itself to slo-mo.


What You Get Isn't What You Got
Q Is it too much to hope for an image on my computer to look anywhere close to how it looked in my camera? I use a DSLR and shoot in RAW format, using my histogram for proper exposure. When any image is downloaded and opened with Photoshop Elements 5, everything is overexposed by several stops. The image that looks the best when printed on paper is adjusted to appear underexposed on my computer monitor. I'm so frustrated with digital that I'm thinking of going back to film.
D. Rea
Erie, Pa.

A If your LCD is set to the middle brightness setting, the image it shows you should look the same as it does on the computer. And if the histogram when viewed on the LCD indicates proper exposure, that rendition should be the same when viewed on the computer. I suspect the problem lies in your software, which is an older version that may not support the RAW format from your DSLR. You may achieve an immediate fix by upgrading to the current version (Elements 9). To test this out, download the 30-day free trial.

But if you want to run some tests first to clearly isolate the problem, take your capture media, with the original RAW files, and ask someone else to upload them to his or her computer. If the files read accurately on a different computer with newer or different software, then the problem definitely isn't in your camera or media, but rather in your own post-capture processing system.

If colors and brightness display properly when you're performing other tasks on the computer (such as working on the Internet), the problem probably isn't your monitor. If it looks good otherwise, consider whether the display is of comparable quality to the LCD screen on your camera. Older monitors aren't up to the task of digital photography. You also should calibrate your monitor periodically to set the display to standardized color rendition. Calibration has a strong connection to optimal printer output because you need to know that your computer and your printer interpret color data in the same way.

That said, most images will need to be fine-tuned as they're printed, and the photographer's ability to accomplish this without a wet lab is one of the best things about digital. To achieve the best output, invest in a photographic printer with a wide range of ink colors; these are available from Epson, Canon and HP. One of the best features of the Canon printers is the ability to make small adjustments to color and saturation with software that "plugs in" to Elements and Photoshop, and to save those changes as a particular set of instructions that you can apply to the same image again and again.

There's no doubt that learning to process digital images can be frustrating, especially if your equipment isn't up to the task. But once the photographer has gained the necessary skills, digital imaging can be far easier and more versatile—and produce much better results—than film. I personally have no desire to ever shoot another roll of film. But that's just me.


False Magnification?
Q I notice in your captions, you state the lens used and the effective focal length of the camera/lens combination, i.e., "100-400mm at 400mm (640mm with 1.6x crop factor)." As I understand crop factor, there's no additional magnification, but a perception based on a field of view equal to 640mm due to the sensor being smaller than a 35mm-sized sensor, although there are many people who think they're getting the equivalent magnification of a larger lens. Is it important to state the crop factor in caption info?
R. Gilbert
Via the Internet

A We've addressed this point on several occasions, but I really believe it's important, so we'll talk about it again.

The discussion begins with a holdover from film days. While our digital cameras are equipped with many different sizes of sensors (which record the images we capture), lenses are still standardized to 35mm film (24x36mm), based on the field of view (or angle of view) that the given lens records on a sensor of that size. Canon, Nikon and other manufacturers make cameras with sensors that are full frame (24x36mm, like 35mm film) and smaller. Given the same lens, a smaller sensor records a lesser field of view than the full-frame sensor, essentially cropping the image so that only the center is recorded. The relationship of the field of view achieved by the smaller sensor compared to the full-frame sensor is called "a crop factor" or a "focal length multiplier," and while each type of sensor has its own specific name, it's commonly expressed in terms that suggest magnification, such as Canon's 1.3x and 1.6x sensors, Olympus' 2x sensors and Nikon's 1.5x sensors. The Canon PowerShot SX30 IS advanced digital compact camera has a true focal length range of 4.3mm to 150.5mm, but the effect (angle of view) as compared to 35mm full frame equals 24mm to 840mm. The extended reach of the lens by a factor of about 5.6x is real, whether it's called magnification, a multiplier, the crop factor or angle of view. I always try to provide this information in my captions, but I certainly don't think it's necessary for all photographers to do so.

Some photographers with highly technical approaches are unhappy with this characterization of the phenomenon, but there's no reason to get emotional about it. We don't really need to continue to define everything about digital photography in terms of film equivalents. Rather, I hope that photographers can begin to recognize the benefits and drawbacks of the various options and choose the ones that are best suited to their photography. For example, cameras with full-frame sensors are excellent choices for landscapes where a wider view is desirable, while smaller sensors that extend the reach of the lens are especially suited to wildlife photography. Smaller sensors generally yield an image of less quality, but even this digital axiom is being challenged as digital technology advances and all sensors are optimized for their particular uses.

For information about upcoming seminars and digital-imaging workshops, visit www.georgelepp.com. If you have any tips or questions, address them to: OUTDOOR PHOTOGRAPHER, Dept. TT, George Lepp, 12121 Wilshire Blvd., Suite 1200, Los Angeles, CA 90025-1176 or online at www.georgelepp.com.

2 Comments

    I’m not sure the answer on “False Magnification” did the subject justice. As someone who used to struggle with this conceptually, I can understand where many people get hung up.

    Yes the smaller sensor is “cropping” the view and not optically “zooming” in any further, BUT here’s the catch, when viewed (screen or print), the effect is that the image IS magnified.
    Consider: a full-frame image and a crop-sensor image both printed out to an 8×10 image. Obviously the crop-sensor image results in more effective “zoom.”

    So now we begin to understand that the extra “zoom” effect is also a function of how the image is viewed. In the viewfinder, on the printed page, on the computer screen… The limitations of image size (ie pixels) will come into play when the images to be viewed “as large as possible”. (more in next comment)

    (False Magnification comment continued) If I took an image from a full-frame sensor and cropped off the edges (in Photoshop or on a physical print) then I’ve made the image smaller. So we think a crop sensor isn’t really “zooming” or magnifying. It’s simply lost the edges of what could have been viewed. Yes correct. The angle of view is smaller. However, when a crop sensor image is viewed in the same size print (say, both images are printed as 10″x10″), then the crop sensor image has indeed been enlarged. So why not simply crop the full-frame image for the same effect? Sure no problem, this is the same thing. But wait, what is the disadvantage? You are throwing away pixels/information. Image the sensors have the same pixel count, say 18MP, then it’s like you took those 18MP and compressed them into the smaller image space and you effectively have a higher resolution image to enlarge. Hope that helps.

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