Shooting Video for Mobile Videos
Submitted by Pocketcine on February 9, 2007 - 3:00pm.
In a recent test, we compared how well four different projects compared in terms of their compressed data rates. It did not surprise us that a 3D animated short compressed to the smallest file relative to its running length. Nor did it surprise us that video shot on a high end consumer camera produced the largest file relative to its running length.
Think Small
Shooting video for a mobile video has special challenges because of the wide diversity of delivery platforms, from cell phones with 2 inch screens to iPhones and other portable media with much larger screens and higher video resolutions. If you want your mobile viral video to travel far and wide, then you need to think small and short. A typical mobile video resolution is 176x144, with file sizes ranging from 100kb to 1 megabyte. iPod resolution, 320x240, is becoming more common.
If you are producing a mobile video short that will be shared using the cell phone's multimedia messaging (MMS) capability, then a 100 Kb file size is the (current!) target. For perspective, that's about 10-12 seconds of video, assuming a video resolution of 176x144 pixels.
The rule in video is to shoot with the editing in mind to make sure you have the kinds of shots needed to tell a coherent story. So you should shoot with a storyboard that maps out what angles on the subject you plan to capture, close-ups, establishing shots and so on.
In mobile video there is an additional rule that takes precedence over all other rules. The rule in mobile video is to shoot with compression in mind. This is the same rule that applies to shooting video for web delivery, but given the limited resources of most mobile devices, the rule quickly makes other video rules redundant.
Compression works by finding redundancy within video frames (like a flat green wall with no shadows on it) and between video frames (like a talking head against a flat green background). Backgrounds that are moving, that have detail, that have lots of edges or contrasty lighting do not compress well, and reduce the amount of detail you can have in your foreground subject.
In the next section we provide tips for optimizing shooting for compression.
Eleven Tips for Shooting Mobile Video
Many of these tips will not apply to cell phone video cameras or consumer video cameras with no manual controls. Try to work out a strategy for overcoming these limitations. For example, shoot your subject against the sky if you do not have control over your camera's depth of field.
Think Small
Shooting video for a mobile video has special challenges because of the wide diversity of delivery platforms, from cell phones with 2 inch screens to iPhones and other portable media with much larger screens and higher video resolutions. If you want your mobile viral video to travel far and wide, then you need to think small and short. A typical mobile video resolution is 176x144, with file sizes ranging from 100kb to 1 megabyte. iPod resolution, 320x240, is becoming more common.
If you are producing a mobile video short that will be shared using the cell phone's multimedia messaging (MMS) capability, then a 100 Kb file size is the (current!) target. For perspective, that's about 10-12 seconds of video, assuming a video resolution of 176x144 pixels.
The rule in video is to shoot with the editing in mind to make sure you have the kinds of shots needed to tell a coherent story. So you should shoot with a storyboard that maps out what angles on the subject you plan to capture, close-ups, establishing shots and so on.
In mobile video there is an additional rule that takes precedence over all other rules. The rule in mobile video is to shoot with compression in mind. This is the same rule that applies to shooting video for web delivery, but given the limited resources of most mobile devices, the rule quickly makes other video rules redundant.
Compression works by finding redundancy within video frames (like a flat green wall with no shadows on it) and between video frames (like a talking head against a flat green background). Backgrounds that are moving, that have detail, that have lots of edges or contrasty lighting do not compress well, and reduce the amount of detail you can have in your foreground subject.
In the next section we provide tips for optimizing shooting for compression.
Eleven Tips for Shooting Mobile Video
Many of these tips will not apply to cell phone video cameras or consumer video cameras with no manual controls. Try to work out a strategy for overcoming these limitations. For example, shoot your subject against the sky if you do not have control over your camera's depth of field.
- Use the best equipment you can afford or rent. Cheap equipment introduces artifacts into sound and visuals that are difficult to remove and makes good compression impossible.
- Shoot on a tripod. The background should be absolutely still. If you are shooting with a cell phone, support your arm and hold the cell phone steady.
- Frame for a landscape orientation. Most phones use landscape orientation.
- Shoot close-up. Portable movies are intimate because they have to be.
- Avoid a moving subject. Even subjects moving against a still background can add to your pixel budget.
- Use Depth of Field to your advantage. Throwing the background into soft focus makes it much easier to compress and allows compression to focus on your subject.
- Use slow shutter speeds. If you are using a video camera with a manual shutter speed adjustment, use a shutter speed of 1/60 sec. for NTSC or 1/50 sec. for PAL. This will produce very natural looking motion blur that is easier to compress.
- Use simple, flat backgrounds. If you have the choice between shooting your subject against a barn wall or a corn field, the barn wall will compress much better than plants waving in the breeze. Avoid stripes and other patterned backgrounds.
- Avoid camera moves. Do not pan, tilt, zoom, dolly.
- Use soft lighting, avoid contrasty lighting. Contrasty creates hard edges and multiplies the number of different textures in the scene. Use soft, diffuse, even lighting. Shoot outdoors where there is lots of bounce lighting. Watch out for hot spots, small bright highlights on objects.
- Record DV audio at 48kHz 16 bit. Optimum compression is accomplished with the highest quality audio. Do not use the microphone on your video camera. Use the best external mic or lavaliere that you can afford.
- Pocketcine's blog
- Login to post comments
