The Buffer

A major consideration to anyone intending to shoot a rapid sequences of images can be caused by the buffering speed of the camera. Buffering is the process that allows a short continuous flow of images to be taken without interruption. These are stored in a temporary facility, the buffer, before being transferred to the Microdrive or CF card at the end of a sequence. The buffer acts as a ‘go-between’ that prevents an image from being sent directly to the digital film medium as soon as it is captured. Without the buffer there would be a several second period of inactivity between every frame shot while the file was downloading. During this period the camera would cease taking photographs in a process known as a ‘lock out’. Obviously, if this was allowed to occur every time you pressed the shutter it would make digital photography totally impractical and would render any kind of shooting flow impossible. Unfortunately lock outs will still occur until technology reaches a point where the buffer can be developed with infinite capacity. This is accepted as a negative aspect of digital capture that can be a nuisance when it causes photographic opportunities to be missed. The number of images the buffer can hold is known as the ‘burst size’ and this varies in number depending on the camera model and whether RAW or JPEG files (more later) are being captured. If you are shooting JPEGs the smaller file size is less of a concern allowing longer sequences to be captured. Nevertheless it is important to be aware of the effects of buffering. Many digital camera owners are unaware that this is the cause when their camera suddenly stops firing and they wrongly assume that it has become faulty. But the manufacturers have not made things easier because Information about buffering is not easy to find and it is not always mentioned in camera instruction books or included in the maker’s specifications. With this in mind, if you intend to shoot sequences of images, especially in RAW format, you will need to be familiar with the number of frames the buffer can hold before lock out occurs as this may influence your choice. Buffering should not to be confused with the number of frames the camera is capable of shooting per second although the buffer may limit this capability.

I still use an ageing Kodak DCS Pro 14n that in full resolution RAW mode claims a burst depth of approximately 8 images which can cause me problems maintaining an uninterrupted work flow even on studio portrait sessions. Nikon claims up to 20 frames in RAW format, 70 in JPEG with their D3 camera, which is infinitely better and Canon uses a dual buffer system that allows more images to be captured before lock out occurs.

Next: The Buffer