13. Drive: The Advantage Of Buffer Memory

For everyday shooting, our two models both performed perfectly. Digital cameras have often been criticized for latency, but it wasn't perceptible here; even though the D50 did seem a bit quicker in its response, it was more of an impression than a quantifiable difference. On the other hand, when we switched to continuous mode, significant differences were discernible. We should point out that our tests were made using the same memory card, a basic 512 MB Kingston SD. A faster card would undoubtedly have boosted performance, but the difference between the two cameras would have surely remained constant. And most of you are probably not going to invest a fortune in a faster card. A good deal of the difference has to do with buffer memory - its capacity and how it's managed.

The maximum burst rate claimed is about the same for both models - a little under 3 frames per second (fps). In JPEG mode, the D50 produced 6 images in 2 seconds (3 fps) and 10 images in 4 seconds (2.5 fps). After that the memory was full and we got one image approximately every 2 seconds. The istDL only succeeded in producing 4 images in 2 seconds (2 fps) and 6 images in 4 s (1.5 fps). In fact, after 6 images in approximately 3 seconds, the buffer memory was full and we were able to get one image every two seconds, as with the Nikon. That's almost certainly a limit imposed by the rate of transfer to the memory card.

In RAW mode, the Nikon's memory held four photos, shot in a little over a second, so the basic rate remained the same. Then we got one shot approximately every 3 seconds. With the Pentax, the buffer memory held only three images obtained in approximately 1 second; after that we had to wait 6 seconds between images! Part of the reason for this is the size of the RAW files produced by the Pentax, but we'll get back to that issue later.

Nikon D50 in JPEG mode

Nikon D50 in RAW mode

Pentax istDL in JPEG mode

Pentax istDL in RAW mode

As always, our tests are conducted by taking real shots. Operating on the buffer memory reflects the maximum effective shooting speed possible. After that, the rate is related in part to the performance of the memory card used. Keep in mind that these models are not made to compete with professional cameras. You may not be aware of any lag when taking ordinary, single shots, but don't expect to be able to shoot in long, rapid bursts!

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