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"Picky Details" for the Pentax S4i digital camera
(Timing, Power, and Storage Info)

When you press the shutter release on a camera, there's usually a lag time or delay before the shutter actually fires. This corresponds to the time required for the autofocus and autoexposure mechanisms time to do their work, and can amount to a fairly long delay in some situations. Since this number is rarely reported on (and even more rarely reported accurately), and can significantly affect the picture taking experience, I routinely measure both shutter delay and shot to shot cycle times for all cameras I test, using a test system I designed and built for the purpose. (Crystal-controlled, with a resolution of 0.001 second.) Here are the numbers I collected for the Pentax S4i:


Pentax S4i Timings
Power On -> First shot
LCD turns on and lens extends forward. About average.
2 - 4.5
First time is time to retract lens, second time is worst-case buffer-clearing time. About average
Play to Record, first shot
Time until first shot is captured. Quite fast.
Record to play
4.1 - 0.5
First time is that required to display a large/fine file immediately after capture, second time is that needed to display a large/fine file that has already been processed and stored on the memory card. Rather slow for the first number, pretty fast for the second.
Shutter lag, full autofocus
0.38 / 0.88
First time is at full wide-angle, second is full telephoto. At wide angle, quite a bit faster than average, but only average at telephoto.
Shutter lag, prefocus
Time to capture, after half-pressing shutter button. Blazingly fast!
Cycle Time, max/min resolution

2.64 /

First number is for large/fine files, second number is time for "TV" mode (640x480) images. Times are averages. No buffer memory, every shot takes this long. About average speed these days, slower than some full-sized cameras with buffer memory, but decently fast for a sub-compact model.
Cycle Time, continuous mode, max/min resolution 2.2 / 0.95
(0.45 / 1.05 fps)
First number is for large/fine files, second number is time for "TV" size images. Times are averages. No buffer memory, all shots are this fast. (Or this slow, depending on your perspective.) Fairly slow, the S4i definitely isn't a camera for fast-paced, continuous-shooting action.

Like most subcompact cameras, the S4i isn't a speed demon, but by the same token, it isn't horribly slow either. Standouts are its very quick shutter response when shooting at wide angle focal lengths, and its blazing speed when you "prefocus" by half-pressing and holding down the shutter button before the shot itself. Cycle times are somewhat leisurely, but not as bad as some subcompact models.


The Pentax S4i uses a custom rechargeable LiIon battery for power, and the lack of an external power connection meant that I couldn't perform my usual detailed power tests. I did time how long it would run in its worst-case power-consumption mode (capture mode with the LCD turned on), and found that it lasted a pretty respectable 100 minutes. This is better than average for such a compact digicam, but a good bit less time than the best full-sized digicams will last. As usual, I strongly recommend that you purchase a second battery right along with the camera.

Storage Capacity
The Pentax stores its photos in an internal 10 MB buffer, or on optional SD / MMC memory cards. (I strongly recommend buying at least a 64 MB card, preferably a 128 MB one, to give yourself extra space for extended outings.) The chart below shows how many images can be stored in the internal 10 MB buffer at each size/quality setting. (You can see what a paltry capacity it has, particularly for the best-quality images.)

Image Capacity vs
10 MB Internal Buffer
Fine Normal
2,304 x 1,728 Images
(Avg size)
2.9 MB
1.5 MB
1.0 MB
4:1 8:1 12:1
1,600 x 1,200 Images
(Avg size)
1.2 MB
719 KB
513 KB
5:1 8:1 11:1
1,024 x 768 Images
(Avg size)
565 KB
308 KB
236 KB
4:1 8:1
640 x 480
(Avg size)
257 KB
164 KB
123 KB
4:1 6:1


Download Speed
The Pentax connects to a host computer via a USB interface. Downloading files to my Sony desktop running Windows XP (Pentium IV, 2.4 GHz), I clocked it at 774 KBytes/second. That's faster than cameras with USB v1.1 interfaces can go, but slower than most that support the USB 2.0 high-speed standard. Still, it's fast enough that you probably won't feel the need for a separate card-reader. (Cameras with slow USB interfaces run as low as 300 KB/s, cameras with fast v1.1 interfaces run as high as 600 KB/s. Cameras with USB v2.0 interfaces run as fast as several


S4i Review
S4i Test Images
S4i Specifications
S4i "Picky Details"
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