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"Picky Details" for the Sony DSC-W7 digital camera
(Timing, Power, and Storage Info)

 

Timing

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 Sony DSC-W7:

Sony DSC-W7 Timings
Operation
Time
(secs)
Notes
Power On -> First shot
1.3
LCD turns on and lens extends forward. Very fast.
Shutdown
1.3 - 23
First time is time to retract lens, second time is worst-case buffer-clearing time. First time is very fast, second is long, but it corresponds to clearing over 100 small/basic JPEG files from the memory buffer.
Play to Record, first shot
0.2
Time until first shot is captured. Extremely fast.
Record to play
2.7 / 0.3
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. First time is about average, second is extremely fast.
Shutter lag, full autofocus
0.34 / 0.51
First time is at full wide-angle, second is full telephoto. Much faster than average, an excellent performance.

Shutter lag, continuous autofocus

0.33
As usual, no benefit to continuous AF with a stationary subject, but at least there's no penalty for using it, as is the case on some cameras.
Shutter lag, manual focus
0.21
Very fast.
Shutter lag, prefocus
0.012
Time to capture, after half-pressing shutter button. Extremely fast.
Cycle Time, max/min resolution

1.27 /
1.14

First number is for large/fine files, second number is time for "TV" mode (640x480) images. Times are averages. In both modes, clears the buffer after each shot and continues at this pace indefinitely. Excellent speed, particularly in light of the 7 megapixel resolution and lack of any buffer limit. These times measured with Memory Stick PRO card, standard Memory Sticks run this fast for the first 7 frames in rapid sequence, then slow to just under 3 seconds/frame.
Cycle Time, continuous mode, max/min resolution 0.91 / 0.77
(1.1 / 1.3 fps)
First number is for large/fine files, second number is time for "TV" size images. Times are averages. In large/fine mode, shoots a burst of five frames, clears the buffer in about 5.4 seconds, and is ready for five more. In TV mode, maintains this pace for over 100 frames, and clears the buffer in 19 seconds. Reasonable speeds, but not as fast as I was expecting, given how zippy the camera is in its other modes.
Cycle Time, Multi Burst mode 7.5 - 30 fps Camera captures 320 x 240 pixel images, stores them in 4x4 arrays inside normal 1280x960 files. Frame rate can be set to 30, 15, or 7.5 fps. Every 16 shots, the camera pauses for about a second to write the images to a file, after which it captures another 16 frames. Very fast, handy feature for studying things like golf or tennis swings.

Excellent shutter response, excellent cycle times. The Sony DSC-W7 is a surprisingly fast digital camera. It starts up and shuts down quickly, and its shutter lag of 0.34 - 0.51 second is much better than the current industry average. Shot to shot cycle times are also very good (at 1.27 seconds/frame), particularly for a camera with a 7-megapixel CCD.

 

Power

The Sony DSC-W7 uses a pair of NiMH rechargeable AA cells for power. It ships with a pair of Sony-brand cells rated at 2100 mAh capacity, and a small charger. Because the W7 lacks a conventional external power connector, I wasn't able to conduct my usual direct power-consumption measurements. The camera did seem to run for quite a while on its NiMH AA cells, supporting Sony's claim that a freshly-charged set of batteries will last about 190 minutes of on-time (with the LCD), capturing up to 380 full-resolution images. With alkaline batteries, that rating drops sharply to 35 minutes of battery life and around 70 images. As always, I recommend a second set of high-capacity NiMH cells. Check out my NiMH battery shootout page to see which batteries currently on the market are the best.

 

Storage Capacity

The Sony DSC-W7 stores its photos on Memory Stick memory cards or in approximately 32 MB of internal memory, and a 32 MB card is included with the camera. (I strongly recommend buying at least a 128 MB card, preferably a 256 MB one, to give yourself extra space for extended outings. Note too, that you probably want to get a Memory Stick PRO for use with the DSC-W7, to take full advantage of its high-speed/high-quality movie modes.) The chart below shows how many images can be stored on the included 32 MB card at each size/quality setting.

Image Capacity vs
Resolution/Quality
32 MB Memory Card
Fine Normal
3072
x
2304
Images
(Avg size)
8
3.8 MB
16
1.9 MB
Approx.
Compression
6:1 11:1
2592
x
1944
Images
(Avg size)
11
2.7 MB
22
1.4 MB
Approx.
Compression
6:1 11:1
2048
x
1536
Images
(Avg size)
18
1.7 MB
33
952 KB
Approx.
Compression
6:1 10:1
1280
x
960
Images
(Avg size)
45
705 KB
82
387 KB
Approx.
Compression
5:1 10:1
640
x
480
Images
(Avg size)
181
176 KB
454
70 KB
Approx.
Compression
5:1 13:1

 

Download Speed

The Sony DSC-W7 connects to a host computer via a USB interface. Downloading files (from a Memory Stick PRO) to my Sony desktop running Windows XP (Pentium IV, 2.4 GHz), I clocked it at 3,306 KBytes/second, an incredibly fast rate. Even with a conventional Memory Stick, download speed was impressive, at 1,329 KB/second. (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 megabytes/second.)

W7 Review
W7 Test Images
W7 Specifications
W7 "Picky Details"
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