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"Picky Details" for the Pentax Optio 750Z 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 Pentax Optio 750Z:

Pentax Optio 750Z Timings
Operation
Time
(secs)
Notes
Power On -> First shot
4.0
LCD turns on and lens extends forward. A little slow.
Shutdown
2.9 - 42
First time is time to retract lens, second time is worst-case buffer-clearing time. First time is average, second time is very slow, but corresponds to emptying the buffer of more than 100 small/basic images in continuous mode.
Play to Record, first shot
1.8
Time until first shot is captured. About average.
Record to play
6.3 / 2.1
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.
Shutter lag, full autofocus
0.844 / 0.931
First time is at full wide-angle, second is full telephoto. About average. (Average is a range of 0.8 - 1.0 second.)
Shutter lag, prefocus
0.217
Time to capture, after half-pressing shutter button. Quick enough to catch fast-breaking action, but slower than average for prefocused operation.)
Cycle Time, TIFF, max resolution

13.1

Times are averages. No buffer memory, all shots take this long. Slow, but actually not bad for 7-megapixel TIFF images.
Cycle Time, max/min resolution 3.11 / 3.06 First number is for large/fine files, second number is time for "TV" size images. Times are averages. Shoots 5 large/fine images at this rate, then slows to an irregular rate of about 4.7 seconds apart. In TV mode, shoots continuously at this speed. Buffer clears in 9 seconds for large/fine images, about 2 seconds for lowest resolution. Rather slow.
Cycle Time, continuous mode, max/min resolution 1.4 / 1.16
(0.71 / 0.86 fps)
First number is for large/fine files, second number is time for "TV" size images. Times are averages. Shoots 5 large/fine images at this rate, then slows to an irregular rate of about 3.3 seconds apart. In TV mode, shoots continuously at this speed. Buffer clears in 9 seconds for large/fine images, about 1 second for lowest resolution. Not very fast for a continuous mode.

Average shutter response, slower than average cycle times. With full-autofocus shutter lag ranging from 0.84 - 0.93 second, it's solidly in the middle of the average range of shutter response. Its shutter response when "prefocused" (by half-pressing and holding down the shutter button prior to the shot itself) is fast enough to capture fleeting action, but at 0.22 second, is slower than average these days. Shot to shot cycle times are slower than average, a bit over 3 seconds between shots in single-shot mode, and fully 1.4 seconds for large/fine JPEG images in continuous mode.

 

Power

The Pentax Optio 750Z uses a custom rechargeable LiIon battery for power. Here are the power drain numbers I measured in various operating modes, along with projected run times based on the stated capacity of its battery pack.

Operating Mode
Power
(@4.5 volts on the external power terminal)
Est. Minutes
(1800 mA LiIon cell)
Capture Mode, w/LCD
576 mA
154
Capture Mode, no LCD
410 mA
216
Half-pressed shutter w/LCD
567 mA
157
Half-pressed w/o LCD
418 mA
121
Memory Write (transient)
604 mA
n/a
Flash Recharge (transient)
1365 mA
n/a
Image Playback
286 mA
310

With a worst-case run time of 154 minutes in capture mode with the rear-panel LCD enabled, and 216 minutes in capture mode with the LCD turned off, the Pentax Optio 750's battery life is well above average. In playback mode, the camera should be able to run for over 5 hours on a freshly charged battery. While I always recommend purchasing an extra battery right along with your digital camera, the Pentax 750z's battery life is good enough that most users will probably be able to get by with just the battery pack that's included with the camera.

 

Storage Capacity

The Pentax 750z stores its photos on Compact Flash memory cards, 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.) 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
Basic
TIFF
3056 x 2296
Images
(Avg size)
7
4.1 MB
15
2.0 MB
23
1.3 MB
1
22.2 MB
Approx.
Compression
5:1 10:1 16:1 -
2592 x 1944
Images
(Avg size)
10
2.9 MB
21
1.5 MB
33
945 KB
2
15.5 MB
Approx.
Compression
5:1 10:1 16:1 -
2048 x 1536
Images
(Avg size)
17
1.8 MB
33
945 KB
50
629 KB
 -
Approx.
Compression
5:1 10:1 15:1  -
1600 x 1200 Images
(Avg size)
28
1.1 MB
55
579 KB
74
430 KB
 -
Approx.
Compression
5:1 10:1 14:1
1024 x 768 Images
(Avg size)
60
607 KB
107
344 KB
148
197 KB
 -
Approx.
Compression
5:1 8:1
11:1
 -
640 x 480
Images
(Avg size)
128
278 KB
175
180 KB
241
115 KB
 -
Approx.
Compression
4:1 5:1
7:1
 -

 

Download Speed

The Pentax Optio 750z 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 805 KBytes/second, a very respectable rate. (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.)

 

O750Z Review
O750Z Test Images
O750Z Specifications
O750Z "Picky Details"
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