Pentax K-x Review

 
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Pentax K-x Performance


Timing and Performance

Very good speed for a consumer digital SLR.

Startup/Shutdown

Power on
to first shot

0.6 second

Time it takes for camera to turn on and take a shot.

Shutdown

~0.2 second

How long it takes to turn off.

Buffer clearing time

6 seconds *
after 25 LF JPEGs

Worst case buffer clearing time. -- This is the delay after a set of shots before you can remove the card. Some cameras won't shut down until the buffer is cleared.

7 seconds *
after 5 RAW files
7 seconds *
after 4 RAW + LF JPEGs

*Note: Buffer clearing times measured with a SanDisk Extreme III 8GB SDHC memory card. Slower cards will produce correspondingly slower clearing times. Slow cards may also limit length of bursts in continuous mode. ISO sensitivity and other settings such as D-Range or NR can also affect cycle times and burst mode performance.

The Pentax K-x's startup and shutdown times are about average for an SLR. Buffer clearing time depends on the image size and quality, burst length and how fast the card is.

 

Mode Switching

Play to Record,
first shot

~0.2 second

Time until first shot is captured.

Record to Play

1.3 seconds

Time to display a large/fine file immediately after capture.

Display
recorded image

~0.2 second

Time to display a large/fine file already on the memory card.

Mode switching time is good for an SLR, though switching from Record to Play was a bit on the slow side.

 

Shutter Response (Lag Time)
Optical Viewfinder

Full Autofocus, Single-Point AF (center point)

0.097 second

Time from fully pressing shutter button to image capture (with Sigma 70mm f/2.8 prime).

Full Autofocus,
Auto-Area AF
0.122 second
Time from fully pressing shutter button to image capture (with Sigma 70mm f/2.8 prime).

Full Autofocus, Single-Point AF
Flash enabled

0.225 second

Time from fully pressing shutter button to image capture, Auto Flash enabled (with Sigma 70mm f/2.8 prime).

Pre-focused

0.082 second

Time to capture, after half-pressing and holding shutter button.

Continuous AF
0.083 second
This mode usually shows no speed increase with our static subject; we have no way to measure performance with moving subjects.
Manual focus
0.082 second
For most cameras, shutter lag is less in manual focus than autofocus, but usually not as fast as when the camera is "pre-focused."
Live View Mode

Full Autofocus, Phase-Detect AF

0.448 second

Time from pressing the AF button and pressing shutter button to image capture (with Sigma 70mm f/2.8 prime).

Full Autofocus, Contrast-Detect AF

2.567 seconds

Time from pressing the AF button and pressing shutter button to image capture (with Sigma 70mm f/2.8 prime).

Pre-focused

0.427 second

Time to capture, after pressing and holding the AF button.

Full autofocus shutter lag using single-point (center) AF mode is excellent, at 0.097 second with our reference Sigma 70mm f/2.8 lens. Switching to auto-area AF mode increased lag slightly to 0.122 second, but that's still very fast for a consumer model. Enabling the flash increased the lag to 0.225s, which is still very good. "Pre-focus" time is also quite fast, at 0.082 second (pre-focusing means half-pressing and holding down the shutter button before the final exposure). Continuous autofocus lag and Manual focus lag weren't much slower than prefocused, at 0.083 and 0.082 second respectively.

As expected, Live View mode shutter lag was a lot slower than using the optical viewfinder. Using Phase-Detect mode, full autofocus lag averaged about 0.448 second with our Sigma 70mm f/2.8 reference lens. That increased to 2.57 seconds when using Contrast-Detect mode. Prefocused, Live View mode shutter lag was a tolerable 0.427 second.

To minimize the effect of different lens' focusing speed, we test AF-active shutter lag with the lens already set to the correct focal distance. We also use the same Sigma 70mm f/2.8 macro with every camera (on all platforms except Four Thirds/Micro Four Thirds and Nikon consumer models lacking an in-body focus motor), to further reduce variation, and because our tests showed that focus-determination time with this lens was close to the fastest, across multiple camera bodies from different manufacturers. Being an older design with a non-ultrasonic motor, it wouldn't be the fastest at slewing from one focus setting to another, but that's exactly the reason we measure focus determination speed, which is primarily a function of the camera body, vs focus adjustment speed, which is primarily a function of the lens.

 

Cycle Time (shot-to-shot)
Single Shot mode
Large Fine JPEG
0.39 second

Time per shot, averaged over 50 shots, 3 seconds to clear.

Single Shot mode
RAW

0.43 second

Time per shot, averaged over 10 shots, 7 seconds to clear.

Single Shot mode
RAW + LF JPEG

0.29 second

Time per shot, averaged over 5 shots, 8 seconds to clear.

Early shutter
penalty?

No

Some cameras refuse to snap another shot if you release and press the shutter too quickly in Single Shot mode, making "No" the preferred answer.

Continuous Hi
Large Fine JPEG
0.23 second (4.32 frames per second);
25 frames total;
6 seconds to clear
Time per shot, averaged over buffer length of 25 frames. Once buffer is full, slows to an average of 0.40 second or 2.50 fps, with a lot of variation.

Continuous Hi
RAW

0.22 second (4.55 frames per second);
5 frames total;
7 seconds to clear

Time per shot, averaged over buffer length of 5 frames. Once buffer is full, slows to an average of 0.98 second or 1.02 fps.

Continuous Hi
RAW + LF JPEG

0.22 second (4.55 frames per second);
4 frames total;
7 seconds to clear

Time per shot, averaged over buffer length of 4 frames. Once buffer is full, slows to an average of 1.40 seconds or 0.72 fps, with a lot of variation.

Continuous Lo
Large Fine JPEG
0.54 second (1.85 frames per second);
50+ frames total;
1.5 seconds to clear
Time per shot, averaged over 50 frames. Buffer length is longer.

Continuous Lo
RAW

0.55 second (1.83 frames per second);
12 frames total;
7 seconds to clear

Time per shot, averaged over buffer length of 12 frames. Once buffer is full, slows to an average of 0.95 second or 1.05 fps.

Continuous Lo
RAW + LF JPEG

0.54 second (1.85 frames per second);
6 frames total;
6 seconds to clear

Time per shot, averaged over buffer length of 6 frames. Once buffer is full, slows to an average of 1.56 seconds or 0.64 fps, with a lot of variation.

Flash recycling

3.3 seconds

Flash at maximum output.

*Note: Buffer clearing times measured with a SanDisk Extreme III 8GB SDHC memory card. Slower cards will produce correspondingly slower clearing times. Slow cards may also limit length of bursts in continuous mode. ISO sensitivity and other settings such as D-Range or NR can also affect cycle times and burst mode performance.

Shot-to-shot cycle times are very good for a consumer SLR, ranging between about 0.3 and 0.4 second, depending on the image quality setting. Continuous speeds are also quite good, at about 4.3 to 4.6 fps, depending on the image quality in Continuous Hi mode. JPEG buffer depth is pretty good too, at 25 Large Fine JPEG frames. This drops to 5 and 4 frames in RAW and RAW + LF JPEG modes respectively. (Note that our target image for this test is difficult to compress, so you'll likely get longer bursts with more typical subjects.) The flash takes 3.3 seconds to recharge after a full-power shot, which is also pretty good.

 

Download Speed

Windows Computer, USB 2.0

11,417 KBytes/sec

Typical Values:
Less than 600=USB 1.1;
600-769=USB 2.0 Low;
Above 770=USB 2.0 High

Connected to a computer or printer with USB 2.0, download speeds are very fast as well.

Bottom line, the Pentax K-x is pretty fast in just about every aspect of its operation. Continuous mode speeds are best-in-class, and shutter lag and cycle times are quite fast, too. Very good performance overall for an entry-level model.

Battery and Storage Capacity

Battery
Below average battery life with rechargeable NiMH batteries.

Operating Mode Number of Shots
4 x NiMH Rechargeable Batteries,
Optical Viewfinder
(CIPA standard)
420
4 x NiMH Rechargeable Batteries,
Live View LCD
Not Specified

The Pentax K-x uses four AA-type batteries for power, and ships with a set of ordinary alkaline cells. Battery life is below average when using the optical viewfinder, and will most certainly be much less when using the LCD in Live View mode. We strongly recommend you pick up a couple sets of rechargeable NiMH batteries and a good quality charger, as they'll save you many times their cost over the life of the camera. We found, however, that the K-x didn't work well with one our favorite brands on NiMH batteries, Sanyo Eneloops, sometimes reporting low batteries when fully charged. We instead used disposable Lithium batteries for our testing. (Note: Pentax has released a firmware update (version 1.01) which corrects this issue. After the update, our Eneloop NiMH batteries worked fine. You can download the firmware update here.)

The table above shows the number of shots the camera is capable of (on either a fresh set of disposable batteries or a fully-charged rechargeable battery as appropriate), based on CIPA battery-life and/or manufacturer standard test conditions.

(Interested readers can find an English translation of the CIPA DC-002 standards document here. (180K PDF document))

Storage
The Pentax K-x accepts SD/SDHC memory cards, and no card is included with the camera.

Image Capacity with
1GB Memory Card
Fine
(***)
Normal
(**)
Basic
(*)
RAW RAW
+ LF JPG
4,288 x 2,848
Images
(Avg size)
140
7.3 MB
247
4.1 MB
487
2.1 MB
49
20.9 MB
36
28.4 MB
Approx.
Compression
5:1
9:1 17:1
0.9:1
-
3,936 x 2,624
Images
(Avg size)
166
6.2 MB
292
3.5 MB
569
1.8 MB
-
-
Approx.
Compression
5:1
9:1 17:1
-
-
3,072 x 2,048
Images
(Avg size)
271
3.8 MB
472
2.2 MB
903
1.1 MB
-
-
Approx.
Compression
5:1
9:1 17:1
-
-
1,728 x 1,152
Images
(Avg size)
808
1.3 MB
1,396
733 KB
2,560
400 KB
-
-
Approx.
Compression
5:1
8:1 15:1
-
-

We strongly recommend buying either a large capacity SDHC card, at least a 2GB card, preferably a 4-8GB one, to give yourself extra space for extended outings. (Check the shopping link above, cards are really cheap these days, so no reason to skimp.)

 

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Note: For details, test results, and analysis of the many tests done with this camera, please click on the tabs at the beginning of the review or below.

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