Pentax K-5 Review

 
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Pentax K5 Video Recording

When Pentax launched its preceding K-7 model, video capture was still a relatively new feature in the digital SLR market, and the company stood out by offering what was -- at the time -- a pretty leading-edge feature set. In just a couple of years, though, the video-capable SLR market has seen rapid development, and the bar has been raised to new heights, leaving the K-7's video capabilities looking a little dated.

With the debut of the Pentax K-5, the company has added a number of new video capture features that make it quite a bit more capable than its predecessor. Unfortunately in a few areas the K-5 hasn't kept up with its prosumer competitors, and in some cases it even lags behind lower-cost consumer DSLRs from the likes of Canon and Nikon. Most notably, the K-5 lacks the ability to use autofocus during movie capture, or to control exposure and audio levels manually.

The result is something of a mixed bag. The K-5 offers up a feature set that would've seemed great just a couple of years ago, but now feels like something of an afterthought, an impression which is somewhat reinforced by the distinct separation between the camera's still and video capture functionality. That's not to say you can't get great movies out of the K-5 -- indeed, even the previous K-7 model is capable of seriously impressive things, in the hands of a talented videographer. (Futuristic Films' short film "Uncle Jack", shot with the earlier K-7, is a nice example of what's possible, as are several other videos available on Pentax's official YouTube channel.)

Professional videographers may find themselves wishing for more manual control, though, and amateurs may find it challenging learning to pull focus manually.

Pentax K-5 Video: Image Size, Frame Rate, and Encoding

Full HD video. The Pentax K-5 offers three resolution levels for video recording, including Full HD for the first time. Unlike the K-7, all three resolutions match existing standards -- 1080p, 720p, and VGA / 480p.

The Pentax K5's all-new CMOS image sensor records high definition video at a maximum resolution of 1,920 x 1,080 pixels, otherwise known as "Full HD" or 1080p, with a rate of 25 frames per second. In addition, there are two lower-resolution modes that downsample the video stream to produce either 1,280 x 720 (720p) high-definition movies, or 640 x 480 (VGA or 480p)standard-def movies (a 3:2 ratio again). Although the new 1080p mode is restricted to a maximum of 25 frames per second, both lower resolutions provide an option of either 30 or 25 frames per second. By contrast, the K-7 offered only 30 fps capture across the board. Pentax hasn't stated a reason for not offering a 30fps mode at 1080p, but it's reasonable to presume that it's due to bandwidth limitations somewhere within the imaging pipeline. Note that while the 720p resolution is carried over from the K-7, the 1080p and VGA modes together replace two non-standard resolutions that were offered in the earlier camera. The Pentax K-5 no longer has either a 1,536 x 1,024 pixel or 640 x 416 pixel mode.

Like its predecessor, the Pentax K5 records its movies as Motion JPEG-compressed .AVI files, rather than the AVCHD format favored by most manufacturers these days. The AVCHD format used by most of the K-5's rivals is a subset of the broader H.264 video compression spec, which places fairly heavy constraints on the recorded bitrate, hence allowing smaller file sizes. Unfortunately, these constraints also conspire to cause a severe loss of image quality in AVCHD video when a lot of the image changes from one frame to the next, as is the case when panning or in closely-cropped video of a rapidly-moving subject. Some cameras with sufficient processing power instead use H.264 encoding at higher bitrates to avoid some of the limitations of AVCHD, but as well as increasing file sizes, this comes with the requirement of greater processing power to encode and decode. Compared to these formats, Motion JPEG is much less processor-intensive than H.264, and avoids AVCHD's compression-related quality loss during panning. The downside, though, is that the Pentax K-5 yields extremely large file sizes: just one minute of 1080p video can very easily produce file sizes on the order of 600MB or so, depending on subject matter.

Recording is only part of the story, of course: editing and playback are equally important aspects to be considered. When it comes to editing, the Pentax K5's AVI format is much easier to deal with than H.264-encoded video (including AVCHD), at least currently. The more sophisticated encoding used in the H.264 standard requires quite a bit of processor power to pull it apart and put it back together again, so frame-accurate editing of H.264 requires a fast processor and capable editing program. When it comes to playback, it's perhaps a bit of a toss-up between the two main formats: AVI plays back much better on computers with relatively modest processors, while AVCHD files can be read directly by some television sets, and played back with better quality on HDTVs through the Pentax K5's HDMI port.

Here's a list showing what to expect for file sizes with the Pentax K-5's video recording:

Pentax K-5 Video Options
Motion JPEG Format (.AVI files)
Menu Designation
Resolution and
Frame Rate
Quality Level
File Size

Full HD 25

1,920 x 1,080
25 fps
(1080p HD)

Best (***)

500 - 600 MB/minute

Better (**)

420 - 450 MB/minute

Good (*)

320 - 330 MB/minute

HD 30

1,280 x 720
30 fps
(720p HD)

Best (***)

330 - 375 MB/minute

Better (**)

235 - 245 MB/minute

Good (*)

170 - 175 MB/minute

HD 25

1,280 x 720
25 fps
(720p HD)

Best (***)

245 - 310 MB/minute

Better (**)

180 - 200 MB/minute

Good (*)

140 - 145 MB/minute

VGA 30

640 x 480
30 fps
(VGA / 480p SD)

Best (***)

115 - 130 MB/minute

Better (**)

45 - 85 MB/minute

Good (*)

55 - 60 MB/minute

VGA 25

640 x 480
25 fps
(VGA / 480p SD)

Best (***)

80 - 110 MB/minute

Better (**)

40 - 70 MB/minute

Good (*)

45 - 50 MB/minute

(Measurements were made with a hard-to-compress digital noise image, and a blank white screen, to show the extremes in terms of high and low bitrate, respectively.)

Compared to the K-7, our tests of the K-5's frame size and compression levels showed a more even reduction in file sizes as compression levels ramped up, although the Medium and Low quality settings yielded barely any difference with highly compressible subjects at the lowest frame size. In fact, while less compressible subjects yielded smaller file sizes with the lowest 'Good' quality setting in VGA mode, we actually achieved slightly smaller files with the 'Better' setting with a more compressible subject than we did using the 'Good' setting.

The file-size results correspond to what we found in the K-5's video files: The best image quality is definitely achieved in its Full HD mode, but you'll need to pay the piper in terms of flash card space. Stepping up from 720p to 1080p while retaining the same frame rate and compression level literally doubles file sizes, and at the maximum quality setting, 1080p capture will chew through 2GB of card space in somewhere from 100 to 120 seconds. While the Better quality setting offered a reasonable balance between file sizes and compression artifacts in the Full HD mode, there was certainly a noticeable loss in detail, and at lower resolutions we felt that recording at anything less than the highest quality setting simply produced too many JPEG artifacts for our tastes.

Here are some examples of video from the Pentax K-5, showing typical results under daylight and night conditions.

Pentax K-5 Video Samples
shot with smc PENTAX DA 17-70mm F4 AL (IF) SDM lens
Daytime Videos

1,920 x 1,080, 25fps, Best (***) Quality
View on Vimeo | Download Original
(12.0 seconds, 118 MB)
1,280 x 720, 30fps, Best (***) Quality
View on Vimeo | Download Original
(12.0 seconds, 73.8 MB)
1,280 x 720, 25fps, Best (***) Quality
View on Vimeo | Download Original
(12.0 seconds, 61.6 MB)
1,280 x 720, 30fps, Better (**) Quality
View on Vimeo | Download Original
(13.0 seconds, 52.2 MB)
1,280 x 720, 30fps, Good (*) Quality
View on Vimeo | Download Original
(12.0 seconds, 34.6 MB)
640 x 480, 30 fps, Best Quality
View on Vimeo | Download Original
(14.0 seconds, 29.4 MB)
Night Videos
Note: The popping / clicking noise on the Vimeo versions of the night clips below is not present in the original videos. We're currently in communication with Vimeo to resolve this issue. Apologies for the inconvenience!
1,920 x 1,080, 25fps, Best (***) Quality
View on Vimeo | Download Original
(11.0 seconds, 108 MB)
1,280 x 720, 30fps, Best (***) Quality
View on Vimeo | Download Original
(11.0 seconds, 67.7 MB)
1,280 x 720, 25fps, Best (***) Quality
View on Vimeo | Download Original
(13.0 seconds, 67.0 MB)
640 x 480, 30fps, Best (***) Quality
View on Vimeo | Download Original
(11.0 seconds, 23.1 MB)

640 x 480, 25fps, Best (***) Quality
View on Vimeo | Download Original
(11.0 seconds, 19.3 MB)



Pentax K-5 Video-Mode Focusing

When we first saw a prototype of the earlier K-7 model prior to its announcement, were excited to see that it supported contrast-detect autofocus during movie recording, something that would've been unique among prosumer DSLRs at the time. Unfortunately, this feature was absent in final production models of the K-7, and the K-5 retains the status quo in this regard. Unfortunately, digital SLR video capture has come a long way since the launch of the K-7, and many competing cameras do now offer this feature. Notably, Canon introduced the ability to perform single AF operations with its Rebel T2i in February 2010, and Nikon followed suit with full-time AF in the D3100 from August 2010, and both companies have since introduced the same in-movie AF options in their prosumer models as well. Hence, where the omission of in-video AF was merely a shame in the K-7, it now stands out as an area where the K-5 lags its main rivals.

While the absence of in-video AF isn't likely of any importance to professionals, a significant portion of the K-5's target market is made up of enthusiastic amateurs, and for many, the requirement to focus manually is a step too far. It takes significant practice and no small dose of talent to pull focus manually, and doubly so if you're also having to pay attention to image framing, etc. Even bearing in mind that the earlier Pentax K-7 prototype's contrast-detect AF cycle was rather slow, visible in the video, and quite audible via the built-in microphone with most lenses, we think that many enthusiast videographers would welcome its presence in Pentax's DSLR lineup all the same. Audio issues can be solved by using an external mic, and for those who can't master the arts of pulling focus manually, brief moments of contrast-detect "hunting" would likely still prove more acceptable than blurry video -- or no video at all.

As it is, focusing in movie mode with the Pentax K-5 is much the same as used to be the case with most other video-capable DSLRs last year: You can trigger a contrast-detect AF cycle prior to the beginning of a recording by hitting the AF button on the camera's rear panel, but there's no autofocus during recording. You can manually focus the lens during a recording, though, and the true manual operation of AF on Pentax's lenses means you can do this more or less silently, simply by being careful about turning the focus ring. (Some cameras we've tested, such as the Olympus E-P1, use "fly by wire" focusing, whereby the focus ring only instructs the camera to move the lens elements rather than moving them directly via a mechanical coupling. This means that small clicks can be heard on the audio track every time the camera changes the focus setting, regardless of how slowly you turn the focus ring. With true manual operation of its lenses, the Pentax K-5 doesn't have this problem.)

As is the case in Live View mode, pressing the Info button on the camera's rear panel lets you zoom in up to 6x when AF is enabled, or as far as 10x when set to manual focus mode, to assist with precise focusing, but note that this is only possible before recording has started: Once the camera has begun recording, only the normal 1:1 view is available. A new function of the K-5's pre-capture contrast detection autofocus is that during the AF operation, the live view feed automatically zooms in on the focus point -- whether it is manually selected, or set using face detection -- making it much easier to see if the lock was accurate. The zoom isn't performed instantly, but rather the view gradually zooms in to help reinforce where within the frame the camera is focusing. This function is something of a mixed blessing, however, in that it can't be disabled, and operates even when in AF-C mode, where you'd expect to be shooting a moving subject. (It does return to a normal view shortly after the initial focus lock, so you do at least see the full image view in between AF operations.) The zoomed view can make it very tricky to continue to follow your subject and keep them inside the image frame while focusing, though, and we'd really like to see the option to disable this otherwise useful feature -- at the very least when Continuous AF is disabled, and preferably at any time of the photographer's choosing.

As we've noted in other SLR reviews, the good news with focusing for video is that you can get surprisingly good depth of field in video mode by stopping the lens down, thanks to the relatively low resolution of the video image. With a pixel resolution of only 2.1 megapixels in the Pentax K-5's Full HD mode, 0.9 megapixels in 720p mode, and just 0.3 megapixels in VGA mode, images that would be unacceptably blurred as 16 megapixel still shots look perfectly fine as video frames. This not only provides greater depth of field at any given aperture, but is also more forgiving of diffraction limiting at very small lens apertures. Diffraction at small apertures means you'd usually want to avoid f/16 or f/22 for still images, but again, the results generally look perfectly fine at video resolutions. Bottom line, with the K-5's lens set to f/16 or f/22 (assuming you're shooting under fairly bright conditions), you'll be surprised by how little focus adjustment is needed during a typical video recording.

Pentax K-5 Video Exposure Control


Pentax K-5 Aperture Control / Depth-of-Field
shot with smc PENTAX DA 17-70mm F4 AL (IF) SDM lens
Aperture-priority, f/4.0

1,280 x 720, 30fps, Good (*) Quality
View on Vimeo | Download Original
(5.0 seconds, 14.6 MB)
Aperture-priority, f/22.0

1,280 x 720, 30fps, Good (*) Quality
View on Vimeo | Download Original
(5.0 seconds, 14.4 MB)

The level of exposure control available when shooting video with current SLRs varies widely. Many cameras -- especially those aimed at consumer use -- still opt to keep things simple with fully automatic exposure control. Manual exposure control is also now a reasonably common option, though, especially in prosumer and professional models. Like its predecessor, the Pentax K-5 offers somewhere in between these extremes, giving you a choice of either automatic or aperture-priority exposure modes. In Auto aperture mode, the camera adjusts the aperture as needed, but just like the K-7, doesn't report the current value on the LCD screen. (We'd still like to see Pentax change this behavior to allow aperture display regardless of exposure mode, at the videographer's option.) In aperture priority mode -- referred to in the menu system as Fixed Movie Aperture Control -- the current aperture is displayed in the lower left corner of the LCD screen, and can be changed by rotating the rear command dial. You can't adjust it during recording, but whatever value you set before you begin your clip is the one the camera will use. This is a great feature that gives a fair degree of creative control over the look of videos, although it doesn't go as far as some cameras in allowing direct control over shutter speed or aperture.

In common with most other video-capable SLRs, the Pentax K-5 offers the full range of white balance settings in movie mode, including four different options for fluorescent lighting, and Kelvin values ranging from 2,500 to 10,000. You can also select any of the K-5's Custom Image modes, including Bright, Natural, Portrait, Landscape, Vibrant, Muted, Bleach Bypass, Reversal Film, and Monochrome. As with still-image shooting, settings for saturation, hue, high/low key adjustment and contrast can be adjusted independently for each mode. A sharpness setting is available as well, which affects the sharpness of the video images to a very noticeable degree. (Note that turning the sharpness up too high will make the JPEG compression artifacts much more evident, though.) Unlike its predecessor, the K-5 now allows a subset of its digital filter modes -- and one filter specific to the Movie mode -- to be used during video capture. Modes available for both stills and movies include the Toy Camera, Retro, High Contrast, and Extract Color, with each offering varying degrees of control over the look of the effect. The still-image Soft, Starburst, Fish-eye, and Custom filters are not available in Movie mode, but you gain a Color filter mode that allows a red, magenta, blue, cyan, green, yellow filter effect at either light, standard, or dark intensity levels. The K-5's Cross Processing function, which is also available for stills, can be used in Movie mode as well, and its effect -- which emulates a technique from the days of film photography -- can also be combined with the digital filters. If Cross Processing is active, both white balance and custom image mode must be controlled automatically, however.

Two movie-mode exposure parameters that the Pentax K-5 unfortunately doesn't let you control are its shutter speed and ISO sensitivity. The shutter speed appears to be tied to the frame rate: regardless of the light level involved, rapid motion is always blurred to about the level you'd expect with a 1/25th - 1/30th second exposure time, with the ISO sensitivity being used to maintain the metered exposure level. You can, however, attempt to bias the camera's exposure towards your desired result with judicious use of the exposure compensation, auto-exposure lock, and metering mode controls, all of which are applicable not only before, but also during video capture. (Although the metering mode lever in particular is extremely difficult to move without jostling the camera, unless you're using a rock-solid tripod.) Of course, all of these control adjustments -- if made during video capture -- are likely to result in objectionable camera handling noise on the audio track, to varying degrees.

Pentax K5 Video: Image Stabilization

The Pentax K-5's body-based image stabilization can be used when recording movies. Not only does this make any lens you're recording with into an IS model, but we found that the image stabilization worked exceptionally well when recording videos. We've recorded videos with other SLRs using IS lenses, but the level of stabilization available in Pentax's flagship K5 (and its predecessor) seemed better than we're average. Because the Pentax K-5's Shake Reduction system provides such a high degree of stabilization, there's a bit of a "floating" feeling when recording videos with IS enabled: As you move and pan the camera, the video image tends to lag a little behind your motions, "catching up" when you come to a rest. A related IS effect is that the subject can drift up or down or from side to side slightly during recording. This can be slightly disconcerting, but the upside is that your videos will be much more stable than otherwise, even holding the camera at arm's length, or when shooting with a long telephoto lens.

Note, however, that while image stabilization is available for movie capture, one of the unique aspects of Pentax's Shake Reduction design available in still image shooting -- automatic horizon leveling -- doesn't carry over to Movie mode. You can, however, use the composition adjustment function in Movie mode, allowing you to fine-tune image framing in both horizontal and vertical axes, as well as rotationally, but should you choose to do so this will disable image stabilization -- which makes sense, given you'd be unlikely to use composition adjustment unless you were shooting on a tripod.

Pentax K-5 Video: Audio recording

Like the vast majority of SLRs with video recording capability, the Pentax K5 sports an internal microphone that can record an audio track. Internal mics can be somewhat problematic, in that they're prone to picking up noise produced by moving your hands on the camera or actuating any controls while recording. In the case of the Pentax K-5, the issue can be exacerbated if you choose to use the body-based image stabilization system during movie recording, depending on the degree to which the system is operating. You can hear the IS in the audio track if the camera is jostled a good bit during recording, but not when it's being held relatively steadily: The light clacking sound audible in the face of significant camera movement seems to be the result of the sensor unit bumping up against its stops. If the camera is held even reasonably carefully, you're unlikely to hear any IS-related noise at all, even in a quiet office environment. In normal usage, you thus shouldn't face any problems using the IS system during video capture, unless you're panning quite a bit, or if unstable footing results in a lot of camera movement.

Like that of the K-7 before it, we found that the Pentax K-5's built-in mic does a good job of picking up ambient sound, with good sound quality and sensitivity. At the same time, it seemed to be less sensitive to sounds picked up from focus adjustment or hand movement on the body than some other cameras we've tested. As with that of its predecessor, the built-in mic in the K-5 is monaural, rather than the stereo mics that are becoming more common these days. It's also not directional, so it will pick up noise from behind or alongside the camera body, not just from in front, but for many purposes where a degree of ambient noise is desirable, that can be a good thing.

Of course, if you need a stereo or more directional mic, the Pentax K-5 sports a microphone jack on its left side, to which you can attach an external microphone of your choice. This capability is now rather more common -- especially among prosumer SLRs -- than was the case when the earlier K-7 model debuted, and it's a very worthwhile feature. Although we didn't have an external mic on hand during our testing of the K-5, Pentax provided a Røde Stereo VideoMic shoe-mounted stereo microphone for us to use with the earlier K-7 model, and we found it to be an excellent addition. Røde has since announced a smaller model aimed at use with DSLRs and camcorders, the VideoMic Pro, which seems like it would pair nicely with the K-5's relatively compact body, and of course other notable names in audio such as Sennheiser also offer a variety of options for shoe-mount and other microphone types. If you plan to use the Pentax K-5 for any serious video recording, we strongly suggest that you invest in a quality external mic.

Unfortunately, the K-5 does lack one feature that pros in particular would find desirable. Unlike some of its competitors, Pentax hasn't gifted the K-5 with any manual control over audio recording levels -- instead, the camera will determine these automatically, and may adjust them on the fly, resulting in the levels ramping up and down in response to sudden changes in ambient noise levels. For amateur use, this might well be desirable, helping reduce complexity and ensuring that at least the majority of the audio is recorded at roughly the right level. For professional use, though, the lack of any way to adjust the recording levels manually, or to lock them at a particular level, will likely mean that pro videographers will want to rely on an external device for audio capture, simply replacing the camera's own audio in post-processing. This is easy enough to do, and a variety of relatively affordable, compact, high quality external audio recorders from the likes of Zoom make this possible even for enthusiastic amateurs, but it's nonetheless an extra step in the process which could likely be avoided courtesy of a firmware update.

Pentax K-5 Movie Recording User Interface

The Pentax K-5's movie mode is still accessed via a separate position on the camera's mode dial, rather than being initiated from within still-picture Live View mode, and just like in the K-7, there's still no separate control button to start/stop movie recording:. Instead, pressing the shutter button begins recording, and pressing it again stops it. Many DSLRs these days have a dedicated button to start/stop movie recording, and while newcomers will likely find the K-5's use of the shutter button more intuitive, it draws a very clear dividing line between the camera's still imaging and movie capture functionality. This takes away somewhat from the ability to quickly grab spontaneous, unanticipated video clips, as you have to pay attention to changing the camera's operating mode before you can switch from still to video capture, or vice versa.

Our feelings about having a separate mode for video capture do depend somewhat on the rest of the camera's user interface. On some cameras, combining video capture with normal still-capture mode would increase menu complexity too much, but that wouldn't be an issue with the K-5, given its menu layout. Providing video direct from Live View mode would require the addition of one more button to the rear of the camera to control video recording, though, and the K-5's tight control layout leaves little or no room for that. However, with the functionality of the Raw / Fx button on the camera's left panel now available for the use to change, it seems like that would be an ideal way in which to offer movie capture from the standard live view mode. For that reason, we'd really like to see Pentax provide the ability to access video capture functionality from other modes, at the user's option.

Setting adjustments in movie mode are made via screen 4 of the Record Menu, where the Movie option leads to a whole sub-menu. We found this a little awkward when making frequent adjustments to video settings, as the extra level of menu selection meant more button-pressing to make the changes than would have been required if they'd been available from the main shooting screen via a "quick menu," as some cameras have. That said, the more commonly accessed options for white balance and Custom Image settings were easily accessible via the 4-way control buttons on the camera's back panel, and the K-5 can at least be configured to remember which menu tab was most recently accessed, saving a few button presses over the earlier K-7 model.

The Pentax K-5's Record Menu options for video recording are:


Pentax K-5 Record Mode Menu Movie Options
Top-Level
Selection
Second-Level
Notes
Recorded Pixels
- Full HD 25 (1,920 x 1,080, 25 fps)
- HD 30 (1,280 x 720, 30 fps)
- HD 25 (1,280 x 720, 25 fps)
- VGA 30 (640 x 480, 30 fps)
- VGA 25 (640 x 480, 25 fps)
No 30fps mode is available when recording at Full HD (1080p), but at the lower 720p and VGA resolutions, you have a choice of frame rate, unlike in the K-7.
Quality Level
- *** (Best)
- ** (Better)
- * (Good)
Although three quality levels are available, we found the lowest 'Good' setting introduced too many artifacts across the board, and felt the 'Better' setting only provided an acceptable trade-off at Full HD resolution.
Sound
- On
- Off
Audio capture with internal or external microphones can be disabled altogether, if desired.
Cross Processing
- Off
- Random
- Preset 1
- Preset 2
- Preset 3
- My1 (Favorite 1)
- My2 (Favorite 2)
- My3 (Favorite 3)
New since the K-7, this functions identically to its still-image equivalent, and allows color and contrast effects similar to those achieved by cross-processing traditional film. If enabled, you won't be able to control white balance or custom image modes, however.
Digital Filter
- Toy Camera
- Retro
- High Contrast
- Extract Color
- Color
Also new since the K-7, the K-5 now allows use of several of its digital filter functions during movie capture. Note that the still image Soft, Starburst, Fish-eye, and Custom filters are not available in Movie mode. The Color filter is an additional option not available in still image mode, and allows either a red, magenta, blue, cyan, green, yellow filter effect at either light, standard, or dark intensity levels.
Movie Aperture Control
- Auto
- Fixed
"Fixed" lets you set aperture via the rear-panel control dial before -- but not during -- video capture.
Shake Reduction
- On
- Off
Shake reduction can be disabled if you're shooting on a tripod, or if the level of shake would be likely to cause too much objectionable noise in your audio track. Note that if you're using the Composition Adjust feature, shake reduction is disabled regardless of this setting.



Rolling Shutter Artifacts

Pentax K-5: Rolling Shutter Artifacts
shot with smc PENTAX DA 17-70mm F4 AL (IF) SDM lens

1,920 x 1,080, 25fps, Good (*) Quality
View on Vimeo | Download Original
(4.0 seconds, 20.3 MB)
1,280 x 720, 30fps, Good (*) Quality
View on Vimeo | Download Original
(5.0 seconds, 14.1 MB)
1,280 x 720, 25fps, Good (*) Quality
View on Vimeo | Download Original
(4.0 seconds, 9.4 MB)
640 x 480, 30fps, Good (*) Quality
View on Vimeo | Download Original
(5.0 seconds, 5.0 MB)
640 x 480, 25fps, Good (*) Quality
View on Vimeo | Download Original
(4.0 seconds, 3.3 MB)

Essentially every video capable DSLR currently on the market exhibits motion-related distortions called rolling shutter artifacts. These are caused because the image data is captured and then read off the chip sequentially by rows, rather being captured all at once. In the case of the Pentax K-5, with its variable frame rate, this means that image data for the last row of a given frame is captured and read out anywhere from 1/25th - 1/30th second after the data for the top row was captured. The effect on moving objects is similar to that of a focal plane shutter in an SLR, but more pronounced, because the video frame is read out much more slowly than the slit of a focal plane shutter moves across the sensor.

For a camera that scans video frames vertically (as all do that we're aware of), rolling shutter artifacts will be most noticeable for subjects that are moving rapidly side to side, or when the camera itself is being panned horizontally. Verticals in the scene will appear tilted to the right or left, depending on the direction of camera motion. As an example, consider the case of a camera being panned from left to right, with a flagpole or other vertical object in the middle of the scene when recording for a particular frame begins: If the top of the object was centered horizontally when the first line of the video frame is acquired, by the time the last line of the frame has been captured, the bottom of the object will have shifted to somewhere left of center: As a result, the vertical object would appear to be leaning to the right.

The visual impact of rolling shutter artifacts on the Pentax K-5, like those of the K-7 before it, seemed greater than those from some other cameras with similar frame rates, leading us to wonder whether some cameras actually capture and transfer each frame of video somewhat faster than the frame rate itself would indicate. (That is, while some cameras might have a 30fps frame rate, each frame might actually be acquired and read out in less than 1/30 second.) Whatever the case, while this isn't a scientific test, we felt that the K-5's movies were somewhat more subject to rolling shutter artifacts than those from some other 25-30fps video systems we've seen.

The upside for the K-5 relative to rolling shutter artifacts is its excellent IS system. While you can avoid the worst effects of a rolling shutter by panning slowly, even minor jiggling of the camera due to hand-holding can produce a jelly-like appearance in the video output from some models. The K-5's IS system stabilized the video well enough that we experienced no such effects when the camera wasn't being panned. If our shooting required both stationary shots and rapid panning in the same segment, though, we had to shoot with the IS system disabled to avoid clacking noise in the audio track from the internal mic. With an external mic, this was much less of an issue.


Computer Requirements for Viewing HD Video

A typical computer these days has little trouble dealing with still images, but high-definition video can be another matter. Depending on the file format involved, it can take a pretty beefy computer to handle HD-resolution video playback without stuttering or dropping frames. The Motion JPEG image compression used by the Pentax K-5 is one of the less compute-intensive formats, but its uprated 1,920 x 1,080 pixel resolution means there's a good bit more data to deal with in each video frame than there was with the K-7's non-standard 1,536 x 1,024 pixel maximum resolution, let alone its standard high-def 720p mode. As long as it's a relatively recent and reasonably powerful model, you should have no problem playing video files from the K-5 on your computer. We don't have a specific benchmark for this, but if your computer is less than 3 years or so old, it should have no problem with the K-5's video streams. (By contrast, to play AVCHD or other keyframe-encoded video formats at full 1,920 x 1,080 resolution can demand a very powerful CPU and video card, to keep up.)

That said, the Pentax K-5's video codec doesn't appear to be particularly efficient, as it produces extremely large file sizes at its best quality setting, even though the compression level seems a little higher than that of the K-7. (And as noted earlier, its lower quality settings introduce a significant enough level of JPEG artifacts into the image stream that you'll likely want to use the highest quality setting almost exclusively.) So, while you might be able to play its videos on an older computer, you'll almost certainly need to increase your hard drive capacity. With video files occupying up to 600 MB/minute, it's a good thing that terabyte hard drives are so cheap these days. (At that pace, a terabyte hard drive could hold about 30 hours of video footage. That's a lot of footage if you primarily use the K-5 for casual "video snapshots," but if you're a serious video user, it can go by very quickly.)

 

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