Pentax K-1 Review

Performance and Burst Mode

During our testing of the K-1, we evaluated the camera's performance in a variety of areas, including burst buffer size, image processing time, file size, transfer speeds, and general operation.

Overall we are satisfied with the K-1's performance, and generally-speaking, its PRIME IV engine delivers improved performance over what was offered by previous Pentax bodies.  There are a few areas in which the camera falls short of expectations, however.  Read on for details.

File Storage Types

The Pentax K-1 has three ways of saving photos:

  • "Sequential mode" saves to a single card
  • "Backup" mode saves a copy of each file to both cards
  • "RAW/JPEG split" mode places RAW files on one card and JPEGs on the other

For the majority of our tests, we employed the sequential mode, as the K-1's hardware cannot write to both cards simultaneously, hence necessitating longer write times in the other modes.  More details on this will follow during our continuous burst tests.

The SanDisk SD cards we tested

Throughout our tests, we used two pairs of SanDisk Extreme Pro 64GB (95 MB/s read & 90 MB/s write) and Extreme Plus 64GB (90 MB/s read & 60 MB/s write) SDXC cards in the K-1.

File Size

A consequence of K-1's 36-megapixel resolution is large file size— especially in RAW.  The table below summarizes typical file sizes we encountered (i.e. daytime scenes with plenty of detail) at base ISO.

JPEG RAW HDR RAW Pixel Shift RAW
Full Frame 17-22MB 40-60MB 100-130MB 140-160MB
Crop Mode 7-9MB 20-30MB 50-65MB 70-80MB

Table 1: K-1 file sizes, typical, at maximum resolution

Since RAW files in HDR and Pixel Shift mode contain multiple embedded full-size images, they are 3 to 4 times larger than standard RAW files.

The K-1's DNG and PEF RAW files contain identical contents and are losslessly compressed.  Compression becomes less effective as noise level increase, so larger file sizes are to be expected at higher ISOs— up to approximately 1.5 times.

ISO Filesize (MB)
JPEG RAW
100 20 42
200 21 43
400 22 44
800 22 45
1600 23 46
3200 24 49
6400 25 52
12800 26 55
25600 26 59
51200 28 62
102400 30 54
204800 31 67

Table 2: File size changes at increasing ISO

We anticipate that most users will utilize either RAW or RAW+ mode and thus recommend the use of at least 32 GB cards when shooting in sequential mode, or 64 GB cards when saving simultaneously.

16GB 32GB 64GB 128GB
Full Frame JPEG 820 1649 3280 6560
RAW 320 710 1420 2840
RAW+ 200 400 800 1600
Crop JPEG 2000 4000 8000 16000
RAW 640 1280 2560 5120
RAW+ 485 970 1940 3880

Table 3: Estimated SD card capacity for various image formats

With falling memory prices, the necessity of large card sizes is not a big obstacle.  However, older computer setups with limited RAM or CPU power may suffer considerable delays in processing the K-1's large files, so we recommend that prospective K-1 owners plan accordingly.

PC File Transfers

While transferring files from the K-1 to a PC using a USB cord, we measured a sustained transfer speed of  approximately 12MB/s in both MSC and PTP mode.  Although we miss the USB 3 port that we saw on the Pentax K-3 and 645Z, the K-1's data transfer rate is still well below the practical maximum of the USB 2 standard.

With the Pentax K-3, we measured a file transfer rate of 30 MB/s in USB 3 mode and 19 MB/s in USB 2 mode.  Thus, we can conclude that the K-1 has slower internal hardware, which is mildly disappointing.

Using a USB 3 card reader is a viable workaround.  With a card reader, we were able to achieve transfer rates of 95 MB/s with the aforementioned SanDisk Extreme Pro card.  Faster transfer speeds might be possible with UHS-II cards, though these cards will revert to UHS-I mode when used with the K-1 and may not deliver the same level of performance as top-tier native UHS-I cards.

File Write Speed

We tested how quickly the K-1 can write files to its memory cards in two different modes: HDR single shot, and continuous-hi burst.  In both cases, we set the camera to full-frame mode and selected the RAW file format.  Files were stored to a single memory card only (sequential mode).  We divided the total amount of data written by the card access light illumination time to obtain these figures.  All results are an average of 5 trials.

HDR Mode
Burst Mode
Extreme Pro 32 MB/s 26 MB/s
Extreme Plus 30 MB/s 26 MB/s

Table 4: K-1 measured max. file write speed

These results suggest that the K-1 writes well below the capabilities of the high-speed memory card we tested.  Interestingly, however, the Extreme Pro card showed higher performance when saving the large 100MB+ files in HDR mode.  We believe this could be because SanDisk's top-shelf card is capable of slightly faster minimum sustained speeds (both cards must only support at least 30MB/s per the U3 specification; there is no upper limit).

Burst Mode Tests

As the K-1 is Pentax's first venture into full-frame territory, we were eager to test just how many frames it could capture in burst mode.

For our tests, we set the camera to continuous-hi mode (4.4 FPS in FF, 6.5 FPS in crop), manual focus, and ran the shutter on a well-lit daytime scene until the frame rate slowed.

We measured the number of frames captured and the total time the camera spends writing the files to the card (after the end of the burst).

Tables 5 and 6 compare the performance of the two SD cards.  All tests were performed twice and the quoted figures are an average of the results (though in nearly all instances, those results were identical across both trials).

Prior to proceeding to read our findings, please note that practical results may vary (slightly) from our tests.  File size depends on the scene itself, so less detailed scenes can lead to longer burst sequences, and vice-versa.

Frames Captured
before FPS drop

Time
card access light illuminated
after FPS drop
Full Frame JPEG
97 31s
JPEG
+corrections
22 12s
RAW 16 24s
RAW+ 12 24s
Crop JPEG 194 25s
JPEG
+corrections
67 16s
RAW 54 32s
RAW+ 40 36s

Table 5: Burst mode performance, extreme plus card, sequential mode

Frames Captured
before FPS drop

Time
card access light illuminated
after FPS drop
Full Frame JPEG
97 31s
JPEG
+corrections
22 12s
RAW 16 24s
RAW+ 13 24s
Crop JPEG 216 24s
JPEG
+corrections
67 16s
RAW 54 32s
RAW+ 40 32s

Table 6: Burst mode performance, extreme pro card, sequential mode

These results are consistent with the previous test in that there is not a big difference between the two cards.  The K-1 boasts quite a large buffer in JPEG mode, and the advertised limit of 100 frames in crop mode is easily exceeded in JPEG crop mode.

On the contrary, the RAW and RAW+ bursts are fairly short, and write time is moderately long but still tolerable.

More interestingly, however, the most taxing setting on burst performance is geometric distortion correction in JPEG mode.  With this enabled, bursts become considerably shorter, even in JPEG mode.  We therefore recommend that distortion correction be disabled for optimal performance.

On an unrelated note, one great thing about the K-1 is that unless distortion corrections are enabled, shortly after the burst ends, the user regains access to the camera's menu system and/or live view.  This greatly enhances usability, since settings can quickly be changed on the fly.

Next, let us take a look at performance in backup mode, when the camera saves a copy of its files to the second card.  Due to the similar performance of the two SD card types, we only tested the extreme pro card for the remaining tests.

Frames Captured
before FPS drop

Time
card access light illuminated
after FPS drop
Full Frame JPEG
78 83s
JPEG
+corrections
18 32s
RAW 13 54s
RAW+ 12 70s
Crop JPEG 80 58s
JPEG
+corrections
63 42s
RAW 36 72s
RAW+ 28 75s

Table 6: Burst mode performance, extreme pro card, backup mode

Write times more than doubled in this mode, and the number of frames captured per burst decreased.  We are disappointed by the fact that the K-1's hardware cannot access both cards simultaneously, since this decrease in performance extends to other modes as well (single shot, bracketing, etc.).

Frames Captured
before FPS drop

Time
card access light illuminated
after FPS drop
Full Frame RAW+ 11 29s
Crop RAW+ 30 40s

Table 7: Burst mode performance, extreme pro card, split mode

Split mode also carries a slight performance penalty, though to a lesser extent than backup mode.

In conclusion, we believe that the K-1 has a satisfactory buffer size and burst performance given the fact that it isn't a camera primarily designed for action photography.  The APS-C crop mode delivers a respectable frame rate of 6.5 FPS for times when this secondary role is needed.

General Performance

The Pentax K-1 is very quick at performing everyday tasks, such as starting up and processing images.  Our tests show that the camera is much quicker to enter playback mode than the Pentax K-3, even in RAW+ mode.  Other measurements are similar.

Pentax K-3 II
Pentax K-1
Startup to 1st shot 0.9s 1.3s
Startup to live view on 1.5s 2.2s
Single file deletion 1.3s 1.3s
Saving a single JPEG
(time to playback)
1.1s 1.2s
Saving a single RAW
(time to playback)
2.6s 1.2s
Saving a RAW+JPEG
(time to playback)
3.0s 1.2s
Lens correction
processing time
(single file)*
1.1s (all) 0.8s (distortion)
1.1s (all)
Clarify enhancement N/A 2.3s
Skin tone correction N/A 1.4s
Pixel shift (FF)* Not measured 3.8s
Pixel shift (Crop)* 1.5s
Shadow/highlight
processing time*
0.1s 0.1s

Table 8: Everyday performance measurements (*on top of the time it takes to save the file)

In general, the camera never got in our way during typical use.  We would like quicker file deletion, though, since this seemingly simple task results in a progress bar.

Shutter Sound

Despite having a much larger shutter mechanism, the K-1's shutter sound is not significantly louder than that of the APS-C K-3, which is considered to be a fairly quiet camera.

Note that in the video below, you can also hear additional sounds, including the SR system re-aligning itself following each capture, as well as the aperture actuator sound in live view.  The actuator may or may not stop the lens down while in live view, depending on ambient light and the current shooting mode.  These sounds can easily be heard by the photographer, but not by someone standing at a distance.

Live View

Live view almost always delivers a smooth frame rate, even with focus peaking on.  An annoying quirk is that whenever the user tries to access the Control Panel or main menu, the mirror flips down.  This behavior slows the user down a little bit, but moreover it places unnecessary wear on the shutter and mirror mechanism.

Bugs and Issues

We are not aware of any quality-control issues related to the K-1. 

The only software bug/incompatibility that affects users is freezing with certain older Sigma autofocus lenses, such as the 70-200mm EX DG and EX DG II.  Effective live view autofocus with certain Sigma lenses may also not be possible.  It's likely that the only resolution to this problem would be through a lens firmware upgrade by Sigma.

Verdict

For a high-resolution camera, the Pentax K-1 passed most of our tests with flying colors.  Its crop mode delivers a fast frame rate and excellent buffer performance, and it does well in full-frame mode, too.  The camera feels responsive and it is certainly enjoyable to use.

The most disappointing aspect is the slow USB transfer rate and the relatively slow card write speed, though the latter likely won't affect users shooting outside of burst mode.  Still, transferring gigabytes of 36-megapixel files to a PC can take quite a while at a speed of just 12MB/s; we therefore recommend using an external USB 3 card reader.  We expected the K-1 to be at least as good as the 3 year old K-3 in terms of transfer speed, but this is not the case.  The K-3's USB connection is more than twice as fast.

It can still be beneficial to opt for the fastest SD cards available for the K-1 due to faster transfer speeds in a card reader, but just about any UHS-I U3 card should satisfy the K-1's write speed needs in burst mode.

We would have also liked to see faster performance when saving photos to both memory cards.

Lastly, be sure to have plenty of large SD cards and a fast computer to work with 36-megapixel files.


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