Pentax K-S1 Review
Performance
Thanks to its latest-generation PRIME M II processor, the K-S1 feels fast and responsive during everyday use. The camera starts up and is ready to shoot in just under a second. Once powered on, like almost any other DSLR, there is virtually no shutter lag.
Although the menu system does lock up while data is being written to the card, you will only really experience this when shooting long bursts, which can take several seconds to be saved. Having a fast card will help speed this process up, but like the K-50, the K-S1 maxes out as a write speed of around 30 Mb/s and cannot leverage the speed of faster UHS-I cards. Fortunately, even while the camera is writing data, you can continue shooting through the viewfinder.
The K-S1's playback speed never gets in your way. You can quickly scroll through your photos without having to wait for the camera to catch up, even when viewing multiple thumbnails at once. Like other Pentax models, the K-S1 takes about a second to delete individual photos, a process that many other manufacturers have managed to make instant.
When switching modes (such as going from P to M) while in live view, the K-S1 keeps the mirror up, unlike the K-50. This is a major usability improvement that saves time and makes the camera quieter overall. The mirror still unnecessarily comes down when making quick settings changes via the control panel (or the main menu), something we're sure will be fixed in a future model.
Live View Framerate
The live view framerate is a smooth 60FPS which only slows in extremely low light, since the camera attempts to always to keep the live view exposure correct rather than offering a real-time preview based on the current shooting settings. If you see lights flickering, check the Flicker Reduction setting in the camera's setup menu.
Shutter Sound
The K-S1 has a loud shutter and mirror. Switching in and out of live view is noisy, as is shooting in burst mode. The video below shows how the camera sounds in various modes:
Dust Removal
Pentax has fitted the K-S1 with the conventional Dust Removal (DR) system that attempts to remove dust particles by shaking the sensor. DR can be configured to run at startup, shutdown, or on demand. It produces a loud rumbling noise and the noise is perfectly normal.
The DR system is effective in keeping the sensor free of large dust particles, but it does not replace manual cleaning or a blower after prolonged use.
More expensive bodies like the K-3 or K-5 have inaudible ultrasonic DR II systems.
Burst Mode
The K-S1's maximum burst framerate is 5.4 frames per second. It can capture about 20 JPEG files at this speed, and up to 100 at the reduced framerate of 3 FPS in continuous low mode. Unfortunately, its buffer fills up almost instantly when shooting RAW files: expect only 5-8 frames.
If you have an SD card with a write speed of 30Mb/s or above, you can expect optimal buffer performance from the K-S1, as it cannot leverage the latest ultra-high-speed cards.
Filesize
During our field tests, our typical low-ISO daytime JPEG files from the K-S1 were between 10 and 12Mb, while RAW files were 18-19Mb. Compare this to the 16-megapixel Pentax K-50 which averaged 6-7Mb for JPEGs and 13-14 Mb for RAWs.
High-ISO RAW files will occupy more space since they cannot be compressed as efficiently.
Battery Life
The D-Li109 battery used by the K-S1 has a relatively low capacity. According to the specifications you can expect around 480 shots with 50% flash use; in practice we found it to be good for 400-500 photos with moderate live view and playback use instead of the flash.
AA batteries cannot be used with the K-S1, nor is a battery grip available.
Verdict
We find that Pentax engineers have done a good job of improving the K-S1's hardware to support its 20-megapixel sensor resolution. In the hands of a casual user, the Pentax K-S1 will feel like a responsive, high-end piece of equipment. More advanced photographers will be annoyed by the relatively small RAW buffer and somewhat short battery life.
The only issue that really stands out for both crowds is the loud shutter and noisy dust removal system, both of which should have been improved for a camera in the K-S1's price class.