Pentax K20D Flash
The Pentax K20D features a built-in, pop-up flash, which operates in either Auto, Flash On (forced flash), Auto + Red-eye reduction, Flash On + Red-eye reduction, or Wireless mode. First and Second Curtain sync modes are available, as well as Slow-sync. The flash is not auto pop-up. To release the flash from its compartment, press the Flash Up button on rear panel, left of the eyepiece. Close it again by pushing the flash head back down.
The Pentax K20D's built-in flash has a guide number rating of 13 meters (43 feet) at ISO 100, translating to a range of about 15 feet at ISO 100 with an f/2.8 lens. That's an improvement over the K10D's GN of 11 meters (36 feet). A Flash Exposure Compensation feature controls the flash exposure -2.0 to +1.0 stops in 1/2 or 1/3-stop increments. Maximum sync speed is 1/180 second, though if an external flash that supports high-speed sync is used, such as the Pentax AF540FGZ or AF360FGZ, maximum shutter speed with flash is 1/4,000 second.
In Wireless mode, the built-in flash can be used as a controller to multiple wireless slave flashes (including the Pentax AF540FGZ and/or AF360FGZ flash units). The built-in flash can be set to contribute to the exposure, or to act only as a controller. The Pentax wireless flash system offers four control channels, so up to four camera/flash setups can be used in the same area without interfering with each other. The K20D can connect on any of the four control channels: You program it by setting a flash unit to the desired channel, attaching that flash to the camera and then half-pressing the shutter button. This sets the camera to the channel the flash was set up for. After this, the flash may be removed and used as a remote unit, controlled by the camera.
Normally, all flashes used (whether on-camera or remote) contribute equally to the exposure, however each external flash can be set to one of the following ratios: 1/1, 2/3, 1/2 or 1/3. Additionally, each flash can be adjusted to under- or overexpose in 0.5 stop increments from -3.0 stops to +1.0 stop. All of this is relative to the overall flash exposure that can be adjusted on the camera by from -2.0 stops to +1.0 stop. Alternately, the Pentax flash units offer a Contrast-Control-Sync mode (CCS for short), which drops a flash's power to half of normal. Units set to CCS mode can thus be used to provide "fill" illumination. When used with the K20D, and when the K20D's internal flash is also contributing to the exposure, the external flash in CCS mode will expose normally, while the K20D's built-in flash will cut its exposure contribution by half.
The Pentax K20D also has a top-mounted hot shoe for attaching an external flash unit. A dedicated PC-sync terminal is also provided.
Flash Test Results
Coverage and Range
Good flash performance and intensity. Much lower than average positive exposure compensation required.
 |
 |
| Normal Flash, Default Exposure | Slow-Sync Mode, Default Exposure |
Coverage. We normally include images showing flash coverage (how evenly the flash illuminates the frame), but since that is lens dependent, they are not presented for the K20D. We can, however, comment on flash exposure. The Pentax K20D's flash performed very well, requiring no exposure compensation (0.0 EV) for a bright image using our new flash coverage scene. With the camera's slow-sync flash mode, results are quite bright and probably could have used -0.3 EV compensation, though the longer shutter time results in a much stronger orange cast from the ambient background lighting.
| Manufacturer-Specified Flash Range |
|---|
 15.2 feet ISO 100 |
Manufacturer-Specified Flash Test. The Pentax K20D's guide number is 13 meters in auto mode at ISO 100, which translates to about 15.2 feet at f/2.8, the aperture used on our Sigma 70mm f/2.8 test lens. In the shot above, the K20D seems to perform at least as well as Pentax says it will, producing a bright exposure at the rated distance with its ISO set to 100.
Note: Our standard test method for flash range uses a fixed setting of ISO 100, to provide a fair basis of comparison between cameras. With the above test, we're also looking at whether their stated specification rings true.
Fujifilm GFX 50S Review
Fujifilm X-T3 Review
Olympus E-M5 III Review
Follow Imaging Resource