Pentax K-5 Flash

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Pentax K-5 Flash

The Pentax K-5 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 modes available depends on the current exposure mode. The flash is not auto pop-up. To release the flash from its compartment, press the Flash button on pentaprism housing. Close it again by pushing the flash head back down.

The Pentax K-5'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. Flash coverage is rated by Pentax at 28mm equivalent. 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 1/8,000 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 K-5 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. Units set to CCS mode can thus be used to provide "fill" illumination. When used with the K-5, and when the K-5's internal flash is also contributing to the exposure, the external flash in CCS mode will cut its output to two-thirds, while the K-5's built-in flash will cut its exposure contribution to one-third.

The Pentax K-5 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
A fairly powerful flash, with uneven coverage at wide-angle. Lower than average exposure compensation required.


18mm	55mm

Normal Flash +0.3 EV	Slow-Sync Flash Default

Coverage and Exposure. Flash coverage was rather uneven at wide-angle (18mm) with the 18-55mm WR kit lens, though that's not unusual. Coverage was much more uniform at telephoto (70mm), if a bit dim. In the Indoor test, the Pentax K-5's flash required a less than average +0.3 EV exposure compensation adjustment to get bright results. (Most cameras we've tested required about +0.7 EV for this scene.) We did notice that increasing the flash exposure compensation above +0.7 EV had little effect. The camera's Slow-Sync flash mode produced slightly brighter and more even results with no exposure compensation, though with a stronger pinkish-orange cast from the room lighting.

Flash Range: Wide Angle
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100
12 ft	13 ft	14 ft	15 ft	16 ft
1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100	1/50 sec f3.5 ISO 100

Flash Range: Telephoto
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100
12 ft	13 ft	14 ft	15 ft	16 ft
1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100	1/100 sec f5.6 ISO 100

ISO 100 Range. At 18mm, f/3.5 and ISO 100, flash shots started out bright at 6 feet, peaked in brightness at about 8 feet, and remained reasonably bright out to about 14 feet. At 55mm and f/5.6, flash exposure started out slightly dim at 6 feet, and decreased in brightness from there, falling off more rapidly at 9 feet and beyond.

Manufacturer-Specified Flash Range
Wide Angle	Telephoto
12.2 feet ISO 100	7.6 feet ISO 100

Manufacturer Specified Flash Test. The Pentax K-5's flash is rated with a GN of 13 meters at ISO 100. That translates to 12.2 feet at f/3.5 and about 7.6 feet at f/5.6, the maximum aperture of the 18-55mm kit lens at wide-angle and telephoto respectively. In the shots above, the K-5's flash under-performed somewhat compared to Pentax's specifications, producing slightly dim (but usable) exposures at the rated distances. The above flash shots are approximately 1/3 to 1/4 f-stop underexposed. Our standard test method for flash range uses a fixed setting of ISO 100, to provide a fair basis of comparison between cameras. We've now also begun shooting two shots using the manufacturer-specified camera settings, at the range the company claims for the camera, to assess the validity of the specific claims.