Sigma SD1 Merrill Flash

Coverage and Range
Good power from the flash, though uneven and narrow coverage. Our standard shots required a slightly above average amount of compensation.

Coverage. Flash coverage was rather uneven at wide-angle (17mm) showing rather dark corners (though some of the fall-off is from the lens itself), and the upper half of the flash beam is brighter than the lower. There's also a shadow from the 17-50mm f/2.8 lens at wide-angle, though that's not unusual. Flash coverage was much more even at full telephoto (50mm).

Exposure. The Sigma SD1's flash required +1.0 EV exposure compensation adjustment to produce bright results in our Indoor Portrait test, which is a little higher than average among the cameras we've tested. (The average is +0.7 EV for this shot.) The camera's Slow-Sync flash mode produced very bright results without any compensation, though with a stronger orange cast from the ambient room lighting.

ISO 200 Range. Exposures were quite inconsistent in our flash range series test. At wide-angle, flash exposures were very dim at 6, 7 and 8 feet, but abruptly became overly bright at 9 feet. Exposure at 10 feet was dim, but 11 feet wasn't too bad with brightness dropping off from there. We got inconsistent results at full telephoto too, with 15 feet being the brightest, while brightness at other distances varied. You may need to experiment with exposure compensation to get good flash exposures with the SD1 in the real-world.

Manufacturer Specified Flash Test. The Sigma SD1's flash Guide Number (GN) is 11 meters in auto flash mode at ISO 100, which translates to a range of about 18.2 feet at ISO 200 and f/2.8, the maximum aperture of our zoom lens (it's a constant aperture lens, so we don't have separate telephoto results.) Exposure is bright in the flash shot above, indicating the flash range specification is accurate. Our standard test method for flash range now uses a fixed setting of ISO 200, to provide a fair basis of comparison between cameras. We also shoot using manufacturer-specified camera settings, at the range the company claims for the camera, to assess the validity of specific claims.