Pentax K10D Flash Reflection Tests

Results are (c) Copyright UK 2008, Matthew Page. All rights reserved.

Setup is:

	* Pentax K10D, firmware 1.3
	* Tripod mounted
	* AF540-FGZ mounted on camera first, then on 5P lead
	* Subject approx 2m away
	* SMC-FA 24-90 lens, at 45mm
	* Dim conditions.
Some fairly informal tests. Trying to pin down what causes the underexposure when there is a reflection.
IMGP7588ISO100, 1/125, f/8
IMGP7589ISO200, 1/125, f/8
IMGP7590ISO400, 1/125, f/8
IMGP7591ISO800, 1/125, f/8
IMGP7592ISO200, 1/125, f/8 (partially obscuring reflection)
IMGP7593ISO200, 1/80, f/8
IMGP7594ISO200, 1/50, f/8
IMGP7595ISO200, 1/40, f/8
IMGP7596ISO200, 1/125, f/8
IMGP7599ISO200, 1/125, f/8
IMGP7600ISO200, 1/125, f/8
IMGP7601ISO200, 1/125, f/8
IMGP7602ISO200, 1/80, f/8
IMGP7603ISO200, 1/40, f/8
IMGP7604ISO200, 1/40, f/8
IMGP7605ISO1600, 1/50, f/8
IMGP7606ISO800, 1/50, f/8
IMGP7607ISO400, 1/50, f/8
IMGP7608ISO200, 1/50, f/8
IMGP7609ISO100, 1/50, f/8
IMGP7611No Flash, ISO100, 1/50, f/8. The no flash tests illustrate the difference between the ambient light and the the AF540 illumination.
IMGP7612No Flash, ISO200, 1/50, f/8
IMGP7613No Flash, ISO400, 1/50, f/8
IMGP7614No Flash, ISO800, 1/50, f/8
IMGP7615No Flash, ISO1600, 1/50, f/8
IMGP7617Manual ISO100, 1/50s, f/5.6. Flash at 1/64 manual. Shows that the camera can control less than 1/64 of flashgun power when in P-TTL mode.
IMGP7618Manual ISO1600, 1/50s, f/5.6. Flash at 1/64 manual. I suspect that in P-TTL the camera is trying to release the smallest amount of light possible from the flash (which is less than 1/64) - which is why the exposure changes with ISO rating in this test.
IMGP7619P-TTL ISO1600
IMGP7620P-TTL ISO100
IMGP7623Preflash and Main flash reflected, ISO100
IMGP7624Preflash Reflected, Main not reflected, ISO100. This is most surprising! It seems to indicate that the reflection is being detected on the MAIN flash, and not the preflash!!
IMGP7625Preflash not reflected, Main reflected, ISO100. This confirms the previous thought - that the camera is detecting the reflection on the MAIN flash!