Read EXIF and determine if the flash has fired

Question

I have been reading some EXIF data with my PHP script. I want to determine for a certain image if the flash has been used. Here are the values returned by EXIF reader

0x0     = No Flash
0x1     = Fired
0x5     = Fired, Return not detected
0x7     = Fired, Return detected
0x8     = On, Did not fire
0x9     = On, Fired
0xd     = On, Return not detected
0xf     = On, Return detected
0x10    = Off, Did not fire
0x14    = Off, Did not fire, Return not detected
0x18    = Auto, Did not fire
0x19    = Auto, Fired
0x1d    = Auto, Fired, Return not detected
0x1f    = Auto, Fired, Return detected
0x20    = No flash function
0x30    = Off, No flash function
0x41    = Fired, Red-eye reduction
0x45    = Fired, Red-eye reduction, Return not detected
0x47    = Fired, Red-eye reduction, Return detected
0x49    = On, Red-eye reduction
0x4d    = On, Red-eye reduction, Return not detected
0x4f    = On, Red-eye reduction, Return detected
0x50    = Off, Red-eye reduction
0x58    = Auto, Did not fire, Red-eye reduction
0x59    = Auto, Fired, Red-eye reduction
0x5d    = Auto, Fired, Red-eye reduction, Return not detected
0x5f    = Auto, Fired, Red-eye reduction, Return detected

Which of them mean that the flash has been used?

Best regards, Mladjo

Answer 1

The flash property is actually a combination of the following flags:

0:  FlashDidNotFire
1:  FlashFired
2:  StrobeReturnLightDetected
4:  StrobeReturnLightNotDetected
8:  CompulsoryFlashMode
16: AutoMode
32: NoFlashFunction
64: RedEyeReductionMode

To check if the flash has fired, bitwise AND the flash property with 1:

$flashfired = ($exifflashproperty & 1) != 0;

Answer 2

I believe if you convert the Hex value to binary, the right most digit then indicates if the flash actually fired or not.

Therefore:

+-------------------------------------------------------+------+----------+-------+
|                        Status                         | Hex  |  Binary  | Fired |
+-------------------------------------------------------+------+----------+-------+
| No Flash                                              | 0x0  | 00000000 | No    |
| Fired                                                 | 0x1  | 00000001 | Yes   |
| "Fired, Return not detected"                          | 0x5  | 00000101 | Yes   |
| "Fired, Return detected"                              | 0x7  | 00000111 | Yes   |
| "On, Did not fire"                                    | 0x8  | 00001000 | No    |
| "On, Fired"                                           | 0x9  | 00001001 | Yes   |
| "On, Return not detected"                             | 0xd  | 00001011 | Yes   |
| "On, Return detected"                                 | 0xf  | 00001111 | Yes   |
| "Off, Did not fire"                                   | 0x10 | 00010000 | No    |
| "Off, Did not fire, Return not detected"              | 0x14 | 00010100 | No    |
| "Auto, Did not fire"                                  | 0x18 | 00011000 | No    |
| "Auto, Fired"                                         | 0x19 | 00011001 | Yes   |
| "Auto, Fired, Return not detected"                    | 0x1d | 00011101 | Yes   |
| "Auto, Fired, Return detected"                        | 0x1f | 00011111 | Yes   |
|  No flash function                                    | 0x20 | 00100000 | No    |
| "Off, No flash function"                              | 0x30 | 00110000 | No    |
| "Fired, Red-eye reduction"                            | 0x41 | 01000001 | Yes   |
| "Fired, Red-eye reduction, Return not detected"       | 0x45 | 01000101 | Yes   |
| "Fired, Red-eye reduction, Return detected"           | 0x47 | 01000111 | Yes   |
| "On, Red-eye reduction"                               | 0x49 | 01001001 | Yes   |
| "On, Red-eye reduction, Return not detected"          | 0x4d | 01001101 | Yes   |
| "On, Red-eye reduction, Return detected"              | 0x4f | 01001111 | Yes   |
| "Off, Red-eye reduction"                              | 0x50 | 01010000 | No    |
| "Auto, Did not fire, Red-eye reduction"               | 0x58 | 01011000 | No    |
| "Auto, Fired, Red-eye reduction"                      | 0x59 | 01011001 | Yes   |
| "Auto, Fired, Red-eye reduction, Return not detected" | 0x5d | 01011101 | Yes   |
| "Auto, Fired, Red-eye reduction, Return detected"     | 0x5f | 01011111 | Yes   |
+-------------------------------------------------------+------+----------+-------+