15. Exposure corrections
The automatic exposure systems are adjusted to a subject reflection factor of 25%, this being the average reflection factor for subjects shot with flash.
Dark backgrounds that absorb a lot of light, or bright backgrounds that reflect a great deal of light (e.g. backlit scenes), can result in overexposure or under- exposure of the subject, as the case may be.
Exposure corrections in auto mode
To compensate the above described effect, exposure can be corrected by opening or stopping down the camera’s aperture. If the background is mainly bright, the flashgun’s sensor will cut off the flash too soon with the result that the subject will be underexposed. With a dark background the flash is cut off too late so that the subject looks too light.
☞Bright background:
open the aperture 1/2 to 1
Dark background:
close the aperture 1/2 to 1
Exposure corrections in TTL mode
Many cameras have an adjusting facility for exposure correction which can also be used in TTL flash mode.
☞Note: Please observe the corresponding explanations in the Operating Instructions for the camera or SCA adapter.
Here, exposure correction by changing the aperture on the lens is not possible. This is because the camera’s automatic exposure system will regard the changed
16. Technical Data
Partial light output | Flash duration | Guide number |
| |
P=Flash Power | in seconds |
| at ISO 100 |
|
|
|
| 50 mm zoom |
|
1 | 1/200 | 1 | 40 |
|
1 - 1/3 |
| 1_ |
|
|
1/2 + 1/3 |
| 2¯¯ |
|
|
1/2 | 1/600 | 2 | 28 |
|
1/2 - 1/3 |
| 2_ |
|
|
1/4 + 1/3 |
| 4¯¯ |
|
|
1/4 | 1/1500 | 4 | 20 |
|
1/4 - 1/3 |
| 4_ |
|
|
1/8 + 1/3 |
| 8¯¯ |
|
|
1/8 | 1/3000 | 8 | 14 |
|
1/8 - 1/3 |
| 8_ |
|
|
1/16 + 1/3 |
| 16¯¯ |
|
|
1/16 | 1/5000 | 16 | 10 |
|
1/16 - 1/3 |
| 16_ |
|
|
1/32 + 1/3 |
| 32¯¯ |
|
|
1/32 | 1/8000 | 32 | 7 |
|
1/32 - 1/3 |
| 32_ |
|
|
1/64 + 1/3 |
| 64¯¯ |
|
|
1/64 | 1/13000 | 64 | 5 |
|
1/64 - 1/3 |
| 64_ |
|
|
1/128 + 1/3 |
| 128¯¯ |
|
|
1/128 | 1/20000 | 128 | 3,5 |
|
1/128 - 1/3 |
| 128_ |
|
|
1/256 + 1/3 |
| 256¯¯ |
|
|
1/256 | 1/26000 | 256 | 2,5 |
|
|
|
|
|
|
Table 1: Flash durations at the individual partial light output levels
54 | 55 |
