Effect f/numbers and Exposure Compensation
As the lens focuses closer to a subject the amount of light reaching the film decreases. Exposure Compensation is not necessary due to TTL (Through The Lens) exposure metering. When using a separate exposure meter or non-TTL flash, it is necessary to compensate the exposure reading .
Magnification and Exp sure Factors
The exposure factor refers to the amount of exposure compensation necessary for the proper exposure when using a separate meter or non-TTL flash. The tables below show the exposure factors covered into an aperture compensation number for various magnifications
*One exposure degree equals +1f/stop
| Effective f-No. |
1:10
|
1:5
|
1:3
|
1:2
|
1:1.5
|
1:1.2
|
1:1
|
| Distance (m) |
2
|
1.20
|
.84
|
0.66
|
0.57
|
0.51
|
0.48
|
| Effective f-No. |
3.8
|
4
|
4.3
|
4.7
|
5
|
5.4
|
5.8
|
| Exposure Factor |
1.18
|
1.32
|
1.52
|
1.80
|
2.01
|
2.41
|
2.74
|
|
Compensation Amount (f/stops)*
|
0
|
+2/3
|
+1
|
+1 1/3
|
|
0
|
+1/2
|
+1
|
+1 1/2
|
