F Number at infinity focus for optimum Depth
of Field for Common roll film Formats
| Magnification |
For 35mm Film |
For 6x4.5cm Film |
|
| 3:1 |
7.8 |
13 |
15.3 |
| 2:1 |
10.4 |
17.4 |
20.5 |
| 1:1 |
15.6 |
26.1 |
30.7 |
| 1:2 |
20.8 |
34.8 |
40.9 |
| 1:3 |
23.5 |
39.1 |
46 |
| 1:4 |
25 |
41.7 |
49.1 |
| 1:5 |
26.1 |
43.5 |
51.1 |
| 1:10 |
28.4 |
47.4 |
55.8 |
| Circle Of Confusion Used |
0.03mm |
0.05mm |
0.0588mm |
| Lines Per mm Used |
33 |
20 |
17 |
What this means is simple -- keep your F number lower than
these values or diffraction will limit the sharpness of your photos. For
landscapes open up at least one or two stops from the F number used at
1:10 lifesize. For Macro these numbers are pretty much the upper limits
as to what you can hope to achieve in terms of depth of field, bracket
a couple of stops down in F number (smaller number!).
Note:
All F numbers are for infinity
focus (ie.: Are as marked on the lens!)
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