Astronomical Society of Coonabarabran

The following table displays a systems depth of focus in microns for different f-ratios at various frequencies of light. The depth of focus is the amount of focus travel about a point of perfect focus where an image will still be in focus.

The formula used is (depth of focus) = 4.88 * (wavelength of light) * (f-ratio of optical system) * (f-ratio of optical system).

Depth of focus in microns for different f/ratio optical systems at different wavelengths of light.

f/ratio	300 nm	400 nm	500 nm	550 nm	600 nm	650 nm	700 nm	800 nm	900 nm	1000 nm
1	1.5	1.95	2.4	2.7	2.9	3.2	3.4	3.9	4.4	4.9
2	5.9	7.8	9.8	11	12	13	14	16	18	20
3	13	18	22	24	26	29	31	35	40	44
4	23	31	39	43	47	51	55	62	70	78
5	37	49	61	67	73	79	85	98	110	122
6	53	70	88	97	105	114	123	141	158	176
7	72	96	120	132	143	155	167	191	215	239
8	94	125	156	172	187	203	219	250	281	312
9	119	158	198	217	237	257	277	316	356	395
10	146	195	244	268	293	317	342	390	439	488
11	177	236	295	325	354	384	413	472	531	590
12	211	281	351	386	422	457	492	562	632	703
13	247	330	412	454	495	536	577	660	742	825
14	287	383	478	526	574	622	670	765	861	956
15	329	439	549	604	659	714	769	878	988	1098
16	375	500	625	687	750	812	874	999	1124	1249
17	423	564	705	776	846	917	987	1128	1269	1410
18	474	632	791	870	949	1028	1107	1265	1423	1581
19	529	705	881	969	1057	1145	1233	1409	1586	1762
20	586	781	976	1074	1171	1269	1366	1562	1757	1952
21	646	861	1076	1184	1291	1399	1506	1722	1937	2152
22	709	945	1181	1299	1417	1535	1653	1890	2126	2362
23	775	1033	1291	1420	1549	1678	1807	2065	2323	2582
24	843	1124	1405	1546	1687	1827	1968	2249	2530	2819
25	915	1220	1525	1677	1830	1982	2135	2440	2745	3050