PC052
Circular Polarizing Filter

Circular polarizers are mainly used in consumer applications, such as with camcorders or SLR cameras that have a beamsplitter that send part of the light coming through the lens to a viewfinder and part to a light meter. Light entering the exposure meter is partially polarized by the beamsplitter. A linear polarizer over the lens would act as a secondary polarizer and block light going to the meter (but not the sensor or film), resulting in incorrect exposures. A circular polarizer ovecomes this problem with the addition of a ¼-wave retarder, which rotates the linearly polarized light 90° so that it appears unpolarized to the light meter, resulting in proper exposure.

Obviously this is of no importance in most machine vision applications, where viewfinders and light meters using beamsplitters are not employed. For this reason we recommend using linear polarizers for all machine vision applications.

Download Excel Spreadsheet with data and curve for this filter.

Examples of filter effectiveness.

Standard Threaded Mounts:
We offer standard filter sizes from stock – 22.5mm to 62mm – for same- or next-day shipping. Larger filters – 67mm to 105mm – are made to order and are normally not returnable.

Click here for PDF drawing of standard mounts

Slip Mounts:
If your lens does not have threads for mounting a filter, Slip Mount adapters are available. Slip Mounts can attach a regular filter to a lens or attach a very large filter to accommodate a wide angle lens. Please call to order Slip Mount adapters.

C-Mounts:
3mm thick threaded mount for adding a filter between lens and camera
Click here for PDF drawing of c-mounts

Transmission chart (typical)
Passes visible (340nm+) and IR
Absorbs UV 200-340nm

1100
1090
1080
1070
1060
1050
1040
1030
1020
1010

1000
990
980
970
960
950
940
930
920
910

900
890
880
870
860
850
840
830
820
810

800
790
780
770
760
750
740
730
720
710

700
690
680
670
660

72.05
71.66
71.19
70.78
70.24
69.80
69.33
68.97
68.51
68.02

67.55
67.09
66.68
66.12
60.54
60.03
59.46
58.81
58.09
57.37

56.75
56.02
55.20
54.34
53.51
52.63
51.78
51.05
50.32
50.96

51.11
51.26
51.54
51.88
51.62
51.90
52.16
52.87
53.75
54.64

53.63
52.79
52.08
51.55
51.24

650
640
630
620
610
600
590
580
570
560

550
540
530
520
510
500
490
480
470
460

450
440
430
420
410
400
390
380
370
360

350
340
330
320
310
300
290
280
270
260

250
240
230
220
210

51.17
51.52
52.20
51.82
52.69
54.07
55.33
54.52
52.41
53.92

50.78
48.42
47.97
47.46
46.95
46.41
45.93
45.43
44.76
42.96

42.60
42.08
41.27
40.32
39.50
38.51
36.69
34.50
33.67
32.70

30.25
24.17
10.05
1.16
0.08
0.00
0.00
0.00
0.00
0.00

0.00
0.00
0.00
0.00
0.00