New to pinhole photography

[christopher walrath]

Well, I finally made it here. I have been on the periphary of pinhole photography for sometime but, now that I am finally able to develop my own B&W I'm going for it. I took an old folder (6x6 Wirgin) and removed the bellows/lens assembly to make a 35mm perspective control lens and I was trying to come up with another fate for the folder body than the trash receptical. Then it dawned on me. Medium format pinhole. I reassembled the innards (roll film brackets, film tensioners) and then set about to building the front of the camera. I cut cardboard from the back of a Steno pad about 10mm larger than the old lens window and cut a hole in the center of that and then covered it with black electrical tape. I then cut a 5cm square piece of aluminum foil, rubbed it flat and taped it to the inside of the pinhole board. Then I mounted that to the front of the body and marked the center on the inside. Took a regular sewing needle and applied very light pressure while rolling it slightly in my fingers until the needle tip just pierced the foil. Then I cut out another square of cardboard, smaller this time and covered it, taped a hinge onto it and mounted it over the pinhole. I also fix a couple loops of thread so that I could more easily open the cover. Put a piece of tape over the tripod hole inside the camera body, loaded film, tied the lid closed with a thin black shoe string and christened it the Walra-Lux 2008.

Now I have made a couple of exposures. But I need to test this camera a little bit. I have TMX-120 loaded and the aperture is around f/256 (needle tip miked at about .2mm and the focal length is about 27mm). This would require any meter reading calling for an exposure at EV16 about one second exposure. Which means EV 10 would need a little over a minute mathematically. How would I figure reciprocity adjustments? Since Kodak publishes an additional 5 seconds if a meter reading requires ten seconds, I'm figuring that you should add about four seconds to a reading that would call for an 8 second exposure. And since that same publication says to adjust a 100 second required exposure by doubling it so probably about the same for a two minute exposure, expose for four minutes. But waht about in between? Do I do what Kodak did and just bracket it until I get the matching exposure and publish it or has anyone here already done pinhole and reciprocity with TMX and can shed some light on the subject (no pun intended)? Any comments would be greatly appreciated. Thank you very much.

Chris

[murrayatuptowngallery]

Hey Chris (ran into you on APUG, I think).

Either interpolate from Kodak's data sheet (1 sec = 1/3 stop or 26% time increase, 10 sec = 0.5 stop or 41% increase, 100 sec = x2), or here's a quick crude curve fit on Excel.

tc = 1.2123*t^1.1003 Fits within about 8% at the three points given on Kodak's datasheet (1,10,100)

Below are corrected times (tc) vs t for this film. Sorry I have the order unconventionally backward. Hope it displays OK (tbd). I extended it to 120 sec.

tc t
1.2 1
2.6 2
4.1 3
5.6 4
7.1 5
8.7 6
10.3 7
11.9 8
13.6 9
15.3 10
17.0 11
18.7 12
20.4 13
22.1 14
23.9 15
25.6 16
27.4 17
29.2 18
30.9 19
32.7 20
34.5 21
36.4 22
38.2 23
40.0 24
41.9 25
43.7 26
45.6 27
47.4 28
49.3 29
51.2 30
53.0 31
54.9 32
56.8 33
58.7 34
60.6 35
62.5 36
64.4 37
66.4 38
68.3 39
70.2 40
72.1 41
74.1 42
76.0 43
78.0 44
79.9 45
81.9 46
83.8 47
85.8 48
87.8 49
89.7 50
91.7 51
93.7 52
95.7 53
97.7 54
99.7 55
101.7 56
103.7 57
105.7 58
107.7 59
109.7 60
111.7 61
113.7 62
115.7 63
117.7 64
119.8 65
121.8 66
123.8 67
125.9 68
127.9 69
129.9 70
132.0 71
134.0 72
136.1 73
138.1 74
140.2 75
142.3 76
144.3 77
146.4 78
148.4 79
150.5 80
152.6 81
154.7 82
156.7 83
158.8 84
160.9 85
163.0 86
165.1 87
167.2 88
169.2 89
171.3 90
173.4 91
175.5 92
177.6 93
179.7 94
181.8 95
184.0 96
186.1 97
188.2 98
190.3 99
192.4 100
194.5 101
196.6 102
198.8 103
200.9 104
203.0 105
205.1 106
207.3 107
209.4 108
211.5 109
213.7 110
215.8 111
218.0 112
220.1 113
222.2 114
224.4 115
226.5 116
228.7 117
230.8 118
233.0 119
235.1 120

[christopher walrath]

Yes, Muraay, from APUG. And don't care, this is great stuff. Thank you very much. I'll burn that roll today. THanks again.

[christopher walrath]

Yeah, Murray, set the Excel up here and every row beneath S/S of 1 second is set to be '=Product(A(?)81.26) to get what one might find on a light meter. So here we go.

1 second = 1
2 seconds = 2.6
4 seconds = 5.6
8 seconds = 12
16 seconds = 25.6
32 seconds = 55
64 seconds = 117.9
128 seconds = 252.8
256 seconds = 542.1

[Marv]

You might take a look at the Pinhole Designer here. It has proven simple and accurate for my purposes. Oh and welcome aboard. You might wamt to post over at F295's Pinhole Forum, the alt side dosen't get near the traffic for straight pinhole work.

I look forward to your photos and maybe you could share a shot of the camera.