Hi Shelly, Here is another way to look at it. This is a chart, in inches, that I created in Excel to help me decide which size of tube or cyninder cameras, like an oatmeal box, to use in various circumstances. Diameter is how wide the box is across. This is the focal length. Circumference is how big the circle around the outside of the box is, which tells you how big a piece of paper will fit inside (if you were to wrap it 360 degrees). 1/2 circumference is 180 degrees, or half of the circle. 1/2 circle is will give a full image without too much light falloff. It is also where light banding can start, but that is a completely different topic. The more the negative goes beyond the 1/2 circumference measure, the more likely you will get extreme or complete fall-off, especially in the corners of the image, since they are farthest from the center of the light cone that Ed mentioned.
How big was the oatmeal box? My guess is somewhere between 3.5 and 5.5 inches. A 10-inch-wide piece of paper would fit in any of these tubes; but the smaller the focal length, the greater the likehood of vignetting. Diameter Circumference 1/2 Circ 2.00_________ 6.28_________ 3.14 2.50_________ 7.85_________ 3.93 3.00_________ 9.42_________ 4.71 3.50_________11.00_________ 5.50 4.00_________12.57_________ 6.28 4.50_________14.14_________ 7.07 5.00_________15.71_________ 7.85 5.50_________17.28_________ 8.64 6.00_________18.85_________ 9.42 6.50_________20.42_________10.21 7.00_________21.99_________11.00 7.50_________23.56_________11.78 8.00_________25.13_________12.57 Tom Miller -----Original Message----- From: pinhole-discussion-admin@p at ??????? [mailto:pinhole-discussion-admin@p at ???????]On Behalf Of Ed Kirkpatrick Sent: Tuesday, April 22, 2003 9:06 AM To: pinhole-discussion@p at ??????? Subject: RE: [pinhole-discussion] Image not filling out paper Shelley, The dark areas are caused because that part of your paper lies outside the image cone as it projects through the pinhole into your camera. The diameter of the image circle expands outward from the pinhole at about 3.5" diameter per inch of focal length so if you can imagine the cone formed in your camera you will see why this effect occurs. Ed Kirkpatrick Ed Kirkpatrick Photography www.edkirkpatrick.com -----Original Message----- From: pinhole-discussion-admin@p at ??????? [mailto:pinhole-discussion-admin@p at ???????] On Behalf Of Rauch, Shelley Sent: Monday, April 21, 2003 1:29 PM To: pinhole-discussion@p at ??????? Subject: [pinhole-discussion] Image not filling out paper Okay... another newbie question. One of the cameras that I am using is an oversized oatmeal can. I'm using 8X10 paper, which fits perfectly when placed horizontally. The image isn't taking up the entire area, and I'm wondering what exactly causes this, and what I can do to get it closer to the edges. Here is an example of what I'm talking about: http://www.pbase.com/image/15725356 Shelley C. Rauch Acquisitions Dept. (757)890-5116 Tabb-York County Public Library 100 Long Green Blvd. Yorktown, VA 23693-4138 _______________________________________________ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??????? unsubscribe or change your account at http://www.???????/discussion/ _______________________________________________ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??????? unsubscribe or change your account at http://www.???????/discussion/
