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| EQUIVALENT FOCAL LENGTHS FOR NINE FORMATS | |||||||||||||||||||
| Michael K. Davis | |||||||||||||||||||
| [email protected] | |||||||||||||||||||
| Most discussions of equivalent focal length assume comparisons of full image diagonals. This calculator allows that, but also provides a comparison of focal lengths when it is known that the final product will be printed at a 4:5 aspect ratio. This considerably alters comparisons between some formats. | |||||||||||||||||||
| Diagonals (magenta) may be modified to equal measurements taken from negatives produced by your cameras. Then you might want to lock them. | |||||||||||||||||||
| Input focal lengths (yellow), are used to specify a focal length for which you want to find an equivalent length in a different format. | |||||||||||||||||||
| Notice that the 1st table uses diagonals that are only that portion of the negative used to make 4:5 aspect ratio prints. The 2nd table is for full diagonal. | |||||||||||||||||||
| If you want to calculate equivalent focal lengths for a different aspect ratio, copy an entire table and calculate diagonals for each format at that ratio. | |||||||||||||||||||
| FOR 4:5 ASPECT RATIO PRINTS: | |||||||||||||||||||
| Format | 35mm | 6x4.5cm | 6x6cm | 6x7cm | 6x9cm | 4x5in | 5x7in | 8x10in | 11x14in | ||||||||||
| Diagonal (4:5) | 38.4 | 1.5 | 66.4 | 2.6 | 70.4 | 2.8 | 87.1 | 3.4 | 88.0 | 3.5 | 153.7 | 6.1 | 193.7 | 7.6 | 310.6 | 12.2 | 442.2 | 17.4 | |
| mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | ||
| Focal Lengths: | |||||||||||||||||||
| Specify 35mm | 28.0 | 1.1 | 48.4 | 2.8 | 51.4 | 2.0 | 63.5 | 2.5 | 64.2 | 3.7 | 112.1 | 4.4 | 141.2 | 5.6 | 226.4 | 8.9 | 322.4 | 12.7 | |
| Specify 6x4.5cm | 40.5 | 1.6 | 70.0 | 2.8 | 74.2 | 2.9 | 91.8 | 3.6 | 92.8 | 3.7 | 162.0 | 6.4 | 204.2 | 8.0 | 327.4 | 12.9 | 466.2 | 18.4 | |
| Specify 6x6cm | 40.9 | 1.6 | 70.7 | 2.8 | 75.0 | 3.0 | 92.7 | 3.7 | 93.8 | 3.7 | 163.6 | 6.4 | 206.3 | 8.1 | 330.7 | 13.0 | 470.9 | 18.5 | |
| Specify 6x7cm | 39.7 | 1.6 | 68.6 | 2.7 | 72.8 | 2.9 | 90.0 | 3.5 | 91.0 | 3.6 | 158.8 | 4.4 | 200.2 | 7.9 | 321.0 | 12.6 | 457.0 | 18.0 | |
| Specify 6x9cm | 43.6 | 1.7 | 75.4 | 3.0 | 80.0 | 3.1 | 98.9 | 3.9 | 100.0 | 3.9 | 174.5 | 6.9 | 220.0 | 8.7 | 352.7 | 13.9 | 502.2 | 19.8 | |
| Specify 4x5in | 37.5 | 1.5 | 64.8 | 2.6 | 68.7 | 2.7 | 85.0 | 3.3 | 85.9 | 3.4 | 150.0 | 5.9 | 189.1 | 7.4 | 303.1 | 11.9 | 431.6 | 17.0 | |
| Specify 5x7in | 41.6 | 1.6 | 72.0 | 2.8 | 76.4 | 3.0 | 94.4 | 3.7 | 95.5 | 3.8 | 166.6 | 6.6 | 210.0 | 8.3 | 336.7 | 13.3 | 479.4 | 18.9 | |
| Specify 8x10in | 37.1 | 1.5 | 64.1 | 2.5 | 68.0 | 3.4 | 84.1 | 3.3 | 85.0 | 3.3 | 148.4 | 5.8 | 187.1 | 9.4 | 300.0 | 11.8 | 427.2 | 16.8 | |
| Specify 11x14in | 39.1 | 1.5 | 67.6 | 2.7 | 71.7 | 2.8 | 88.6 | 3.5 | 89.6 | 3.5 | 156.4 | 6.2 | 197.1 | 7.8 | 316.0 | 12.4 | 450.0 | 17.7 | |
| FOR DIAGONAL OF ENTIRE IMAGE AREA: | |||||||||||||||||||
| Format | 35mm | 6x4.5cm | 6x6cm | 6x7cm | 6x9cm | 4x5in | 5x7in | 8x10in | 11x14in | ||||||||||
| Image Diagonal: | 43.3 | 1.7 | 69.7 | 2.7 | 77.8 | 3.1 | 87.5 | 3.4 | 102.1 | 4.0 | 153.7 | 6.1 | 208.7 | 8.2 | 312.5 | 12.3 | 447.8 | 17.6 | |
| mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | mm | in | ||
| Focal Lengths: | |||||||||||||||||||
| Specify 35mm | 28.0 | 1.1 | 45.1 | 2.8 | 50.3 | 2.0 | 56.6 | 2.2 | 66.1 | 4.0 | 158.1 | 3.9 | 135.0 | 5.3 | 202.2 | 8.0 | 289.8 | 11.4 | |
| Specify 6x4.5cm | 43.5 | 1.7 | 70.0 | 2.6 | 78.1 | 3.1 | 87.9 | 3.5 | 102.5 | 4.0 | 154.3 | 6.1 | 209.6 | 8.3 | 313.9 | 12.4 | 449.7 | 17.7 | |
| Specify 6x6cm | 41.7 | 1.6 | 67.2 | 2.6 | 75.0 | 3.0 | 84.4 | 3.3 | 98.4 | 3.9 | 148.2 | 5.8 | 201.2 | 7.9 | 301.3 | 11.9 | 431.8 | 17.0 | |
| Specify 6x7cm | 44.5 | 1.8 | 71.7 | 2.8 | 80.0 | 3.1 | 90.0 | 3.5 | 105.0 | 4.1 | 99.4 | 3.9 | 214.6 | 8.4 | 321.4 | 12.7 | 460.6 | 18.1 | |
| Specify 6x9cm | 42.4 | 1.7 | 68.3 | 2.7 | 76.2 | 3.0 | 85.7 | 3.4 | 100.0 | 3.9 | 150.5 | 5.9 | 204.4 | 8.0 | 306.1 | 12.1 | 438.7 | 17.3 | |
| Specify 4x5in | 42.2 | 1.7 | 68.0 | 2.7 | 75.9 | 3.0 | 85.4 | 3.4 | 99.6 | 3.9 | 150.0 | 5.9 | 203.7 | 8.0 | 305.0 | 12.0 | 437.1 | 17.2 | |
| Specify 5x7in | 43.5 | 1.7 | 70.1 | 2.8 | 78.3 | 3.1 | 88.1 | 3.5 | 102.7 | 4.0 | 154.7 | 6.1 | 210.0 | 8.3 | 314.5 | 12.4 | 450.7 | 17.7 | |
| Specify 8x10in | 41.5 | 1.6 | 66.9 | 2.6 | 74.7 | 3.5 | 84.0 | 3.3 | 98.0 | 3.9 | 147.5 | 5.8 | 200.3 | 9.4 | 300.0 | 11.8 | 429.9 | 16.9 | |
| Specify 11x14in | 43.5 | 1.7 | 70.0 | 2.8 | 78.2 | 3.1 | 87.9 | 3.5 | 102.6 | 4.0 | 154.4 | 6.1 | 209.7 | 8.3 | 314.1 | 12.4 | 450.0 | 17.7 | |
[Ed. note: the Excel 5.0+ spreadsheet is already unzipped as .xls linked
below:]
Excel Spreadsheet Download
From: "Michael K. Davis" [email protected]
Newsgroups: rec.photo.equipment.misc
Subject: Equivalent Focal Lengths Calculator (Excel)
Date: 20 Jun 1998
Here's an Excel 5.0+ spreadsheet that calculates equivalent focal lengths
for nine formats from 35mm through 11x14 given a focal length for any one
of the nine. It offers two solutions, one to compare focal lengths using
the entire image area of respective formats, the other using only that
portion of each format that can produce a 4:5 aspect ratio print.
The following is a uuencoded zip file of an Excel 5.0+ spreadsheet named
LENSES3.XLS. You must uudecode it, pkunzip it, then open it using
MS-Excel.
If you would prefer I send it to you as a straight .XLS file,
MIME-attached to an e-mail, just let me know.
Enjoy!
Mike Davis