![[★]](https://i0.wp.com/l.yimg.com/g/images/spaceball.gif){kind=small}
Equivalent Lens Focal Lengths For Different Film Sizes
Photographers usually are most familiar with one camera format, typically 35 mm. They have a good feel for the angle of coverage of lenses in this familiar format but find that their instincts fail them when they switch to a different size film. The following table shows which lenses provide equivalent angles of coverage among film formats.
Determining the 35 mm focal length equivalent for a 2 1/4 Square format camera lens is an apples to oranges comparison unless you set some specifications for framing and print aspect ratio. Once you do that, the principle of similar triangles makes it quite easy to calculate. Here is a table of 35 mm lens equivalences for various Hasselblad lens listed in terms of equivalent angle of coverage for the specified print aspect ratio conditions:
| 6×6 cm Lens | Largest Square | Largest 8 X 10 | Largest 11 X 14 | Full 35 mm |
|---|---|---|---|---|
| 40 mm | 17.3 mm | 21.6 mm | 22.0 mm | 26.0mm |
| 50 mm | 21.6 mm | 27.1 mm | 27.6 mm | 32.6mm |
| 60 mm | 26.0 mm | 32.5 mm | 33.1 mm | 39.1mm |
| 80 mm | 34.6 mm | 43.3 mm | 44.1 mm | 52.1mm |
| 120 mm | 51.9 mm | 64.9 mm | 66.1 mm | 78.1mm |
| 150 mm | 64.9 mm | 81.2 mm | 82.7 mm | 97.7mm |
| 180 mm | 77.9 mm | 97.4 mm | 99.2 mm | 117 mm |
| 250 mm | 108 mm | 135 mm | 138 mm | 163 mm |
| 350 mm | 151 mm | 189 mm | 193 mm | 228 mm |
| 500 mm | 216 mm | 271 mm | 276 mm | 326 mm |
| FACTOR | 0.433 | 0.541 | 0.551 | 0.651 |
These calculations are based upon stock Hasselblad 120 mm and Nikon 35 mm film apertures. The Hasselblad aperture measures 2.15 inches square. The Nikon aperture measures 0.93 inches high by 1.40 inches wide.
- The factor for largest square is calculated as follows: 0.93 inches / 2.15 inches = 0.433
- The factor for largest 8 X 10 is calculated as follows: ((0.93 inches / 8 inches) X 10 inches) / 2.15 inches = 0.541
- The factor for largest 11 X 14 is calculated as follows: ((0.93 inches / 11 inches) X 14 inches) / 2.15 inches = 0.551
- And finally, the factor for full 35 mm frame is calculated as follows: 1.40 inches / 2.15 inches = 0.651
These lens conversion factors can be used to find the 35 mm equivalent focal length of unlisted 2 1/4 Square format lenses. Just multiply the 2 1/4 Square format lens focal length by the appropriote factor to get its 35 mm equivalent focal lenth.
The same method can be used to compare 4×5 view camera lenses with 35 mm focal lengths.
| 4×5 Lens | Largest 8×10 | Largest 11×14 | Full 35 mm |
|---|---|---|---|
| 90 mm | 22.4 mm | 22.8 mm | 26.9 mm |
| 127 mm | 31.62 mm | 32.1 mm | 38.0 mm |
| 135 mm | 33.6 mm | 34.2 mm | 40.4 mm |
| 150 mm | 37.4 mm | 38.0 mm | 44.9 mm |
| 210 mm | 52.3 mm | 53.1 mm | 62.8 mm |
| 240 mm | 59.8 mm | 60.7 mm | 71.8 mm |
| 300 mm | 74.7 mm | 75.9 mm | 89.7 mm |
| 500 mm | 125 mm | 127 mm | 150 mm |
| 800 mm | 199 mm | 202 mm | 239 mm |
| 1000 mm | 249 mm | 253 mm | 299 mm |
| 2000 mm | 498 mm | 506 mm | 598 mm |
| FACTOR | 0.249 | 0.253 | 0.299 |
Note: To use this table with an 8×10 view camera either divide the 35 mm lens focal lengths by 2 or multiply the 4×5 lens focal lengths by 2.
The 4×5 lens calculations are based upon a film holder aperture of 3.74 inches by 4.68 inches.
- The factor for largest 8 x 10 is calculated as follows: 0.93 inches / 3.74 inches = 0.249
- The factor for largest 11 x 14 is calculated as follows: ((0.93 inches / 11 inches) x 14 inches) / 4.68 inches = 0.253
- The factor for full 35 mm format is calculated as follows: 1.40 inches / 4.68 inches = 0.299
The traditional definition of a normal lens is that its focal length is equivalent to the film diagonal length. In the case of a 2 1/4 Square format it might be useful to modify this definition to specify the largest 8×10 print area of the 2 1/4 film aperture (which coincidentally is closer to 80 millimeters than the square’s diagonal). A normal lens typically has an angle of coverage of about 50 to 55 degrees and is roughly comparable to the useful or working angle of coverage of human vision (the peripheral vision areas serving mostly as a motion detection system).
Comparing lens focal lengths between formats in this way assures equivalent angles of coverage for ultimate print aspect ratio. It is easy to see that 80 mm and 150 mm lenses are normal focal lengths for 2 1/4 Square and 4×5 formats respectively. You can also see that 180 mm and 300 mm lenses are ideal portrait focal lengths for 2 1/4 Square and 4×5 view camera formats.
via Equivalent Lens Focal Lengths For Different Film Sizes – photo.net.
About Rolleiflex – Short but Nice and Informative Write-up
David Haardt | Rolleiflex TLRs.
Introduction
Rolleiflex is the most famous make of TLR (twin-lens reflex) cameras, i.e. on top you have a viewing lens with a fixed mirror and a screen (waist-level finder, but various prisms are also available), and below that a taking lens with a leaf shutter leading directly to 6x6cm roll film (see the figure at the right). The result is a rather compact, quiet and light-weight camera with no mirror blind during exposure and no mirror slap. The downside is fixed lenses (apart from the Mamiya TLR cameras), no depth-of-field preview, and parallax, i.e. the closer you focus, the more difference is between what you view with the viewing lens and what you will photograph with the taking lens.
History
Franke and Heidecke of Braunschweig, Germany, the founders of Rollei, developed the original Rolleiflex, the concept of which should remain the main professional tool until the introduction of the medium format system SLR by Victor Hasselblad of Gothenburg, Sweden. TLR cameras are still being used by professionals and amateurs, especially by wedding photographers due to their flexibility and discreetness. The Rolleiflex 2.8FX is still being manufactured by Rollei, but only in rather limited numbers, and at a very high price. A few years ago, Rollei manufactured the 2.8GX, which has the same appeal as the 2.8FX.
Rolleiflex variants
Basically, there are two different Rolleiflex TLR families, the 3.5 (75mm) and the 2.8 (80mm), which also let us know the maximum aperture of the taking lens. The models were named from A to F (actually only the 2.8 series was fully named like this, the earlier 3.5 series had different, non-systematic, names earlier on), so the 2.8F is the most recent model (apart from the 2.8GX already mentioned above). Some people believe that the f/3.5 lenses are a bit better than the comparable f/2.8 lenses, but obviously Rollei didn’t think so when they decided to resume 2.8 rather than 3.5 production. Of course the 2.8 cameras are more expensive and heavier than their 3.5 counterparts.
Rolleicord and Rolleiflex T budget variants, Rolleiflex Baby 4x4cm cameras
In addition, there is the Rolleicord series which was designed as a budget line with comparable build quality but less bells and whistles and less extraordinary lenses. Lateron, the Rolleiflex T was introduced, closing the gap between Rolleiflex and Rolleicord. The Rolleiflex Baby cameras use (obsolete) 4x4cm (12 frames onto type 127) rather than 6x6cm (12 frames onto type 120 or 24 frames onto type 220) roll film. efke R100 127 is the only type 127 film still in regular production.
Taking lenses used
There were five types of taking lenses used, which can be ranked in three quality groups: First, the Carl Zeiss Planar and the Schneider-Kreuznach Xenotar, which are the very best, second, the Carl Zeiss Tessar and the Schneider-Kreuznach Xenar, which are only a bit behind, third, the Carl Zeiss Triotar which is the budget lens but yet good.
Taking lens quality comparisons
The Planar is almost identical to the Xenotar, the Tessar to the Xenar. While most people feel that the Carl Zeiss lenses are of the same optical quality as their Schneider-Kreuznach counterparts (some people believe that either one of the two manufacturers is a bit better), the reputation of the Carl Zeiss name has led to the fact that a Rolleiflex with a Planar is more expensive than a comparable one with a Xenotar, the same holds true for Tessar vs. Xenar.
Brand name issues Jena vs. Oberkochen
It should be noted that Carl Zeiss lenses on Rolleiflex cameras made for the Eastern European market were labelled “Opton” rather than “Carl Zeiss” due to the brand name issues between the original Carl Zeiss factory in Jena (former GDR, Eastern Germany) and the “Western” Carl Zeiss factory in Oberkochen (former FRG, Western Germany). Similar policies hold true for other Carl Zeiss products exported from West to East (i.e. 1949-1990 Hasselblad and Rollei SLR lenses, etc.) Vice versa, the products made by Carl Zeiss Jena for the non-communist world (e.g. 35mm lenses for Praktica cameras and medium format lenses for Pentacon cameras) were labelled “aus Jena” (“from Jena”) rather than “Carl Zeiss Jena”.
Going beyond normal focal length
All Rolleiflex/Rolleicord TLR cameras are limited to a single focal length, that’s why a Rolleiflex Wide (“Rolleiwide”, 55mm) and a Rolleiflex Tele (“Telerollei”, 135mm) model were introduced which are quite valuable today. There are also two converters available called Carl Zeiss Mutar (0.7x and 1.5x) which can be used on the regular Rolleiflex/Rolleicord models resulting in only slight quality loss (make sure to get the correct size, as they are both available in various Rollei Bay sizes).
TLRgraphy 