Wideangle lenses for small sensor APS-C DSLRs
One of the disadvantages of small sensor APS-C Digital SLRs (basically everything but the Canon 1D and 1Ds series cameras) is that the 1.6x "multiplier/crop" factor makes all your existing 35mm wideangle lenses into "not so wide" angle lenses. Nikon cameras are slightly better, with a 1.5x "multiplier/crop", but still basically suffer from the same problem. On a 20D or Digital Rebel XT your 24mm lens has the same field of view as a 38mm lens would have on a full frame camera. Your wide 20mm becomes a moderate 32mm and even your superwide 16-35 zoom becomes a mid-range 26-56 lens. Even the widest rectilinear prime lens you can get for 35mm a 14mm - turns into only a 22.5mm lens.
So what can you do? Well , you have to turn to one of the new ultrawide zooms made specifically for small (APS-C) sensor digital cameras. Last year there were one of two, this year there are five, so things are getting a little better! There is one other alternative, and that's to use a fisheye lens, and I'll deal with that later.
For now here is a comparison of the Ultrawide zooms available for the D20/Digital Rebel XT:
Lens |
Coverage | Mount | Weight | Length/Diam | Street Price (est.) |
| Tamron 11-18/3.5-5.6 | APS-C | EF | 375g | 78mm/82mm | $520 |
| Tokina 12-24/4 | APS-C | EF | 570g | 89.5mm/84mm | $500 |
| Canon 10-22/3.5-4.5 | APS-C | EF-S | 385g | 90mm/83.5mm | $800 |
| Sigma 12-24/4.5-5.6 | Full frame 35mm | EF | 615g | 100mm/87mm | $690 |
| Sigma 10-20/4-5.6 | APS-C | EF | 470g | 81mm/83.5mm | $475 |
The following table shows the 35mm full frame equivalent focal length (in terms of fiedl of view) for lenses from 10mm to 24mm on an APS-C DSLR.
| APS-C | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 |
| 35mm | 16 | 17.6 | 19.2 | 20.8 | 22.4 | 24 | 25.6 | 27.3 | 28.8 | 30.4 | 32 | 33.6 | 35.2 | 36.8 | 38.4 |
Though the wide end of these lenses only differ by 1 or 2 mm, at these focal lengths that does make quite a difference in terms of angle of view and field of view as the following table shows
| Lens focal length | 10mm | 11mm | 12mm |
| APS-C Horizontal angle of view | 96.7 degrees | 91.3 degrees | 86.3 degrees |
| APS-C Horizontal field of view at 100ft | 225ft | 204ft | 187ft |
| The Tamron 11-18/3.5-5.6 is wider than the Tokina 12-24/4 or Sigma 12-24/4.5-5.6 at the wide end of the range and it is also faster. It's the smallest and lightest of the 4 lenses and second least expensive. In the review section of this website up can find a full, hands-on, test of the Tamron 11-18/3.5-5.6 | |
| The Tokina 12-24/4 has a wider zoom range than the Tamron 11-18/3.5-5.6 and, at a constant f4, is the fastest of the 4 lenses. However it's "only" 12mm at the wide end (vs. 11mm for the Tamron 11-18/3.5-5.6 and 10mm for the Canon 10-22/3.5-4.5 and Sigma 10-20/4-5.6). It's the least expensive of the five, but it's almost as heavy as the Sigma 12-24/4.5-5.6. | |
| The Canon 10-22/3.5-4.5 is the widest lens of all and has the widest zoom range (2.1x), though it's also the most expensive. Being an EF-S lens it can't be mounted on a full frame body. The Tamron 11-18/3.5-5.6, Sigma 10-20/4-5.6 and Tokina 12-24/4 can be used on all EOS bodies, but they will vignette at the wide end of the range. The Canon 10-22/3.5-4.5 has a USM motor with full time manual focus. Optical quality is excellent. See my hands-on review of the EF-S 10-22 for more details | |
| The Sigma 12-24/4.5-5.6 is the only lens with full frame 35mm coverage. However it's the heaviest of all four lenses and the second most expensive. The full frame coverage means the hood is designed for 35mm, and so won't be optimal when used with an APS-C sensor body. It also takes rear mounted gel filters (the other 4 lenses take 77mm screw in front filters). Incidentally 12mm is the widest rectilinear lens made by anyone for full frame 35mm use. | |
| The Sigma 10-20/4-5.6 is the widest lens (along with the Canon) and the leat expensive along with the Tamron 12-24/4. It doesn't zoom as far as the Sigma 12-24/4.5-5.6, the Canon 10-22 or the Tokina 12-24/4 and it's a little heavier than the Canon 10-22/3.5-4.5 and Tamron 11-18/3.5-5.6. |
Which of these superwide zooms is best for you depends somewhat on what you shoot, whether weight is an imporatnt factor and how much you want to spend. If you shoot both APS-C digital and 1.3x and/or full frame film or digital, then the Sigma 12-24/4.5-5.6 lens has a lot of appeal since it's the only one with full frame coverage. The Canon is nice and wide - but expensive and EF-S mount only. The Tamron is small, light and wide, but the Tokina has a little more zoom range - though it's not as wide and is larger and heavier. The Sigma 10-20/4-5.6 is wide and the least expensive, but a little heavier than two of the others.
Full Reviews
So what about the fisheyes.....see part II of this article!
Next: Part II - Fisheye Lenses
