|The Rokinon 24mm f/1.4 compared to the Canon EF24mm f/1.4 on the right ($550 vs. $1750)|
Although I have long recommended this and two other lenses made by the Samyang Optics, I have recently received several email messages from prospective buyers, worried about negative reviews they have seen about this lens. This lens is not for general use. It is a totally manual lens —no electronic linkage to the camera, whatsoever. Despite this, it is well suited for astro photography.
Advantages of a f/1.4 Aperture: I have several lenses that I use for astro-landscapes. All but the Rokinon 24mm lens have f/2.8 as their widest aperture. The Rokinon 24mm's f/1.4 provides several nice options.
- Using f/1.4 allows you to lower your ISO, or...
- Shorten your exposure time (to reduce star trailing), or...
- Do both: reduce ISO and shorten your exposure time, or you can...
- Stop down to f/2.0 to increase sharpness and reduce lens vignetting
A typical exposure with the an ultra wide angle lens is f/2.8 for 25 to 30 seconds @ ISO 6400. With the 24mm f/1.4 you could go f/1.4 @ for 25 to 30 seconds @ ISO 1600. However, because of it's longer focal length, you'll get less star movement by going 13 to 15 seconds @ ISO 3200. And if you've got a good low-noise camera sensor, you won't mind going to ISO 6400 and closing down to f/2.0 for the increase in depth of field (for close foreground objects) and significantly reducing the lens' vignetting (see "My Personal Preferences", below).
Comparison: Let me share a comparison I did with my $1,750 Canon EF24mm f/1.4L II USM and the $550 Rokinon 24mm f/1.4. (The Rokinon is also branded as a Samyang or Bower. They are all the same lens, made by Samyang Optics.) The following test photos were taken about 15 miles away from Salt Lake City, at the Brighton Ski Resort. Being this close to SLC, the skies are still polluted with light from the valley below, but for a 30-minute drive, it still allows one to record the medium to bright stars.
|Full-Frame comparisons: The color rendition of the Rokinon is slightly different from the Canon,|
but the most significant difference is lens vignetting. For the extra $1,200 you pay for the
Canon lens, you get about one-stop less lens vignetting in the corners. However, this
can easily be corrected in the Adobe Raw Converter software. (Click to enlarge)
|Center enlargements @ 100%: Neither lens exhibits coma in the center, but the Canon is slightly|
less sharp and has a touch more color fringing (click to enlarge).
Conclusion: I find the Rokinon 24mm f/1.4 lens offers great performance, especially when one considers the price. The advantage of having an f/1.4 aperture in your arsenal of lenses provides many options that other lenses don't offer.
Pro: Low price. Good sharpness. Excellent coma corrections. Fast, f/1.4 aperture. Good construction. Cons: Significant lens vignetting, but this can be mostly corrected with software. Many non-critical (low-tolerance) components are made of plastic to reduce cost. This does not affect performance, but can affect long-term durability in rough environments and handling. Manual everything: Manual focus, manual aperture, and no electronic coupling to your camera body (no EXIF info can be transmitted to the image file).
The Rokinon 24mm is available through B&H in the Canon mount, Nikon mount, and Sony mount. Note: The Nikon mount includes an electronic focus confirmation and auto aperture chip that adds about $50 to the price.