Thursday, April 18, 2013

The New Sigma f/1.8 Zoom Is The First Lens of The Post-Speed Booster Era

I said that the world had changed after Metabones announced their Speed Booster image-reducing lens adapter. To recap, what the Speed Booster does is take all of the light gathered by a full-frame lens and squeeze it down into an image circle that just fits an APS-C sensor. This does two things, first it eliminates the need for crop factor. Since the APS-C sensor is no longer taking only a small, center crop of the FF lens' image, it's no longer acting like a zoom. A 50mm full-frame lens no longer equals a 75mm APS-C lens. The final image is the same.

Second, it makes the image brighter. An f/2.8 full-frame lens increases in brightness to f/1.8 when all of that light is focused on the smaller APS-C sensor. It's wonderful.

There was nothing stopping lens companies from doing this. Canon, Nikon, et al., they could have made their FF lenses brighter on APS-C cameras with relatively small alterations to their FF lens optics. They did not do this because of greed.

Canon, Nikon, Sony: all of the camera companies make more money by restricting freedom. If they give you flexibility in how you manage your hardware, they limit their ability to squeeze money from your pockets. As such, it has taken them this long to simply take larger, FF lenses and squeeze them onto the APS-C sensor.

Indeed, even companies that exist solely as a discount alternative to system lenses, such as Sigma, display this greed.

Sigma is the first to respond, though. They have released an f/1.8 constant aperture zoom lens for APS-C sensors. It has an 18-35mm range, which equate to 27-52.5mm on full-frame, give or take a milimeter.

Usually, designing a lens and bringing it to market can take a long time — one to two years. I don't think that was the case with this lens. I suspect that they basically took an extant optical design and simply installed a Speedbooster-like optical element at the back of the lens.

Sigma does not have a FF lens with those specs, but they do have a discontinued lens that is 28-70mm f/2.8. That lens would equal around an 18-44mm f/1.8 on the Speed  Booster.

Moreover, if we analyze the measurements of the lens, we find similarly corroborating evidence. The 28-70mm Sigma lens weighs 18oz. The new 18-35mm lens weighs 28.6 oz. (If nothing else, the sheer weight and size of the lens confirms FF optics)

The Metabones Speed Booster with AF support weighs 7oz, giving the 28-70mm a weight of 25oz. Not exact, but close.

Similarly, the 28-70mm is 2.91" in diameter. Very close to the 18-35mm's 3.1". The length of the 28-70mm with the Metabones adapter attached is 4.43". Decently close to the 4.8" of the new 18-35mm, but not definitive.

All things considered, I think that this lens was a relatively quick rejiggering of an optical design they already had. When Sigma says that the design was difficult, I think they are lying. They are lying because they want to justify the very high price they are undoubtedly going to ask for it. Remember, this is the same company that tried to sell the SD-1 for $10,000.

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