Last week, Fotodiox Pro released the Excell+1, a product that had many of us extremely excited because it seemed to be a far less expensive counterpart to the popular Metabones Speed Booster. Cut to one week later. Many of the new units have made their way into the hands of eager filmmakers, and a few have put the Excell+1 up against the Speed Booster, only to find that the Fotodiox has some major focusing and sharpness issues at apertures wider than f/2.8. The folks at Fotodiox have released a few new videos in an attempt to explain more about what the Excell+1 can and cannot do, and to offer people who were expecting Speed Booster performance a full refund for their purchase.
First up, here's a video directly from Fotodiox Pro explaining the differences between the Speed Booster and Excell+1, and what the Excell+1 is ideally used for.
Here are photo comparisons of the Excell+1 and the Speed Booster, both on a Nikon 50mm f/1.4 at varying apertures. The results here are very clear at this size, but you can click for the full size versions.
It's extremely clear that the Excell+1 is not able to compete with the Metabones Speed Booster in terms of sharpness at any aperture really, but especially not at any aperture wider than a 4.0. Any higher than and it looks like someone stacked a pile of mist filters in front of the lens (and not in a good way). For people who specifically want the additional stop of light provided by these products, they'll definitely want to spend the extra cash on the Metabones, because you need to stop way down to get a usable image on the Excell+1.
With that said, Fotodiox says that it is marketing the Excell+1 as a focal reducer (as opposed to a speed booster), so its primary function is to reduce the crop factor that you get on smaller sensor cameras. If you're looking for a product specifically for that reason, then the Excell+1 might be worth a look simply because of its significantly lower price. However, you should be aware that the device is practically unusable at any stop wider than a 4.0. Here's how the Excell+1 compares to the Speed Booster just in terms of focal reduction.
Ultimately, the two provide a nearly identical field of view, but the Metabones is still the clear winner in terms of sharpness. The Excell+1 also seems to induce some kind of warm/magenta into the image, whereas the Speed Booster is neutral in color rendition.
Finally, for those who purchased an Excell+1 last week with the hopes that it would provide Speed Booster-like performance at higher apertures, Fotodiox is offering a full refund for that purchase. If you're not satisfied with the product, just send it back. Lastly, for those of you who want to keep the Excell+1, Fotodiox is offering you a $50 credit towards your next purchase on their website.