Viltrox – frans goes blog

I have long been thinking about a longer, telephoto range zoom lens, as this is perhaps the main technical bottleneck in my topic selection currently. After finding a nice offer, I made the jump and invested into Sigma 150-600mm/5.0-6.3 DG OS HSM Contemporary lens for Canon. It is not a true “professional” level wildlife lens (those are in 10 000+ euros/dollars price range in this focal length). But his has got some nice reviews on its image quality and portability. Though, by my standards this is a pretty heavy piece of glass (1,930 g).

The 150-600 mm focal range is in itself highly useful, but when you add this into a “crop sensor” body as I do (Canon has 1.6x crop multiplier), the effective focal range becomes 240-960mm, which is even more into the long end of telephoto lenses. The question is, whether there is still enough light left in the cropped setting at the sensor to allow autofocus to work reliably, and to let me shoot with apertures that allow using pretty noise-free ISO sensitivity settings.

I have only made one photo walk with my new setup yet, but my feelings are clearly at the positive side at this point. I could get decent images with my old 550D DSLR body with this lens, even in a dark, cloudy winter’s day. The situation improved yet lightly when I attached the Sigma into a Viltrox EF-M Speed Booster adapter and EOS M50 body. In this setup I lost the crop multiplier (speedboosters effectively operate as inverted teleconverters), but gained 1.4x multiplier in larger aperture. In a dark day more light was more important than getting that extra crop multiplier. There is nevertheless clear vignetting when Sigma 150-600 mm is used with Viltrox speedbooster. As I was typically cropping this kind of telephoto images in Lightroom in any case, that was not an issue for me.

The ergonomics of using the tiny M50 with a heavy lens are not that good, of course, but I am using a lens this heavy with a monopod or tripod (attached into the tripod collar/handle), in any case. The small body can just comfortably “hang about”, while one concentrates on handling the big lens and monopod/tripod.

In daylight, the autofocus operation was good, both with 550D and M50 bodies. Neither is a really solid wildlife camera, though, so the slow speed of setting the scene and focusing on a moving subject is somewhat of a challenge. I probably need to study the camera behaviour and optimal settings still a bit more, and also actually start learning the art of “wildlife photography”, if I intend to use this lens into its full potential.

My SIGMA 150-600 mm / Canon EOS M50 setup.

Attaching EF lenses to M mount camera requires an adapter – which adds a bit to the bulk of a small camera, but is also an interesting opportunity, since it is possible to fit new electronic or optical functionalities inside that middle piece.

I have both the official, Canon-made “EF-EOS M” mount adapter, which keeps the optical characteristics of the lens similar to what they would be if used on an EF-S mount camera (crop and all). The other adapter is “Viltrox EF-EOS M2 Lens Adapter 0.71x Speed Booster” (a real mouthful), which has the interesting capability of multiplying the focal length by factor of 0.71. This is a sort of “inverted teleconverter” as it reduces the image size that the lens produces, allowing more light to fit into the smaller (APS C) sensor, and almost eliminates the crop factor.

Most interestingly, as the booster collects more light into the sensor, this also has an effect of increasing the maximum aperture of my EF/EF-S lenses in an M mount camera. When I attach Viltrox into my 70-200 mm F4, it appears to my M50 camera as an F2.8 lens (with that constant aperture over the entire zoom range). The image quality that these “active speed booster adapters” produce is apparently a somewhat contested topic among camera enthusiasts. In my personal, initial tests, I have been pretty happy: the sharpness and corner vignetting also appear to be well controlled and the images produced of rather good quality – or good enough for me, at least.

When I put this into my 50 mm F2.8 portrait lens, this lens functions as having F1.2 maximum aperture. This is pretty cool, e.g. the capability to shoot in lower-light conditions is much better this way, and the narrow depth of field is similar to much more heavy and expensive, full frame camera system when using this adapter.

In my tests so far, all my Canon EF lenses have worked perfectly with Viltrox. However, when testing with the Tamron 16-300 mm F/3.5-6.3 Di II VC PZD super-zoom lens, there are issues. The adapter focuses light in a wrong manner when using this lens, and the result is that the corners are cut away from images (see the picture below). So, your mileage may vary. I have written to Viltrox customer service and asked what they suggest in the Tamron case (I have updated the adapter into the most recent available firmware – this can be done very simply using a PC and the built-in micro-usb connector in the adapter).

You can read a bit more about this technology (in connection to the first, Metabones product) from here: https://www.newsshooter.com/2013/01/14/metabones-speed-booster-adapter-gives-lenses-an-extra-fstop-and-nearly-full-frame-focal-lengths-on-aps-c-sensors/