X-T3 + Fringer EF-FX Pro II + Sigma 150-600mm C

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ialarmedalien Contributing Member • Posts: 994
X-T3 + Fringer EF-FX Pro II + Sigma 150-600mm C

I picked up a Sigma 150-600mm F5-6.3 Contemporary a little while ago but hadn't had a chance to test it out properly. This weekend, I went on a trip up to Bempton Cliffs, the UK's largest mainland seabird colony, to photograph gannets and other assorted wildlife, so I took both the Sigma 150-600 and my usual wildlife long lens, the FujiFilm XF 100-400mm, to compare the two. I don't have a Canon body so I cannot compare the performance on the "native" body (Sigma has reverse engineered the Canon AF protocol) to that on the X-T3.

Gannet skydiving team enjoying the strong winds atop Bempton Cliffs. XF100-400mm.

Lens set up

Sigma sells an optional dock which can be used to tailor the lens settings to your liking, update firmware, adjust focus (more relevant to cameras with mirrors), etc. One of the cooler features is being able to set up custom AF settings, including focus limits and AF speed. I created two custom focus settings, both with the highest AF speed setting (you might want to use lower speed AF changes for video work), and one setting with focus from 5m - infinity, and the other 10m - infinity. The lens also has three distance settings, 2.8-10m, 10m - infinity, and full focal range. For the majority of my shooting, I had the lens set to full range and switched between the two custom settings depending on where the birds were.

A gannet approaching its cliffside residence. Sigma 150-600 C.

Camera settings

I used the same camera set up for both lenses, including the same AF-C settings. Although I have the fancy Fringer that allows you to vary the lens aperture via a fake aperture ring on the adapter, in practice I shot wide open because AF performance at 600mm was dodgy at f/7.1 and unusable at f/8.0, even in very bright conditions.

AF at f/7.1 was very hit and miss; this seemed like a hit when I pressed the shutter but on closer examination, proved to be a miss. Sigma 150-600 C.

Although I usually shoot the XF 100-400mm at f/8, the Sigma produces a darker image, so I had to compensate by boosting the ISO by about a stop to achieve the same shutter speed.

I have posted the OOC JPG images so that differences between the lenses are not obscured by post-processing.


I don't have a gimbal head so I shot both lenses handheld. One of the big differences between the two lenses is the size and weight; that extra 555g of the Sigma can feel like a lot more if you're trying to focus on a small perched bird or waiting for a bird to take off; tracking moving objects is not too bad, although my arm and shoulder started aching after a while (I will have to adjust my gym routine). On the plus side, the XF 100-400 felt like a feather in comparison. I didn't test out the OIS particularly thoroughly as most of the time I had the shutter speed high enough that the effects were not noticeable. One of the nice features of the Sigma is the ability to lock the lens into place at whatever focal length you choose; you can unlock it manually or by a vigorous twist of the lens, which is handy if you want to quickly change focal length.

AF Performance

My main photographic targets were gannets, huge white and brown birds (2m wingspan!), at fairly close quarters, mostly against the backdrop of the sky or the ocean, so I expected a high success rate from both lenses. I also took quite a few shots of fulmars, which are smaller gulls, and a few perching birds for good measure.

Gannet portrait. XF100-400mm.

Gannet portrait (taken in flight), Sigma 150-600 C.

In general, I found the AF performance of the 150-600mm to be very good, and looking through the results, there were actually more missed shots using the XF100-400mm than the Sigma! This could be because I was more cautious with the Sigma, and waited until I was sure I had focus, or it may just be sampling error from the smallish set size.

Shooting with the Sigma is a more tactile experience than the Fuji lens; you can feel the motor moving as it keeps the subject in focus, which I liked. That also makes it clearer when nothing is happening; there were a couple of occasions where I just couldn't get focus, and from looking at the distance meter on the lens, it had obviously gone through the range and reached infinity without finding anything to focus on. I had to "reset" the focus at those times by pointing at something nearby as it took too long for the AF system to decide to recheck. I'm not sure if that's an issue specific to the lens or if it's a FujiFilm AF issue. I plan to contact the Fringer developer with feedback on it.

Another issue that I believe is a FujiFilm AF implementation problem is tracking small distant objects; I was excited to see a peregrin falcon, but was extremely annoyed when the camera lost it--I could see the blurry dot moving in the centre of the AF zone, but the camera couldn't seem to pick it up. I've had similar problems when trying to get ID shots of distant birds or aeroplanes; I believe the issue cropped up in the X-T3 v3 firmware update, but that may just be rose-tinted memories of AF-C performance in days of yore. It isn't a massive issue, since the target will be so small in the resulting images that you're not going to be able to do much with it, but I do find it annoying.

Peregrin falcon before it flew beyond the reach of the AF. Sigma 150-600 C.

The last quirk was some difficulty in obtaining focus on flying fulmars in bright conditions where the sun was sparkling off the sea behind them. I didn't have the XF 100-400mm with me for that session so I couldn't compare the performance of the two lenses directly, unfortunately.

I had a lot more difficulty in getting decent shots of small perched birds with the Sigma than I do with the XF 100-400. The combination of the weight of the lens, the very narrow depth of field, not being able to use smaller apertures with AF, weather conditions (strong blustery wind), and uncooperative small birds made it difficult to get anything usable. Time to start watching eBay for a decent gimbal head...

A small bird who was willing to have his photo taken. Sigma 150-600 C.


I was pleased and impressed with the Fringer + Sigma performance. I was aware that I was "holding back" somewhat with the Sigma due to unfamiliarity with it, and anticipate results improving as I use it more.

At the end of the day, I was very pleased with the performance of the Sigma 150-600C.

I'm happy to answer questions or post more photos if anyone has anything specific they would like to see.

Fujifilm X-T3
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