Which Sigma telephoto lens is best for Fujifilm wildlife shots?

Question

So I’ve been staring at my shopping cart for like three days now and I just cant make up my mind on which Sigma to grab for my X-T4 before I head up to the Scottish Highlands in about three weeks. Im finally making the jump into some serious wildlife stuff—mostly wanting to catch the red deer and maybe some golden eagles if Im lucky—but the choice between the two main Sigma X-mount options is really weighing on me.

My logic was originally to go with the 100-400mm Contemporary because its so much lighter and more compact. Since I’m gonna be hiking like 10 miles a day through some pretty rough terrain, I really dont want a massive brick hanging off my neck or taking up all the space in my bag where my food and waterproofs need to go. Plus my budget is strictly under 1100 bucks right now and that lens fits perfectly. But then I start thinking about those eagles... will 400mm actually be enough even with the crop factor?

Then theres the 150-600mm Sports. It looks like an absolute beast and the reach is obviously incredible for birds. But I’m worried it’s just gonna be too heavy to carry around all day without a tripod, and I really prefer shooting handheld when I can. My concern is if I get the 100-400 will I just end up cropping everything so much that I lose all my detail anyway? Or is the 150-600 just way too much lens for a hobbyist like me who mostly does forest trails?

I was even looking at the Fuji native 70-300 with a teleconverter but honestly the Sigma price points are way more attractive for the quality of glass you get. I just dont know if the extra weight and cost of the 600mm is worth the physical pain of lugging it up a mountain or if the 400mm is the actual sweet spot for a Fuji setup. If anyone has used both on an X-series body I’d love to know if the autofocus speed is actually different between them or if they’re pretty much the same...

BitPhantom · Accepted Answer

TL;DR: The Tamron 150-500mm is the secret middle ground choice. Like someone mentioned, weight is everything. You might want to consider the Tamron 150-500mm f/5-6.7 Di III VC VXD Fujifilm X Mount for about 1200. It sits right between your two choices for size and reach. Be careful with the Scottish weather tho... Sigma and Tamron sealing isnt always as reliable as a native Fujifilm XF 70-300mm f/4-5.6 R LM OIS WR in heavy rain.

DataVortex · Answer

Saw this earlier and I'd be real careful about taking those Sigmas into the Highlands rain. For your budget and safety on long hikes, I would suggest finding a used Fujifilm XF 100-400mm f/4.5-5.6 R LM OIS WR. It is fully weather-sealed and much more reliable in the wet. Buying used keeps you under $1100 easily and it's a far safer choice for your gear's health.

MidnightKernel · Answer

I would 100% recommend you grab the Sigma 100-400mm f/5-6.3 DG DN OS Contemporary Fujifilm X Mount for those Highlands trails! I am a big believer in staying mobile for safety reasons and lugging the Sigma 150-600mm f/5-6.3 DG DN OS Sports Fujifilm X Mount for 10 miles sounds like a recipe for a sore back or an accidental equipment drop. The 100-400mm is just so light and the optical stabilization is absolutely amazing for handheld shooting! I love how reliable this lens is... the autofocus is super snappy on the X-T4 and I rarely miss a shot. Even for eagles, that 600mm full-frame equivalent reach is fantastic! You get a lot of detail without the massive weight. Its the safer bet for a hobbyist because you will actually want to carry it with you everywhere. Trust me, you dont want to be struggling with a tripod when a deer jumps out!