(click on the images to see them bigger)
There is a lot of misinformation out here on the web. If you take it too seriously you'll either miss some good opportunities or you'll fall flat on your face. I mentioned in a previous post that most reviewers of lenses (exceptions being people with test benches and people who know how to use them or people with decades of experience using all manner of lenses professionally) have the manufacturer of the lens they are interested in testing (for affiliate clicks) send them a lens to "test" for a week. In amongst their many weekly chores, such as answering comments, having coffee, buying small hats, grooming their beards, attending manufacturer's press junkets and making Vlogs, they may take the lens (without updating firmware in either camera or lens) out for a few hours of shooting. They'll take along whomever they are dating at the time to serve as a model. Then, with a coffee in one hand and a camera in the other they will proceed to (vaguely) handhold the camera and the test lens at ridiculously slow shutter speeds (with an almost religious belief in the supreme power of image stabilization technologies) and then shoot at whatever catches their eyes. In some instances I believe that they just point the camera randomly and keep the shutter button pressed down, hoping to fix up whatever they manage to get on their memory cards in post production (which they insist on calling "editing.").
You can see where I'm going with this, right? Their methodologies, honed by weeks of experience, might work okay if testing is being done on wide angle lenses; maybe even medium focal length lenses but as they zoom inward toward the longest focal lengths the ever magnifying angle of view shows up more and more of their bad/awful/faulty technique. Which they then blame on the "poor imaging qualities" of the long ends of (nearly every) telephoto zoom lensed they test.
I have read in several places about the long end of the Fujifilm 100-400mm lens being somewhat "soft." I thought I'd better test the copy I got last week in the unlikely case that the less capable testers might have gotten it right just this once. I wanted to find out any bad news while I was still able to return the lens for a refund.
I shots some frames with the lens bolted to an XH-1 which was bolted to the biggest, strongest tripod Gitzo makes. I aimed at targets with lots of fine detail; targets which themselves were immobile. The lens was nicely sharp at the longest focal length, even when used wide open. So that became the gold standard for my tests. I might have been able to slightly improve my results by using the camera's self timer but I was satisfied (for my uses) with what I was getting in these studio test conditions. I could have made the images even sharper had I used short duration electronic flash for everything..... but that's a digression.
My next test was to go outside and shoot the lens the way I might normally use it. And the way even the most inept web-tester might use it. I put the same camera and lens on a Leica monopod and headed to the Pfluger Pedestrian Bridge that spans Lady Bird Lake. I put the camera in aperture priority, chose the wide open aperture (f5.6 at 400mm), AF-C, and proceeded to photograph people as they biked, walked, scootered (is that how we say it?) and jogged across the bridge. Almost every frame was shot at the longest focal length of 400mm. The exceptions were the grouping of downtown building shots (taken from about half a mile away) that start at 100mm and go in steps out to 400mm, just so you can see the range.
It was a two coffee day for me but the monopod neutralized the overall effects of caffeine poisoning fairly well. While none of the frames are absolutely perfect I would chalk that up to the fact that it was my first real outing with the lens and I've previously confessed to not using the longer focal lengths too often. Click on the images and see what you think.
Could they be improved? Yes! I could stop down to f8 or f11 and I'm sure I'd pick up a bit of sharpness as a result. I could ask everyone to stop moving so I could carefully manually focus, etc. But the bottom line is my studio results told me what the potential of this lens is and this test outside shows me what I can expect in non-studio, actual environmental use might be. Would I buy the lens again? Yeah.
After further thought and evaluation this morning I thought I'd add this: Besides being sharp all over the zoom range of this lens I should mention two other things; first, the lens is really lightweight and compact for the range it covers and the speed it offers. You can actually handhold this lens if you have to. You won't get the sharpness you'd get using it on a monopod or tripod but you won't get it from any other lens in this range either. Secondly, I didn't mention how good the image stabilization is. Beyond just taking out the jitters we humans add to the equation the I.S. steadies the viewfinder image which makes it easier, at longer focal lengths, to more effectively compose the image. At up to 250mm (estimated) I can get sharp images, free from camera shake, if I use the I.S. and take my time to let the system settle and for my breathing to settle. Might want to skip the extra cup of coffee if your intention (with any lens) is to rely on I.S. for long focal length, handheld shots.....
All I.S. systems take time to settle. Don't rush.