I agree with you that these images are disappointing. Despite the small subject being quite a long way from the lens at 400mm I would expect them to be sharper. I use a Fuji 100-400 and am satisfied with its sharpness. As an example of what this lens is capable of, see Alan Hewitt’s image of a puffin in flight with the same lens at 400mm, noting it was taken from a boat; see:
https://www.dpreview.com/forums/post/68061054
Is it the focus system? The lens? Or some other issue? Perhaps, in the spirit of helping, I can offer a view as a satisfied 100-400 user. DJ STU-C’s advice above about testing on a tripod is sound. I apologise for the slightly lengthy reply, but we aim to help you obtain sharp images from the lens. My comments below focus on technique, but also consider how sharpening is applied in post processing, although I doubt this is the cause of unsharp images here.
I also do not know your experience of telephoto lenses. I come at using telephoto lenses from the point of view of having been a marksman in rifle shooting. To be a marksman, and I was formally trained and spent years practicing, four attributes of high performance are necessary: settings; technique; training; and practicing. I believe these four attributes are also necessary to perfect telephoto lens use.
Looking at settings, for a static subject I set Focus S, AF Mode/Single Point and Single drive, a small focus box and mechanical shutter. For static subjects hand-held at 400mm, I use at least 1/1200 (400mm x 1.5 to give FF equiv of 600mm then times 2 = 1/1200). For moving subjects, I set Focus to C, AF Mode either Wide/Tracking generally or sometimes Zone, and Drive to CL. I use AF-C Custom 6 with tracking sensitivity set to 3, speed tracking sensitivity set to 1 and zone area switching set to Front. For moving subjects hand-held at 400mm, I use at least 1/2000, but this does depend on the speed of movement and the angle of motion relative to the camera. This works for running dogs and deer and galloping polo ponies (doing 25mph+). I do not do much in the way of bird in flight photography (Morris’s settings are best for this genre), which is far more demanding.
Looking at technique (non tripod use), which covers standing, holding, breathing and triggering.
- I stand with my left leg slightly forward and taking about 2/3 of my weight and with the weight of the lens over my left leg to provide a stable platform.
- I hold the weight of the 100-400 in the left hand with the elbow wedged against the ribcage. I have removed the tripod mount from the 100-400 to make hand holding more comfortable (and put black electrical tape over the screw holes). I hold the camera body with the right hand with the elbow against the body and it is the right hand that adjusts the direction of the lens. The camera is stabilized a little by my forehead looking through the view finder. Together with standing, this gives a reasonably stable platform.
- For breathing, I breath in and at the top of the inhale, when the body is relaxed and stable, take the shot. During the inhale and exhale the core of the body is moving, which translates into movement of the lens as one holds it. At the top of the inhale the body is momentarily still. Therefore, take the shot at the top of the inhale when the body core and the lens are momentarily still (avoid taking the shot when breathing in or out as the body core is moving).
- For triggering, one needs to roll the forefinger gently over the shutter release to avoid a sudden jabbing movement (the same as caressing a rifle trigger), which would cause movement of the camera body (a movement that few IBIS/OIS systems could compensate for). In rifle shooting, jabbing the trigger is a cause of missing.
Looking at training, where one pulls the settings and techniques together using any convenient subject as a target and then analyse the results. Initially, take several shots concentrating solely on standing, then take shots concentrating solely on holding, then take shots concentrating solely on breathing, then shots concentrating solely on triggering, and then pull all four techniques together over many shots. Once satisfied, practice to hone the skills.
Apologise if this sounds like I am preaching to an experienced user, but I have found that by focusing on settings, techniques and training/practicing my hit rate improves. If, after this approach, the hit rate does not improve, then I would look to the calibration of the lens.
Hope that helps. I think Alan’s shot of a challenging subject nails it (and I hope he does not mind me citing it as an exemplar excellent 100-400 usage).
