Previously good 100-400 now soft

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euanmax Regular Member • Posts: 124
Previously good 100-400 now soft

I've had the 100-400 for nearly 3 years and have had some great results with it over that time. However, recently there has been a significant drop in performance at 400mm, almost all images taken at f5.6 are soft, f8 improves things and f11 improves things further still.

Bear in mind that I'm not new to this lens and have over 2 years of excellent results. I've tried the lens on different bodies (X-T3/X-T20), tried it with Image Stabilisation on and off, at very high shutter speeds (1/4000th) and also on a tripod. Nothing seems to give sharp results other than stopping down. If I stop down to f8, things improve but are still sub par, if I stop down to f11, things improve further.

So, before we start, here are some shots prior to the recent issues to prove that I know how to use the lens:

All of these were taken handheld and, while I'm not saying they're fantastic, I can at least get acceptable (to me) sharpness.

Now, compare these results to those I have had over the past week where I have been out with the lens every day. The sharpest (by far) f5.6 shot I have managed is this one which is okay, all the other shots I've taken this week have been a LOT worse!

Here are three taken of some barbed wire which I though would be useful as it rules out any missed focus issues as you can clearly see the sharpest point on the length of wire. I didn't have my tripod with me but they were all taken at 1/4000th sec at f5.6, f8 and f11 respectively with Image Stabilisation turned off. If you zoom in to 100%, on the f5.6 images, you can see the lack of sharpness

Another stopping down test:

Another thing that seems to be increasingly affecting my results is a sort of white ghosting around areas of high contrast, zoom in on this one and look at the tops of the white lettering:

I've. bombarded you with enough sample photos for now! Things I have tried to rule out some common issues:

* Switch between IS mode 1 and 2

* Crank up the shutter speed to, for example 1/4000th with both IS on and off (my better results have actually been at lower shutter speeds with IS on with the lens stopped down significantly)

* Tried the lens on my backup body (X-T20)

* Set the lens up on a tripod for consistency

* Compared sharpness to my 55-200 (which beats it) under the same conditions.

* Ruled out atmospheric conditions, I've shot side by side with my son's FZ1000 from the same vantage point, the FZ1000 is a lot sharper

* Tried different focus strategies: C-AF, BBF, manual focus with peaking

I haven't provided sample images from all of these tests but can do, but you can safely take my word for it.

Any ideas as to what might be wrong here? Have I missed anything obvious do you think?

Apologies for the long and photo-heavy post!

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 euanmax's gear list:euanmax's gear list
Ricoh GR III Fujifilm X-T20 Fujifilm X-T3 Fujifilm XF 35mm F1.4 R Fujifilm XF 55-200mm F3.5-4.8 R LM OIS +9 more
Fujifilm XF 100-400mm F4.5-5.6 OIS WR Panasonic FZ1000
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