Weird effect on XF 18-55 2.8-4 Lens

Hello everyone. I posted a long time ago regarding some issues that I could find sometimes with my lens (out of warranty). Today I made the propper testing comparing it with a brand new from the store. I would like you to see the results for a proper diagnosis and possible solutions. The first picture was taken with my lens, the second with a brand new and the third with my lens and IS turned off. All the pictures were taken: 1/1600s, 55mm, f4, ISO 200, automatic focus and focus point is the furthest sign which says "Museo Picasso". It is weird for me that the focus point is completely blurred while the "Le Courtois" sign is somehow more focused. In the brand new lense, everything looks as expected and perfectly sharp. This effect is stronger with this specific conditions: strong and one bounced light and it is less noticeable in controlled environments (charts and home or shades). My theory is that it could be due to decentering. However, I am not completely sure (the decentered chart did not show clear problems) and might need some experts opinion.

I have a similar effect, but it only happens occasionally …. Never have got to the bottom of it. I’m using mine on an XT2 and was wondering if it was an AF issue, but more likely a lens issue. I must find the time one day to see if I can reproduce and see if is only at certain aperture or certain shutter speed, or IS related. It does seem to be an issue at 55mm … haven’t seen it at wider focal lengths. Thanks for your post, seems I’m not the only one with this issue …

I have seen couple more posts that show the exact same issue during my 1.5 year in this forum but if I recall correctly that happened after the lens was dropped (on one of the cases at least). Did it start to happen randomly or was it after any impactful incident ?

btw I remember your older post with the beach scenes.

GKN wrote:

I have a similar effect, but it only happens occasionally …. Never have got to the bottom of it. I’m using mine on an XT2 and was wondering if it was an AF issue, but more likely a lens issue. I must find the time one day to see if I can reproduce and see if is only at certain aperture or certain shutter speed, or IS related. It does seem to be an issue at 55mm … haven’t seen it at wider focal lengths. Thanks for your post, seems I’m not the only one with this issue …

I think GKN you found the right words. Same here. Very occasionally. No real explanation. Hypothesis is that it has to to sth with OIS/floating lens elements. Not sure.

Look at this one. It is nowhere really sharp. Focus was on the ice cracks.

X-T20, XF 18-55, 55 mm, 1/640 s, f/5.6, ISO 200

Otherwise the XF 18-55 is a great lens and I have tack sharp photos with it.

I recently went for the famous XF 16-55 and I haven't encountered such an issued so far; all my photos are satisfactory in terms if IQ (the man behind the lens is the limiting factor). That lens obviously has no OIS. It is heavy and - hypothesis - mitigates possible shutter shock through its mass inertia.

BR,

Martin

And if you suspect your lens is decentered, I recommend this simple and effective test:

https://www.dpreview.com/forums/post/63756500

Since I "discovered" it, I do it with every purchase.

My opinion: forget all the star charts. This one is easier, quicker and more effective.

Kind regards,

Martin

Nicolas Det wrote:

Does your lens have the latest firmware ?

i updated to the latest firmware and it didn’t resolve it. An earlier firmware did list something like this as an issue addressed…… but it still causes occasional grief for me. I have noticed parts of the image as sharp (foreground), while the background which was focused on, is out of focus. This happened without ever being dropped.