200600mm +1.4x TC @ infinity focus - Sharpness issues.

Susurus wrote:

Hi!

I am using Sony 200-600mm lens with 1.4x TC on both A9 and RIV almost from the moment the lens first became available.

I have not eperienced any focusing issues others were / are randomly describing with RIV combo. Works with A9 great as well - as expected.

However, there is a wierd issue which I have recently noticed again, and thought I would ask for some help. Maybe it is something related to the TC which never actually comes off the lens normally.

I have noticed already last year at some random points that when focusing to some object / subject which is more than ~30m far away, the camera(s) confirm focus fine in different modes, but the subject / object is kind of soft in a picture.

First, I noticed it with some wild ducks on both cameras (daytime). I think I tried variety of settings, and it might have been that switching from mech to electronic shutter helped with a few images if I remember correctly. But it could have been just my subjective thought as well.

Anyway, as cropping relatively small subject (smaller bird) so distand did not usually got any acceptable results in any case for me - I forgot about it. Anything more close works great.

This week I noticed the issue again. Few days ago I took some handheld random series of evening moon (sun was still visible). I think it was f/9, ISO100 and 1/320 (A9). All images were tack sharp, good detail.

Yesterday, just for testing I tried focusing on a distant large mobile network tower around 150m away, and I believe the outcome was acceptable as well.

However, afterwards I tried to test with a distant bird standng in a field, maybe 50m away, and, no matter what I did on my A9 - the picture was pretty soft (AF-C / tracking or single spot).

In the evening it was full moon - and I wanted few pictures with A9. This time the focus was always confirmed (also RTT or Single Spot) but the moon was kind of soft in every single picture. Settings were f/9, up to 1/500, and ISO 200-800 / handheld. I certainly understand that it is long lens, ‘slow’ shutter, higher ISO, etc., but at least few images should have been sharp. No blur mostly, just too soft. I have deleted them all.

Is anyone experiencing something similar with distant objects / subjects? Maybe some TC wierdness? Some specific settings maybe needed?

P.S. Stabilisation mode was @ 1. I could have tried manual focus maybe with ‘static’ object but did not at that point.

Sounds symptomatic of heat haze.  Was the full moon near the horizon?  If so, you were shooting through more atmosphere (due to angle) and likely warmer air layers (due to proximity of ground) than if it was overhead.