Suddenly my Sony 200-600mm will not autofocus correctly. I have been using this combo with the same settings for over a year without any issues. Every photo has the same level of softness, so it's consistently bad. I also think the background look strange. I have attached a RAW file for reference. Any thoughts would be appreciated..

_SRP2989.ARW

Hi had a look at you photo when you say Every photo has the same level of softness was that on the day at the same event ?

if that was the case this might be worth a  look at 

 

https://www.picturecorrect.com/how-heat-affects-your-lens-and-distorts-your-photos/

I was thinking that might be the issue because the problem suddenly appeared yesterday and today. However, I've shot at this venue before and it was only 60 to 70 F today and yesterday while it's better warmer at previous shoots. That photo background makes it look blistering hot but it wasn't. I have checked and re-checked all the settings, hard reset my A7riii, cleaned everything. Truly baffling me. 

What I meant by consistently bad is they all look "off" by the same amount.

Edited June 19, 20223 yr by clockworkman

Certainly looks like a heat haze. Hope it sorts its self out 🙏

I did some testing today and it turns out you were correct, thank you for saving me the trip and cost to the repair shop.

What is perplexing is I've shot at this venue before in much warmer weather with no issues, very strange phenomena!  Maybe something to do with the cooler nights then rapid heating by the sun in the morning?

Edited June 20, 20223 yr by clockworkman

I don't see much wrong with the picture at all.  You shot at 588mm focal length f6.3, and the subject in focus is the lacrosse player.  You have barest minimum depth of field at the above setting so of course the background would be out of focus - even the player is only partially in focus.  Try shooting at f11-16 so at least the subject would be in better focus.  With a very slow lens like your 200- 600 f6.3, you don't have a whole lot of depth of field to work with because diffraction becomes an issue at smaller aperture.

I agree with tadwil. DoF, or rather the lack of it, is your most likely culprit.  I use a Tamron G02 150-600mm on my A7iii and get similar results if I open up to f6.3 to get a high shutter speed (1/2,000th) and as low an ISO as possible.

Edited June 25, 20223 yr by alasdairmac

Thank you both for the comments. I've attached another photo of my usual results. You can see even at 600mm F6.3 the focus is extremely sharp, even the flying blades of grass are crisp. To me it is night and day compared to the results I was getting per the original photo. Both days were sunny and warm, very similar conditions. You can also see in this photo the out of focus background is smoothly blurred where the original photo of this post there is almost a wavy pattern to the blur. I haven't been back out shooting the lacrosse games since this post, hopefully results will return to what has been the norm over the past 2 years. Will update.

RAW Image

https://drive.google.com/file/d/1w8zJogFEsGC9n47KwikcGsai7o47WUnb/view?usp=sharing

Edited June 26, 20223 yr by clockworkman