I'm using an A7r4 with subject tracking AF. Although the camera is not new to me, it's got around 450000 actuations on it from doing repro work, in its retirement I've taken it for personal use. I've never really used it for AF before though. My last real AF experience is from the 5D3 many moons ago as a pro event shooter. Since then and for repro work I strictly use manual focus.
I've tried the tracking subject AF with AF-C and was really impressed with it but this was using the Tracking Expand Spot mode. It was also using my wife's 16-50mm in crop mode for testing, stolen off her A6000.
Fast forward and I bought myself a VIltrox 50mm f2 Air. I've been very impressed with the images I've seen from it on this forum and wanted a small 50mm.
Did some testing last night taking some static photos of the kids at home.
The tracking subject AF does not seem to be all that good. In indoors lighting it was very often backfocusing or choosing background subjects if they were more contrasty. I switched to Tracking Spot S which but again the focus was mostly backfocused. I changed AF Tracking Sensitivity to 'Locked On' and Priority Set in AF-C to 'AF'. The latter helped but what helped the most was simply changing to Flexible Spot S and moving the focus point to the subject rather than using the tracking mode and recomposing. Seemed rather counter intuitive as this is hardly an advance from the DSLR days. The 'tracking' thing is supposed to be the Sony party trick.
Is this simply a combination of 3rd party lens, f2 and low light? Is it that Tracking in general is a tool which cannot be relied on for accurate focus wide open on an older generation of camera like this and a more modern generation camera would be more accurate?
Bought my lightly used A7RIV here on FM B&S just about 5 years ago. It was an upgrade to my A7RIII and the AF was much improved over the A7RIII. Use it for mostly indoor/outdoor portraits and found the Tracking feature to be worthless even with Batis and Sony GM prime lenses. However the Eye detect AF feature is excellent and that is how I shoot to this day, very happy with the results.
Also tried the Tracking feature with my 100-400 GM for airplane photos and most times it was OK on bright sunny days. But with clouds, it backfocused a lot, so I quit using it for these types of photos as well.
I did some more testing today in brighter light, tracking subject AF unreliable, backfocusing consistently when recomposing. Eye focus brilliant when/if it works and catches the correct eye which isn't all that often, switching left/right seems to do practically nothing. Otherwise single small spot is the only reliable option. I'd expected better to be honest from all the hype.
My results with Eye detect AF are great. In a typical portrait session of 200-300 shots, the A7RIV eye detect has a hit rate of about 93% average, compared to my newer A7CR which is 98%. But I am not using low cost Chinese lenses, which I have read many times have AF accuracy problems.
I tried updating the firmware on the lens, the camera now seems to find the eyes better but the only setting which gives consistent accurate focus is AF-S with face/eye turned off. I'm assuming it's the lens not the camera. I've used eye focus with a Sigma 70mm before with about 60-70% accuracy, it was certainly better than this. It does seem though that to come to any kind of conclusion about the eye focus and tracking I need a modern Sony built lens.
