Why when there is nothing in focus will Sony lenses not drive the lens to find focus? So many times pointing the lens at a subject with S,M,L focus point at an OOF subject the lens just plays 'dead' and won't even try to focus? Have had this issue with Sigma and Sony lenses so it is certainly an issue with what the body tells it to do or not do IMO.
Scenario, you have just photographed a bird at 30-50ft and a bird comes in at 10-15ft, you point the lens on that bird and nothing happens to begin to try to focus? If I remember correctly from my Canon (non-mirror) days the lens would go from min to infinity to 'search' for focus. So many times when in closer shooting small birds the lens simply sits idle to an OOF subject, pumping the focus button most often never helps.
Am I totally missing something that I don't have set correctly or is this a shared experience with others? Curious on whether Nikon of Canon has the same issue as well?
I have that only happen when the distance is less than the minimum focus distance and the green square (or the little squares when you are in tracking mode) does not appear. Outside of that I suspect it is poor or dirty contacts.
I've had that happen using the 200-600 under exactly the scenario you describe: you shoot first at some distance and then try to refocus to a shorter distance and it won't do it - I think because it would be locked on some distant point and wouldn't let it go (just my hypothesis). I would quickly point the camera at the ground at something near MFD, then try again to focus on the bird and it would work. Of course by then the bird has flown.
I think the dirty/poor contact idea is quite possibly the culprit. My old A9 made poor contact with the 200-600 unless I manually torqued the lens against the body sometimes.
I've noticed this fairly often with the Sony FE 85mm F1.8.
Phase-detect focusing relies on pattern recognition in the phase domain. I suspect the shape of the out-of-focus point-spread can cause false positives. Somewhat similar to the focusing problems with undercorrected spherical abberation like the Sigma 45mm F2.8--except with those are more not detecting when they should.
Remember Sony mirrorless can only detect contrast horizontally. Point at horizontal high-contrast. Bumping the ISO up to the second gain also seems to help in lower contrast situations.
Karl Witt wrote:
Am I totally missing something that I don't have set correctly or is this a shared experience with others? Curious on whether Nikon of Canon has the same issue as well?
Karl
Canon and Nikon also have the issue. It's a critical limitation of the MILS, supposedly due to the small effective baselength and inability to detect degree and direction of defocus as well as the optical PD in the base of the SLR mirror box. Most sensors only see one direction rather than croos point. I keep the left hand ready to give the lens a turn with the big teles like Nikon and Canon 500/4 or 600/4 if it stalls. With zooms you can you can zoom wider to pick up AF again.
If you complain too much the MILS "Mafia" will just try to drown you out about how great MILS are, not remembering what we lost.
Karl. don't know why but I have the same problem with my 200-600. There is a firmware update available but it seems aimed at image stabilization more than focus. Arbitrage mentioned in one of his posts that he was going to test the update. Firmware updates on the new Macs are a bit of a PITA so I'm waiting for more info. IS is not really an issue for my use.
EB-1 wrote:
Canon and Nikon also have the issue. It's a critical limitation of the MILS, supposedly due to the small effective baselength and inability to detect degree and direction of defocus as well as the optical PD in the base of the SLR mirror box. Most sensors only see one direction rather than croos point. I keep the left hand ready to give the lens a turn with the big teles like Nikon and Canon 500/4 or 600/4 if it stalls. With zooms you can you can zoom wider to pick up AF again.
If you complain too much the MILS "Mafia" will just try to drown you out about how great MILS are, not remembering what we lost.
Mirrorless is capable of Blackout free shooting without light loss, higher fps shooting, 100% coverage viewfinder, lower cost (no prism), eye detect, smaller lenses due to smaller flange distance and better low light autofocus (with fast primes). Back focusing is also mostly eliminated.
We certainly lost the “speed of light” optical viewfinder and according to you cross type phase detect autofocus (this is new to me)
The Canons that have it are the R1 and R3, and that was done by alternating orientation of verticals/horizontals. OM cameras with quad pixels have it. AFAIK Nikon and Sony don't have it.
It was a major source of frustration with my Nikon Z8 and Z9 (and Sony A1) cameras.
However, having recently switched back to Canon (R5 Mark II, firmware 1.30) I've noticed this is rarely ever an issue now. It made me wonder if Canon had tweaked their AF algorithms at some point since I had last used these cameras.
I really don't understand why other manufacturers do what Panasonic does, and let you program one button to AF near, and a separate button for AF far. It totally eliminates the issue of the AF system being so far out of focus it doesn't know which way to search.
@EB-1 covered the direct technical reason why the on-sensor PDAF pixels can be blind to a severely-OOF subject and not know which way to drive the lens (or by how much). Why many MILCs choose to give up in this scenario and do nothing rather than at least attempt a speculative focus, even if it involves a time-consuming focus rack from infinity <-> MFD or alternatively, a contrast-detect cycle, is what's surprising. This tells me perhaps there are other, more common scenarios that yield the same PDAF pixel blindness, where those time-consuming focus-seeking actions would be more disruptive. For example, perhaps when there are temporary obstructions on a tracked subject (like a passing vehicle) that would yield the same blindness and make such speculative AF movements undesirable.
I've had this happen a few times with my A7CR and been puzzled. The camera just wont acquire a subject which is in plain view. I dont recall having the same problem with my A7R4 but maybe I never noticed, since it doesnt happen often. I thought it might be the computational power of the A7CR running out of steam, but it can happen with the latest A1 also.
In this video the same problem is examined, beginnning at about the 16.5" point Duade Paton clearly prefers Canon and Nikon in this respect. Similarly in this video from Jan Wegener he prefers Canon and Nikon for subject acquisition.
I'm not sure what the best workaround is -- MF? DMR? or AF elsewhere then back again to 'reset' the system?
I think many of us knew this going into mirrorless and adapted.
Most just get used to quickly pointing at something (very) roughly at a similar distance and focusing on that so the lens is far more likely to focus on the actual subject.
To be honest, in my case, barely an adaption. I used the same technique with DSLR but it was more of a speed issue.
The DSLR would usually force lens to move to extent of focus range and back trying to achieve focus.
For Canon, there was even a menu setting Lens drive when AF impossible. Using the point and focus at convenient alternate subject was just quicker than waiting.
As far as I know, Olympus is the only manufacturer to actually implement a work around.
We lost a little, gained much more.
EB-1 wrote:
Canon and Nikon also have the issue. It's a critical limitation of the MILS, supposedly due to the small effective baselength and inability to detect degree and direction of defocus as well as the optical PD in the base of the SLR mirror box. Most sensors only see one direction rather than croos point. I keep the left hand ready to give the lens a turn with the big teles like Nikon and Canon 500/4 or 600/4 if it stalls. With zooms you can you can zoom wider to pick up AF again.
If you complain too much the MILS "Mafia" will just try to drown you out about how great MILS are, not remembering what we lost.
I just had a quick search, just something on DPReview with reference to a video that is now missing.
Surprisingly, AI Overview actually provided good information:
Like many modern mirrorless systems, Sony’s on-sensor phase-detection autofocus (PDAF) works in strips. Because these pixels are primarily aligned to detect contrast along vertical lines, the camera can sometimes "hunt" or struggle to lock onto subjects dominated strictly by horizontal lines
I suspect the fact that Sony has never implemented cross type points but Canon has, yet seemingly only rarely talked about indicates there is not much advantage.
In the days of DSLR, the increasing number of cross type AF points and the conditions determining when they were available were one of the major talking points.
Canon 1DXII AF points had 41 cross type of 61 total. (20 were horizontal only).
Many 1DXII users moved to Sony A9 and were very happy with what they thought was superior AF, despite some negatives.
A9 - A9II - A1- A9III - A1II and still vertical only.
aCuria wrote:
We certainly lost the “speed of light” optical viewfinder and according to you cross type phase detect autofocus (this is new to me)
I did back to back testing of the Canon R1 vs Sony A1II to see if the X sensors on the R1 made any difference in this situation of going far to near.
Nope....the Sony actually drove focus in more often than the Canon. And Canon MILCs still have the Lens Drive when AF not possible setting but it doesn't help if the camera already has the far subject in focus.
IME, if the camera has the distant target in focus (or close to in focus) it has no reason to try and drive in to what to it looks like just a blurry near target partially obscuring the focused far target.
On Sony if you use a Small or Expand Flex Spot it will sometimes drive in. But to force it to the quickest way is to aim down where nothing is in focus anymore as the distant focused scene is not on the sensor anymore. Then it will drive and search for focus.
The alternative is a quick DMF override to get it focusing closer.
arbitrage wrote:
I did back to back testing of the Canon R1 vs Sony A1II to see if the X sensors on the R1 made any difference in this situation of going far to near.
Nope....the Sony actually drove focus in more often than the Canon. And Canon MILCs still have the Lens Drive when AF not possible setting but it doesn't help if the camera already has the far subject in focus.
IME, if the camera has the distant target in focus (or close to in focus) it has no reason to try and drive in to what to it looks like just a blurry near target partially obscuring the focused far target.
On Sony if you use a Small or Expand Flex Spot it will sometimes drive in. But to force it to the quickest way is to aim down where nothing is in focus anymore as the distant focused scene is not on the sensor anymore. Then it will drive and search for focus.
The alternative is a quick DMF override to get it focusing closer....Show more →
Yep, I wouldn't expect X sensors to make a difference since if a subject is completely OOF there wont be any discernible phase differential on either axis.
jowul wrote:
I have that only happen when the distance is less than the minimum focus distance and the green square (or the little squares when you are in tracking mode) does not appear. Outside of that I suspect it is poor or dirty contacts.
Hmm, has happened with multiple lenses and on every body I have owned. Not often using tracking mode either. Most often on static subjects. Thanks
