paul cool
Senior Member
Who said it was insignficant in this situation it probably is though .
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Interesting AF comparison A1 vs Z9 vs R3
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SQLGuy
Forum Pro
The readout speed is the same regardless of the exposure time. So, for 1/1000th exposures (or anything at or above X-sync), you're actually losing more of your between frames time when shooting continuously.
That's a main reason why these cameras can do 20 or 30 FPS with continuous AF, while earlier cameras had limitations like locking AF on the first frame. Without the stacked sensor, there simply wasn't time to AF between frames.
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A7R4a with SEL2470Z, 55Z, and a number of adapted lenses (Canon FD, Minolta AF, Canon EF, Leica, Nikon...); A7R converted to IR.
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paul cool
Senior Member
Yes and
and i doubt any will be shooting at x -sync speed for action shots
No the limitation is the mechanical shutter.It can not do 20 or 30 fps regardless of sensor read out speed in any form of auto focus single or c-af .
SQLGuy
Forum Pro
X-sync on the A1 is 1/400th.
So, on models with silent shutter, like the A7III, A7R3, etc, max FPS should be higher than with mechanical shutter, right? Except, no, it's not. That 1/13th or so readout speed is the bottleneck here.
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A7R4a with SEL2470Z, 55Z, and a number of adapted lenses (Canon FD, Minolta AF, Canon EF, Leica, Nikon...); A7R converted to IR.
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paul cool
Senior Member
1/13th is a bottle neck for e/s for sure ,but it is the choice you can easily make
SQLGuy
Forum Pro
Whether the sensor is being read out as it's exposed, or read out after it has been hidden behind the second curtain, it still takes 1/13th to read it. You just notice it more with electronic shutter. So, with EFCS or full mechanical, you have to wait that 1/13th after the second curtain closes before the shutter can be rewound and AF can begin again.
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A7R4a with SEL2470Z, 55Z, and a number of adapted lenses (Canon FD, Minolta AF, Canon EF, Leica, Nikon...); A7R converted to IR.
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paul cool
Senior Member
rewound you make my a7r3 sensor sound like a reel of film ,i am certainly not waiting for 13 th of sec and who is to say the camera really is ,it is not like the af has to start all over again it will still be roughly in position for the next frame.also even at 1/13th it is still fast enough not to be a bottleneck at 10fps which would be 1/10th or slower to be a bottleneck i guess under your theory,
https://www.flickr.com/photos/58365044@N05/
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SQLGuy
Forum Pro
Do the math. At 10 FPS, you have 3/13ths of a second "left over", if the shutter could be rewound instantaneously (which is only true for the electronic shutter), and if the exposure is extremely short, for the sensor to update AF, AE, and the EVF between frames. This is why the EVF shows the previous frame rather than attempting to repaint during continuous high shooting.
But the stacked sensor reads out is more like 1/120th to 1/250th, depending on model. So, at 10 FPS, you instead have at least 110/120ths left over for AF/AE operations, rewinding the shutter, and actual exposure, every second.
So, the stacked sensor in the A9 has 4X as much time between frames at 10 FPS, and the A1 has about 8X as much time. That's assuming that stacked sensors cannot update AF/AE during exposure, which I think they probably can.
Realistically, 3/13ths over 10 frames is 23ms per frame, so about 1/40th. I would guess that rewinding the shutter takes at least 1/200th (this is probably really generous, and it probably takes a lot longer), or 5ms. However, let's skip that and go with 0ms to reset an electronic shutter. In that case, 1/40th would be the longest exposure you could do at 10FPS, and that would allow no time at all for AF unless the frame rate slows down. If you shot at 1/1000th (1ms), you would have 22ms per frame for AF. The A7III is claimed to make 30 AF calculations per second = 33ms which is longer than the time between frames even at 1/8000th. Maybe it's using partial data at this point and updating AF every other frame?
How about the A9? Well, it has 92ms per frame between frames and does 60 AF calculations per second (16ms each), so, plenty of time for AF between frames, even at 20FPS.
You can say charged if you prefer, instead of rewound. Both terms are used, but charging gets confused with battery charging in modern cameras, while rewinding is clearly talking about the shutter.
paul cool
Senior Member
So this explains the reason for using 8fps to get live view same for r4
you are not going to be using the 10fps to much on the a1 or a9 ,so in fact would you get a better c-af if you used half the frame rate available on a stacked sensor as it will make even more calculation on the subject ? or is this just figures
These are lot of calculations the way your making it sound is as though the camera is not continously focusing almost like s-af in burst mode ,is this soley a mirrorless issue as dslrs used a off sensor af array and probably avoided the on sensor pdaf
To be honest its all lost on me ill take it my A1 is the better focusing of the camera,s over my a7r3 although i never found it to be a slouch especially with some one running at me .The lag and seeing the previous frame in 10fps was more of a issue especially when over period the subject would move to the edge of frame.
SQLGuy
Forum Pro
If the system is focusing during exposure and capture (with electronic shutter) then it shouldn't make much of a difference. If it's not, then probably, yes.
That's basically what I'm saying, that at 10 FPS, especially with mechanical shutter (EFCS or not), these non-stacked sensors don't really have time to measure AF every frame. The 4D AF stuff introduced with the A6000, though, should at least allow for updating of AF based on the subject continuing to move in the same direction through the burst.
DSLRs wouldn't have any advantage, because they rely on the mirror to direct light to the AF array, and that mirror is up during exposure.
The Sony SLTs, though, should be able to focus during exposure, since their mirrors are fixed.
A potential conjuring trick as he shows the viewfinder display, but not the resulting images.
It could be that the A1 is optimistic and the others pessimistic about when they acquire acceptable focus.
(Don't get me wrong, I'm not an A1 knocker. In fact I'm thinking of getting one as it is less bulky than the others, but also wondering, given Sony's turnover, whether I should wait for the A2, which could leapfrog the others.)
no, he put up links where he posted the images, you can download 'em for yourself.
i'll re-post the example of what those pics look like, see below, it's pretty obvious.
how long do you want to wait? it was over two years between the a9 vs. a9ii, and they both use the same sensor... given the dismal market conditions right now, it could be another two years or more until we see an a2 with a new sensor.
at this point the only competition to sony is canon, and canon is still way behind the technology curve, they can't even come up with linear voice coil af motor technology... strangely enough nikon beat 'em to the punch with their new 400/2.8, it'll be the first nikon lens with a cutting-edge focus motor... we'll see what the r1 looks like, but i'm not expecting much.
the a1 is clearly the most complete well-rounded camera of the three, and it has the stickiest most accurate af, plus the best lens lineup by far, but it's not cheap.
Get the A7IV for now, I can't prove it but I think it's af is even better than the A1, I also like the image quality of the A7IV better than any of the HR sensors like the A1/Z7II and R5. OK, this is no A1 in terms of silent/blackout free shooting but if that's not an issue A7IV is incredibly good!
networker
Well-known member
LOL
?
daran
Senior Member
You think that due to gut feeling? Reading tee leaves? Comparing them in the same situation?
Yes, it's probably not so in reality! The thing is because I had the A1 I sort of thought ok I can get the FE 100-400 and crop to 600, so really that's where everything falls down imo, having hr sensors lulls you into a false sense of security imo, well it did for me anyway! Had I stuck with the 200-600 in the first place, maybe I'd see things differently!
Couple of things I like over the A1;
EVF, again, having such high resolution you really need absolute top notch lenses all the time, some of the time I could not judge in evf review what I was getting with a lens like the 24-105, back in raw/post everything seemed normal, but through the evf I don't know judging sharpness seemed tricky! For framing everything was big/expansive/detailed it was just in review and the rear lcd is the other way!
FAS screen I now prefer over the tilt screens
AF, I don't know it just seems ever so slightly more responsive, imagination/gut feeling, possibly but it just seems to be "on it". I'm not bothered about the burst being 10fps in compressed, too many frames already at 8/10!
Things I don't like;
The e-shutter probably won't cut it for anything other than outdoor static
why doesn't the camera have pixel shift?
why doesn't it still not have focus stacking?
apart from that ibis seems not too bad with this iteration and the body is nice to hold and ergonomic. There's a reason to go for the A1 and I was probably never it's target audience but in terms of af I can definitely feel that A1 family resemblance and it might be dumbed down in fps but it's definitely one of the best if not the best af camera right now, next to the R5/A1, I haven't used the Z9 or R3.
My friend just tested the a7 mk4 for birding one week. He is also A1 owner, he says that A1 af subject tracking is still on another level.
a7 mk4 has slightly better bird eye tracking but that is only good for slow moving bird.
SilvanBromide
Veteran Member
The a1 sensor scans at nearly ten times the speed of the a7iv sensor, which means it is able to calculate and adjust AF about ten times in the time it takes for the a7iv to adjust AF once.
That makes it hard to imagine that they could be in the same league, even if the a7iv algorithm is more advanced - it's still going to be limited by the speed of the hardware.
Interesting. I can believe that the bird EyeAF algorithm has evolved. But I'm not sure how useful it is that tracking is improved but "only for slow moving subjects". Slow moving subjects are the least challenging for tracking...
It's a bit like saying someone is a math genius but they can only work out simple sums. ; )
Sorry but I'd need to test it myself to believe that! But it could be, but I doubt it, he's equating fps to performance! What lens is he using?
Hmm, well then he admits the bird eye tracking is improved, so its not my imagination
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