On-sensor PDAF, will it be as good as mirrored cameras?

Started 10 months ago | Discussions
havoc315
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to EinsteinsGhost, 10 months ago

EinsteinsGhost wrote:

havoc315 wrote:

EinsteinsGhost wrote:

Technological possibility and reality don't always meet, and that is my point. Nobody has suggested that f/2.8 lenses are not possible for E-mount, but the fact is, Sony is clearly favoring f/4 to keep size and weight down, which bodes well with a key selling point of the E-mount. The opposite is true for A-mount (a reason SLTs grew in size substantially, from A33/A55 to A65/A77).

Yes, but for anyone that doesn't mind the size, they can simply use their 2.8 A-mount lens on the E-mount camera, with an adapter. Thus, they don't need an A-mount camera to be able to use an A-mount lens.

So you actually believe that Sony would make A-mount lenses because it takes more resources to do so than would A-mount bodies which can share most parts with E-mount (except for the mount and firmware differences)?

Huh? The question was "the unique benefits" of a mirrorless a-mount.  In other words, features that cannot exist for Sony dSLTs or for e-mounts.  Use of 2.8 lenses is not unique to a mirrorless a-mount, since those same lenses can be used on dSLTs and also on e-mount bodies with adapters.

I wasnt judging Sony production.  Though, you are missing the real cost of producing 2 nearly identical mounts -- you lose profit when you compete with yourself.  It would be more profitable to sell 200 e-mounts, than to sell 100 a-mounts and 100 e-mounts.  (Because of increased marketing costs, inventory costs, production costs, etc, etc, etc).

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havoc315
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to EinsteinsGhost, 10 months ago

EinsteinsGhost wrote:

havoc315 wrote:

EinsteinsGhost wrote:

So, if the mirrorless AF system matches SLT AF performance, AND with elimination of mirror, improves high ISO performance, what exactly is it that you believe would be a step back?

Where are you getting that mirrorless AF system will match SLT AF performance?

SLR to SLT transition was that (which you deflected with the excuse on high ISO noise). I expect a similar SLT to mirror-less transition on A-mount. The question is, why would you prefer to assume otherwise?

It has nothing to do with my preference.  It's simple science.  Scientifically, a translucent mirror -- the whole point -- was to preserve dSLR dedicated pdaf. Scientifically, to date, there has still never been ospdaf that can match.

We won't know until products are actually out and tested, but according to the source cited in the first post -- Mirrorless AF system will NOT match SLT AF performance.

Then refrain from drawing conclusions, like you just did (again).

I'm not drawing unfounded conclusions.  That's you.  I was citing a published report.

So far, the best OSPDAF still doesn't quite match dedicated PDAF. Not in the Nikon 1 cameras, not in the Canon 70D. And according to the rumors, not in the Sony A7.

So? And there is no reason to believe that Sony will stick with the OSPDAF system you speak of, to replace the mirror.

You're right.  The new camera will be made out of fairy dust.

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WaltKnapp
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to EinsteinsGhost, 10 months ago

EinsteinsGhost wrote:

Actually, it is P&S shooters who need all the focusing help they can get from their camera, and in this case, auto focusing.

That explains why so many are going for E mount cameras so they can mount and use antique MF film lenses as their primary shooting lenses.

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Albino_BlacMan
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Re: Some related thoughts.
In reply to Bruce Oudekerk, 10 months ago

Z axis movement isn't a new idea... Contax did it with the AX is 1996 (I think that's the year at least). At the time they had to move a whole roll of film so moving a sensor seems minor in comparison (well not minor but it shows it wouldn't be impossible).

There are some shortcomings however as it only really works with wide angle and maybe normal lenses. Anything else needs the sensor to move too far (so it won't work with telephoto lenses) and it can't achieve focus for things like macro (look at an old MF lens (50mm(ish)) and look how far the front element moves to achieve MFD and add that to the depth of the camera).

It's a nice idea but it won't be a game changer and won't help Sony sell lenses.

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Bruce Oudekerk
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Re: Some related thoughts.
In reply to Albino_BlacMan, 10 months ago

Albino_BlacMan wrote:

Z axis movement isn't a new idea... Contax did it with the AX is 1996 (I think that's the year at least). At the time they had to move a whole roll of film so moving a sensor seems minor in comparison (well not minor but it shows it wouldn't be impossible).

There are some shortcomings however as it only really works with wide angle and maybe normal lenses. Anything else needs the sensor to move too far (so it won't work with telephoto lenses) and it can't achieve focus for things like macro (look at an old MF lens (50mm(ish)) and look how far the front element moves to achieve MFD and add that to the depth of the camera).

It's a nice idea but it won't be a game changer and won't help Sony sell lenses.

I knew about the Contax attempt to do this but had no idea how much Z axis movement it could generate and just assumed it wasn't much given the complex issues of dealing with film. I also assumed that any lens would be set on infinity and the Z axis 'throw' of the sensor would determine the MFD.  I realize the longest tele and definitely macro would be severely limited.  (I took one look at my old auto Canon bellows unit to realize this). However these would be a very small percentage of the lenses. If this limited sensor 'throw' can't reasonably accommodate, lets say, a 200mm lens... it will probably just be a curiosity. That focal length of 200mm is probably a good threshold for usability, APS-C or FF. But if it can do this, it would, or could, be amazing. Almost all modern lenses have internal focusing elements but I seem to remember that my oldest manual lenses had what I would think would be a reasonable Z axis 'throw' and thus I assumed it would be possible.

I hope you are being too conservative in you estimates of what can be done but you are dashing my hopes:(

Bruce

BTW...the link to your Photobucket images broke.

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Bruce Oudekerk
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Ouch
In reply to Bruce Oudekerk, 10 months ago

Instead of talking about it...I searched around and dug up an early 70's vintage manual focus Vivitar 200mm f3.5 prime that I had lying around. I hadn't even looked at this lens in 15 or 20 years.

When I close focused, it cantilevered out across the room and I was shocked. At an arbitrary focal distance of approximately 9 feet it had extended 17mm. I didn't bother measuring its actual MFD as I was too disheartened.

The whole z axis process might work but it will have limitations I hadn't fully anticipated.

Bruce

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EinsteinsGhost
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to havoc315, 10 months ago

havoc315 wrote:

EinsteinsGhost wrote:

havoc315 wrote:

EinsteinsGhost wrote:

Technological possibility and reality don't always meet, and that is my point. Nobody has suggested that f/2.8 lenses are not possible for E-mount, but the fact is, Sony is clearly favoring f/4 to keep size and weight down, which bodes well with a key selling point of the E-mount. The opposite is true for A-mount (a reason SLTs grew in size substantially, from A33/A55 to A65/A77).

Yes, but for anyone that doesn't mind the size, they can simply use their 2.8 A-mount lens on the E-mount camera, with an adapter. Thus, they don't need an A-mount camera to be able to use an A-mount lens.

So you actually believe that Sony would make A-mount lenses because it takes more resources to do so than would A-mount bodies which can share most parts with E-mount (except for the mount and firmware differences)?

Huh? The question was "the unique benefits" of a mirrorless a-mount. In other words, features that cannot exist for Sony dSLTs or for e-mounts. Use of 2.8 lenses is not unique to a mirrorless a-mount, since those same lenses can be used on dSLTs and also on e-mount bodies with adapters.

You're missing the point. What do you think is an issue for Sony to maintain two mounts? That it would prefer to sell only one mount, and no adapters between mounts? That it would prefer to make lenses for two mounts, but bodies only for one (on assumption that it would be more expensive to make A-mount bodies than to make A-mount lenses AND adapters with A-mount?)

I wasnt judging Sony production. Though, you are missing the real cost of producing 2 nearly identical mounts -- you lose profit when you compete with yourself. It would be more profitable to sell 200 e-mounts, than to sell 100 a-mounts and 100 e-mounts. (Because of increased marketing costs, inventory costs, production costs, etc, etc, etc).

And why do you think making A-mount lenses and EA adapters and selling only E-mount bodies would be more cost effective? And, are you sure Sony E-mount with even more air space than in A3000, for FF bodies would make more sense eventually because people do demand larger and heavier bodies?

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EinsteinsGhost
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to havoc315, 10 months ago

havoc315 wrote:

EinsteinsGhost wrote:

havoc315 wrote:

EinsteinsGhost wrote:

So, if the mirrorless AF system matches SLT AF performance, AND with elimination of mirror, improves high ISO performance, what exactly is it that you believe would be a step back?

Where are you getting that mirrorless AF system will match SLT AF performance?

SLR to SLT transition was that (which you deflected with the excuse on high ISO noise). I expect a similar SLT to mirror-less transition on A-mount. The question is, why would you prefer to assume otherwise?

It has nothing to do with my preference. It's simple science. Scientifically, a translucent mirror -- the whole point -- was to preserve dSLR dedicated pdaf. Scientifically, to date, there has still never been ospdaf that can match.

Science is precise. Science is non-science when it prefers to overlook gains from a technology and further improving it (which would be the ultimate goal with getting SLT like AF performance at the minimum, and no fixed or slapping mirror to deal with for AF/metering and maximize it to the sensor.

We won't know until products are actually out and tested, but according to the source cited in the first post -- Mirrorless AF system will NOT match SLT AF performance.

Then refrain from drawing conclusions, like you just did (again).

I'm not drawing unfounded conclusions. That's you. I was citing a published report.

What report?

So far, the best OSPDAF still doesn't quite match dedicated PDAF. Not in the Nikon 1 cameras, not in the Canon 70D. And according to the rumors, not in the Sony A7.

So? And there is no reason to believe that Sony will stick with the OSPDAF system you speak of, to replace the mirror.

You're right. The new camera will be made out of fairy dust.

Not really. But you sure have been relying on that... complete with the idea that current OS-PDAF is the future mirror-less AF system, and it can't be anything else. Why?

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jackgreen
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to havoc315, 10 months ago

Interestingly this massive thread is mostly off-topic.

I'm bothering with the same question, is on-sensor PDAF any good. And when it becomes good enough to replace SLT?

My first hand on-sensor PDAF experience is only with Samsung NX200. It's marketed as very fast and etc... In real life it did not perform as marketed. Lot of AF errors all the time. Did some street photography walk and got too many photos to reject because of AF issues.

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Samsolar
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to WaltKnapp, 10 months ago

WaltKnapp wrote:

EinsteinsGhost wrote:

Actually, it is P&S shooters who need all the focusing help they can get from their camera, and in this case, auto focusing.

That explains why so many are going for E mount cameras so they can mount and use antique MF film lenses as their primary shooting lenses.

P&S shooters are not the ones buying old lens Walt

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K E Hoffman
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to jackgreen, 10 months ago

jackgreen wrote:

Interestingly this massive thread is mostly off-topic.

I'm bothering with the same question, is on-sensor PDAF any good. And when it becomes good enough to replace SLT?

My first hand on-sensor PDAF experience is only with Samsung NX200. It's marketed as very fast and etc... In real life it did not perform as marketed. Lot of AF errors all the time. Did some street photography walk and got too many photos to reject because of AF issues.

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If you look at the Canon 70D tests DPR did..

The On Sensor Focusing looks more accurate  than the normal AF

They just don't have the software working yet for tracking.  So for portrait and landscape it might already be a better choice..

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EinsteinsGhost
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to WaltKnapp, 10 months ago

WaltKnapp wrote:

EinsteinsGhost wrote:

Actually, it is P&S shooters who need all the focusing help they can get from their camera, and in this case, auto focusing.

That explains why so many are going for E mount cameras so they can mount and use antique MF film lenses as their primary shooting lenses.

It ain't those who can't do without AF Walt, and that would be practically all P&S upgraders unless they are very serious about photography, much less taking full control of it, that these MF lenses demand.

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Bruce Oudekerk
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to jackgreen, 10 months ago

jackgreen wrote:

Interestingly this massive thread is mostly off-topic.

The question here is much more complex, I think, than 'just' the issue of PD on-sensor.

Fundamentally PDAF works differently than CDAF and the lenses themselves are different. Presumably this is why Alpha mount lenses on NEX cameras focus MUCH MORE slowly under contrast detect than a native E-mount lens. Conversely I'm wondering if the E-mount lenses CAN focus any faster using any form of PD or if they are limited by their optimization for CD. The PDAF on-chip specific question for e-mount lenses should be answered fairly soon with the new cameras. So the real question might be PDAF on-sensor with what lenses? We can look to Olympus for some hints. The 4/3 lenses that were optimized for PD were relatively slow on CD micro 4/3 cameras but now the latest M1 has made significant headway with on-chip PD. Its not there yet but getting closer. And as stated elsewhere we can look to Canon 70D where PD gets focusing essentially there with a final CD check. Slower but perhaps more accurate in some situations....or not. So it might be better for many and not so good for some photographers.

The next issue that I believe the topic assumes is that mirrored cameras are the end...to end all... in focusing. Quite frankly focusing in general is sloppy on almost all mirrored cameras (OK... all cameras) unless you are using a single point and even then the hit rate is not guaranteed to be 100%. If anything, good CD is more accurate than good PD. The catch there is speed and that has been a trade off for quite a while regardless of PD or CD. When I bought my a850 there were studies that indicated that is had very accurate center point focus...more so than much of the competition... but it was slower. I have found this to be true. And that's judging PD to PD. When judging CD to PD (off topic) or on-sensor to off-sensor PD (on topic), the 'Will it be as good' question becomes fuzzy and qualifications immediately branch the issue out into other areas. No wonder the answers are off topic. Although admittedly my comments have been more off topic (ish) than most:)

The last issue is operator error and how that interacts with the strategies that different cameras employ during the focusing process. These strategies vary according to a variety of other fundamental camera parameters. For example, when the camera has faster focus lock it can afford to perform more complex tasks, which in my experience often tend to lower the hit rate in certain situations. These qualifications will invariably be a consideration when judging CD to PD on-chip and in judging PD on-chip to PD off-chip.(ie mirrored cameras)

With that said, we are ALL waiting on information that will give us a frame of reference to this question and the inevitable compromises that will manifest themselves.

Bruce

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Brian_Smith
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to havoc315, 10 months ago

IF such a thing were to exist, it might not be as good. It might be better...

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Bruce Oudekerk
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to Brian_Smith, 10 months ago

Brian_Smith wrote:

IF such a thing were to exist, it might not be as good. It might be better...

I'm hoping to see you again at the Photo Plus Expo later this month in NYC, smiling and holding just such a contrivance... assuming it exists.

Bruce

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JamieTux
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to Brian_Smith, 10 months ago

Brian_Smith wrote:

IF such a thing were to exist, it might not be as good. It might be better...

IF something does get announced at some point and you happen to have experience will you come back and share your experience with us as soon as you can after any hypothetical announcement?

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havoc315
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to EinsteinsGhost, 10 months ago

havoc315 wrote:

EinsteinsGhost wrote:

havoc315 wrote:

EinsteinsGhost wrote:

So, if the mirrorless AF system matches SLT AF performance, AND with elimination of mirror, improves high ISO performance, what exactly is it that you believe would be a step back?

Where are you getting that mirrorless AF system will match SLT AF performance?

SLR to SLT transition was that (which you deflected with the excuse on high ISO noise). I expect a similar SLT to mirror-less transition on A-mount. The question is, why would you prefer to assume otherwise?

It has nothing to do with my preference. It's simple science. Scientifically, a translucent mirror -- the whole point -- was to preserve dSLR dedicated pdaf. Scientifically, to date, there has still never been ospdaf that can match.

Science is precise. Science is non-science when it prefers to overlook gains from a technology and further improving it (which would be the ultimate goal with getting SLT like AF performance at the minimum, and no fixed or slapping mirror to deal with for AF/metering and maximize it to the sensor.

We won't know until products are actually out and tested, but according to the source cited in the first post -- Mirrorless AF system will NOT match SLT AF performance.

Then refrain from drawing conclusions, like you just did (again).

I'm not drawing unfounded conclusions. That's you. I was citing a published report.

What report?

So far, the best OSPDAF still doesn't quite match dedicated PDAF. Not in the Nikon 1 cameras, not in the Canon 70D. And according to the rumors, not in the Sony A7.

So? And there is no reason to believe that Sony will stick with the OSPDAF system you speak of, to replace the mirror.

You're right. The new camera will be made out of fairy dust.

Not really. But you sure have been relying on that... complete with the idea that current OS-PDAF is the future mirror-less AF system, and it can't be anything else. Why?

Published report... See the first post.

I don't make assumptions. I rely on facts. I rely on technology as it exists. Certainly, over time, it will improve. But until such improvements are actually known and seen, you can't assume.
Some day, I believe we will communicate with life from other planets.
So will the next Sony a-mount camera include an alien communication device?
Why not? Why are you assuming it won't include this technological advancement?

I suspect Sony would put it's very best ospdaf in the a7.

You are making a weird assumption that they would intentionally put an inferior ospdaf system in this premium camera, just to hold back the better version for a-mount?

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jackgreen
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Re: On-sensor PDAF, will it be as good as mirrored cameras?
In reply to Bruce Oudekerk, 10 months ago

True, CD and PD AF lenses are different. Thats why there is pretty bad mess with Olympus OM D5. On-chip AF requires 4/3 lens, not M4/3 lens as it used to be with CDAF.

But I believe, that on-chip PDAF uses same focussing motors and alhoritms as older SLT/SLR PDAF systems. This is indeed my speculation.

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Photomonkey
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Eventually, it will be better
In reply to havoc315, 10 months ago

Assuming the state of development will be static is foolish.

We have seen a steady arc of improvement of every digital imaging technology. Why do you assume that will stop today?

Already we have seen very large improvements in on-mirror PDAF the existence of which is itself a recent development.

CDAF has also bounded forward in speed though still not as appealing as PDAF.

Mirrorless will rule the day AND it eventually will make us wonder why we loved mirrors.

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jackgreen
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Re: Eventually, it will be better
In reply to Photomonkey, 10 months ago

We all agree, but question is when?
I mean, when can we believe the marketing about fast and accurate focussing?

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