February 24, 2018, 07:32:47 PM

Author Topic: What if... DPAF with optical VF  (Read 927 times)

Pitbullo

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What if... DPAF with optical VF
« on: February 15, 2018, 10:27:44 PM »
Just a thought. What if Canon swapped their normal AF chip with a mirrorless sensor, even very low res to make it very accurate and sensitive, to implement dual pixel AF in a dslr. Wouldn’t we then get the benefit of DPAF and optical VF? They could have way better AF coverage, true eye AF etc., tracking and metering all in the new DP chip.
VF already have LCD overlay screens so getting the info in the VF should not be that hard.

The only downside is that they would not eliminate the need for AFMA, but maybe that could be fixed with an (optional) micro adjustment from the DPAF on the image sensor itself, just to dial it in perfect as the shot is being taken.

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What if... DPAF with optical VF
« on: February 15, 2018, 10:27:44 PM »

3kramd5

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Re: What if... DPAF with optical VF
« Reply #1 on: February 15, 2018, 10:53:25 PM »
So two image sensors and a mirror, without the advantages of large discrete AF sensors? Hmm
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Mt Spokane Photography

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Re: What if... DPAF with optical VF
« Reply #2 on: February 15, 2018, 11:02:39 PM »
Canon has several patents to have a optical viewfinder with liveview at the same time.  Each has its drawbacks.  While its possible to put multiple sensors in a camera body, the cost and space required to do so probably makes it too difficult to sell.  Sensors are large, and probably the most expensive component in a camera.

MoeGravey

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Re: What if... DPAF with optical VF
« Reply #3 on: February 15, 2018, 11:08:12 PM »
I believe it would be one or the other. in a SLR, light does not hit the actual image sensor until the shutter goes.   


  "Most DSLR cameras use what’s called a phase-detection focusing system – whereas most mirrorless cameras, point-and-shoots, and mobile phones use a separate system called contrast-detect. In a DSLR, most of the light coming through the lens is reflected upwards by the mirror, to the optical viewfinder, which lets you see precisely what the camera lens sees.

However, a tiny bit of light is also sent downward to a series of sensors that are capable of figuring out whether the image is in focus. The science behind this involves splitting the incoming light, and comparing two beams, to essentially see if they match up. If not, an electronic signal is sent to the focusing motor, to adjust the lens until the image is in focus. All this happens in a fraction of a second, but these fractions matter in photography, and can often be the difference between a tack-sharp image and a blurry shot."




Quoted from::
https://digital-photography-school.com/understanding-normal-and-cross-type-focusing-points/

Pitbullo

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Re: What if... DPAF with optical VF
« Reply #4 on: February 15, 2018, 11:13:49 PM »
There would be drawbacks, but the new Sensor with DPAF don’t have to be a FF sensor (1” perhaps), even if it sits in a FF camera. Also, price wise, there would be savings since they don’t have to use normal AF sensor or metering sensor.

I just would love to se a Canon equivalent to the eye-focus. That is not a gimmick, just a fantastically useful feature.

This could be a good idea, or maybe not  ;D

Mt Spokane Photography

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Re: What if... DPAF with optical VF
« Reply #5 on: February 15, 2018, 11:16:23 PM »
I believe it would be one or the other. in a SLR, light does not hit the actual image sensor until the shutter goes.   


  "Most DSLR cameras use what’s called a phase-detection focusing system – whereas most mirrorless cameras, point-and-shoots, and mobile phones use a separate system called contrast-detect. In a DSLR, most of the light coming through the lens is reflected upwards by the mirror, to the optical viewfinder, which lets you see precisely what the camera lens sees.

However, a tiny bit of light is also sent downward to a series of sensors that are capable of figuring out whether the image is in focus. The science behind this involves splitting the incoming light, and comparing two beams, to essentially see if they match up. If not, an electronic signal is sent to the focusing motor, to adjust the lens until the image is in focus. All this happens in a fraction of a second, but these fractions matter in photography, and can often be the difference between a tack-sharp image and a blurry shot."




Quoted from::
https://digital-photography-school.com/understanding-normal-and-cross-type-focusing-points/

People in the forum know how a DSLR works.  The OP as I read it was suggesting that the  AF sensor become a PDAF sensor.  That is entirely possible, but besides being slower to autofocus, there are other disadvantages.

Pitbullo

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Re: What if... DPAF with optical VF
« Reply #6 on: February 15, 2018, 11:18:36 PM »
I believe it would be one or the other. in a SLR, light does not hit the actual image sensor until the shutter goes.   


  "Most DSLR cameras use what’s called a phase-detection focusing system – whereas most mirrorless cameras, point-and-shoots, and mobile phones use a separate system called contrast-detect. In a DSLR, most of the light coming through the lens is reflected upwards by the mirror, to the optical viewfinder, which lets you see precisely what the camera lens sees.

However, a tiny bit of light is also sent downward to a series of sensors that are capable of figuring out whether the image is in focus. The science behind this involves splitting the incoming light, and comparing two beams, to essentially see if they match up. If not, an electronic signal is sent to the focusing motor, to adjust the lens until the image is in focus. All this happens in a fraction of a second, but these fractions matter in photography, and can often be the difference between a tack-sharp image and a blurry shot."


Quoted from::
https://digital-photography-school.com/understanding-normal-and-cross-type-focusing-points/

And here is the idea, dslr form factor, with mirrorless autofocus, combined. Either the best of both worlds, or the worst... the compromise is we lose the strength from today’s AF modules, and gain the strengths from DPAF with a dslr style of operation. Also, DPAF is phase detection.

Edit:moved my text to outside the quote...

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Re: What if... DPAF with optical VF
« Reply #6 on: February 15, 2018, 11:18:36 PM »

mistaspeedy

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Re: What if... DPAF with optical VF
« Reply #7 on: February 16, 2018, 12:22:25 AM »
Mirrorless seems to be the future, and Sony have proven with their A9 that it is possible to have incredibly fast AF on-sensor. It's just a matter of time before all manufacturers go that route totally, and stop making DSLRs for all but some retro lovers.

We're not there yet, and there will be further improvements in AF for the traditional DSLR... but I doubt anyone is really trying to push this tech a lot further when the advances in other AF methods have come so far and offer many benefits.
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3kramd5

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Re: What if... DPAF with optical VF
« Reply #8 on: February 16, 2018, 05:24:52 PM »
I believe it would be one or the other. in a SLR, light does not hit the actual image sensor until the shutter goes.   


  "Most DSLR cameras use what’s called a phase-detection focusing system – whereas most mirrorless cameras, point-and-shoots, and mobile phones use a separate system called contrast-detect. In a DSLR, most of the light coming through the lens is reflected upwards by the mirror, to the optical viewfinder, which lets you see precisely what the camera lens sees.

However, a tiny bit of light is also sent downward to a series of sensors that are capable of figuring out whether the image is in focus. The science behind this involves splitting the incoming light, and comparing two beams, to essentially see if they match up. If not, an electronic signal is sent to the focusing motor, to adjust the lens until the image is in focus. All this happens in a fraction of a second, but these fractions matter in photography, and can often be the difference between a tack-sharp image and a blurry shot."


Quoted from::
https://digital-photography-school.com/understanding-normal-and-cross-type-focusing-points/

And here is the idea, dslr form factor, with mirrorless autofocus, combined. Either the best of both worlds, or the worst... the compromise is we lose the strength from today’s AF modules, and gain the strengths from DPAF with a dslr style of operation. Also, DPAF is phase detection.

Edit:moved my text to outside the quote...

If they made a dual-diode DPAF capable sensor with huge pixels (think m4/3 format with say 1MP), maybe you’d start getting towards the best of both worlds.

But generally I’m afraid you’d be giving up too much just to save the OVF.
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IglooEater

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Re: What if... DPAF with optical VF
« Reply #9 on: February 16, 2018, 07:00:28 PM »
I guess such a sensor could double as a metering sensor now, as that’s basically what the metering sensor already is.  One less chip, but a higher power one.  I’m not under the impression DPAF is quite up to normal phase-detection chips, but I might be wrong.

Pitbullo

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Re: What if... DPAF with optical VF
« Reply #10 on: February 17, 2018, 03:39:53 PM »
I guess such a sensor could double as a metering sensor now, as that’s basically what the metering sensor already is.  One less chip, but a higher power one.  I’m not under the impression DPAF is quite up to normal phase-detection chips, but I might be wrong.

That is where I also was thinking the savings could be done, combine af and metering, thus give us the goodies from mirrorless with eye tracking AF etc. in the OVF.
I also think you are right that the DPAF is not quite up to the speed dedicated PDAF sensors are working at, but we are getting there.

Mt Spokane Photography

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Re: What if... DPAF with optical VF
« Reply #11 on: February 17, 2018, 04:23:44 PM »
Also, DPAF is phase detection.

DPAF starts with phase detection and finishes with contrast detection.  Thats likely because there is too much error in the phase detection part to be used all by itself.

Canon has several patents that result in ovf while the mirror is up, but since they use some of the light that would otherwise go to the main sensor, they are a compromise resulting in dim viewfinder and higher ISO setting for the sensor needed.  There always seems to be a downside so its a compromise.  I think Canon has learned their lesson about sharing light between sensor / film and viewfinder in their multiple failed attempts with film cameras.  People do not like dim OVF's plus higher ISO.

9VIII

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Re: What if... DPAF with optical VF
« Reply #12 on: February 17, 2018, 04:57:40 PM »
I've been thinking along the same lines for a while, but with different reasons.

Whenever shooting macro I get way, way more heat noise from 10 second exposures, ideally I want the sensor completely inactive for at least a few seconds before taking a picture.
The fact that mirrorless cameras are constantly reading off the sensor has got to be degrading image quality. This is one reason I will probably always have an SLR design camera (though you can turn the display off on some cameras, It's hard to say how that affects the sensor though, and it's still not an ideal solution).

The best idea I can come up with is to split the mirror into top and bottom halves, that way it would only need to protrude 12mm out beyond the sensor and would easily fit within a short flange mount, and you wouldn't need phase detect photosites on the sensor itself (ok that would be more beneficial to other companies since DPAF is both AF and color capturing across the whole sensor).

The downside, I really like the electronic shutter in my new Fuji X-E2S, I don't think I've actuated the mechanical shutter more than 50 times.
The idea of a "solid state" camera is appealing, with an E-shutter the lifespan of the camera is effectively infinite, and it's totally silent.
At the very least I wish mirrorless cameras would have better cooling, maybe even active cooling, and given how much heat is a problem with 4K recording maybe I won't have to wait too long.

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Re: What if... DPAF with optical VF
« Reply #12 on: February 17, 2018, 04:57:40 PM »