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Author Topic: The P1 XF Autofocus, future possibilities?  (Read 7857 times)

Transposure

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Re: The P1 XF Autofocus, future possibilities?
« Reply #20 on: March 31, 2016, 05:41:06 pm »

DrakeJ,
I hear you with your need/desire for more focus points.  I primarily shoot people professionally.  And I have historically used 1 series Canons to do so.  I have always set up my AF on those cameras to be the "ring of fire" as it's called.  So, as I move and the model moves, and I recompose, I have a ring of focus points (in an oval shape) tied to the rear dial.  I can be on the floor, standing, squatting, kneeling or upside down on my head and I spin the rear dial to select the point that is closest to the model's eye.  I hit the back button focus and then the shutter button.  In a fraction of a second I have framed the shot, grabbed accurate focus and captured the shot with 99% focus accuracy.  I do this at f2.0, f2.8 and f4.0 primarily.  No greater DOF usually.  Splendid.

Now, when I use the XF, it is strictly focus and recompose using the center point.  I typically shoot at either f2.8 or f4.0.  My focus accuracy is probably 90% if I had to guess.  The XF focuses very fast (just as fast as the Canon 1Dx) but the lack of a red focus point and the proximity of left eye, nose and right eye, sometimes yields some OOF shots.  I am getting better as I get more accustomed to the XF.

But something of interest, the XF does have an accelerometer/gyro in it.  And I am sure Phase is well versed on the nature of Hassy's True Focus.  I would have to wonder if one of the future rollouts will be some non-patent-infringing True Focus clone, thus adjusting for the new spatial orientation of the camera during recomposition.  Food for thought.

eronald

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Re: The P1 XF Autofocus, future possibilities?
« Reply #21 on: March 31, 2016, 07:19:58 pm »

This is the first time I've heard that a medium format camera can focus as fast as Canon's 1Dx, which was marketed as the world's fastest SLR AF. They really must have an incredible sensor and also some really  strong new motors to push that heavy MF glass around! Maybe Canon needs to learn from Phase how it's done. Or maybe I should reinterpret your comment as meaning that the 1Dx has a mediocre AF system for a pro dSLR?

Anyway, I am sure that the gyro issue is a trivial engineering problem for Phase, and right next week they will have engineered an endrun around the Hassy IP, and it will be there and work perfectly.

You must excuse me now, I need to go back to some gyro code in my 5 year old's Lego kit, I've spent a week trying to figure this out, how to start up and reset the gyro cleanly, and the gyro keeps drifting and drifting, and this robot falls over not all the time but some of the time, and I need to figure out a way to filter out the drift, but there's some sort of stutter in the timing and so any integration is off; it's certainly obvious, now if I just had one of those genius Phase engineers to help me, or maybe I just need to wait until my boy turns 6 :)

Edmund

PSssst. I've heard the Hassy rep say that next week a new version of Phocus is coming out, which will be just as good as C1 ... you think that's true? My experience in getting accuracy out of a gyro makes me think that maybe the Hassy guys are smarter than the Phase fans think.


DrakeJ,
I hear you with your need/desire for more focus points.  I primarily shoot people professionally.  And I have historically used 1 series Canons to do so.  I have always set up my AF on those cameras to be the "ring of fire" as it's called.  So, as I move and the model moves, and I recompose, I have a ring of focus points (in an oval shape) tied to the rear dial.  I can be on the floor, standing, squatting, kneeling or upside down on my head and I spin the rear dial to select the point that is closest to the model's eye.  I hit the back button focus and then the shutter button.  In a fraction of a second I have framed the shot, grabbed accurate focus and captured the shot with 99% focus accuracy.  I do this at f2.0, f2.8 and f4.0 primarily.  No greater DOF usually.  Splendid.

Now, when I use the XF, it is strictly focus and recompose using the center point.  I typically shoot at either f2.8 or f4.0.  My focus accuracy is probably 90% if I had to guess.  The XF focuses very fast (just as fast as the Canon 1Dx) but the lack of a red focus point and the proximity of left eye, nose and right eye, sometimes yields some OOF shots.  I am getting better as I get more accustomed to the XF.

But something of interest, the XF does have an accelerometer/gyro in it.  And I am sure Phase is well versed on the nature of Hassy's True Focus.  I would have to wonder if one of the future rollouts will be some non-patent-infringing True Focus clone, thus adjusting for the new spatial orientation of the camera during recomposition.  Food for thought.
« Last Edit: March 31, 2016, 07:31:33 pm by eronald »
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Transposure

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Re: The P1 XF Autofocus, future possibilities?
« Reply #22 on: March 31, 2016, 09:43:50 pm »

To clarify my comment..
Example:  When I have the focus set to a far subject with my 1Dx with 70-200mm f2.8 and I press the AF button to focus on a near subject, it is incredibly similar in speed-to-focus as the XF with the 110mm LF.  Additionally, these are also incredibly similar in speed-to-focus as my Sony a6000 with the 28-70mm.

And my only point was that the XF is incredibly/surprisingly fast and accurate to focus.  Much, much better than my old DF and DF+.


This is the first time I've heard that a medium format camera can focus as fast as Canon's 1Dx, which was marketed as the world's fastest SLR AF.

eronald

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Re: The P1 XF Autofocus, future possibilities?
« Reply #23 on: March 31, 2016, 10:06:19 pm »

To clarify my comment..
Example:  When I have the focus set to a far subject with my 1Dx with 70-200mm f2.8 and I press the AF button to focus on a near subject, it is incredibly similar in speed-to-focus as the XF with the 110mm LF.  Additionally, these are also incredibly similar in speed-to-focus as my Sony a6000 with the 28-70mm.

And my only point was that the XF is incredibly/surprisingly fast and accurate to focus.  Much, much better than my old DF and DF+.

Sarcasm off: I believe you. But whether this means there is an issue with the Canon or the XF is incredibly good is something I wouldn't know.

Usually a Ferrari wins against a Mercedes saloon, and this is no aspersion on the Mercedes. If the Mercedes wins, one tends to wonder whether the Ferrari is not a bit sub-par :) 

BTW, what d'you think of the 1Dx image quality? Now they are appearing on the used market, I'm thinking of getting one.

Edmund
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aztwang

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Re: The P1 XF Autofocus, future possibilities?
« Reply #24 on: March 31, 2016, 11:44:56 pm »

Off-center focus is what I live for. Perhaps an IQ back mated with a H5x would be the best solution. I'm a sucker for good design however, and the XF is pretty cool. However, if I'm not getting critical focus reliably when shooting people, it's basically an extremely expensive paperweight to me.

I was secretly hoping that Phase is just a software upgrade away from doing a bit of technical trickery to allow the sensor to achieve off-center focus, but I guess that's not in the cards.

DrakeJ..What aperture are you shooting at? Available light or strobes?

Don
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Transposure

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Re: The P1 XF Autofocus, future possibilities?
« Reply #25 on: April 01, 2016, 12:57:22 am »

Edmund,
I wasn't sure if you were being sarcastic.  ;~)
There is clearly a difference between the granularity of the focus abilities.  The 1Dx has 63 points(?) I think.  And when you select one by any means (my method or other methods) it is a clearly defined point that you can place precisely on an eye or an object and you will get focus, each and every time.  It is almost telepathic once you get in the groove.  Nothing better in my opinion.  But, the speed, or better put, the snappiness of the motors to grab focus from one subject to another is nearly equal, if not equal.  The problem is there isn't a refined granularity with the XF.  You have a big area in the middle that you try to lay on your target and it may get the eye, or the nose or the other eye.  So, to use your analogy, if the 1Dx is the Ferrari (or Porsche as I am a Porschephile lol), the XF is an Aston Martin.  A little levity in there somewhere.

As for how I like the 1Dx, well, completely frankly, it is the best camera I have ever owned.  And I have owned the 1Dx, 1Dx2, 5D2, 5D3, 1Dx3, 1Dx, DF, DF+, XF, NEX7, A7R and a6000.
I shoot people, professionally.  And I have to say, the 18.xMP sensor provides the perfect mix of high ISO performance, and beautiful rendition that prints beautifully.  I have printed up to 30"x40" in regular prints and up to 60"x40" in a gallery wrap and, wait for it, up to 20 FEET x 3' for a composited mounted banner for a client.  We needed to rent a truck to get it from the lab to the client!  But I digress.  I cannot recommend the 1Dx highly enough.
Regards,
Ken


Sarcasm off: I believe you. But whether this means there is an issue with the Canon or the XF is incredibly good is something I wouldn't know.

Usually a Ferrari wins against a Mercedes saloon, and this is no aspersion on the Mercedes. If the Mercedes wins, one tends to wonder whether the Ferrari is not a bit sub-par :) 

BTW, what d'you think of the 1Dx image quality? Now they are appearing on the used market, I'm thinking of getting one.

Edmund

eronald

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Re: The P1 XF Autofocus, future possibilities?
« Reply #26 on: April 01, 2016, 06:42:47 am »

There might be an XF camera setting there to narrow the single focus zone on the XF, but I'm not sure a smaller zone would be marked properly on the "new" focus screen which I haven't seen. Maybe check the latest manual and ask your dealer about this? 

The problem is that even if you have good center focus, geometry means that once you recompose, it's often off. That's what the Hassy tech gets around.

Thanks for your opinions on the 1Ds. I got a D4 at the time, and it wasn't so good, and I'm thinking of crossgrading now.

Edmund


Edmund,

The problem is there isn't a refined granularity with the XF.  You have a big area in the middle that you try to lay on your target and it may get the eye, or the nose or the other eye.
« Last Edit: April 01, 2016, 06:45:54 am by eronald »
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DrakeJ

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Re: The P1 XF Autofocus, future possibilities?
« Reply #27 on: April 01, 2016, 04:46:48 pm »

DrakeJ..What aperture are you shooting at? Available light or strobes?

Don

I am basically always using artificial lighting. Aperture? Shooting portraits I often use wide open, or close to wide open. That's when I need reliable focus the most.

I received my demo XF today, will do extensive testing during the weekend. Spot focus seems to work well, but I'm disappointed the viewfinder doesn't show how large the focus point is.

aztwang

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Re: The P1 XF Autofocus, future possibilities?
« Reply #28 on: April 03, 2016, 01:30:56 am »

I am basically always using artificial lighting. Aperture? Shooting portraits I often use wide open, or close to wide open. That's when I need reliable focus the most.

I received my demo XF today, will do extensive testing during the weekend. Spot focus seems to work well, but I'm disappointed the viewfinder doesn't show how large the focus point is.

To my knowledge, when set at spot autofocus the inner brackets are you're focusing point.
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DrakeJ

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Re: The P1 XF Autofocus, future possibilities?
« Reply #29 on: April 03, 2016, 02:18:36 am »

To my knowledge, when set at spot autofocus the inner brackets are you're focusing point.

There are no inner brackets in my demo XF viewfinder. It looks nothing like the manual.

Christopher

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Re: The P1 XF Autofocus, future possibilities?
« Reply #30 on: April 03, 2016, 03:49:49 am »

Then it only had the old  screen. The new/current one has two brackets. One for spot and one for average.


Christopher Hauser
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Doug Peterson

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Re: The P1 XF Autofocus, future possibilities?
« Reply #31 on: April 03, 2016, 10:45:41 am »

There are no inner brackets in my demo XF viewfinder. It looks nothing like the manual.

The old focus screen doesn't show you where you are focusing which leads to a lot of guess work as to what it's locking onto. It can also lead to unexpected hunting when you place the small AF area on an area of no contrast (but think you're placing it on something with contrast that falls in the falsely large AF area etching on the old ground glass).

Your dealer should be able to provide a new one; they have been shipping for several months.
« Last Edit: April 03, 2016, 10:55:33 am by Doug Peterson »
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DrakeJ

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Re: The P1 XF Autofocus, future possibilities?
« Reply #32 on: April 04, 2016, 07:05:45 am »

The old focus screen doesn't show you where you are focusing which leads to a lot of guess work as to what it's locking onto. It can also lead to unexpected hunting when you place the small AF area on an area of no contrast (but think you're placing it on something with contrast that falls in the falsely large AF area etching on the old ground glass).

Your dealer should be able to provide a new one; they have been shipping for several months.

Well, that's good to hear. Still, it does not substitute having a moveable focus point or a Hasselblad variant of "true focus".

eronald

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Re: The P1 XF Autofocus, future possibilities?
« Reply #33 on: April 04, 2016, 07:11:32 am »

Well, that's good to hear. Still, it does not substitute having a moveable focus point or a Hasselblad variant of "true focus".


One thing I've noticed is that every single one of my "pro" 35mm bodies has needed some service realignment of the focus system after I got it. As an example, my 1Ds3 seems to have the "real" focus point slightly offset with respect to the viewfinder marks. The same for my Nikon D3x.

This has real consequences in practice. Focus on an eye and you may get the lashes rather than the iris, focus on the altar cross or the face of a priest inside a church and you may backfocus onto the back end of the nave. If your eyes are ok, you will catch the error while pressing the button, if your eyes are bad you will only see it when looking at the file.

A friend once remarked to me that on a pro camera *everything* is designed to be adjusted, but one needs to convince the service people to do the job, usually they will first try to tell you it's not possible.


Edmund
« Last Edit: April 04, 2016, 07:17:09 am by eronald »
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Chris Livsey

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Re: The P1 XF Autofocus, future possibilities?
« Reply #34 on: April 04, 2016, 08:23:31 am »

I seem to be quoting Bythom a lot today:

"Light goes through a partially silvered mirror that needs to be at just the right angle to another mirror that needs to be at just the right angle to another mirror that needs to be at the right point to a separator lens set that needs to be properly positioned to the autofocus sensors, which also need to be properly positioned in 3D space. Oh, and all that alignment needs to agree with the focus screen, prism, and viewfinder alignment (otherwise you might try to refocus something that was actually in focus), plus the imaging sensor itself.

On top of this, the geometry of phase detect generates pretty small numbers that need clear differentiation. Then, once the camera has accurately generated that number, it needs to know that the lens will go exactly to the right position it tells it to. So the lens elements also need to be properly positioned with no slop in their positioning mechanism and the focus motor must repeat the exact same move every time it is instructed to.

Oh, and did I mention that everything in the above has to be absolutely repeatable every time you press the focus button (shutter release)? Anyone that knows about system designs knows if you look at a close enough level, repeatability is a “range” not a binary yes/no.

Thing is, even a really small tolerance error somewhere in all that I’ve described can produce image results where the focus plane isn’t quite where it was supposed to be. As we get higher and higher sampling at the sensor—more megapixels—it gets clearer and clearer when we have small “misses” by the focus system."
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siddphoto

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Re: The P1 XF Autofocus, future possibilities?
« Reply #35 on: April 07, 2016, 03:44:21 am »

In their latest update (#2) release, they say:

Improvements have been made to increase accuracy in low light conditions, ensure focus of various low contrast materials in even light, and improved precision when using the XF Camera System handheld with behavior changes initiated from the systems several accelerometers.


.. which makes me wonder if they have implemented something like Hasselblad's TrueFocus under the hood. I mean, most likely with all the gyroscopes, it is possible that all the hardware capability is there. And if that is true, it's just a matter of using them in the software.
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eronald

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Re: The P1 XF Autofocus, future possibilities?
« Reply #36 on: April 07, 2016, 03:02:40 pm »

In their latest update (#2) release, they say:

Improvements have been made to increase accuracy in low light conditions, ensure focus of various low contrast materials in even light, and improved precision when using the XF Camera System handheld with behavior changes initiated from the systems several accelerometers.


.. which makes me wonder if they have implemented something like Hasselblad's TrueFocus under the hood. I mean, most likely with all the gyroscopes, it is possible that all the hardware capability is there. And if that is true, it's just a matter of using them in the software.


It's easy to test for. Focus and recompose on a whiteboard, and if it's sharp you're happy.

Edmund
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siddphoto

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Re: The P1 XF Autofocus, future possibilities?
« Reply #37 on: April 07, 2016, 04:37:42 pm »

I don't have an xf. Maybe somebody who had one can do a quick test :)
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digitalBerg

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Re: The P1 XF Autofocus, future possibilities?
« Reply #38 on: April 07, 2016, 04:39:44 pm »

It doesnt work


Best regards, Terje
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