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Author Topic: Arca Swiss Rm3d review  (Read 8914 times)
tho_mas
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« Reply #20 on: July 17, 2009, 02:26:31 PM »
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Quote from: David Grover / Hasselblad
Not sure I understand (sorry!).  Do you mean the number of AF points?
well, my bad English... sorry!
I mean the size/diameter of the (center) AF point.
« Last Edit: July 17, 2009, 02:41:03 PM by tho_mas » Logged
David Grover / Phase One
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« Reply #21 on: July 17, 2009, 03:19:15 PM »
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Quote from: tho_mas
well, my bad English... sorry!
I mean the size/diameter of the (center) AF point.

Page 88 of the H3D manual...

The point of focus is determined according to the vertical and horizontal areas (see illus 4.) within the central rectangular zone on the focusing screen.

See attachment!

[attachment=15498:Picture_2.png]
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David Grover
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tho_mas
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« Reply #22 on: July 17, 2009, 03:28:55 PM »
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Quote from: David Grover / Hasselblad
Page 88 of the H3D manual...
I have neither the H3D nor its manual, sorry  
Thank you!

So when you shoot a motif from a very steep angle (10 or so) you'll have massive frontfocus, right? And if you want to shoot through a grid or a fence they will be sharp but if you want the background sharp you have to focus manually.
I assume your solution works very well on flat, contrasty motifs... but those motifs are not always the case.
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David Grover / Phase One
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« Reply #23 on: July 17, 2009, 03:32:44 PM »
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Quote from: tho_mas
I have neither the H3D nor its manual, sorry  
Thank you!

So when you shoot a motif from a very steep angle (10 or so) you'll have massive frontfocus, right? And if you want to shoot through a grid or a fence they will be sharp but if you want the background sharp you have to focus manually.
I assume your solution works very well on flat, contrasty motifs... but those motifs are not always the case.

Actually not in my experience, no.  (Regarding front focus)

The actual AF target area is very small in the viewfinder so you can easily place focus accurately - is shooting through a grid or a fence as you mention.

Please try it (if you can!) on an H3D.

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David Grover
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tho_mas
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« Reply #24 on: July 17, 2009, 03:43:57 PM »
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Quote from: David Grover / Hasselblad
Actually not in my experience, no.  (Regarding front focus)
I mean this constellation, here with a ruler... but maybe at a steeper angle as the ruler in this image.
[attachment=15499:Hscreen.jpg]

How should the AF know that you don't want the outer circle of the AF field in focus?

Anyway... I think you agree that there are situations where you need manual focus. And here live view (or other tools) help a lot. So as good as your AF might be, it's not appropriate for all purposes.
« Last Edit: July 17, 2009, 03:44:29 PM by tho_mas » Logged
wolfnowl
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« Reply #25 on: July 17, 2009, 05:23:42 PM »
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Quote from: David Grover / Hasselblad
It has been present in the H3D for sometime except it is carried out in the factory.

If you look in the System Status menu, there is a unique Focus Calibration ID which is created in the factory during final assembly.  This ensures that whatever lens is used, AF is where the customer placed it.  No individual adjustment of lenses if required as I assume our manufacturing tolerances are tighter than Nikon and Canon.

We also compensate automatically for aperture dependent focus shift.

Therefore I do not think the D3x is the best Autofocus camera in the world.  

Best,


David

David:  No intention of being belligerent here, but (assuming for a moment) that Phase One and Hasselblad are creating somewhat equivalent products... in the video Michael states that he runs into trouble using autofocus with his Phase One/ Mamiya camera and the P65+ back, to the point that he uses the Mamiya 2X magnifier on the viewfinder and a microprism focusing screen to ensure accurate focus.   Are you saying that such focusing problems don't exist with the H3DII-50 for example?  I don't mean to put you on the spot, but I'm sure others would like to know as well.

Mike.

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David Grover / Phase One
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« Reply #26 on: July 17, 2009, 06:07:01 PM »
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Quote from: wolfnowl
David:  No intention of being belligerent here, but (assuming for a moment) that Phase One and Hasselblad are creating somewhat equivalent products... in the video Michael states that he runs into trouble using autofocus with his Phase One/ Mamiya camera and the P65+ back, to the point that he uses the Mamiya 2X magnifier on the viewfinder and a microprism focusing screen to ensure accurate focus.   Are you saying that such focusing problems don't exist with the H3DII-50 for example?  I don't mean to put you on the spot, but I'm sure others would like to know as well.

Mike.

Well, it is very nice of Michael to say he has autofocussing issues with his P65+.   ;-)

I do agree though that focussing accurately manually can be a challenge so I assume a 2x magnifier would help.  I did not sit through the whole video so I am not sure in which context Michael's comments were made.

Anyway, yes please do put me on the spot!

We recognised a few years back that as the resolution of sensors began to increase, the precision of the system was much more important.  Not just the focussing but also things like fitment of the digital back to camera had to be tighter, flatter for example with a lower tolerances of error.  Even minor things such as the flatness of the IR filter glass can cause issues!

Film and smaller sensors (think 16MP) were very good as masking inefficiencies in manufacturing, larger (think 50 / 60 MP) are very unforgiving!

With the 16MP we had virtually no complaints of focus errors but as we began to introduce 22MP and more so 39MP we saw the need for some changes to protect for the future.  

The 'mechanical' method was solved with the Imacon backs by supplying shims to adjust back position to film / sensor plane.  The smallest shim is only 50microns and this WILL make a positive difference to focussing accuracy.  So you can see how important precision really is.

The beauty of controlling all parts of the camera system is that as well as tightening up manufacturing tolerances we also have a large amount of data from all these parts which again can add more degrees of accuracy.

So as I mentioned above every camera is custom calibrated in final production with regards to focus precision.  Then further accuracy is achieved by correcting aperture dependent focus shift.

In summary, as we manufacture all parts and have all the necessary data AND the ability to communicate all useful data (The camera parts are 'networked on a databus) we can make incremental steps in increasing precision.

So after my long winded reply I would absolutely say I don't believe there are auto focussing accuracies with the H3D.  It would be nice to have multi AF points but we do what we can!

....and for those reasons I would not say that Phase One and Hasselblad are creating somewhat equivalent products.

Best,


David
« Last Edit: July 17, 2009, 06:09:47 PM by David Grover / Hasselblad » Logged

David Grover
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tho_mas
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« Reply #27 on: July 17, 2009, 06:21:36 PM »
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David, so a dead on AF but no solution for manual focussing?
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BernardLanguillier
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« Reply #28 on: July 17, 2009, 07:49:31 PM »
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Quote from: David Grover / Hasselblad
Bernard, we are not being belligerent in not offering this feature.  It is simply not available (yet) at sensor level.  Of course, if it were possible we would use it!

Just because a medium format system doesn't have live view does not then render it impossible to focus.  That is a rather naive attitude.

David,

Sure, using the back on a body offering AF capability like the h3d helps if it accurately calibrated, but the focus () of the current post was about using a back on a LF like camera.

Cheers,
Bernard

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BobDavid
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« Reply #29 on: July 17, 2009, 09:20:38 PM »
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I migrated from a Mamiya AFD to a Hassey H2F primarily for the improvement in AF. The difference is dramatic, especially in low light situations. Of course AF on the H platform isn't as fast as it is on Canons and Nikons; it's stupid to compare apples to oranges. The H platform may have its flaws, but all things considered, it's a great camera.
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David Grover / Phase One
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« Reply #30 on: July 18, 2009, 12:47:26 AM »
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Quote from: tho_mas
David, so a dead on AF but no solution for manual focussing?

If using the H3D focus confirmation in the form of information in the viewfinder is still active.

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David Grover
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fmo
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« Reply #31 on: July 18, 2009, 03:52:21 AM »
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I am quite new to this forum, but so tired about this Hasselblad discussions in almost every thread I read. Could someone consider to give these issues a dedicated subforum so that all the other users can find relevant information on the topics they originally wanted to learn about?
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tho_mas
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« Reply #32 on: July 18, 2009, 07:32:47 AM »
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Quote from: David Grover / Hasselblad
If using the H3D focus confirmation in the form of information in the viewfinder is still active.
see also:
Quote from: kers
If the D3x says it is sharp - and the Dot  appears - I can make within the room of the dot six pictures - only one is truly sharp. If i use auto focus at near infinity with lots of small detail the auto focus is near but not accurate...


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Dustbak
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« Reply #33 on: July 18, 2009, 10:09:12 AM »
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Quote from: fmo
I am quite new to this forum, but so tired about this Hasselblad discussions in almost every thread I read. Could someone consider to give these issues a dedicated subforum so that all the other users can find relevant information on the topics they originally wanted to learn about?

Maybe you should get used to hearing Hasselblad or Phase in virtually every thread since they are basically the only 2 remaining 'Large Sensor capture device' (I believe we are not allowed to call them MFDB's anymore) manufacturers
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vandevanterSH
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« Reply #34 on: July 18, 2009, 10:11:20 AM »
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Is the "Live Video" function in Phocus useful for critical focusing?

Steve
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David Grover / Phase One
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« Reply #35 on: July 18, 2009, 12:14:27 PM »
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Quote from: vandevanterSH
Is the "Live Video" function in Phocus useful for critical focusing?

Steve

Very much so, especially as you can control the focussing remotely as well without having to touch the camera.

It takes a bit of care setting up, as Live Video works best in lower light so you can open the aperture fully to make focussing easier.

Entering live video automatically raises the mirror and then from Phocus you can control the aperture for optimum results.  When leaving live video the aperture is reset to the capture value.

Hope that helps!

D

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David Grover
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schaubild
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« Reply #36 on: July 18, 2009, 11:49:54 PM »
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Quote from: David Grover / Hasselblad
Very much so, especially as you can control the focussing remotely as well without having to touch the camera.

It takes a bit of care setting up, as Live Video works best in lower light so you can open the aperture fully to make focussing easier.

Entering live video automatically raises the mirror and then from Phocus you can control the aperture for optimum results.  When leaving live video the aperture is reset to the capture value.

Hope that helps!

D


Hi David.

And when are you going to make that available on the H3D-50? The camera is sold since last year....
(could it be that you missed this question in Dick's and my repeated posts?)

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jing q
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« Reply #37 on: July 19, 2009, 12:35:49 AM »
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Live view in Phocus is useful especially being able to adjust autofocus in increments in Phocus itself for the H3D

However, Live View is also very light sensitive and does not work properly in daylight (slightly cloudy day)
So just take note that if you're going to use it on a technical camera for landscapes you need to put on some strong ND filter
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eronald
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« Reply #38 on: July 19, 2009, 05:07:32 PM »
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My experience with the D3x is that AF is very good, but the focus adjustment varies with the focus distance and over time.

At F:4 I consistently get nice images with whatever lens I use or subject. Anything below that and front or backfocus becomes perceptible from time to time; it's not really the fault of the camera, apparently, just inconsistencies of the measurement method.  On a ruler test I'll get a focus difference of less than 1cm at 1 meter; not a lot but enough to throw off an eye at F1.4. On a distant object again there is a slight focus issue, but this time it'll go the other way ... In the end the only thing one can do is grin and accept that 2009 technology has limits.

Edmund
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teddillard
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« Reply #39 on: July 21, 2009, 06:47:03 AM »
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Thanks for the review, and sorry to take this off the focus issues, but one little question...  what's the deal on this camera actually shipping?  

...guess I'm getting jaded, but is this just really nice, expensive vaporware?
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Ted Dillard
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