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Thread: registration of MFDB problem

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    registration of MFDB problem

    Alpa offers different adapter for leaf and phase one for mamiya 645 :
    "ALPA adjustable back adapter MA645A (Phase One)
    Adjustable with shim kit, max. +/- 3/10 mm, for digital backs only. ALPA back adapters are interchangeable and reversible: horizontal/vertical.
    Please indicate wether you are using a Leaf or Phase One back as due to their different measures two ALPA adapters exist."


    The new kapture group sliding back :
    "This Sliding Back seamlessly integrates your Arca Swiss Rm3d to our most compact sliding back. A new feature permits the discriminating photographer to fine tune the plane of focus (if needed) precisely to a specific digital back assuring accurate lens focus at infinity."

    I've also heard that the registration from back to back (same model) can vary.

    Considering the new 80MP sensor, and top of the range wide angle lenses... i can imagine that tolerance value decrease again...

    A friend of mine just bought a brand new P45+, and faces the problem... the answer from his dealer isn't clear for now... considering the prices of MFDB, i can't understand why all MFDB are not perfectly tune !


    Anyone over here is facing such a problem ? is it typical with M645 mount ?

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    Re: registration of MFDB problem

    Physics says there is always variation in any machining. The pertinent question is always what tolerance the variation falls within, and what the procedures/provisions are when any particular unit is out of that acceptable tolerance.

    Having worked with many many photographers it is my feeling that the variation from back-to-back is more than you would assume if you had not looked into it, but less than reported sporadically online by the likes of, for instance Joseph Holmes (a very intelligent and diligent) perhaps because in any random-variation study outliers tend to unduly influence the perception of the norm.

    The issue only arrises in the first place because backs are capable of producing such a high amount of detail that the tolerances needed to achieve that super high level of detail. In a lower resolution system (even something like a P25+) the tolerances can be much less strict. It kind of reminds me tangentially of the old saying "the price of freedom is eternal vigilance". Well the price of very high-end photographic capture is vigilance (at least if achieving the best your system can perform is an important goal to you). You have to learn new rules about hand-hold-ability, tripod best-practices, new support gear, diffraction, post-processing, lens correction, and also deal with the nuances and quirks of each system (every system has a few).

    Anyway the point is your friend should work with his dealer to make sure he is happy with what he receives from them. Whether that means a replacement back, an adjustment at the factory, having the dealer help calibrate his technical camera body (or lenses depending on the system) to ensure proper registration in the system, or some other solution. In fact one could say a dealer is there for precisely for this reason - to help with the unforeseen, and to work with the photographer to make sure they get the most out of their system.

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    Re: registration of MFDB problem

    Having personally seen the difference that shimming makes with my Alpa for critical infinity resolution, I'm surprised that Phase One/Mamiya don't have a similar capability for their MF camera body to match a particular back accurately. That said, if you're shooting anything less than infinity on a non tech then the overall accuracy could be masked by the lens focusing (AF vs MF accuracy) plus lens tuning/variability too.

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    Re: registration of MFDB problem

    on the 45+ datasheet we can reed :
    Wide angle & technical cameras
    Possible via the Phase One FlexAdaptor & third party adaptors. Arca Swiss, Cambo, Horseman, Linhoft, Toyo, Sinar, Plaubel, Horseman.

    same on the P25+, and leaf Backs... so they should be calibrated the same way...


    Retro focus lenses found on reflex camera allowed a lees strict registration, but they sell the back for technical camera as well !

    I can understand variation in machining, so when you are making a digital back you have to deal with it, with an internal shimming system... otherwise you are selling a so-so product... that cost much more than a D3X...

    My friend have two backs, one leaf on phase one and one camera... he can't use the same technical camera... very confusing !

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    Re: registration of MFDB problem

    For us, this was one of the factors in choosing the RM3D, since it can be very accurately adjusted without using shims.

    You can get very fine variability in registration not only from back to back, but also from lens to lens. With a shim-based adjustment, you may have to adjust the shims for each lens (and each back), which requires removing the digital back for each lens and often not very practical in the field.

    With the in-camera helicoid approach of the RM3D, you simply dial in the appropriate "shim distance" needed for each lens, which we found to be much simpler and faster, and without removing the digital back. Furthermore, the RM3D helicoid can be adjusted continuously with a precision of 0.007mm (less than 0.0003 inches), which is much finer than any shim.

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    Re: registration of MFDB problem

    is the point here to ensure that if the focus on the lens is set at infinity, the back will be in exact focus if properly shimmed?
    Surely every intermediate focus point will require some visual judgment for focus and this is independent of any need for shimming. So if you have to judge for all points short of infinity, is also judging at infinity such a pain?

    I suppose the accuracy of the RM3D helicoid could allow one to use calibration marks on the barrel for distance, but then you are subject to the inaccuracy of measuring subject distance for each composition.

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    Re: registration of MFDB problem

    Quote Originally Posted by jlm View Post
    I suppose the accuracy of the RM3D helicoid could allow one to use calibration marks on the barrel for distance, but then you are subject to the inaccuracy of measuring subject distance for each composition.
    Leica Distometer has a meter-to-subject accuracy of something around 1mm.

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    Re: registration of MFDB problem

    Quote Originally Posted by David Klepacki View Post
    For us, this was one of the factors in choosing the RM3D, since it can be very accurately adjusted without using shims.

    You can get very fine variability in registration not only from back to back, but also from lens to lens. With a shim-based adjustment, you may have to adjust the shims for each lens (and each back), which requires removing the digital back for each lens and often not very practical in the field.

    With the in-camera helicoid approach of the RM3D, you simply dial in the appropriate "shim distance" needed for each lens, which we found to be much simpler and faster, and without removing the digital back. Furthermore, the RM3D helicoid can be adjusted continuously with a precision of 0.007mm (less than 0.0003 inches), which is much finer than any shim.
    Absolutely. This was one of the most impressive parts of the RM3D (now RM3Di) to us. In addition if you purchase the eModule you can dial in the needed calibration factor into the eModule so that the current-focus-distance is correct, including the indications of depth of field for hyperfocal distance focusing.


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    Re: registration of MFDB problem

    i use laser devices quite a bit, both distance measuring and leveling. They are very difficult, if not impossible to use in bright outdoor light, made much worse at distances over 40'. is the leica distomeasure different?
    does it send out a beam and focus on the dot?

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    Re: registration of MFDB problem

    Hey Jim, the Leica is the same - great for short distances and dim light, but useless for longer distances and/or daylight. I was really disappointed, especially since it cost so much and seems to be a great product otherwise - at least a saved a good bit of cash buying refurb, thanks to Terry here. Mine sits in the bag most of the time.

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    Re: registration of MFDB problem

    I guess it depends on which Leica distance meter you are using. We use the Leica DISTO D8 model, and it works great for us in sunlight and/or at longer distances. The DISTO D5 and D8 models are the only ones that have the Digital Pointfinder feature with 4x zoom and color lcd display. Of course, if you do not use a laser meter that has this feature, then I can see that it would indeed be more difficult to measure distance under such conditions.

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    Re: registration of MFDB problem

    I use the D5 and it does not work in sunlight nor at long distances, even at 4x - very disappointing and I don't recommend anyone spend the cash on this guy. $500 was hard enough to swallow for a simple laser.

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    Re: registration of MFDB problem

    Quote Originally Posted by archivue View Post
    Anyone over here is facing such a problem?
    all in all I have been using 5 different backs on my cameras and they were all a bit different.
    "A bit different" refers to being very, very critical about focus tolerances.

    Actually I am finding it quite trouble-free to shim the screens in my Contax (it requires appropriate shims, of course).
    On my Cambo WRS I am simply adjusting the lenses to focus very accurately for infinity. My feeling is the adjustment of the lenses is so little (in my case) that it absolutley does not affect focusing accuracy on the groundglass... at least I have no issues focusing near and mid distances on the GG of my WRS with a 6x loupe (not even if I focus a certain number on a ruler or so... so I'd say it works very well).
    Bottom line: my kit(s) required some careful fine adjustments here and there... but the outcome is really usable.
    Without question I am really appreciating Alpa's and in particular Arca's approach ... but by now I am not missing the respective features on my WRS (for my works).

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    Re: registration of MFDB problem

    Quote Originally Posted by Joseph Woodland View Post
    Hey Jim, the Leica is the same - great for short distances and dim light, but useless for longer distances and/or daylight. I was really disappointed, especially since it cost so much and seems to be a great product otherwise - at least a saved a good bit of cash buying refurb, thanks to Terry here. Mine sits in the bag most of the time.
    Are you using the LCD screen to visually see the area the laser is pointing towards? I haven't had an issue that way.

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    Re: registration of MFDB problem

    Quote Originally Posted by dougpetersonci View Post
    Leica Distometer has a meter-to-subject accuracy of something around 1mm.
    I'm curious to know how this is used in practice, obviously anything handheld is not going to achieve this kind of accuracy. Is the Distometer mounted on the camera? And how do you align it with the sensor plane? I suppose a fixed offset distance is ok, but how do you find that?

    Cheers, -Peter

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    Re: registration of MFDB problem

    Peter,

    You do not need to have an absolute distance measurement, as long as you use the same reference point each time. In other words, once you calibrate the lenses with the laser distance meter measurements, then every succeeding laser distance measurement taken from the same location relative to the sensor will result in high precision focus, even if it is not the true absolute distance (i.e., the systematic error cancels out).

    Of course, hand-holding the laser meter will not work well at all. You must always mount the laser meter in the same fixed position (on the camera body or tripod).

    David

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    Re: registration of MFDB problem

    Terry - yes, I've been using the screen when I can't see the red dot - and when I get the dreaded "255" error at 1x then I switch to 4x - sometimes it will register "256". It works great for short distances, and in dim light, but just not for anything over about 50-100 feet in sunshine.

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    Re: registration of MFDB problem

    Quote Originally Posted by David Klepacki View Post
    Peter,

    You do not need to have an absolute distance measurement, as long as you use the same reference point each time. In other words, once you calibrate the lenses with the laser distance meter measurements, then every succeeding laser distance measurement taken from the same location relative to the sensor will result in high precision focus, even if it is not the true absolute distance (i.e., the systematic error cancels out).

    Of course, hand-holding the laser meter will not work well at all. You must always mount the laser meter in the same fixed position (on the camera body or tripod).
    David
    Thanks David, this is what I figured, thank you for explaining.

    Cheers, -Peter

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    Re: registration of MFDB problem

    Quote Originally Posted by Joseph Woodland View Post
    Terry - yes, I've been using the screen when I can't see the red dot - and when I get the dreaded "255" error at 1x then I switch to 4x - sometimes it will register "256". It works great for short distances, and in dim light, but just not for anything over about 50-100 feet in sunshine.
    I havent had an issue yet because with the Arca and my 35mm lens if I focus at 50 feet I'm at 1.1 on the focus ring. At 60 ft I'm at .9, 70ft at .8, and so on. So, with that lens I haven't gotten too hyper. I might feel differently when using my 90mm lens that I'm waiting for. I will be using the Arca and Disto a lot next week when we head to Yosemite and the eastern Sierra.

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    Re: registration of MFDB problem

    Quote Originally Posted by David Klepacki View Post
    For us, this was one of the factors in choosing the RM3D, since it can be very accurately adjusted without using shims.

    You can get very fine variability in registration not only from back to back, but also from lens to lens. With a shim-based adjustment, you may have to adjust the shims for each lens (and each back), which requires removing the digital back for each lens and often not very practical in the field.

    With the in-camera helicoid approach of the RM3D, you simply dial in the appropriate "shim distance" needed for each lens, which we found to be much simpler and faster, and without removing the digital back. Furthermore, the RM3D helicoid can be adjusted continuously with a precision of 0.007mm (less than 0.0003 inches), which is much finer than any shim.
    HUH? if you don't know diddly about alpa, why do u insist on making comparisons between the alpa and rm3d and present them as fact? the fact is: once you shim your digital back, you never have to shim it again for each lens! shim once for your digital back and that's it! YIKES! it's hard to take anything you say seriously when you post things like this. i know you like to say a bunch of positive things about the rm3d - that's ok, if u want to be the rm3d spin doctor - but by trying to say negative things about the alpa that are patently not true doesn't strengthen your case, in fact it makes it weaker. and another point: the shim kit that alpa provide allows one to make extremely fine adjustments. AND the idea that you need only shim ONCE is huge. it's nice knowing that one's digital back is optimally aligned with the camera - and one never needs to address it again unless one buys a new digital back.

    richard
    Last edited by photohagen; 14th October 2010 at 19:51.

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    Re: registration of MFDB problem

    Quote Originally Posted by photohagen View Post
    HUH? if you don't know diddly about alpa, why do u insist on making comparisons between the alpa and rm3d and present them as fact? the fact is: once you shim your digital back, you never have to shim it again for each lens! shim once for your digital back and that's it! YIKES! it's hard to take anything you say seriously when you post things like this. i know you like to say a bunch of positive things about the rm3d - that's ok, if u want to be the rm3d spin doctor - but by trying to say negative things about the alpa that are patently not true doesn't strengthen your case, in fact it makes it weaker. and another point: the shim kit that alpa provide allows one to make extremely fine adjustments. AND the idea that you need only shim ONCE is huge. it's nice knowing that one's digital back is optimally aligned with the camera - and one never needs to address it again unless one buys a new digital back.

    richard

    richard
    richard,

    You are obviously unaware or delusional about the variation among lenses. There can indeed be variation in lens accuracy, which you will only find out if you test them yourself. If you don't believe me, just ask Joe Holmes who was able to find only two "good" lenses among eleven from Schneider and Rodenstock (and mostly using Alpa cameras). You can read his review here: http://www.josephholmes.com/news-med...precision.html

    All I am saying is that I find it easier to manipulate any needed fine adjustment, whether it be for a back or a lens, by the Arca-Swiss method of adjusting the body helicoid setting, instead of adjusting shims. You are simply "assuming" that you will never need to do this, but Joe Holmes study indicates otherwise. I always test the lenses I will use and indeed have found need for fine adjustments, especially in cases where I find slight focus shift from one f-stop to another on the same lens.

    I do not mean to denigrate the Alpa cameras. They are obviously fine photographic instruments and are serving the photographic community very well. I am merely pointing out my own preferences, so that others may better evaluate their own specific needs and preferences, which may or may not align with my own. You are free to disagree with me and spend your own money any way you wish. I have nothing to gain or lose either way.

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    Re: registration of MFDB problem

    Quote Originally Posted by David Klepacki View Post
    richard,

    You are obviously unaware or delusional about the variation among lenses. There can indeed be variation in lens accuracy, which you will only find out if you test them yourself. If you don't believe me, just ask Joe Holmes who was able to find only two "good" lenses among eleven from Schneider and Rodenstock (and mostly using Alpa cameras). You can read his review here: http://www.josephholmes.com/news-med...precision.html

    All I am saying is that I find it easier to manipulate any needed fine adjustment, whether it be for a back or a lens, by the Arca-Swiss method of adjusting the body helicoid setting, instead of adjusting shims. You are simply "assuming" that you will never need to do this, but Joe Holmes study indicates otherwise. I always test the lenses I will use and indeed have found need for fine adjustments, especially in cases where I find slight focus shift from one f-stop to another on the same lens.

    I do not mean to denigrate the Alpa cameras. They are obviously fine photographic instruments and are serving the photographic community very well. I am merely pointing out my own preferences, so that others may better evaluate their own specific needs and preferences, which may or may not align with my own. You are free to disagree with me and spend your own money any way you wish. I have nothing to gain or lose either way.

    as far as alpa shimming is concerned: shimming is for correction of the digital back. period. alpa shimming is not meant to correct for any lens problems. you said in your original post that one would have to shim every time a different lens was used. this is a ridiculous notion. once your digital back is shimmed it is optimally in registration with your digital back sensor. an optimally shimmed digital back will make more apparent any abnormalities with your lenses. sometimes when lens elements are not seated perfectly - even being off by a fraction of a mm - you can see it. in a case like this, it is advisable to send the lens back to the manufacturer for realignment. the point is: in the alpa world, shimming is for the digital back NOT the lens.

    richard

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    Re: registration of MFDB problem

    to what end are you shimming?

    seems to me the standard should be that the DB is shimmed to match the ground glass adapter (or gg adapter shimmed to match the DB), period.

    does anyone want to actually rely on lens barrel distance markings, even for infinity?

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    Re: registration of MFDB problem

    Quote Originally Posted by photohagen View Post
    as far as alpa shimming is concerned: shimming is for correction of the digital back. period. alpa shimming is not meant to correct for any lens problems. you said in your original post that one would have to shim every time a different lens was used. this is a ridiculous notion. once your digital back is shimmed it is optimally in registration with your digital back sensor. an optimally shimmed digital back will make more apparent any abnormalities with your lenses. sometimes when lens elements are not seated perfectly - even being off by a fraction of a mm - you can see it. in a case like this, it is advisable to send the lens back to the manufacturer for realignment. the point is: in the alpa world, shimming is for the digital back NOT the lens.

    richard
    In a world of absolutely perfect lenses you would be right, but such is not the case. Indeed, I agree that shimming is not meant to correct for any lens issues. This is precisely the limitation of shimming that I am pointing out.

    With the Arca-Swiss helicoid, you can not only "shim" your digital back for proper registration, but also you can use it to apply any fine adjustments that may be needed to obtain more precise focusing. Even if the lens registration is absolutely perfect, a lens typically has some amount of spherical aberration that causes slight focus shift within its f-stop range. These types of very fine focusing adjustments can be overcome easily and systematically with the Arca-Swiss helicoid. I find their helicoid mechanism to be more versatile in addressing any need for fine focusing adjustment, precisely because it is has this additional capability over shims.

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    Re: registration of MFDB problem

    Quote Originally Posted by David Klepacki View Post
    In a world of absolutely perfect lenses you would be right, but such is not the case. Indeed, I agree that shimming is not meant to correct for any lens issues. This is precisely the limitation of shimming that I am pointing out.

    With the Arca-Swiss helicoid, you can not only "shim" your digital back for proper registration, but also you can use it to apply any fine adjustments that may be needed to obtain more precise focusing. Even if the lens registration is absolutely perfect, a lens typically has some amount of spherical aberration that causes slight focus shift within its f-stop range. These types of very fine focusing adjustments can be overcome easily and systematically with the Arca-Swiss helicoid. I find their helicoid mechanism to be more versatile in addressing any need for fine focusing adjustment, precisely because it is has this additional capability over shims.
    david, i took issue with you when you made a couple alpa references that were totally off the mark. i myself own a few alpas and feel you can't beat the quality and workmanship. i know very little about the arc-swiss helicoid and therefore i can't comment about it. that said, i do find it very unusual that it can simultaneously correct digital back and lens registration issues. hmmmmm, this is something i will have to confirm for myself.

    richard

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    Re: registration of MFDB problem

    Quote Originally Posted by photohagen View Post
    david, i took issue with you when you made a couple alpa references that were totally off the mark. i myself own a few alpas and feel you can't beat the quality and workmanship. i know very little about the arc-swiss helicoid and therefore i can't comment about it. that said, i do find it very unusual that it can simultaneously correct digital back and lens registration issues. hmmmmm, this is something i will have to confirm for myself.

    richard
    For the record, I never mentioned "Alpa" in my original posting here. I only commented about my preference of the Arca-Swiss helicoid in relation to shimming in general. I was drawing upon my own experience with the Sinar system that I had recently owned which uses shims. Unfortunately, most people think of Alpa whenever the topic of shimming comes up, but Alpa is not the only company that offers a shimming solution.

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