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Fun with MF images - ARCHIVED - FOR VIEWING ONLY

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darr

Well-known member
Fantastic view Wayne! I LOVE my Max. I just ordered my second Alpa lens after my trial run.

Kind regards,
Darr
 

Jack

Sr. Administrator
Staff member
First field trip with my new Alpa setup. Nothing spectacular, but a couple of nice things. I enjoyed the experience and challenge of using the system, and was really pleased with the sharpness of the files even into the corners.


Alpa 12max, Schneider 47mm XL, PhaseOne p65+
Absolutely gorgeous Wayne!
 

Jack

Sr. Administrator
Staff member
Yeah, I want one too. My dilemma is I also want a sliding back. ALpa says there is no way you can get a sliding back to hold enough precision for high-res digital, but Arca disagrees. In my ideal world, I'd own the Arca RM3D with the Arca Rotaslide, but the Alpa is close second...
 

cmb_

Subscriber & Workshop Member
My dilemma is I also want a sliding back. ALpa says there is no way you can get a sliding back to hold enough precision for high-res digital, but Arca disagrees.
Alpa made a prototype, the Alpa 12 SST - 25mm rise & fall, 25mm shift left & right with a sliding back. They must have seen something they did not like. I wonder if anyone has tried one. Apparently, they made five of them. Would be nice to try one.
 

Leigh

New member
...I also want a sliding back. ALpa says there is no way you can get a sliding back to hold enough precision for high-res digital...
Simple mechanical systems can easily hold position within 1/10,000 of an inch if you want to spend the money. I've designed a number of them.

It's possible that some characteristic of their system prevents them from achieving that kind of precision, but it's not a universal problem.

- Leigh
 

Wayne Fox

Workshop Member
Yeah, I want one too. My dilemma is I also want a sliding back. ALpa says there is no way you can get a sliding back to hold enough precision for high-res digital, but Arca disagrees. In my ideal world, I'd own the Arca RM3D with the Arca Rotaslide, but the Alpa is close second...
It would be nice. I just did the infinity calibration setup with the Alpa, and was actually surprised at how much difference adding .05mm distance was so maybe there's something to what Alpa claims.

However, it certainly seems possible that a sliding back can hold precision. Maybe it can't be tuned into "infinity" as precisely, but if you are focusing with loupe on the ground glass, not sure the infinity thing really applies. I haven't shot the camera yet with infinity set as the focus.

I find myself not putting the ground glass on too often. Just using the viewfinder then taking test shots to lock in composition. Probably would be different if I could just slide the ground glass over.
 

thomas

New member
Yeah, I want one too. My dilemma is I also want a sliding back. ALpa says there is no way you can get a sliding back to hold enough precision for high-res digital, but Arca disagrees. In my ideal world, I'd own the Arca RM3D with the Arca Rotaslide, but the Alpa is close second...
Jack - the arTec is YOUR camera (actually mine, too :confused: ). Integrated sliding back (therefore no issues with alignement), shift and tilt&swing at all focal lengths...
 

thomas

New member
However, it certainly seems possible that a sliding back can hold precision. Maybe it can't be tuned into "infinity" as precisely, but if you are focusing with loupe on the ground glass, not sure the infinity thing really applies.
it's impossible to focus a wide angle lens accurately enough for infintiy on the GG...
That's the nice thing about helical focus mounts - infinity is safe ground (assumed that the lenses/the back are calibrated accurately to infinity).
 

Jack

Sr. Administrator
Staff member
Jack - the arTec is YOUR camera (actually mine, too :confused: ). Integrated sliding back (therefore no issues with alignement), shift and tilt&swing at all focal lengths...
Just having the sliding back integrated with the camera body does not insure perfect alignment. The issue is disparity between the exact GG plane and the exact sensor plane.
 

thomas

New member
Just having the sliding back integrated with the camera body does not insure perfect alignment. The issue is disparity between the exact GG plane and the exact sensor plane.
Sinar knows how to make cameras... I think precision is not a issue here. And even if, I think it's not a big deal to adjust the GG to the exact same distance as the sensor of your digback.
It's more important that the lenses resp. the sensor spacing is calibrated acurrately for infinity. But that is really easy to do with helical focus mount lenses. My lenses focussed beyond infinity ex factory. After (self made) adjustment they are not only tack sharp at infinity... also my groundglass happens to be aligned accurately. At least accurately enough to focus on the GG and get consistent results. The fastest digital LF lenses are f4 anyway... so there is a bit of headroom.
 

Wayne Fox

Workshop Member
Just having the sliding back integrated with the camera body does not insure perfect alignment. The issue is disparity between the exact GG plane and the exact sensor plane.
Imagine how different things would be if they can ever implement live view on an MFDB back with a decent LCD display and 20x zoom for focusing. May never even put a ground glass on the camera.
 

Jack

Sr. Administrator
Staff member
, I think it's not a big deal to adjust the GG to the exact same distance as the sensor of your digback.
It's not only the same distance that is critical, but also having both be perfectly perpendicular to the lens centerline!

It's more important that the lenses resp. the sensor spacing is calibrated acurrately for infinity.
No offense, but this is totally IRRELEVANT if you are using the calibrated GG above to focus, even if your lens happens to over focus infinity!!! However, *IF* you are zone focusing, then yes, calibration is important.

Finally note that many lenses over focus infinity at normal temperatures to accommodate thermal expansion of the lens barrel as temps rise...
 

Jack

Sr. Administrator
Staff member
Imagine how different things would be if they can ever implement live view on an MFDB back with a decent LCD display and 20x zoom for focusing. May never even put a ground glass on the camera.
For sure! FWIW, the Betterlight scanning back has an electronic live-view histogram focus -- this was so accurate you could actually choose which color CHANNEL you wanted in perfect focus! You could see each channel bar in the histogram maximize contrast as you racked focus. It also proved that most APO badged lenses were not truly APO!
 

thomas

New member
It's not only the same distance that is critical, but also having both be perfectly perpendicular to the lens centerline!
this applies to all cameras; not sure why it would be more critical with tech cameras. All the manufacturers work within tolerances of 1/100 mm. With Tilt/Swing things may become more complicated depending on how it is bulit. The arTec has a safe zero lock and as far I am concerned I'd say it works reliable.
Besides I don't think a groundglass is really accurate enough working with wide angles and focussing near infinity. Up from a certain distance (depending on the focal length) everything appears to be in focus. So at wide distances you won't focus on the GG. It's a bit different with longer lenses... IMO... as the magnification factor makes focussing a bit easier.

No offense, but this is totally IRRELEVANT if you are using the calibrated GG above to focus, even if your lens happens to over focus infinity!!!
with helical focus mount when the lens does not quite reach focus at infinitiy (i.e. it focusses slightly closer than infinity) you'll have a problem that is not exactly "irrelevent". In this case the image may very well appear to be sharp on the GG but it won't in the final capture. The other way around: the slightest focussing beyond infinity will render the capture soft... even a lot of DOF won't help. For focussing at closer distances you are right... any infinity calibration of the lens isn't necessary (like on a view camera) but an acurrate alignment of the GG is mandatory.
 

PeterA

Well-known member
Of course gentlemen - lets not forget t make sure that teh chip in teh actual back is aligned perfectly..hmmm
 

thomas

New member
Of course gentlemen - lets not forget t make sure that teh chip in teh actual back is aligned perfectly..hmmm
of course a lot of horrible things can happen all the time...
A misaligned sensor is not a particularity of tech cameras; it would also show up on the 645 camera (unless it's the camera interface of the tech camera that is off).
Tilt, Swing or Rotation of the sensor should be serviced, of course...
 
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