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Author Topic: Alpa Tilt with wide lenses  (Read 16851 times)

dchew

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Re: Alpa Tilt with wide lenses
« Reply #60 on: September 29, 2016, 09:20:52 pm »

Yes Torger's is more involved and so takes a bit more to learn, but it is very customizable (is that a word?) and well-designed.

Thanks Dave, just purchased it too. I gave it a quick look and it sounds neat, but I'll have to read the tutorial to understand what it does.
 
Cheers,
Bernard
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Theodoros

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Re: Alpa Tilt with wide lenses
« Reply #61 on: September 29, 2016, 09:40:32 pm »

I feel sad for the technical cameras designed by you...

Why? ...because you get distortions (that you aren't aware of) in yours?  Let me state it to you once more, ...if you loose focus when you tilt, your system geometry suffers, ...and there is no knowledgeable in this world to tell you otherwise!  ;)
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dchew

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Re: Alpa Tilt with wide lenses
« Reply #62 on: September 29, 2016, 10:44:20 pm »

I'm going to try one more time Theo,
Why? ...because you get distortions (that you aren't aware of) in yours?  Let me state it to you once more, ...if you loose focus when you tilt, your system geometry suffers, ...and there is no knowledgeable in this world to tell you otherwise!  ;)

No one disagrees with this statement. All helical technical cameras have slight refocus requirements because the tilt mechanism is behind, not below, the entrance pupil.

It seems that the Alpa acts like a view camera that has the  tilt bellow shift, while Arca (correctly) the opposite...

THIS is the statement we all disagree with. You are incorrect here Theo. You have been incorrect about the hinge point on the Alpa tilt adapter, incorrect about how the Alpa helical focus mechanism works, and you are incorrect about this too. There is no quality or distortion difference between the Alpa and Arca designs. In fact, there is a slight but very probably unnoticeable advantage to the Alpa design because the hinge point is either 17 or 34mm closer to the entrance pupil vs Arca, depending on which tilt adapter is being used.

NONE of the technical cameras from Arca, Alpa or Cambo have tilt below the shift.

Dave
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Wayne Fox

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Re: Alpa Tilt with wide lenses
« Reply #63 on: September 29, 2016, 10:46:32 pm »

Kind of a debate regarding technical accuracy vs practical usage.

Seems the Alpa and Arca are pretty much the same in where the "tilt" occurs, both effectively tilting right behind the focusing helicoid?  As far as distortion, I would assume this means there isn't a technical camera that avoid this, especially when it comes to a little longer glass (I tilt with my 70 and 90 frequently when doing pano stitches), since the entrance pupil/nodal point is considerably in front of the tilt plane.  This means that whatever distortion might be there, you can't avoid it unless you move to a true bellows focusing system where the tilt is at the lens.

I've never seen any real distortion, so while technically it might be there it seems insignificant to the end goal, and may only be able to exhibit itself with testing and special targets.  This may apply less to other types of photography where manmade geometrical objects are in play.

 I don't use an app to manage my tilt.  I simply use the "focus far/tilt near" method, which to Yunni's point is extremely easy to do with a CMOS back, and to be honest I was pretty good at it with LiveView on my CCD back. 

Also I"m not sure what is meant by the term "hold focus".  Tilting definitely changes the focus on my Arca. It takes a few iterations of "focus far/tilt near" to dial it in, because as soon as you tilt, infinity loses focus and when finished the helicoid isn't anywhere near the normal infinity mark or near the close focus point of the near object in the shot.

I have had both systems. The Alpa can be much smaller, but having the tilt in the body is nice.  Unlike Dave I like the helicoid system of the arca  but admit I had the Alpa system before their new focusing rings. I haven't compared prices on glass, but logic tells me one focusing helicoid on the body should make the lenses assemblies a little less expensive than having to put one in each lens.  My go to lens is the 40mm rodie but have used tilt on the 28mm rodie on occasion.  Again with a cmos back and LiveView either focusing system is fantastic, and the Arca may be a little more cumbersome because of it's extremely fine pitch.

Finally I would agree that tilt is a valuable tool for some images with one of these cameras especially if the style of your work allows the use of tilt.  Obviously as soon as you put tall elements in the foreground you have to resort to focus stacking instead, or you get the top of those elements out of focus. 

From my perspective, shifting is far more valuable than tilting, it's actually pretty rare I don't shift a landscape image anymore, as I tend to keep my camera level and then use shift for the composition.  Only when I hit the edge of the image circle will I then begin to tilt the camera to finalize composition. 

I also do quite a bit of shift stitching, especially panos were I can get a nice format with a 3 shot shift on my 40mm.
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BernardLanguillier

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Re: Alpa Tilt with wide lenses
« Reply #64 on: September 29, 2016, 10:56:59 pm »

Thanks again Wayne.

Cheers,
Bernard

Theodoros

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Re: Alpa Tilt with wide lenses
« Reply #65 on: September 29, 2016, 11:12:05 pm »

I'm going to try one more time Theo,
No one disagrees with this statement. All helical technical cameras have slight refocus requirements because the tilt mechanism is behind, not below, the entrance pupil.


"Bellow" is a resemblance to view cameras in a another (different) conversation... We don't have to mix conversations here, ...do we? We (knowledgeable) know what we are talking about... if a system looses focus, then its geometry is wrong, that is the subject...



THIS is the statement we all disagree with. You are incorrect here Theo. You have been incorrect about the hinge point on the Alpa tilt adapter, incorrect about how the Alpa helical focus mechanism works, and you are incorrect about this too. There is no quality or distortion difference between the Alpa and Arca designs. In fact, there is a slight but very probably unnoticeable advantage to the Alpa design because the hinge point is either 17 or 34mm closer to the entrance pupil vs Arca, depending on which tilt adapter is being used.

NONE of the technical cameras from Arca, Alpa or Cambo have tilt below the shift.

Dave


Who is "loosing focus" then? ...if they all do, they are all wrong... then the "most accurate", is the one that "looses focus" less than the others (the one with the smaller error)... simple isn't it?

EDIT: I just don't like technical cameras having errors... it's not what they are meant to do (by all means)... Still, the Alpa is the one with the most of error... (if focus error is more than the rest)...  where do we disagree? ...I don't see the disagreement existing anywhere...
« Last Edit: September 29, 2016, 11:19:14 pm by Theodoros »
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Wayne Fox

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Re: Alpa Tilt with wide lenses
« Reply #66 on: September 30, 2016, 01:22:19 am »

Who is "loosing focus" then? ...if they all do, they are all wrong... then the "most accurate", is the one that "looses focus" less than the others (the one with the smaller error)... simple isn't it?

EDIT: I just don't like technical cameras having errors... it's not what they are meant to do (by all means)... Still, the Alpa is the one with the most of error... (if focus error is more than the rest)...  where do we disagree? ...I don't see the disagreement existing anywhere...
I think based on what you have said perhaps yes, all Tech cameras if using tilt are "wrong", since they tilt behind the focusing helicoid and perhaps more importantly behind the spacers require for most lenses.  I'm not sure anyone is disagreeing that technically this might be true, I think most of us feel the errors are pretty insignificant and the trade off of using the small tech camera and having tilt available is worthwhile.  The other two options to achieve depth of field have their own issues, either shutting down to f/22 and introducing some pretty serious softness from diffraction, or focus stacking which has it's own issues including not being able to use if there are elements moving in the image such as branches, grasses, etc.  So I guess I'll stick with tilting to accomplish the goal when I can.

As far as Alpa being the worst, from looking at the two systems, the Alpa is tilting a few mm further from the film plane than the Arca.  So maybe there's a slight difference so technically the alpa is "worse", seems the difference if measured and test would be minuscule if even discernible by a viewer. But question, if the Alpa is tilting further from the film plane, it's closer to the entrance pupil/nodal point, so would that mean the alpa tilt might be better than the arca? (I don't have a way to measure where the tilt occurs, I'm just estimating from looking at pictures that the Alpa is this way, which means it's closer to what a bellows camera does when it tilts the lens board.)
« Last Edit: September 30, 2016, 12:31:15 pm by Wayne Fox »
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BernardLanguillier

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Re: Alpa Tilt with wide lenses
« Reply #67 on: September 30, 2016, 03:20:10 am »

I am not sure that accuracy is the main point here in fact.

Some cameras, such as my Ebony 45SU and some Sinar cameras, were designed on purpose with assymetric tilt where the tilt axis is offset from the lens center purposedely in order to ease the focusing process. You start by focusing a line in the landscape aligned with the tilt axis in the viewfinder and the rotate around this line. This removes the need to iterate to reach focus.

Now, with the apps we now have, this may be even less relevant considering that we can measure the camera tilt, its height to the ground and get a very accurate recommendation of tilt angle and focus distance to align focus with a given plane such as the ground.

Just like correcting optical distortion isn't a key lens design criteria anymore since we can correct distortion in software (which enable designers to optimize better other aspects), I believe that the focus of tech camera design is changing also to reflect the way people use these cameras as a result of new tools such as Live view on backs, tilt apps,...

Cheers,
Bernard

dchew

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Alpa Tilt with wide lenses
« Reply #68 on: September 30, 2016, 05:57:02 am »

Thanks for stepping in Wayne. I felt like I was trying to get somewhere with one foot nailed to the floor.

You bring up a good point about helical cost. Alpa is more expensive out of the gate and goes up from there. And, as the number of lenses in the bag increases, so does the weight with Alpa. Torger points this out as an advantage of the Linhof Techno. He carries many lenses but each one is simply mounted on a light lens board.

Dave
« Last Edit: September 30, 2016, 07:53:46 am by dchew »
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Theodoros

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Re: Alpa Tilt with wide lenses
« Reply #69 on: September 30, 2016, 06:46:59 am »

The size of equipment part is definitely a very important one.

I expect that in the near future, very few will invest on systems with MFDB used as image area, the most part will be mirrorless with compatible retrofocus lenses that are meant for mirrorbox cameras. Therefore I expect the technical camera market to expand significantly, but the "mini" monorails to dominate it. Then one can have one (only) line of lenses and share them between his normal shooting and technical camera all the same. I also expect the "mini" monorails to be used for motion picture taking.
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Paul2660

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Re: Alpa Tilt with wide lenses
« Reply #70 on: September 30, 2016, 09:57:05 am »

One other consideration.

I also shift for short pano shots most of the time I use the Arca. I love the fact that you can have the camera in just about any position up or down and since you are moving the back instead of the lens the final pano creation is effortless.  No worries of being level or nodal. It does allow for a lot more composition freedom.

Arca has a screw style mechanism for shifting there is no quick release that allows you to quickly slide from the far left to far right. So doing a lot of shifting means a lot of knob turning.

Cambo has the ability to free up the shifting for fast movement to one far stop to the other or you can switch back to the geared style for precise adjustment. Cambo also has an indent that lets you know when you are centered.

Cambo also just annouced a new camera that is based on their smart L bracket that allows for quick rotation of the back by rotating the camera. Nice design.

Paul C
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Paul Caldwell
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Christopher

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Re: Alpa Tilt with wide lenses
« Reply #71 on: September 30, 2016, 10:02:11 am »

Just to add to the post above. That is correct for the Arca Rm3di. The Rm2d and factum have only one geared shift ( rise and fall) and just a easy push and pull.


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Christopher Hauser
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yaya

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Re: Alpa Tilt with wide lenses
« Reply #72 on: September 30, 2016, 10:31:13 am »

Thanks for stepping in Wayne. I felt like I was trying to get somewhere with one foot nailed to the floor.
Dave

And not to mention that this whole "error" thing is only relevant of you initially set focus in the centre of the image (and the lens)...

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Paul2660

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Re: Alpa Tilt with wide lenses
« Reply #73 on: September 30, 2016, 10:33:56 am »

Just to add to the post above. That is correct for the Arca Rm3di. The Rm2d and factum have only one geared shift ( rise and fall) and just a easy push and pull.


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Thanks Christopher for the catch,  I always forget about the Factum and older Acra's. 

Paul C
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Paul Caldwell
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Christopher

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Re: Alpa Tilt with wide lenses
« Reply #74 on: September 30, 2016, 10:40:16 am »

The Rm2d is newer than the 3d just the smaller version like the Rm3d is the smaller of the RL3di

These names.... ;)


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Christopher Hauser
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dchew

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Re: Alpa Tilt with wide lenses
« Reply #75 on: September 30, 2016, 01:02:15 pm »

Indeed a nice feature; Alpa is the same and I use it all the time. So much so that occasionally when I rotate the STC for rise/fall, I flip that lever by habit and gravity drops the back 18mm.

As usual, the pilot is who holds me back...
 :-[

Dave

Cambo has the ability to free up the shifting for fast movement to one far stop to the other or you can switch back to the geared style for precise adjustment. Cambo also has an indent that lets you know when you are centered.
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Theodoros

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Re: Alpa Tilt with wide lenses
« Reply #76 on: September 30, 2016, 01:16:13 pm »

And not to mention that this whole "error" thing is only relevant of you initially set focus in the centre of the image (and the lens)...

What you mean Yair? The distortion causes the image "circle" projected to have a "eggy" (like an egg) shape, the more the error, the more the shape of the image circle distortion... The whole image captured is affected.
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Tsbphoto

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Re: Alpa Tilt with wide lenses
« Reply #77 on: September 30, 2016, 10:09:50 pm »

What you mean Yair? The distortion causes the image "circle" projected to have a "eggy" (like an egg) shape, the more the error, the more the shape of the image circle distortion... The whole image captured is affected.

when ever you tilt a lens you will get that distortion... what is the problem? 
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Theodoros

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Re: Alpa Tilt with wide lenses
« Reply #78 on: September 30, 2016, 10:17:17 pm »

when ever you tilt a lens you will get that distortion... what is the problem?

You don't get any distortion if you tilt the lens with the entrance pupil positioned at the center of the circle of which the tilt arc is part of the perimeter.... Additionally you take the most out of your lens.
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Tsbphoto

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Re: Alpa Tilt with wide lenses
« Reply #79 on: October 01, 2016, 10:33:50 am »

You don't get any distortion if you tilt the lens with the entrance pupil positioned at the center of the circle of which the tilt arc is part of the perimeter.... Additionally you take the most out of your lens.

you are conflating image distortion with the shape of the projected circle.  rotating around the nodal point will have no image distortion but the image circle projected on the flat image plane will always have a distorted "egg" shape.
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