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Author Topic: Alpa Max Vs Arca Swiss Rm3d  (Read 38984 times)

david_duffin

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #20 on: December 29, 2010, 06:58:13 pm »

With respect to the Alpa vs Arca question & trade offs, it certainly seems like it's a Lexus vs Mercedes type of comparison - i.e. both are stellar systems with slightly different advantages. I like the Alpa simplicity and setup accuracy myself but then again the Arca does offer a better tilt/swing system for all lenses. The shim vs lens calibration offset probably works itself out pretty quickly with whichever you choose and you get used to it. I haven't tried the new accurate focus indicators for the Alpa yet although for me it's not been an issue for me personally but that's probably because of my shooting subjects such as landscapes etc.

Agreed, Graham.  To quote Mark Dubovoy, we're nit-picking here.

The elegant engineering and design of the Arca may prove advantageous though -- at least in theory.  Lenses with Arca mounts do not require the per-lens helical threads, which should make them less expensive...

David
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Anders_HK

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #21 on: December 29, 2010, 08:43:45 pm »

I think David or someone using the Rm3D should elaborate further but basically it's like this:
Let's say your focus point is at 10 meters (measured with a laser distometer). According to the Arca table you should set the respective lens to the numeric value 20 (fictitious example here) to focus at 10 meters. In the actual capture you will see if the focus is spot on or if there is back or front focus. Let's say you have back focus. So you turn the focus ring back until the motif in question at 10 meters is in focus. Read the respective numeric value on the focus ring which is now... for instance... 17. So the offset is -3 and you can use that offset all the time - as mentioned above the scale is linear, so the offset is consistent for all distances (and all lenses, basically). You can store that offset even in the E-Module so that its read-out takes the offset into account.

Why as a PHOTOGRAPHER would we need to go through above indicated process as compared to simply reading and setting a distance on a helical focus ring???  :'(


With the Alpa at least you have to assume that the shimmed back and GG are in agreement. With a 4x loupe I admit that I couldn't really check that out myself to the level of accuracy required to prove it. With the Arca I would assume that you've also got to take it on faith that the lens compensation for the back applies equally to the GG or that it's too small to notice when focusing off the GG I assume.

If I understand correct of Alpa, their cameras, lenses and GG are calibrated/fabricated to absolute exact within tight tolerances. Thus what remains to calibrate is the shimming of the digital back, which does not necessarily adhere to same very tight tolerances as Alpa cameras, lenses and GG.

Assuming Arca provide same tight tolerances as Alpa on cameras, lenses and GG, thus by accounting for the focus error of digital back by applying compensation to focus tables, thus what we focus on GG would require us to after perfect focus on GG apply same compensation to lens after focus as we do to our lens tables…

Dang, I am an is engineer and photo is my advanced hobby. Thus not problem to calculate, but… the Arca focusing is simply too $#(*^(&^$#** complex!!!

Now, one more issue; per my understanding focus of a tech camera is similar to a film 617, thus I will assume that one frequent focus based on hyper focal distance, or at least based on a zone (pretty much like pre-focus on a Leica)? Thus… assuming the back is perfect shimmed to a system with very tight tolerances (= depth of focus is perfect adjusted), then what why would it really matter if the focus ring have the very exact adjustments as Arca does? I do not get it.  ???  ::)

Regards
Anders
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tho_mas

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #22 on: December 29, 2010, 08:54:22 pm »

Why as a PHOTOGRAPHER would we need to go through above indicated process as compared to simply reading and setting a distance on a helical focus ring???  :'(
you don't have to... But you can, if you want the high precision of Arca's focus mount.
As a PHOTOGRAPHER you can also buy the E-Module that shows you the distance in meters and feet and at the same time the DOF.
As a PHOTOGRAPHER you might also appreciate that you can read the E-Module when you are standing behind the camera...
you can even take it in your hands and read it when the camera is mounted above head level.
Now, as a PHOTOGRAPHER I'd say that's pretty cool.
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Rod.Klukas

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #23 on: December 29, 2010, 10:31:00 pm »

The real reason for this variation is that the sensor manufacturers cannot tell you exactly how deeply embedded the pixels are chip to chip.  So a camera manufacturer has to average and let you fine tune to your lenses.  Thus we end up with shimming or a fudge factor.  Even the higher end DSLR cameras have recognized this.  They allow a user to calibrate the focus of the camera for each lens and save the result in the cameras memory.  Canon has this in 7d and above for sure(Not sure on 60d or lower models) and Nikon on D300s and above you can for sure.
So even these cameras with fixed lens mounts need a tweak for their sensors.

Also as someone else cogently said, the easiest way to use the RM3d will be with the eModule by just watching the back of it.  It will not only give you the distance focused, but actually 4 apertures
with the near/far distances for each combination. This will be further enhanced by the fine tuning mentioned for pixel pitch and circle of confusion choices.  The hand held lasers can work, but in daylight are very hard to see at distance unless optical type, or if they are optical, they will not focus close if that is something you are trying.  So when we get it, I believe the eModule will make the RM3di and RM2d the most accurate focusing cameras available at this time.   :)
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David Klepacki

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #24 on: December 29, 2010, 10:54:03 pm »

thus what we focus on GG would require us to after perfect focus on GG apply same compensation to lens after focus as we do to our lens tables…

I think this is where you are having difficulty understanding the Rm3d.  There is no focusing on GG with the Arca.  You can compose with GG (or not), but focusing is done with distance measurement with (or without) the E-module.

Now, one more issue; per my understanding focus of a tech camera is similar to a film 617, thus I will assume that one frequent focus based on hyper focal distance, or at least based on a zone (pretty much like pre-focus on a Leica)? Thus… assuming the back is perfect shimmed to a system with very tight tolerances (= depth of focus is perfect adjusted), then what why would it really matter if the focus ring have the very exact adjustments as Arca does? I do not get it.  ???  ::)

Hyperfocal distance may be meaningful for cameras that do not have any front tilt or swing, which is not the case with the RM3d. 
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Anders_HK

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #25 on: December 30, 2010, 12:37:06 am »

I think this is where you are having difficulty understanding the Rm3d.  There is no focusing on GG with the Arca.  You can compose with GG (or not), but focusing is done with distance measurement with (or without) the E-module.

Hyperfocal distance may be meaningful for cameras that do not have any front tilt or swing, which is not the case with the RM3d. 


Hm.

Alpa:

Shim adjustment of back, together with all other components lends to perfect zone focus and hyperfocal distance focus. Also to viewing and perfect focus using GG. Alpa helical focus sufficient for these.
Using laser distometer one can also set the focus point rather exact using the helical focus.

Correct?

Arca:

No shim adjustment, apply fudge factors, assumes sensor is perfect parallel to camera system (including to shift, rise, lenses and GG).
GG for viewing only (unless perhaps apply same fudge factor as applied to lens focus, at a refocus post GG focus).
Focus tables require a lookup for more or less each shot.
E-module will give accurate the focus and DOF that lens is current set to, but the ultrasound is not at all times reliable. Also add cost and reliability issue.

Above correct?

Very high accuracy helical focus, but is this in reality at all useful compared to Alpa except when photographing tethered?
At tilt/swing how would one accurate determine focus without shooting tethered?

Please do not get me wrong, indeed I find the RM3D and especially RM2D interesting. Not to highjack this threat, but how would Cambo RS compare?

How about the sliding mechanisms of Arca and Cambo, are they as precise (in sliding plane) as are Alpa’s roller bearings?

Thanks!
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fuzzyfoto

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #26 on: December 30, 2010, 12:40:24 am »

Before i shimmed the 45+ I was satisfied with its focus. A friend showed me a before and after and I was amazed at the difference. When I shimmed my back it was off by a very slight fraction. Adding the half shim (plus a full shim) made all the difference in the world. Why should I have returned the back to the dealer? Because it wasn't seated in a fore-aft position but in a skew? Ridiculous! If the sensor is not seated optimally it doesn't matter whether it's fore-aft or skew. No digital back is perfect: calibration errors, dead pixels, misaligned sensors. For calibration errors and such, the digital back gets sent back. For sensor alignment, it's better to compensate with a shim because the next db you get could have the same issue.  My db is great now. When I got my 65+, the first thing I did was reshim my adapter plate. Eeezy-peezy. Do it once and then forget about it until you get a new db.

The Arca has a lot of nice bells and whistles that appeal to a photographer. For me the bottom line is the quality and sharpness of my images. If the sensor is not seated optimally - and this is more than likely the case - then I would want a way to compensate for this, because not doing so would mean that no matter what lens I use and no matter how finely I focus, the final image will not be optimally sharp.



If I found my 45+ was off in a skew (rather than absolute fore-aft position) I would rather send it to Phase for reseating/alignment than start half-shimming a body). Assuming it was under warranty and I had a good dealer relationship that is. But if you would rather buy an Alpa shim kit or a generic shim kit and tape/adhere it to the adapter plate you can accomplish the same thing with an Arca Swiss.

Doug Peterson (e-mail Me)
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David Klepacki

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #27 on: December 30, 2010, 02:12:45 pm »

Hm.

Alpa:

Shim adjustment of back, together with all other components lends to perfect zone focus and hyperfocal distance focus. Also to viewing and perfect focus using GG. Alpa helical focus sufficient for these.
Using laser distometer one can also set the focus point rather exact using the helical focus.

Correct?

"perfect" focus using only GG is not possible.  It is a hard fact to swallow for most photographers, and until you actually prove it to yourself you will most likely remain in a state of denial.  On the other hand, some photographers may have less concern for critical focus than others and do not really care whether they are able to capture 50 lp/mm versus 60 lp/mm of resolution.

Arca-Swiss has chosen to design their R-line of cameras based on this fundamental limitation of GG focusing in order to provide photographers with a tool to improve their focusing precision.  Whether or not you need this capability is an individual choice.

Arca:

No shim adjustment, apply fudge factors, assumes sensor is perfect parallel to camera system (including to shift, rise, lenses and GG).
GG for viewing only (unless perhaps apply same fudge factor as applied to lens focus, at a refocus post GG focus).
Focus tables require a lookup for more or less each shot.
E-module will give accurate the focus and DOF that lens is current set to, but the ultrasound is not at all times reliable. Also add cost and reliability issue.

Above correct?

There are no "fudge factors" involved.  Input data is needed in the form of distance measurements.  A "fudge factor" is something that implies guesswork of unknown origins.  The ultrasound of the E-module is intended for interiors or relatively close distances (e.g., within 30 feet or so) and its precision is proportional to its range (max. error of 0.1%).  For longer distances or more precision, a laser must be used (which can yield accuracy +/- 0.04 inches up to 650 ft.).

Very high accuracy helical focus, but is this in reality at all useful compared to Alpa except when photographing tethered?
At tilt/swing how would one accurate determine focus without shooting tethered?

Again, everything is based on the ability to measure distance.  You can use brute force Scheimpflug algebra to do the math, or you can attempt to make focusing tables for yourself at fixed camera heights, near/far distances, f-stops, and tilt/shift angles.

Please do not get me wrong, indeed I find the RM3D and especially RM2D interesting. Not to highjack this threat, but how would Cambo RS compare?

How about the sliding mechanisms of Arca and Cambo, are they as precise (in sliding plane) as are Alpa’s roller bearings?

Thanks!


I do not find any visible error when moving the rear x-y sled of the RM3D.  I cannot comment on the other cameras, as I have not tested them.
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henrikfoto

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #28 on: December 30, 2010, 08:33:17 pm »

With all these different ways to focus correctly with thse cameras, will they ever be able to focus better than the modern af systems like Phase and Hasselblad? Or is it just the best of what you can get if you need tilt and shift?

Are these new Rodenstock and Schneider lenses better than mf-lenses?
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Graham Welland

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #29 on: December 30, 2010, 10:58:39 pm »

Henrik,

One thing you can rely on is that technical cameras can't focus themselves and rely entirely on the skill of the photographer, whether it be via focusing on the GG, transcribing a laser distometer reading or ultrasonic reading to the lens or zone/hyperfocal focusing. I know that I can do a better job of focusing with my Alpa than my Phase One 645DF can manage although obviously it takes a lot longer to do it.

As regards the lenses, no competition. Rodenstock & Schneider digital lenses are pretty much unmatched by any current AF or MF medium format glass. I don't think that anyone would dispute that.
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Graham

David Klepacki

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #30 on: December 31, 2010, 01:24:40 am »

As regards the lenses, no competition. Rodenstock & Schneider digital lenses are pretty much unmatched by any current AF or MF medium format glass. I don't think that anyone would dispute that.

Technically, the new Leica S2 lenses are optically competitive with the Rodenstock and Schneider digital lenses, as they are diffraction limited designs with low distortion, APO corrected and make prodigious use of exotic and aspheric glass (and also floating lens elements for additional corrections, unlike the Rodenstock and Schneider lenses).  However, these Leica S2 lenses have much smaller image circles and do not offer the photographer any perspective correction with them, and so are basically unusable for architectural work.
« Last Edit: December 31, 2010, 01:27:18 am by David Klepacki »
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henrikfoto

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #31 on: December 31, 2010, 05:36:02 am »

What about tilt for the two systems?

As I understand the Alpa can tilt 6 degrees with some special adapter?
Is that front or back tilt or front tilt?

What about the Arca? How is the tilt done and how much can it be tilted?
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Graham Welland

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #32 on: December 31, 2010, 06:02:51 am »

The Alpa has two tilt/swing adapters. One is 0-6 degrees, the other is 0-12 degrees. I believe that this can be used either in front or behind the camera body to tilt the lens or back. Since this introduces a 34mm spacer into the body/lens width it requires short barrel lenses. What this means in turn is that the minimum focal length that can be used with the T/S adapter is 80mm or longer.
« Last Edit: December 31, 2010, 06:09:42 am by gwelland »
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Graham

henrikfoto

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #33 on: December 31, 2010, 06:11:26 am »

The Alpa has two tilt/swing adapters. One is 0-6 degrees, the other is 0-12 degrees. This can be used either in front or behind the camera body to tilt the lens or back. Since this introduces a 34mm spacer into the body/lens width it requires short barrel lenses. What this means in turn is that the minimum focal length that can be used with the T/S adapter is 80mm or longer.

Thank you, Graham!

Does anyone know how wide lenses can be tilted with the Arca?

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Graham Welland

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #34 on: December 31, 2010, 06:24:03 am »

I have the Alpa but from what I know about the Arca the tilt function is built into the body itself and thus one advantage of that mechanism is that you aren't restricted when it comes to wide lenses with tilt. I'm sure an Arca owner will elaborate ...  ;)
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Graham

tho_mas

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #35 on: December 31, 2010, 06:30:46 am »

Very high accuracy helical focus, but is this in reality at all useful compared to Alpa except when photographing tethered?
IMO the high focusing precision of the Rm3D is useful in particular when shooting non-tethered.
I think the decision also depends a bit on the focal lengths (and subjects) you are shooting. With wide lenses and shooting mostly realtively wide distances at apertures of f8 - f16 you actually don't really need super high precission of the focus mechanism. It is "relatively" easy to handle wide angle lenses with a classical helicoid focus mount (Alpa, Cambo, arTec etc.). The longer the lenses the more you can benefit from the Arca focusing mechnism. The same goes for shooting at wider apertures (f5.6 or even f4 with some Digarons).
IMO ...

Quote
Please do not get me wrong, indeed I find the RM3D and especially RM2D interesting. Not to highjack this threat, but how would Cambo RS compare?
Rm2D vs. WRS: the (lateral) movements on the Rm2D are not geared. In this regard I'd clearly favor the WRS. The WRS also offers larger movements (25mm rise/15mm fall, +/-20mm lateral). Too, the WRS provides a number of little features that add to the usability (it's really a clever design accounting for the compactness).

Quote
How about the sliding mechanisms of Arca and Cambo, are they as precise (in sliding plane) as are Alpa’s roller bearings?
I know that Alpa highlights their roller bearings design... and it's certainly super precise and solid. I can only speak for the WRS... but I have not discovered any issues due to perpendicular misalignement of the rear standard... there is no "tilt" or "swing" or so on the rear standard after 2 years of use. If there is some, it's easy to adjust (at Cambo, not by yourself!).
There are differences in design, in the machining and materials of all these cameras. But I think they are all very accurate...

IMO the decisive point between the Alpa and the Arca is whether you need tilt/swing even for wide or moderate wide lenses (on the Alpa only available for longer lenses... up from 70mm or 80mm I think / the Cambo WRS provides tilt/swing lens panels for almost all focal lengths) and whether you need the higher focusing precision of the Rm3D. Other than that you can't wrong... IMO.
I'd also take into account system integration and accessories. The Rm3D also provides a sliding back and you can use the Rm3D body as a front standard on Arca's M-Line view cameras. IIRC Chr. Barrett once had a short writeup on this on his webblog.



« Last Edit: December 31, 2010, 09:36:06 am by tho_mas »
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tho_mas

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #36 on: December 31, 2010, 08:57:40 am »

here...
CB on the Rm3D: http://christopherbarrett.net/blog/?p=1350
… and the M-Line II: http://christopherbarrett.net/blog/?p=800

An addional note on WRS vs. Max: The most obvious difference is, well, the price. Then the compactness of the WRS.
Now, if the Max offers all the features you need (i.e. if you are fine without tilt/swing for shorter lenses and if you don't need a sliding back...) and if you don't care about the cost you certainly can't go wrong with the Max.
Can you go wrong with the WRS? I would say no, but there are some trade offs (sure, if you consider the price difference).
For instance...
- no back shimming (you have to adjust the infinity lock on the lenses and then have to see if you can still can use the groundglass for focussing; on my kit the GG works fine)
- Jeffrey Totaro (who used to use Cambo... though AFAIK the WDS, not the WRS ... and now the Max) once noted somewhere here on the forum that the coating of the Alpa bodies is better suited to reduce internal flare. I would say I have no issues with flare or contrast in conjunction with my 47XL (resp. the 43XL lately) on the WRS, but with the 70mm. Actually I thought it's just the lens that is prone to show flare so I always adjusted my compendium as tight as possible. However after reading Jeffery's comments I've inserted black velvet in the lens barrel (also on the camera interface). Haven't shot any meaningful subjects with the 70mm since then but I would say there is an improvement.
So bottom line... the WRS possibly requires some "tuning", but still is capable of delivering the desired IQ.
Of course, if you don't mind the price of the Alpa you get it all out of the box.
RE handling me personally I like the WRS better. I often mount the camera above head level and due to some features on the WRS it's really easy to operate the camera "blind".



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Doug Peterson

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #37 on: December 31, 2010, 09:05:21 am »

Does anyone know how wide lenses can be tilted with the Arca?

The tilt is on the body itself. Any lens which mounts to the Arca can be tilted.

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henrikfoto

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #38 on: December 31, 2010, 10:11:36 am »

And how does these cameras compare to Sinar arTec?
Seems to be a lot like the Arca?

And Sinar have been using shimmingsets for many years ;)
But as far as I know not on the newest backs?
« Last Edit: December 31, 2010, 10:13:51 am by henrikfoto »
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buckshot

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Re: Alpa Max Vs Arca Swiss Rm3d
« Reply #39 on: December 31, 2010, 10:22:21 am »

Moved here.
« Last Edit: January 01, 2011, 10:38:09 am by buckshot »
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