Alpa Max Vs Arca Swiss Rm3d

[MNG]

Hi,

I am looking to get either the Alpa Max or the Arca Swiss Rm3di for architecture with a Leaf Aptus II 12.

After shimming the mount on the Alpa Max with your digital back does anyone know which system is more accurate with regards to lens focusing? I'm thinking of a 23mm HR, 32mm HR and a 47mm XL to begin with.

Thanks
Michael

[tho_mas]

On a classical helicoid focus mount (Alpa) the focus ring makes (almost) one turn to focus from near distance to infinity.
On the Rm3D the focus ring makes 3 turns from near distance to infinity.
In other words: the resolution of the Rm3D's focusing mechanism is much higher.
http://www.snap-rent.de/Detail/Arca_Swiss_Rm3D_3.jpg

Alpa just introduced new focus rings (optional accessory).
Here's the scale for the 47XL and you can see the scaling quite good:
http://www.alpa.ch/docroot/tmp/940x550_stamp/articles/2010/photokina-news/news_pics/500200010_DSC4693s.jpg
I would say the scaling is fine enough for most purposes, however by design the focusing precision of the Rm3D is much higher (three time higher, so to say)

[David Klepacki]

Just a minor correction to the above posting by tho_mas.  I have the RM3D camera, and it has five turns from near focus to infinity. 

As tho_mas points out, the Arca-Swiss R-line of cameras currently have the highest focusing precision capability of any technical camera.

[fuzzyfoto]

They are both great systems, but as far as I know there is no way one can shim the Arca Swiss Rm3di. I think this is the weak link with the Arca and a deal breaker. The focusing on the Arca does not make up for shimming. Focusing maximally is not a substitute if the sensor is off-plane. After shimming my digital backs (both a 45+ and then a 65+) with the Alpa adapter, I can tell you it makes quite a difference. You think you have the sharpest image possible until you shim the adapter for the digital back. So unless you have a perfectly positioned sensor on your digital back - which is most likely not the case - shimming is absolutely essential in getting the maximum sharpness from your lenses.

[tho_mas]

They are both great systems, but as far as I know there is no way one can shim the Arca Swiss Rm3di. I think this is the weak link with the Arca and a deal breaker. The focusing on the Arca does not make up for shimming.

On the Rm3D you don't have to shim the back - you just offest the default distance tables.
The focus ring on the Rm3D doesn't show distance indications in meters or feet… it shows numeric values that translate to a respective distance (Arca provides tables for each lens). These indications are linear (as opposed to the logarithmic indications on classical lenses).
So you just have to find out the offset of your sensor's spacing. Once you know the offset you can use it for all your lenses.

[henrikfoto]

Does anyone know a good place to buy a Arca Swiss Rm3d?
And what is the complete price without lenses?

Henrik

[Robert Hart]

Hoi,

Europe
http://www.arca-shop.de/index.php

gr

[Graham Welland]

On the Rm3D you don't have to shim the back - you just offest the default distance tables.

Btw, just to play devils advocate, what do you do if you've left the distance tables back at the house when you picked up the bag at 0'dark thirty?

In all seriousness, what DO you do?

[Doug Peterson]

Btw, just to play devils advocate, what do you do if you've left the distance tables back at the house when you picked up the bag at 0'dark thirty?

In all seriousness, what DO you do?

If you have a good dealer then they make sure you have a copy on your iPhone :-).

If you leave without your iPhone and without your table (which I would leave in the case with the body/lens) - then yes - you're pretty screwed. You could shoot at infinity and focus-bracket like crazy for anything closer, but otherwise you could not selectively focus on a certain distance.

The eModule - if/when it ships to end-users will be a holy grail of focusing. Everyone focuses on the ability to measure a distance using the eModule which I find (at best) moderately helpful. Where everyone should be excited is the real-time and ultra accurate read out of your current focus distance, and front/back focus depth (including ultra easy hyperfocal) which is actually fine tuned for your digital back's sensor (rather than the generic DOF indicators on any other system which are generic-for-film numbers).

That really excites me. It's actually much better than any other focusing option (for tripod based diligent photography). A quick flick of the wrist and you can set your focus for perfect hyperfocal distance every time and know immediately what distance in the foreground will still be tack sharp. This would also allow you to do VERY precise DOF stacking. Of course they have to ship it in significant quantities before it's anything (to me) other than a great idea/promise. Once/if it ships you can expect videos/explanations galore from Capture Integration.

Doug Peterson (e-mail Me)
__________________

Head of Technical Services, Capture Integration
Phase One Partner of the Year
Leaf, Leica, Cambo, Arca Swiss, Canon, Apple, Profoto, Broncolor, Eizo & More

National: 877.217.9870  |  Cell: 740.707.2183
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[Rod.Klukas]

Re: The focus on the RM3d/RM3di.
The focus, as several people have stated, is much finer than the Alpa can provide.  The over ring accessory now available, does give a finer scale to the Alpa but you are still dealing with the limitations of the standard helical provided by the lens manufacturers, so not much help.  As David said, a simple test at the beginning of use, can determine the amount of compensation for an individual back and camera combination.  This won't change unless the back is changed.  I also, for my customers have worked out maximum DOF numbers on a new camera w/lens delivery.  This is sort of a hyper focal/aperture combination for each lens.  ie: on my 72mm Digitar if I set 6 on the aperture ring I get 27' to infinity with no tilt and with 1/2 tilt I set 3 and get 9' to infinity.  These are easy to save as Dave said above and can be useful if cards are lost, etc.  I also work out 2 or three closer settings as well.  It is the most precise currently available.
Any questions email me.
I love my RM!
 

[david_duffin]

@DougPeterson:  Is it possible to be reasonably certain of where the new Arca focusing module is targetting?  Would the depth of focus reading provided by the module make it accurate beyond say 100 feet?

As an aside, no mention has been made here of the iPhone holder now available for the Alpa.  With the "Viewfinder Pro" or similar app I suspect that the iPhone would make a super viewfinder and an effective lens-selection tool.  Its high-res screen and user-settable "etch marks" allow viewing outside the frame, which should be a good aid for quick composition (within the iPhone camera's viewing range).  It may be far superior to the zoom-able finder on the Rm2d/Rm3d which is a bit tricky to set accurately IMHO.

David

[fuzzyfoto]

To all those (including the dealers who sell Arca) who think you can focus your way out of a misaligned sensor: you can not. If the sensor is misaligned - skewed - there is no way you can make up for it through focusing - no matter how "finely" you focus. On my digital back 45+, I had to cut the shim in half to make up for the misalignment.

The emodule as it is conceived is VERY limited. You don't know what you're focusing- especially at 100 feet! I could/would never rely on the emodule.

edit: Unless you have shimmed a digital back or unless you've seen someone shim a digital back and see the before and after, you have no appreciation for the importance of shimming and what a difference it makes. You think you have a sharp image until you see the shimmed version.

[Doug Peterson]

The emodule as it is conceived is VERY limited. You don't know what you're focusing- especially at 100 feet! I could/would never rely on the emodule.

@DougPeterson:  Is it possible to be reasonably certain of where the new Arca focusing module is targetting?  Would the depth of focus reading provided by the module make it accurate beyond say 100 feet?

I stated very clearly "Everyone focuses on the ability to measure a distance using the eModule which I find (at best) moderately helpful. Where everyone should be excited is the real-time and ultra accurate read out of your current focus distance, and [depth of field] [...]"

I would NOT buy the eModule in order to measure subject distance. As you said there is little to know way to be sure what subject it is measuring unless the subject is very large, flat, and parallel to the film plane. A leica distometer or a high-end point and shoot which can tell you the distance it is focused at would be much better for establishing subject distance.

I WOULD buy the eModule because it gives you a very accurate real-time read out of the distance at which the camera is currently focused. This includes a (specific to your digital back) reading of the depth of field. So you can look at the eModule and tell that the lens is e.g. focused at exactly 33 meters and at f/11 depth of field extends from 20 meters to infinity. That to me is revolutionary. Other systems have DOF markings on the focus mount but they are 1) designed for film DOF not for your digital back so you have to come up with a fudge factor and 2) they are not very precise since there may only markings at e.g. 10 ft, 30 ft and infinity.

This means you can skip the paper conversion chart and viewfinder rotatable-DOF-indicator and just have the numbers told to you strait-and-easy. It makes the system a lot more elegant in my opinion.

To all those (including the dealers who sell Arca) who think you can focus your way out of a misaligned sensor: you can not. If the sensor is misaligned - skewed - there is no way you can make up for it through focusing - no matter how "finely" you focus. On my digital back 45+, I had to cut the shim in half to make up for the misalignment.

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)
__________________

Head of Technical Services, Capture Integration
Phase One Partner of the Year
Leaf, Leica, Cambo, Arca Swiss, Canon, Apple, Profoto, Broncolor, Eizo & More

National: 877.217.9870  |  Cell: 740.707.2183
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[MNG]

Hi tho_mas,

how do you find out the offset for your lens and apply this to the camera if there is only the focus ring with the pre-set numbers?

I dont see how the distance only when transferred to the Rm3d focus ring would be accurate if your digital back was out of its plane of focus? Is there a separate dial to allow for the lens offset?

With the Alpa style cameras where the digital back only moves up and down left and right, so I cant see how you can adjust the plane of focus without shimming the back?

Michael

[tho_mas]

To all those (including the dealers who sell Arca) who think you can focus your way out of a misaligned sensor: you can not. If the sensor is misaligned - skewed - there is no way you can make up for it through focusing - no matter how "finely" you focus. On my digital back 45+, I had to cut the shim in half to make up for the misalignment.

that's infact cool with the Apla shimming... that you also can compensate perpendicular misanlignement.
So you can...
- shim the entire back to achieve perfect focus at infinity
- shim the corners of the back to achieve a perfect perpendicular alignement
... but what would you do when the sensor is rotated?
At some point I think you simply should send the digiback back to the maker so that they service it, no?

The emodule as it is conceived is VERY limited. You don't know what you're focusing- especially at 100 feet! I could/would never rely on the emodule.

I'd suggest to re-read Doug's post carefully. As a measurment device it's actually not so great... but as a "display" that is electronically coupled with the lens and therefore providing reference data it's really very useful.

edit: Unless you have shimmed a digital back or unless you've seen someone shim a digital back and see the before and after, you have no appreciation for the importance of shimming and what a difference it makes. You think you have a sharp image until you see the shimmed version.

well, on other systems you can also simply adjust the focus ring on the lens to achieve accurate focus at infinity. Of course you have to see if the grounglass is still usable for focusing... if you use it for focusing at all...

[david_duffin]

I WOULD buy the eModule because it gives you a very accurate real-time read out of the distance at which the camera is currently focused. This includes a (specific to your digital back) reading of the depth of field. So you can look at the eModule and tell that the lens is e.g. focused at exactly 33 meters and at f/11 depth of field extends from 20 meters to infinity. That to me is revolutionary. Other systems have DOF markings on the focus mount but they are 1) designed for film DOF not for your digital back so you have to come up with a fudge factor and 2) they are not very precise since there may only markings at e.g. 10 ft, 30 ft and infinity.

Thank you for the clarity, Doug.  I've been wondering whether my decision NOT to buy an emodule for the Rm2d was correct or not...

David

[tho_mas]

how do you find out the offset for your lens and apply this to the camera if there is only the focus ring with the pre-set numbers?

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.

[david_duffin]

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.

Spot on, Thomas!  That focus ring has fantastic precision, and should prove effective even for future 150mp backs.  I have a P65+.  I calculated the "shim-offset" by taking a shot of a power line for example that was two miles away with the ring set to 0, then repeated the shot with the ring set to 1, 2, and 3 respectively.  The sharpest shot proved to be at 2, but the focus travel is so precise that there was very little difference between the four.  So little difference that I didn't bother continuing the calibration with the dial at 1.9 and 2.1 which would certainly have been possible.  I'm now just adding 2 to the suggested ring settings for all of my shots.

David

[Graham Welland]

that's infact cool with the Apla shimming... that you also can compensate perpendicular misanlignement.
So you can...
- shim the entire back to achieve perfect focus at infinity
- shim the corners of the back to achieve a perfect perpendicular alignement
... but what would you do when the sensor is rotated?
At some point I think you simply should send the digiback back to the maker so that they service it, no?

Once you shim the adapter to the back it doesn't matter about rotation because the Alpa adapter is square and you simply rotate it 90 degrees & refit for portait/landscape. With my P40+ I actually find that there's some disagreement between what the back thinks is level via the electronic horizon vs what my Alpa body & Arca Cube levels indicate. I simply trust the back's indication as it seems to reflect accurately the rotational skew the best. (This is a pet peeve of mine because none of my camera's flash mount/electronic indicator/heads seems to be 100% in agreement on level horizon indications!).

I'd suggest to re-read Doug's post carefully. As a measurment device it's actually not so great... but as a "display" that is electronically coupled with the lens and therefore providing reference data it's really very useful.

That does sound useful. I've had to go through the calibration process of determining the practical DoF for my lenses at f/8 - f/11 for hyperfocal/zone setting. There's a pretty decent tutorial for this by the folks at Optechs Digital that is equally applicable to any camera system, not just Alpa, over at: http://www.optechsdigital.com/Alpa_and_Hyperfocal.html

Having an accurate indication of the focus distance & DoF range, visible easily from behind the camera vs peering over the top/down at the lens certainly seems a useful feature to me. Ditto for accurately being able to set up a focus stack set too. Thumbs up to Arca for that - albeit not for free :-)
 

well, on other systems you can also simply adjust the focus ring on the lens to achieve accurate focus at infinity. Of course you have to see if the grounglass is still usable for focusing... if you use it for focusing at all...

That's a tricky one. 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.

As an aside, no mention has been made here of the iPhone holder now available for the Alpa.  With the "Viewfinder Pro" or similar app I suspect that the iPhone would make a super viewfinder and an effective lens-selection tool.  Its high-res screen and user-settable "etch marks" allow viewing outside the frame, which should be a good aid for quick composition (within the iPhone camera's viewing range).  It may be far superior to the zoom-able finder on the Rm2d/Rm3d which is a bit tricky to set accurately IMHO.

David

I'm waiting for the iPhone holder to ship - I've been told that it's being delayed by Alpa at the moment which is frustrating because I do use Viewfinder Pro for framing myself for particularly the reason you cite, ie. lens pre-visualization & framing. You can zoom and take a sample screen capture too. The other good thing is that you don't need to buy new masks as you add lenses either which I can almost use as a justification for the cost since custom masks (with multiple focal lengths) cost $200+ each time, although obviously some foresight would help you buy a mask for your anticipated lenses vs what you actually have today I guess.

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.

[tho_mas]

... but what would you do when the sensor is rotated?

Once you shim the adapter to the back it doesn't matter about rotation because the Alpa adapter is square and you simply rotate it 90 degrees & refit for portait/landscape.

I was refering to a rotated sensor. So a sensor out of level by 0.1° or 0.2° or so. There is no way to adjust this axis on the Alpa (or any other camera).

well, on other systems you can also simply adjust the focus ring on the lens to achieve accurate focus at infinity. Of course you have to see if the grounglass is still usable for focusing... if you use it for focusing at all...

That's a tricky one. 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.

You are right. It certainly can be tricky. I've adjusted my lenses (i.e. the focus rings) to achieve perfect focus at infinity (focus is also accurate at the 10m and 5m indication... never checked closer distances). My groundglass is still usable for focusing... but if it would not, I'd shim it :-)
However I use the groundglass only for focusing close distances... for mid and wide distances I use a laser disto. Focusing a 47mm (43mm) lens at 16 meters distance or so is almost impossible on the groundglass as the magnification of the subject is too small (I use a 6x asph. loupe... but I feel a loupe with higher magnification only enlarges the grain... it's not really better suited for focusing. At least that's my personal experience).
I've taped additional indications on my lenses so that a laser disto really works good for me (at least as long as the damn laser disto works... in bright sunlight it can be tricky). This is why I am finding the new Alpa HP focusing rings extremely useful... and the Rm3D simply outstanding.