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A Comparison of Technical Cameras

David Klepacki

New member
This year, we decided to invest in a portable technical camera, if it was possible to meet most of our shooting situations. So, for the last six months we evaluated the various smaller technical cameras currently available on the market. Our analysis, or at least our approach, might benefit other photographers who are considering the same investment.

First, we list the major features of importance to us that we deem essential requirements to making such an investment:

1. Front lens tilt+swing with any lens (and retaining infinity focus)
2. Rear x-y shift of MFDB suitable for stitching
3. Sliding back optional
4. Compact and lightweight enough for easy portability, setup and breakdown
5. Schneider and Rodenstock digital LF lens choices from 23mm - 210mm
6. Untethered focus accuracy (other than infinity)
7. Hand holdable w/ accurate focus (other than infinity)
8. Zoomable EVF w/ shift indicator for all supported lenses
9. Compact tilt-able 6x9 magnified (4X-6X) reflex GG finder w/ adjustable diopter

Then, we create a table to indicate which technical cameras either meet or fall short of our desired requirements (see our attached table below).

Our conclusion: Only the Arca-Swiss RM3D came closest to our desired features. Most, if not all of the other technical camera choices could not give us reliable untethered performance and handling as with the RM3D. The only shortcoming that we found with the RM3D is the lack of simultaneous swing, or preferably the multi-directional tilt-swing ability as found in cameras like the Sinar arTec and the Cambo WRS. However, our lens movement needs are predominantly a small amount of tilt, so we are happy with this trade-off in favor of the better untethered performance.
 
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PeterA

Well-known member
David, the artec ( which I dont own) has:

1. An inbuilt sliding back - which is a missing tick on your table,
2. a 3x magnifier with inbuilt bellows to shade from sun (another tick)
3. rear y movements and front X movements ( so I gues only a half tick ) - but controls on photographers side of camera

It also has front tilt AND swivel capability ( but you have no interest in swivel apparently ) so no ticks there

As for lenses - the Sinar uses Sinar mounted rodenstock sourced lenses

and finally - Sinars focussing accuracy via ground glass for ANY focal length - is just fine - so add another tick.

I agree you cant hand hold an artec - but thenm again I wouldnt try and hand hold the arca either ! -:)

Since I have no prejudice or bias or buyers remorse - I am purely interested in the value proposition that this gear delivers on a cost / benfit basis.

One thing I can say - it looks like ( for now) the arca has a definite advantage over the Sinar atec as far as cost goes !!

PS I would another radvantage that arca has over Sinar - and that is teh ability to use mutliple backs on same camera by buying an adaptor?

Pete
 

thomas

New member
re Cambo WRS:
There is a mono reflex viewer for the WRS.
It was designed for the Ultima Sliding Back but it fits on the WRS:
http://www.cambo.com/Html/products_photo/set01/english/internet/Item886.html

Strictly speaking not all the lenses for the WRS are available in T/S mount.
Shortest focal lenght, AFAIK, is 28mm... but only the Rodenstock can be mounted in a T/S lens panel. The shortest Schneider that can be mounted in a T/S panel is the 43XL.
On the other hand it's fair to say that you can get T/S for (almost) any focal lengths on the WRS.
 

thomas

New member
Actually a nice list to get a brief overview!

Just thought to add some thoughts about the uniqueness of the respective cameras (which may tell something about the underlying idea of the cameras) … please feel free to correct me if I am wrong…

BiCam:
smallest, lightest tech camera with movements (limited, though)

Horseman:
lightest tech camera with 4-way shift on the rear (not geared)

WRS:
smallest + lightest tech camera that provides geared, full movements (4-way-shift on the rear & T/S on the lens)
(sole tech camera that provides a dedicated level head)

arTec:
sole camera with integrated sliding back (i.e. the rear standard of the actual camera is designed as sliding back).

Alpa Max:
camera interface can be shimmed (Alpa also seems to provide the most extensive set of accessories)

Techno:
most compact view camera (AFAIK)

Rm3D:
unique focussing mechanism
 

David Klepacki

New member
David, the artec ( which I dont own) has:

1. An inbuilt sliding back - which is a missing tick on your table,
2. a 3x magnifier with inbuilt bellows to shade from sun (another tick)
3. rear y movements and front X movements ( so I gues only a half tick ) - but controls on photographers side of camera

It also has front tilt AND swivel capability ( but you have no interest in swivel apparently ) so no ticks there

As for lenses - the Sinar uses Sinar mounted rodenstock sourced lenses

and finally - Sinars focussing accuracy via ground glass for ANY focal length - is just fine - so add another tick.
Pete,

1. My point is that the arTec sliding back is NOT optional (i.e., it cannot be removed from the camera). So, no tick in our table.
2. The arTec viewer is not a reflex magnifier nor does it give a 6x9 view on the GG. So, no tick.
3. Rear x-movement is critical for horizontal stitching capability. So, no tick.

I do acknowledge the use of Rodenstock lenses on the arTec, but it is important for people to know that the Schneider apo digitars are not available for it.

Focusing accuracy is NOT as fine as you think on GG for any focal length (for any of the technical cameras). Have you actually measured this for yourself? Attached below is an example of the accuracy of the RM3D, shot untethered and without using ground glass focusing. It was taken with a Rodenstock Digaron-S 100mm lens wide open at F4 at a distance of 4.21 feet as measured with a laser meter.

No other technical camera can produce this kind of accuracy without being tethered.
 
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David Klepacki

New member
Actually a nice list to get a brief overview!
Thank you. Actually, we have pages of notes on each of the cameras, and I only provide the summary table to show the net balance among all the cameras. You have summarized nicely the other advantages.

One more thing I should add about the RM3D is that shimming is not necessary as for the other technical cameras. Arca-Swiss made it so that the registration distance to any lens is much shorter than could ever be needed. So, once you calibrate the RM3D to your back using its built-in helicoid mechanism, it is equivalent to the shimming process of Alpa.
 

archivue

Active member
After a lot of research, i've found that the only camera that fits the bill was the Arca RM3D... so i've bought it !

it have all of it.. the only thing missing is an adjustable adapter for MFDB... but now the kapture group can do it !

Alpa coming with new focusing ring + the KG sliding back... it becomes more interesting !
But don't forget that with Arca you can also use your existing RM3D lenses with an M line Two... it requires just a simple adapter plate !
For me, that's a big plus !

1. Front lens tilt+swing with any lens (and retaining infinity focus)
2. Rear x-y shift of MFDB suitable for stitching
3. Sliding back optional
4. Compact and lightweight enough for easy portability, setup and breakdown
5. Schneider and Rodenstock digital LF lens choices from 23mm - 210mm
6. Untethered focus accuracy (other than infinity)
7. Hand holdable w/ accurate focus (other than infinity)
8. Zoomable EVF w/ shift indicator for all supported lenses
9. Compact tilt-able 6x9 magnified (4X-6X) reflex GG finder w/ adjustable diopter
 

thomas

New member
One more thing I should add about the RM3D is that shimming is not necessary as for the other technical cameras.
actually shimming the camera interface is not necessary with any of those cameras (with helical focus mount) as you can easily adjust the lens for infintiy. However the shimming set is a unique offer of Alpa.

Musing about the Techno... if such a camera would just provide additional rails - exchangeable for every lens and with a high resolution distance indication on it - it would be easy to gain the same (or similar) level of accuracy as on the Rm3D. If they would equipp any of those additional rails with a lock for infintiy it would be even usable for architecture or landscape (or any field where you need accurate infinity focus).
well ...
 
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jotloob

Subscriber Member
actually shimming the camera interface is not necessary with any of those cameras (with helical focus mount) as you can easily adjust the lens for infintiy. However the shimming set is a unique offer of Alpa.
Thomas

Not quite true . You can set any lens with a helical mount to infinity and then you believe it is set to infinity . But the flange focal length might be wrong by just 0.02 or 0.05 mm .
I have seen the ALPA technician going thru the shimming procedure for my digital back adapter and I must say , it is very well visible if the flange focal length is incorrect and it is mandatory to have correct adjustment to
obtain the best results (for infinity ?)

The ALPA is the only camera offering this adjustment .

Also , we should not forget , there will never be an "all-in-one" camera suitable for all purposes and having only the goodies we all love so much .

BTW , I am very much looking forward to see (and get) the announced addtional precision focusing device for the ALPA lenses .
 

thomas

New member
Not quite true . You can set any lens with a helical mount to infinity and then you believe it is set to infinity . But the flange focal length might be wrong by just 0.02 or 0.05 mm .
I have seen the ALPA technician going thru the shimming procedure for my digital back adapter and I must say , it is very well visible if the flange focal length is incorrect and it is mandatory to have correct adjustment to
obtain the best results (for infinity ?)
all true. But you can adjust the focus lock position on the lens - which is in effect the same as shimming the back.
See here: http://forum.getdpi.com/forum/showpost.php?p=240696&postcount=4572
 
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smei_ch

Guest
Why should you change a perfectly calibrated focus ring when the tolerances are occuring in the position of the sensor? The advantage of the Alpa is the exchangeability of components between different cameras. Once you have a back with a calibrated mount everything else fits and can be changed.

There are some „experts“ that claim that this kind of calibration is only valid for infinity. This is only half true. If the reference plane for precise flange measurement is the groundglass (which is the case on Alpa's) and the correction is done on the back/adapter to fit there, untethered close range imaging gets more precise too, because the back is now in the exact same position as the groundglass. Looks like an argument to cope more reliably with the shallower DOF.
When you correct on the helical focus, you might get precise infinity with the back, but you move the tolerance to the groundglass. Doesn't sound too promising for me, and is the case for every camera where sensor tolerance correction is done that way.


In my opinion regarding Alpa lens availability and untethered focus precision this chart is not correct.
 

David Klepacki

New member
Also , we should not forget , there will never be an "all-in-one" camera suitable for all purposes and having only the goodies we all love so much .

BTW , I am very much looking forward to see (and get) the announced addtional precision focusing device for the ALPA lenses .
The Alpa is indeed a very nice camera, but it lacks many of the features that we really wanted, especially tilt ability with wide to normal lenses and the option of having high focusing accuracy without being tethered and without swapping out ground glass. Even the newly announced "precision focusing mechanism" for the Alpa lenses will not resolve these issues.

For us, the Arca-Swiss RM3D comes very close to an "all-in-one" camera for our purposes.
 

David Klepacki

New member
In my opinion regarding Alpa lens availability and untethered focus precision this chart is not correct.
Alpa does not offer all Rodenstock lenses. For example, you cannot obtain the Rodenstock APO-Sironar Digital 135mm lens for any Alpa camera.

As for untethered focus precision, the above image that I posted is smoking gun proof. I challenge anyone to repeatedly and consistently obtain such precision without being tethered and without using ground glass focusing on an Alpa or any other technical camera. Maybe you can achieve similar results with a tremendous amount of focus bracketing, but even then it is highly unlikely.
 

thomas

New member
Why should you change a perfectly calibrated focus ring when the tolerances are occuring in the position of the sensor? The advantage of the Alpa is the exchangeability of components between different cameras. Once you have a back with a calibrated mount everything else fits and can be changed.
true

When you correct on the helical focus, you might get precise infinity with the back, but you move the tolerance to the groundglass.
also true.
In my case obviously GG and sensor match. Actually two sensors match...
If not, you would have to adjust the GG, too (well, for instance with shims).

Still, I agree that Alpa's interface shimming is in this regrad the most mature solution, no doubt.
Except for Arca's approach... which is different, but as accurate.

In my opinion regarding Alpa lens availability and untethered focus precision this chart is not correct.
you will never ever match focus precisely at, let's say, 20 meters with the 40HR focussing on a GG - not even on Alpa's GG. The magnification is simply too low.
With the Rm3D you can nail 21,35 meters spot on... without the need of any GG (that you actually rather use for composition on the Rm3D).
I think this is what David is referring to here.
 
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smei_ch

Guest
true

.....

you will never ever match focus precisely at, let's say, 20 meters with the 40HR focussing on a GG - not even on Alpa's GG. The magnification is simply too low.
With the Rm3D you can nail 21,35 meters spot on... without the need of any GG (that you actually rather use for composition on the Rm3D).
I think this is what David is referring to here.
Not the very best example. Even full open with f4 and a very aggressive CoC of 0.032 (equals enlargement to 90*120cm) DOF reaches from approx. 7.8m to infinity. This is an area where focus accuracy is almost irrelevant. Close range is where these things really matter.
Just my 5 cents..... ;)
 

thomas

New member
Not the very best example. Even full open with f4 and a very aggressive CoC of 0.032 (equals enlargement to 90*120cm) DOF reaches from approx. 7.8m to infinity. This is an area where focus accuracy is almost irrelevant. Close range is where these things really matter.
Just my 5 cents..... ;)
oh, the numbers :)
they don't matter a lot as you won't find anything of it reflected in the actual image.
Don't know the 40HR, though, but with the 47XL 20meters are not really sharp when you set the lens to infinity at f8... though the numbers tell something different. Good sharpness starts at around 28 meters meters with the 47XL.
 
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smei_ch

Guest
oh, the numbers :)
they don't matter a lot as you won't find anything of it reflected in the actual image.
Don't know the 40HR, though, but with the 47XL 20meters are not really sharp when you set the lens to infinity at f8... though the numbers tell something different. Good sharpness starts at around 28 meters meters with the 47XL.
My calculated DOF was for a lens set to 21m, not infinity. And if you focus to 25 or 18m doesn't change this much. There absolute accuracy on your focus ring is not really important.
This is different for close distances, where the scales on helicals spread already and a more precise indication will come in handy.
 

thomas

New member
My calculated DOF was for a lens set to 21m, not infinity. And if you focus to 25 or 18m doesn't change this much.
well, but your calulated DOF will not reflect the reality on a high res sensor.
I canceled DOF calculations at all. I do see a difference when I set the 47XL to 18m or 25m... apart from that the last indication on that lens prior to infinity is 10m... but I am not talking about the indications on the lens, but real distances measured with a laser distometer. DOF is extremely shallow on high res DBs... IMO. Too, you will clearly see where the actual focus plane is as contrast in this area is very high. Consequently you also see the spread of DOF. So accurate focussing matters even for wide angles at distances below infinity. Again... IMO.
Do you think the 70HR is sharp at 50meters when the lens is set to infinity (at f5.6)? Nope.
The same goes BTW for my Contax lenses... it's not only related to the high performance (contrast) of digital LF lenses.
 

Jack

Sr. Administrator
Staff member
FWIW, if you want to do DoF calcs for focus testing on digital sensors, I think you need to use the sensor's pixel pitch as your CoC. If you do this, you'll have a CoC of 6u (0.006 mm or 0.00024 inches) for current MF backs, and I suspect you'll find that renders thin DoF's with any lens under 80mm at f8, at any distance under 10 meters. This is where a well-calibrated focus ring will pay for itself time over time...
 

David Klepacki

New member
Close range is where these things really matter.
Just my 5 cents..... ;)
Yes, close range is exactly where you can see the differences in accuracy.

My image posted above was taken with a RM3D at approximately 1.28m away from the target, using a 100mm lens at F4. There is no way an Alpa camera can routinely nail focus like this without being tethered. And, I am only being kind by adding the word "routinely", since there is always that 1-in-a-million lucky shot.
 
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