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A Comparison of Technical Cameras

thomas

New member
Yes, close range is exactly where you can see the differences in accuracy.
you will see a mismatch at any distance below infinity ... the only difference at farther distances is that you have a bit more DOF. But you still see the focus spot.
Actually I am finding to get accurate focus at close distances not so hard focussing on the groundglass. It depends on the subject... if there is sufficient light and the subject in question has enough contrast hitting focus on the GG is relatively easy.
It get's much harder at farther distances when the magnification of the subject on the GG is too small... in particular distances almost but not quite infinity. It's frustrating when you shoot a building and it's actually not really soft but the tree in the foreground of the building is sharp as hell... and IMO there is no way to do this when focussing on a GG.

edit: so another nice thing about the Rm3D's approach is that you can focus even on dark and/or very uniform surfaces (i.e. surfaces without texture and contrast)
 
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Bob

Administrator
Staff member
I never understood what circle of confusion actually is (though I have to admit I've always refused to read about it :rolleyes: ). But what you say meets exactly my experience...
That is the circle of confused photographers wondering why their pictures are not sharp.
-bob
 

PeterA

Well-known member
David

Thanks for starting the thread and also thank you for the time you have spent posting working examples of the focusing ability of the arca - very impressive

for me your preferences underline the simple fact that every knowledgeable user has preferences in work flow and specific expectations regarding how each system choice delivers - each with at the margin relative strengths and relative weaknesses - depending on the photographer and the shooting situation - we arrive at different answers

All this is useful for people considering choice.

If I wish to walk around in fat light with a Schneider 35 or a 24 - I put my Hasselblad back on a 12 series Alpa a little hardrive in a pocket and shoot all day - being stopped occasionally by people asking what is that beautiful retro looking camera with the wooden handles and the crazy viewfinder:bugeyes::)

for me it is much like shooting a Leica with a pocketful of TRX - very liberating and freeing - when I bought my first Alpa - Leica M didn't come in digital - and it was a great use of my Leaf back for editorial and reportage type street shooting.

On a tripod a different type of shooting becomes possible - but as soon as you enter that 'space' - you immediately hunger for shift - and tilt and swing..

so enter artec and now arca - these two are close competitors - but very different animals. the artec gives you everything in one package - the arca gives you a different version of nearly everything - just make sure for both they are on a tripod!

I am not totally convinced about ground glass focussing on these systems - it is why I have never bothered with a ground glass for my Alpas - in the field - too often it is all too dark and when you add tilt/shift and swivel - really it is (for me) too often too hard to see what you are getting.

I ask myself though- how can I see anything ever under any conditions with the arca? back on back off - too much hassle for me . the artec gives me a dedicated solution here .

I like to see compose, frame - what I shoot in the field. In a studio if exactness is required - we all shoot tethered anyway.

So it all boils down to what the photographer likes to use for what purposes - again.

Thank you very much for the post - after Photokina I may contact Arca direct as it is down to one of arca or artec for me and the changeable back mount is a major plus for arca.

pete
 

Terry

New member
I ask myself though- how can I see anything ever under any conditions with the arca? back on back off - too much hassle for me . the artec gives me a dedicated solution here .



pete
Pete- doesn't the rotaslide or kapture group solution eliminate back on back off?
 

PeterA

Well-known member
Hi Terry,

these add ons may well do the trick - and may even do it s well as the artec in built system - i don't know - that is why i am interested in user experiences.

I have tested the artec and will do so again - but down here there is no access to arca. each layer of add on especially f matched to alternate suppliers adds another layer of potential risk/trouble when you live at the bottom of the planet -:)

I look forward to any input from any real user about their experiences - one of the great benefits of forms like this.

Now it is Saturday morning down here - grey skies so no happy shooting conditions - still I might just put the blad on the Alpa and see what I can get -:)

Pete
 

David Klepacki

New member
Pete,

First, with your setup I think either the arTec or the RM3D would complement your particular Alpa and MF cameras nicely, since either would add a new dimension to your shooting that gives you movements. If you do not plan on ever stitching panoramas, then the arTec will give you more lens movement. Otherwise, having a technical camera with rear planar movement is much easier to get better stitching capability.

As far as focusing on any technical camera, there are only four different methods:

1. GG on sliding back (same as arTec)
2. GG without sliding back (back-off/back-on, same as Alpa)
3. No GG, tethered live view (with MFDBs that support live view)
4. No GG, scale focus guessing

With the RM3D, the idea is NOT to focus using any of these four methods, but rather to focus based on measuring distance, and only use the GG for composition (with or without a sliding back). Furthermore, the GG is entirely optional with this distance measurement technique due to the Arca-Swiss EVF. So, this actually adds NEW focusing capabilities that are unique to the RM3D:

5. No sliding back, No GG, untethered, EVF with distance meter

Focusing is done by simply converting the measured distance to the index on the RM3D helicoid scale. This technique is extremely accurate, and the MFDB never moves in this case. Distance can be measured with a good laser meter (like the Leica Disto), or for shorter distances you could optionally use the Arca-Swiss ultrasonic device. The ultrasonic device has the added advantage of serving as a very accurate leveler.
 
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Jack

Sr. Administrator
Staff member
I never understood what circle of confusion actually is (though I have to admit I've always refused to read about it :rolleyes: ). But what you say meets exactly my experience...
I'm sure you're kidding, but in case you're not, OR for posterity, here is a simplified response...


Circle of Confusion or CoC is an integral part of the optical formula for Depth of Field (DoF) calculations. Any point source of light is only rendered as a single point when it is in perfect focus, regardless of aperture or focal length or subject distance. Any time the point source is out of focus (oof) it becomes larger than a single point, it both gains area and looses brightness, and is then referred to as an "airy disk." At a certain diameter, which is now affected by aperture, lens focal length and subject distance as well as viewing distance and our own visual acuity, the airy disk no longer appears as a single point, but rather appears as a fuzzy spot. The maximum diameter we choose as "good enough" to still be considered a sharp point of light, is the "acceptable" CoC.

By default, the absolute smallest "point" we can render in digital imaging is a single pixel. Therefore when viewing images at 100% magnification, the default acceptable CoC is equal to the pixel diameter of the sensor in question.

Simplified, but hope it helps,
 

tjv

Active member
Interesting thread.

Could someone please post a link, picture or explain now the Arca RM3D EVF works and what it looks like? For 2010 it's amazing Arca don't have a web presence to help sell their products. I've often thought that the Alpa SWA with CFV39 or equiv. P1 back would be just the ticket for me. I only need shift to control perspective. Tilt would be nice but I've never needed it in the past. It's the point of focusing accuracy that has always held me back. The Arca solution sounds interesting as I'm more often than not shooting subjects between 3 - 10 meters.

As an aside, is there anyone here that regularly uses one of these systems to take environmental portraits? What about mid length portraits? I'd love to still be using LF sheet film and focusing on the GG for my work but where I live it costs over $11 to process a sheet of 4x5". Is the Arca / Alpa with digital back a viable replacement for a field camera that sees general use?
 

thomas

New 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.
Jack, I think your advice re the pixel pitch as reference for the CoC does make sense… apparently a lot of sense!

Attached a scene from a backyard where I ckeck and adjust my split image screens of my Contax and check focus distances of my LF lenses.
The image was taken with the 70HR wide open and was focussed using the groundglass and my 6x loupe, focus point is the water pipe.
Distance to the water pipe is exactly 12m (based on measurement with laser disto).
Now, when I look at the DOF of the actual capture… the 2.34m DOF according to the DOFmaster calculation (set to 7µm for CoC as I use a P45) seems to match the real outcome quite good...

here's the 100% crop: http://tinyurl.com/33xe3nx
 
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archivue

Active member
so enter artec and now arca - these two are close competitors - but very different animals. the artec gives you everything in one package - the arca gives you a different version of nearly everything - just make sure for both they are on a tripod!
pete
you can use the RM3D hand held by removing the rotaslide... the viewfinder is much better than the Alpa !
 

Paratom

Well-known member
thank you for the list-some points are important to me too, some are not so much (I am fine with just haveing Rodenstock), and few I am missing.

Regarding the Artec: I have to say that with a relativly fast lens and one where you do not need to add a center filter focusing with the loupe and the screen of the Artec works pretty good. (could be different with slower lenses)

There is one other advantage for ALPA: They have various different bodies- so you can choose depending which movements you want/need. Or you could add a TC for handhold/light/compact shooting. I really miss this from Sinar - something like a TC and even though of building it myself.

A nice thing for Sinar is that I can use my back with the swivel-adapter. So I dont have to get the back of the camera at all when shooting.

Rhe R3MD sounds very nice as well. It just wasnt available for so long.
I still have not understood how to focus it-need to read somewhere again.
 

Terry

New member
I still have not understood how to focus it-need to read somewhere again.
The numbered ring is what you use for focus. It doesn't have distances but is very precise as it rotates multiple times. Each lens comes with a small card (which I've taken a photo of and store on my iPhone) which gives you a focus distance and the number to dial into for accurate focus at that point. This can be used in conjunction with the DOF scales that I have for the lens (on both the viewfinder and a chart made for me with the correct COC).


Picture credit Arca Swiss - need to click twice (or three times) to clearly see numbers for focus.
View attachment 35220

Sorry not pretty but perfect size for my iPhone! Not sure why it didn't rotate but you get the idea.
Since the ring rotates more than once, each lens has different colored lines on the mount which correspond to the color listed on the card....on this lens all except for the closest distance is in white. When you get to longer lenses you will use more of the full action of the focus ring. You can then use this in conjunction with traditional DOF/aperture to get your desired results.
View attachment 35221
 
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David Klepacki

New member
Could someone please post a link, picture or explain now the Arca RM3D EVF works and what it looks like?
I am posting some pictures for you below. First, notice that the EVF has both portrait and landscape foot mountings to match the orientation of your back. Basically, Arca-Swiss provides three things with each lens that are unique to the lens focal length: (1) a focusing distance card (shown above by Terry), (2) a lens drum with DOF information that slides into the rear of the EVF, and (3) a numbered magnetic viewing mask with shift indicators that attaches to the front of the viewfinder.

Here is how the EVF works. The top of the EVF contains the information about which numbered viewing mask is required to be mounted based on the focal length of the lens and the format of your back (film or digital). The EVF "zooms" to the appropriate magnification as you can see from the pictures. Any focal length from 24mm to 210mm is set by aligning the focal length value to the bottom of the fixed top part (i.e., the rear/bottom part of the EVF is what moves to zoom the view), and then applying the appropriate mask.

The fixed front/top part shows what number mask is required for your particular digital back or film format. The leftmost column displays the range of digital back formats from 37x37 through 56x36 as well as film formats from 645 through 4x5. The rightmost columns correspond to the range of focal lengths. As an example, look at the image showing the top of the EVF fully extended. If you wish to use a 50mm lens and a 48x36 format back, then you would need to attach viewing mask #7. Or, if you wish to use a 210mm lens and a 48x36 back, then you would need to attach viewing mask #9. If you want to use a 35mm lens and a 48x36 back, then you would still use a #7 mask but you must also zoom the EVF by sliding it forward so that the 35 mark appears just below the fixed top part.

Once the EVF focal length is set for your lens/back combination and the appropriate mask is attached, you can then compose your image. A shift composition is performed by sliding the mask up/down/left/right on the EVF. The mask contains small "holes" in it that can be seen when looking through the EVF. Each "hole" that you see in any x-y direction corresponds to 5mm of shift. For example, if you compose your image and see 1 hole visible on the bottom of the EVF and 2 holes visible on the left side, then you would then shift the rear of the RM3D by 5mm downwards and 10mm to the left (opposite direction as the mask) in order to match the back to your viewing composition.

Once your image is composed, then you set your aperture and focus by measuring distance. For example, you can take a distance measurement with a laser meter. Then, you choose your f-stop based on your desired DOF from the lens drum. The lens drum (see the attached picture) contains DOF information based on the shooting distance and the f-stop for the lens being used. Finally, you focus the lens by using the focusing distance card, which indicates the appropriate RM3D helicoid setting based on the measured distance. Of course, shutter speed and iso are set according to the lighting conditions.

That's it. I explained this perhaps with more detail than necessary, so it might sound complicated, but in fact this procedure all takes place as fast as your ability to compose the shot. However, to get really accurate focus, you must calibrate your lenses with your backs and create your own focusing distance cards and DOF information. This is a one-time-per-lens-per-back effort. This is what I did with my lenses and backs, and you can see the amazing accuracy that I now get from the test shot I posted the other day, without moving the digital back at all, i.e., without shooting tethered, without using a sliding back and without any ground glass focusing.
 
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stephengilbert

Active member
I swore I wouldn't get into this tempest, but what does EVF mean to you?

In the non-Arca world, it means electronic viewfinder. My understanding of what Arca makes is that it is a variable (or adjustable) version of a non-electronic viewing/framing device. Like a "son of Linhof Multifinder." Is that wrong?
 

tjv

Active member
Wow, David. Thanks for posting such a detailed reply. The Arca certainly does seem like a supremely engineered piece of equipment. The EVF seems straight forward to use as well.

Can anyone describe how the Alpa VF works in practice? If I'm not mistaken, it also indicates shift movements? Is it true the Alpa SWA is easier to hand hold and is more compact?

In 2004 I was lucky enough to see Luc Delahaye's "History" series in Amsterdam. I remember reading the text in his book that he uses, among several other cameras like Linhof, an Alpa. I had never seen such big and detailed prints in my life. I see Delahaye is now listed on the Alpa web site as an official user. Not that I want to emulate his way of working, but his approach is close to how I'd like to use such a camera. The only thing that puts me off is the occasions I want / need to make portraits.
 

tjv

Active member
I swore I wouldn't get into this tempest, but what does EVF mean to you?

In the non-Arca world, it means electronic viewfinder. My understanding of what Arca makes is that it is a variable (or adjustable) version of a non-electronic viewing/framing device. Like a "son of Linhof Multifinder." Is that wrong?
Funny you mention this as I got all excited for a moment thinking my prayers had been answered with an electronic vf. That would be a brilliant inovation. Rather than use live view while tethering to a computer in the field a little VF plugs into the back to better assess framing and focus. Anyone listening? Phase One, Hasselblad, Sinar?
 

Terry

New member
Framing and exposure can be done with a point & shoot camera. Jack posted about this on a thread he wrote about the Cambo. The camera that might be tailor made for this application is the Panasonic LX5. Small zoom range is 24-90 and you can set the zoom to step mode so the camera will stop at 24, 28, 35, 50,70, 90. Or a Micro 4/3 GF1.
 
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