Digital back on an Arca-Swiss 4x5?

[badbluesman]

Does anyone know how feasible it is to use a digital back such as the Phase One on an Arca-Swiss 4x5 classic (actually a 5x7 rail with a 4x5 format set)? What about using really short lenses such as 28mm or 35mm? I have the 4x5 synthetic bag bellows. Would I need extra-recessed boards to use those lenses? I currently use the Linhof adaptor board and have all of my lenses mounted on Linhof-type boards. Are camera movements possible with really short lenses such as 24mm, 28mm, 35mm, using the 4x5 Arca?

I have the following lenses that would work in terms of focal length for a digital back: 45mm Grandagon (moderate wide), 75mm Grandagon (normal), 150mm Apo-Sironar-S (portrait lens), 210mm Apo-Sironar-S (telephoto for landscapes); 300 mm Nikkor-M (very long telephoto). Would these lenses work well optically with a digital back?

For a wider lens, would the 35mm Grandagon work? Or would it be better to invest in one of those specially-designed digital wideangle lenses, to avoid color fringing toward the edges?

Does Arca make any special viewing magnifier or replacement ground glass for the much smaller digital format? How would the digital back be mounted onto the camera?

I am aware that Arca-Swiss makes a small, dedicated digital view camera similar to the Horseman. However, I cannot afford to invest in an entirely new system right now. Just buying a Phase One back and a digital wideangle lens will carry a hefty price tag. This is why I hope to be able to use my existing camera and lenses.

[Frank Petronio]

You have a very nice film kit but it would be a frustrating choice for a medium-format 6x4.5cm sensor format. If money is an issue that is preventing you from getting a dedicated and appropriate digital body, then maybe you have to decide and commit to either large format film or medium-format digital?

I suppose you could make a few shots using digital on your film set-up simply to see how you like the files and workflow, but be prepared for a lot of compromises starting with accurately focusing the darn thing.

[Emmanuel BIGLER]

What about using really short lenses such as 28mm or 35mm? I have the 4x5 synthetic bag bellows.

Hello from France !
It might not be totally impossible to focus a 35 mm on an Arca Swiss monorail camera with the right combination of recessed boards and ultra-flat bellows, thanks to the modular design of the system.
However the ultra flat bellows exists only for 110 mm frames. To the best of my knowledge, 5x7" Arca Swiss monorail cameras use either the older 171mm standard or the new 141mm, not the 110 mm.
But I doubt that you could actually focus a 35 with a synthetic bellows designed for the 5x7" model, I am not sure that there exist in 141 or 171 a recessed A/S board so deep that you could easily focus such short focal lengths.
But even doing so, after playing with the bellows and boards, you'll soon be facing a very difficult technical problem for focusing.
With a 35 mm focal length, whatever the lens design and film or sensor format might be, the amount of travel required to change focus from infinity to one metre (3 feet) is only 1.2 mm ; with a 28 this travel drops to 0.8 mm. Now imagine that you have to properly set the focus within a fraction of the previous travel !!
The rack-and-pinion focusing system of Arca Swiss monorail cameras is designed for 20 mm of travel for each turn of the focusing knob.
So make your own conclusions, but if Arca Swiss have introduced the Rm3d and RL3d camera systems with a very fine pitch helical mount, it is not only for the pleasure of machining precision helical mounts... it is simply to meet the requirements of the demanding photographer using medium format silicon sensors, who wants to take advantage of top-class digital lenses recently introduced on the market by Schneider and Rodenstock. And to be able to apply some very precise amounts of tilt. Not 10°, but one degree or even less.

If you want to shoot table-top shots on a "645-size" silicon sensor with relatively "long" focal lengths down to, say, the 75 mm range, you'll have very little problems to properly focus even wih a classical monorail. No more problems than "film" photographers who have used the 75 and the 90 in 4x5" for decades
But focusing the 35 and the 28 is another story.

[erie patsellis]

well, there's always the Betterlight/Phase One scanback approach, 7x10 cm sensor, ~120mm diagonal, extreme resolution, etc. Depends on your patience (and light levels)

[Emmanuel BIGLER]

I can add a personnal experience about focusing tests with short focal lengths on a monorail camera.
I had the opportunity (and pleasure) to make a focusing test on a A/S 6x9 monorail (F-classic) fitted with a 22 Mpix medium format sensor and a range of lenses from a "digital" 35 mm to a classical 180 mm "for film". The focusing system was the standard rack and pinion, 20mm-per-knob-turn, no helical mount on the lenses. The ground glass was the standard 6x9 A/S combo = Fresnel + ground glass designed for the 6x9 format.
The test was conducted in parallel by another professional photographer, 30 years of experience focusing view cameras in all possible professional conditions.
We did not try no cheat and made the focusing like we would usually do in the field i.e. simply and quickly in order to avoid visual stress wich eventually is counter-productive. We paid attention to grossly defocus the camera after each shot in order to avoid that the 2nd photographer could be influenced by the previous focusing position. No cheating at all ;) .
We checked for proper focusing by shooting against A4-size good quality copies of the 1951 USAF resolution target. Various distances to the targets allowed us to actually reach resolution figures that would not be limited by the target itself.
We found no problem to reach the maximum sensor resolution, about 60 cy/mm according to the pixel pitch (and the sampling theorem ;) ), for both of the operators, down to the focal lengths of 55 mm.
For the 35 we really hard times finding the proper focus and we had to do some "focus-bracketing" in order to eventually get the right focus. Clearly, finding the proper focusing with the 35 and the 20mm per turn rack and pinion was out of our control. At least using our usual focusing method, simple & quick and the camera configuration we had in hands : a standard 6x9 F-line with its standard focusing ground glass.
Among lenses that were tested I had brought my vintage Zeiss-Linhof planar 2.8/100 designed for the 6x9 format in the fifties... for film, natürlich !!.
To my satisfaction (I did not know what the test would deliver) the venerable lens performed exceeding well, i.e. we reached the maximum resolution of the sensor, like with other modern "digital" lenses, and this was achieved without spending hours in focusing. And without any special focusing aid, we used the good 6x Rodenstock loupe covering 6x6 but we could have used any good loupe as well.

[Bob Salomon]

Linhof makes an adapter to put Hasselblad V backs (digital or analog) on any 4x5 Graflock camera back.

[rdenney]

well, there's always the Betterlight/Phase One scanback approach, 7x10 cm sensor, ~120mm diagonal, extreme resolution, etc. Depends on your patience (and light levels)

Not just your patience, but the patience of your subjects.

Rick "who can focus a 47 on a Sinar F2--with care" Denney

[erie patsellis]

I have a different perspective, as most of my subjects are inanimate objects, and barring earthquakes, stay pretty still.

[badbluesman]

Thanks, everyone. From the comments above and from a conversation with Rod Klukas at Photo Mark, I have concluded that I have a great system for film, but that digital would require almost an entirely new system based around a camera like the Horseman LD or the Arca-Swiss R3D (not to mention new digital lenses). For the time being I am going to stick with LF film and DSLRs for hand-held work.

[Gordon Moat]

......
With a 35 mm focal length, whatever the lens design and film or sensor format might be, the amount of travel required to change focus from infinity to one metre (3 feet) is only 1.2 mm ; with a 28 this travel drops to 0.8 mm........

Bonjour Emmanuel,

How did you calculate the distance of the focus travel for the lens? Is there a simple plug the number in formula that gives that answer?

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Emmanuel BIGLER]

How did you calculate the distance of the focus travel for the lens?
Ooops ! yes, Gordon, I simply use Newton's formulae ; the displacement of the image of an objet locaced at a distance D, image moving with respect to the focal point (where one finds the image of infinity), is equat to (f*f)/D or f^2/D where f is the focal length and D the finite distance from the lens to the object.
If we take one metre / about 3 feet as the reference distance D, the formula is simply
displacement in mm = (focal lenth in mm)^2 / 1000
e.g. for a focal length of 100 mm you find 1 cm or travel from "infinity" setting to "one metre" ; this is very comfortable with a classical knob, 2 cm per one full turn.
With a 55 you get (55x55)/1000 = 3 mm this is without question accessible to the same focusing knob, 3 mm is 1/6 of a turn 54 degrees of rotation.
With a 35 mm you get (35x35)/1000 = 1.2mm this starts to be difficult @20mm per knob turn,
and with a 28, you get about .8mm, this is really problematic with a conventional rack and pinion@20mm per knob turn, but easy to achieve with an helical , at least if you know where the focus is located.

[Gordon Moat]

Merci Emmanuel! Great explanation of how you got to those figures. This is one answer I will be bookmarking. I have a degree in Fine Art, not mathematics, so I never knew of that formula. I'm more of an artist with a camera, than a technical photographer.

What I hope to do with this is create a template I can print onto adhesive backed paper, and then place onto my 4x5. I am hoping that I could fit focus distance marks for a 90mm, 135mm, and 180mm all onto one tape, or at most two different tapes.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

[Emmanuel BIGLER]

An additional note:
Regarding Newton's formulae as mentioned above : the amount of travel at rear, required to focus to a certain object distance, depends only on the effective focal length, and is totally independant from the lens design. Those formulae are really simple and universal !
In other words, a 360 mm Apo Ronar or a 360 mm Telephoto need exactly the same amount of travel with respect to the focal point, although their flange-to-focal distance is completely different : about 360mm for the apo ronar and 210 mm for the Tele Arton telephoto lens. The extra amount of travel required to focus from infinity to the same object distance is the same for both lenses.

[Gordon Moat]

Awesome! You are one of the great resources in photography. Merci!

[RK_LFteacher]

All of the above are correct. However, there can be a problem for standard bellows cameras when coupled with wide angle lenses and digital backs. You would need to know exactly when you are at infinity. And lenses do vary slightly. And also where the nodal point lies to measure for infinity. With this information you can do an accurate focus adjustment.
The Arca RM3d/RL3d with wide angle lenses are even more precise verses even their great rail cameras. Partially because it is very hard to accurately focus by eye with lenses such as 35mm, 47mm, and the shorter 23/24/28mm objectives. The focus is set at the factory by having an integral helicle in the body on the R cameras.
The Arca rails from about 55mm and longer are very accurate for digital and super accurate for film. Remember that film is thousandths thick and digital is only 1 micron! This means that you must be a minimum of 4 times more accurate at focus to be sharp. Schneider has a great article on their site and copied to my site as well, on this phenomenon called 'Why choose Digitar'. It has great info in general on the difference between focusing for film verses digital. So, in my opinion if you are looking at short lenses for digital and want the most accurate focus the RM3d/RL3d is the way to go. For standard lenses, you can go with traditional cameras and obviously for long focal lengths they are way better. The longer focal lengths have narrower depth of focus and therefore are easier to focus as they pop in and out of focus while you are viewing making it far easier to get sharp focus optically.
Hope this adds information.
Rod