Arca Swiss bellows, rail and lens focal length

[NoBob]

I'm trying to understand the relationship between bellows, rail length and lens focal length.

On an F-Line (171 cm type) camera, would anyone know how they relate?

About the long bellows, if you have the 40cm folding rail, would you need to get a rail extension to use the long bellows? Or use a different rail?

[biedron]

Very roughly speaking the required bellows extension is approximately the lens' focal length. More precisely, it is the "flange focal length" or "flange focal distance" that is the indicator. Here is a table that I usually refer to (scroll down on the page):

http://www.ebonycamera.com/articles/lenses.html

With the folding rail, the max. bellows extension you can get is (a few centimeters shy of) the rail length. You would need an extension rail to get more length. The telescoping or "optical bench" type rail will get you about 50% more extension than the total rail length.

So, you can use the long (50cm or 70cm) bellows with a 40cm folding rail, but you won't be able to go to max extension - you'd need a rail extender.

Hope this helps.

Bob

[NoBob]

Thanks Bob, so the standard bellows at 38 cm (072040, Standard bellows 4x5“, 38cm, synth, according to http://www.largeformatphotography.info/ARCA.pdf) can be fully extended on the 40 cm folding rail.

So am I reading the chart correctly? An F-Line with standard bellows extended to 38 cm on the 40 cm rail, I could use the 360 mm lens below, but not the 480 mm?

Apo-Sironar-N 360mm f6.8 3 435mm 8x10" 333mm
Apo-Sironar-N 480mm f8.4 3 500mm 8x10" 452mm

And even though the focal length of this lens is 180 mm, it would need the bellows almost fully extended?

Makro-Symmar HM 180mm f5.6 1 375mm (1:1) 354.3mm

[Leigh]

The rules of optics apply to all cameras (we'll discuss LF cameras with bellows). The particular brand is irrelevant.

There are two focal lengths of interest, the Flange Focal Length (FFL) and the Optical Focal Length (OFL).
Both dimension are published in the lens data sheets. FFL may be less than, equal to, or greater than OFL.

The the FFL is the distance from the film to the front of the lensboard when the camera is focused at infinity.

As the subject gets closer, focus is achieved by moving the lens forward, away from the film.

If you bring the subject quite close, for a full-size image (1:1), the lens will extend from its infinity focus position
by a distance equal to its OFL, so the distance from film to lensboard = FFL + OFL.

For the 180mm Makro-Symmar HM (FFL + OFL) = 354.3mm, which implies that the FFL = 174.3mm (= 354.3 - 180).

- Leigh

[biedron]

I should have pointed out that the extensions I was quoting were for infinity focus. Focusing closer will require more bellows extension. 354.3mm is almost certainly the close-focus, 1:1 image size focus distance for the 180 Makro-Symmar

And yes, it is my experience that the Arca bellows can be stretched a bit more that the stated size; how far you want to push it depends on your willingness to risk damage. But I think a few cm is well within the bounds. I don't think you could manage the 480mm lens with the 38cm bellows. Note that telephoto design lenses have flange focal lengths less than the focal length of the lens. So, for example you'd be able to infinity focus the Nikkor T ED 500mm lens with the 38cm bellows

Bob

[neil poulsen]

Thanks Bob, so the standard bellows at 38 cm (072040, Standard bellows 4x5“, 38cm, synth, according to http://www.largeformatphotography.info/ARCA.pdf) can be fully extended on the 40 cm folding rail.

So am I reading the chart correctly? An F-Line with standard bellows extended to 38 cm on the 40 cm rail, I could use the 360 mm lens below, but not the 480 mm?

Apo-Sironar-N 360mm f6.8 3 435mm 8x10" 333mm
Apo-Sironar-N 480mm f8.4 3 500mm 8x10" 452mm

And even though the focal length of this lens is 180 mm, it would need the bellows almost fully extended?

Makro-Symmar HM 180mm f5.6 1 375mm (1:1) 354.3mm

What you suggest is correct. You can easily use the 360mm and the 180mm at 1:1. But, you would not be able to use the 480mm.

I don't know too much about the collapsible 40cm rail. Does it come apart? If so, you could possibly get a 300mm bracket and use the two separate 20cm lengths of the collapsible rail to extend the camera's rail to about 550mm (or a little more) for the 480 lens. You would, of course, also need the long bellows.

OR: If it fits on one of the ends of the collapsible rail, it sounds like you could get the 20cm extension to obtain a 60cm rail. But, I'd be concerned about that small bracket that's used to hold the 40cm. Dunno, though? Are those small brackets sturdy enough to hold a 60cm rail? What bracket do you use?

On a related point, one can use both the long bellows and the leather, folding bag bellows and pretty much use any lens from 75mm and up with movements. I did this for a while. I could use the folding bag bellows just fine for my 180mm. For a 250mm or higher, I would need the long bellows.

[Emmanuel BIGLER]

In addition to all good informétion already given here, we can add

- thare are 2 types of Arca Swiss rails, type 1 (discontinued but easily found on the used market) and type 2 (present type).
Type 1 is similar to the older, pre-1984 Oschwald-type rails.
A type 2 rails is thicker and has a circular hole in the middle. With a rail type II, you can screw an extension rail in front of the main rail. Those extension rails exist in 15 cm (6") and 25 cm(10").

- As Neil mentioned, the main problem if you wan to use a 480 mm non-telephoto will be to buy a longer bellows or an intermediate function carrier & format frame and a second bellows, this being the most expensive solution ;)

- Type II collapsible rails are almost exactly similar, once locked, to any type II rail. Hence they can be mounted on almost any type II bracket, with the only restriction that the collapsible rail has a locking pin at one end, preventing the rail to slide completly onto the bracket; this is a minor problem since usually people use either a collapsible rail or a telescopic (rail + bracket) assembly.

- The usual basic rule for Arca Swiss telescopic rails is: bracket twice as long as the rail elements, hence 2 rail elements per bracket, each rail can slide outward by 50% of its length, total lengths = bracket length + 50%. hence a 40 cm bracket can offer 60 cm of maximum extension with two 20 cm rails. But you can use a 20 cm rail plus a 40 cm collapsible rail on a 50 cm bracket and get much more than 60 cm of total extension.

- Using the standard 38 cm bellows with lenses above 40 cm of focal length requires a telephoto lens like the 400 mm apo tele xenar.

[mike rosenlof]

I have an Arca with the optical bench rail that was standard for the 4x5 F-line. 30cm, I think.

For what it's worth, I was able to focus a 360mm apo nikkor down to about 10 feet or so with the rail parts spread as far as I could get them and still get locked down. It was also pushing the extension of the standard bellows. I use the past tense because I have since added an extension rail and longer bellows.