Determining long & short lens boundaries with my Nagaoka

[nicholas_rab1]

Hello all,

 

I am sure the answer to my question is buried somewhere in the

archives, but I can't find it. I tried!

 

I have a ultralight 4x5 wood field camera, a Nagaoka. I think it is

the same camera as the Anba Ikeda. I have been shooting with a 150mm

for quite a while now, and want to add a long and short lens. As I

like to shoot 6x12, I was thinking something as wide as a 75mm would

be nice. How can I tell if this will fit with at least a little bit

of movement?

 

On the other side, I'd like a longer lens. Probably one of the

smaller Fuji's, the 240 or the 300. While I can probably do infinity

on both, how can I tell the close focus distance. Not worried about

macro with this lens, but getting it down to 3 or 4 feet would be nice.

 

Thank you!

[brian_ellis16]

To know how close you could focus you need to know the length to which your bellows will extend. My vague recollection is that the Nagaoka bellows will extend to about 325mm. It that's correct then the extension is basically the same as a Tachihara give or take a few mms. With my Tachihara I could focus a 300mm lens as close as about 10 feet. You probably could focus a 240mm lens to within 3 or 4 feet with that much bellows extension but I didn't use a 240 lens on my Tachihara so I don't know for sure. There's a math formula for determining the precise close focus distance with any given bellows extension but I don't have it handy, maybe someone else can provide it. If my recollection of the bellows length of your camera is wrong then ignore all of this.

 

With respect to the wide angle lens, to be precise you'd need to know the location of the rear nodal point of a particular 75mm lens. But you could get an approximation of how much movement you'd have by focusing your 150mm lens at infinity, meauring the distance from the aperture of that lens to the film plane, then moving the lens back half the distance to the film plane. That's not going to be exact by any means and there probably are better ways but that way is at least easy as long as you can find something a mile or so away on which to focus your 150mm lens.

[michael_briggs2]

The rule of thumb for the longest lens in order to focus to reasonable distances is that you need an extension of about 25% more than the focal length. Is the maximum extension of your camera about 300 mm? Is so, this rule suggests a longest focal length of 240 mm.

 

To see how a 75 mm lens would work, postion the front standard about 70 mm or so in front of the ground glass. Does the bellows have any flexibilty to allow movements?

 

To get a more exact idea, you want to look up the Flange Focal length or distance of the particular lens that you are considering. This is the distance between the back of the shutter (which is the same as the front of the lensboard) and the front of the ground glass when the lens is focused on infinity. Most of the manufacturers provide this on their datasheets. It is available online in some cases. Then try moving the standard and seeing how the bellows behaves.

 

The exact equations for focusing are near the top of the Lens Tutorial: http://www.photo.net/learn/optics/lensTutorial. So you can work out how close you can focus with a 240 mm lens, for example. To be exact, you have to work out the position of the rear nodal point, which is typically about where the shutter is. This is the issue of the Flange Focal Distance versus the focal length. But mostly you can ignore this refinement, except for telephoto lenses. If you really want a lens longer than 240 mm, a true telephoto lens is an option. These lenses focus with less bellows extension than a regular design lens.

[christopher perez]

When I travel I use your Nagaoka's sister camera, the Ikeda Anba. They are nearly identical, except for wood choice and metal parts finish.

 

My camera handles a 75mm Rodenstock Grandagon with ease (enough rise to make it useful). I would have no problems mounting up a 65mm super wide either. On the other end of the spectrum, my camera handles a 300mm Nikkor M and APO Germinar to around 10 feet.

 

Keep in mind that plasmats take more bellows extension than tessars. So if you have a plasmat 300mm it might not work well except at infinity.

[pico_digoliardi]

BRIAN: "With respect to the wide angle lens, to be precise you'd need to know the location of the rear nodal point of a particular 75mm lens."

 

Is that what Schneider and others call "Back Focal Length (S'F')"?

[michael_briggs2]

"Keep in mind that plasmats take more bellows extension than tessars."

 

This doesn't work as a general rule. As an example, here is a comparison of the 300 mm Nikkor-W, a plasmat, and the 300 mm Nikkor-M, a tessar design. Nikon gives the Flange Focal Distance of the 300 mm Nikkor-W as 284.9 mm -- this means that when focused on infinity, the distance between the back of the shutter and the image is 284.9 mm. Nikon gives the corresponding figure for the 300 mm Nikkor-M as 290.0 mm. So for these two particular lenses, the tessar actually requires a large bellows extension, but only by the slight amount of 5 mm.

 

For Nikon lenses, you can find these figures at pages that branch from http://www.europe-nikon.com/category.aspx?countryid=20&languageid=22&catId=148 -- follow the link to a particular lens, then click on "Main Specifications". The paper brochures had drawings showing what the FFD meant. Fuji, Schneider and Rodenstock also make these data available, either on paper or on the web. Schneider definitely has the values on their website, in the pdf files.

[michael_briggs2]

The basic focusing equation giving in the lens tutorial measure the distances to the nodal points or principal planes (another name) -- the front nodal point for the subject distance, the rear for the image distance. To use them to high accuracy you have to know the location of these. For rough work, such as estimating whether a lens will work on your camera, this refinement can be ignored.

 

The symbol S' subscript F is for the Back Focal Distance. Drawings in paper brochures from Schneider make clear that this is the distance from the rear most glass surface to the image (implied when the lens is focused on infinity.) (There was a thread where it was asserted that there used to be a different meaning.) I don't find this figure to be particularly useful. It might tell you how much clearance you have between the lens and the ground glass.

 

The symbol S' subscript A infinity is used by Schneider for the Flange Focal Distance. This is the distance between the back of the shutter (equivalently, the front of the lensboard) and the image when focused on infinity. Generally this is shown by Schneider in their paper and online PDF datasheet drawings. All four manufacturers give the numeric value.

 

The position of the rear nodal point can be calculated from the FFD. For example, for the 300 mm Nikkor-M since the focal length is 300 mm and the FFD is 290 mm, the rear nodal point must be 10 mm in front of the flange. When the lens is focused on infinity, the rear nodal point is one focal length in from of the image. The flange is position at the FFD value from the image. So the difference tells us the location of the rear nodal point.

 

This calculation is most useful for telephoto lenses, which have a FFDs significantly different from their focal lengths. For example, the FFD of the 360 mm Nikkor-T is 261 mm. Instead of being within a few mm of the focal length, it is 28% shorter. If you wanted to use the focusing equations, you would need to take account of this.

[christopher perez]

Michael, thanks for the clarifications.

 

I had noticed a "trend" when shooting with various lenses. The first thing I noticed is that all my plasmats required more bellows than any of my tessars. And that my Heliars require less bellows than the tessars. I didn't realize Nikkor plasmats behaved differently than my small sample set.

 

I see that I had too few data points. Thanks.

 

To the original poster, in my case, the 300 Nikkor M focuses on my Anba to around 10 feet. And the 75mm Rodenstock Grandagon f/6.8 fits with plenty of wriggle room. If you have different lenses than I, please check to make sure they will work in your intended manner.