What lens or technique would work best in this situation?

[Ed Bray]

Thank you everyone! Those suggestions are a great help. I am shooting 4x5. I have access to a 450mm lens and I will try that asap. It will be physically difficult because the camera will be on the ground. I always seem to end up laying on plastic on damp grass, but if I can get what I envisage, it will be worth it.
Geraldine

Couldn't you use some fall to enable you to shoot at a more comfortable height? If the 120mm Macro worked why not try a Super Angulon 120mm or 121mm which I suspect will have a much greater image circle than the Nikkor Macro you tried, this would allow you enough movements to a) not lay on the grass (unless you have a penchant for that) and b) allow more movements to enable you to get the focus in the plane you really want.

[Leonard Evens]

Maybe I am doing the calculation incorrectly, but I get between 3 and 4 mm DOF for a 210 mm lens at f/5.6 on a 4x5 camera focused at 2 feet (610 mm). It wouldn't be much different for an 8 x 10 camera.

I also tried it with my 4 x 5 camera using a 210 mm lens set to f/5.6. I focused on something at 2 to 3 feet. The background, about 100 feet away was pretty out of focus. I could make out general shapes but no detail.

So I don't know just what you want. It might be pretty hard to arrange things so that the background was just a complete blur with nothing whatsoever showing. For example, the hyperfocal distance of a 210 mm lens at f/5.6 using a CoC of 10 mm is about 788 mm. With that criterion for sharpness everything from 394 mm to infinity would be "in focus". A 10 mm CoC would be a pretty coarse criterion for sharpness, but it would still allow you to detect general shapes.

I think the only way to arrange to have nothing at all showing in the background would require the use of a photeditor to blur the background.

[Armin Seeholzer]

If not, go to a smaller format using the same 450mm again at the largest aperture.

This is just wrong, as bigger the format as lesser the DOF!

Cheers Armin

[Drew Bedo]

I have a split +diopter close up accessory lens. Its intended use it to allow sharp focus on both a fore-ground subject and distant background. For your application, I'd try it the other way to throw the trees way out.

[Geraldine Powell]

Re the split diopter accessory lens, I am curious. Where are they sold and do they work for more than more focal length? What are they, exactly?

BTW I got a better result with the 450mm lens, but it is terribly uncomfortable to use close to the ground. I could use one those things on wheels that car mechanics use.
Geraldine

[Leigh]

And a bigger the format as lesser DOF!

Actually, the longer the lens focal length the shallower the DoF.

It has nothing to do with format.

- Leigh

[Ed Bray]

Re the split diopter accessory lens, I am curious. Where are they sold and do they work for more than more focal length? What are they, exactly?

BTW I got a better result with the 450mm lens, but it is terribly uncomfortable to use close to the ground. I could use one those things on wheels that car mechanics use.Geraldine

Why do you need to lie on the ground? The 450mm lens has more than enough coverage to allow you to use fall or raise the bed to enable you to work at a more comfortable height.

[5063]

Actually, the longer the lens focal length the shallower the DoF.

It has nothing to do with format.

- Leigh

Image magnification and aperture rule depth of field. Focal length only has influence as part of the of the make-up of image magnification. If you use a longer lens, but at a further distance to maintain the same framing, you will have the same depth of field. Perspective will change, but DOF will not.

[Leigh]

That's true.

I was __assuming__ a fixed camera position for varying focal lengths, which
changes the magnification and thus the DoF.

The usual reason for changing focal lengths is to change the framing/magnification.
That's the whole reason zoom lenses, which enable you to change focal length, are
more popular than camera stands, which enable you to change camera position.

I can envision few situations in which you would want to
"change the distance and maintain the same framing".

- Leigh

[Nathan Potter]

Drew Bedo above has an excellent suggestion of a split magnification supplementary lens. It would be simple and easy to use and yield a dramatic out of focus section.

These consist of a + diopter lens cut in half that screws into the front filter ring. Usually they are used with the magnifier section bringing the foreground into sharp focus relative to the background thus increasing the effective depth of field of the lens. But it could be used to throw the background out of focus just as easily.

A couple I have come from Cokin filters. They need to be used at fairly large apertures to avoid imaging the cut surface on film. And I'm not sure about coverage for the 4X5 format.

Nate Potter, Austin TX.