Obtaining adequate depth of field

[Andrew Bennett]

I have been feeling my way in LF photography for about 18 months now and I have been reading whatever seems useful. This has included the wealth of information on this site. I am having trouble with a picture I am working on, which is a landscape shot. I am using a Tachihara 5 X 4 with a Nikon 135/5.6 on Ilford FP4+. I have no scanner so I am unable to post the shot. However, I will attempt to describe it and the problem.
The shot is taken on the beach close to where I live in Suffolk, England. I am trying to include foreground detail right in front of the camera, a large dead tree in the middle distance and the sea and horizon beyond. I levelled the camera using a spirit level, focused on the horizon and applied a small degree of forward tilt on the front standard to bring the foreground into focus. I readjusted the focus and repeated this process until as much as possible seemed sharp on the screen. I made several exposures at f32 and f45.

The resulting negatives were pin sharp from foreground to horizon and edge to edge. However, the branches of the tree were not from about two thirds of the way up and where they projected forward towards the camera. This is particularly annoying, as the tree is the main subject.

I also tried taking the shot on a previous occasion with no tilt, just stopping down to
f45, but the depth of field was insufficient.

I would very much welcome any advice on how to rectify this problem.

Thanks


Andrew Bennett
www.biosimaging.com

[Douglas Henderson]

Andrew,

I would suggest not focusing at infinity and instead focus on the tree or more mid-ground. A 135mm lens on a 4x5 focused on mid-ground out to 80 feet or so ought to sharply focus (perhaps matter of opinion) all mid-ground to infinity and quite close foreground at F22 without any movements.

Doug

[ic-racer]

I think the front tilt is hurting you. With wide angle lenses, frequently the best results can be obtained with the front and back parallel. You really need to focus on the correct spot to spread the DOF out evenly. Did you put the focusing standard at the exact metric position between the near and far focal points? Do you recall what the focal spread was in millimeters? If it was less then 10mm, you should have been OK at f45.

[Jerry Bodine]

What ic-racer said. Here's a little more info for that focal length used on 4x5. Based on focusing at the mid-point of the spread:
Spread of 16mm requires f/90
11mm use f/64
8mm use f/45
5.5mm use f/32
4mm use f/22
3mm use f/16
2mm use f/11

This should be way more info than you need for your situation.

Jerry

[Andrew Bennett]

Thank you to the three people who took the time and trouble to reply to my query. I seem to have assumed that just because the camera I am using has movements, they have to be used to achieve the desired effect.
I think I now understand that by focusing at the hyperfocal distance for the format, lens and aperture, I should obtain the required DOF. The website 'Depth of Field Master' has also proved very useful.
I'm still not sure about 'focal spread' and the measurements in millimetres to which Jerry refers.
However, I will persevere !

Thanks again to Jerry, ic-racer and Doug.

Andrew Bennett

[jeroldharter]

A common problem that you are having with near-far focusing is that tilt works great except in circumstances in which you have a vertical object (tree, telephone pole, etc) in the middle of the scene.

The only way to compensate for that is to stop the lens down a lot and to follow the focusing advice given above.

[Bob Salomon]

And remember. Your lens will be in diffraction beyond f22 and degrade the image.

[rdenney]

When you have something orthogonal to the focus plane, stopping down is the only way to pull it into adequate sharpness for a given size print. But there might be a strategy for finding a focus plane that gives you the most of what you want with the least amount of stopping down. After chasing that rabbit hole for a while, though, sometimes it's instructive to just zero all the movements and see if you've done better than with the camera left straight. Sometimes, we just have to give up on the movements and stop down.

And it is true that some visualizations are infeasible.

I made a photo of Mission San Juan in San Antonio, viewed by looking past an old stump in the middle of the mission's plaza. It required an extreme swing, but then I had an issue with trying to get enough depth of field for some grass at the base of the stump. No way--I'd have needed a pinhole camera to get all that to a state of equal out-of-focus. I decided that the perspective was interesting enough to just live with some fuzzy grass, though I did crop most of it out. The image in my head was just not completely feasible. At that point, one has to live with the depth of field as it is, or seek a different composition.

The boundaries of acceptable depth of field are perhaps planar and intersect at the same point the film, lens board, and focus planes intersect when using movements. That means that the depth of field zone is wedge-shaped, with the thicker part of the wedge at the greater distances. Tilting can move the focus plane very close to the camera, but depth of field close to the camera is as narrow as ever.

In this picture below, I used swing to get the right of the opening and the tower both in the focus plane, but gave up on the left edge of the opening. Sometimes we have t make choices.


http://www.rickdenney.com/images/ConcepcionSTwr032793-9_lores.jpg
Mission Concepcion, San Antonio


Rick "noting how the three-dimensional world can confound us" Denney

[Jerry Bodine]

I'm still not sure about 'focal spread' and the measurements in millimetres to which Jerry refers.

Andrew,
The focal spread is the distance (on camera) between the two positions of the focusing standard (i.e., when focused on the far object and when focused on the near object). If your camera lacks a millimeter scale and an index marker that tells you where the standard is positioned, you can make these and place them on your camera.

[Andrew Bennett]

Thanks once again for the latest answers to my original query. I can't wait to retake my 'problem' shot, as soon the weather allows, in another classic English summer !

Andrew

[Peter York]

Also remember that you can assess depth of field on the groundglass while stopping down. In tricky situations it can be a lifesaver, even though the image gets quite dim.

[Leigh]

Remember that regardless of the technique used to increase DoF, your final focus adjustment should be on the main subject.

That's what you and the viewer are most interested in.

- Leigh

[Lon Overacker]

Andrew,

You didn't specifically mention if the tree was vertical, or laying down like a piece of driftwood. I'm assuming from your comments though that the tree is vertical. If that's the case, a couple of folks have nailed the issue already. When you have a strong vertical element trying to focus near/far as you were attempting becomes a frustrating endeavor because that plane of focus - from the near, foreground element and the far horizon is NOT the same or even close to the same plane of focus as the tree, assuming you want all the of tree in focus. So, you end up having to compromise. Still employing tilt, I might focus say 2/3 the way up the tree as the far point and then of course having to rely on a small aperture to bring the horizon in to perceived best focus. You can also still use hyperfocal at this point and perhaps focus slightly past the tree (but that all depends on where it sits in the frame anyway.)

I wrote a guide for this and several other scenarios (http://www.lonoveracker.com/pdf/planeoffocus_v100410.pdf) that may be useful to you, or anyone else who cares to download it. I don't yet have it linked/included on my site, but here's where you can download it. Let me know if it helps or is of any value. I would love the feedback.

Lon

[David Higgs]

thats a great description, so very clear - thanks