Depth of "mid"-field

How do I get the "mid" areas of depth of field sharp? I can get areas at infinity

or in the furthest back of the image sharp and the foreground of the image

sharp. But my mid areas are not as sharp. I'm using a 4X5 Toyo and a new

Schneider super symmar 110 mm aspheric wide angle lens. Do I always have

to use f45? I usually shoot at f16, f22, or f32. Is my lens out of alignment?

Thanks for any info.

If the foreground and distance are in focus this isn't a depth of field issue. I think you have a plane of focus issue. You need to think in terms of a plane that will be in focus and the depth of field being some distance on either side of that plane in focus. The closer to the lens the smaller that distance while at great distances that distance will be greater. My guess is that you have something like a fence near the camera and trees in the distance with a river or something at ground level between them. You adjust so the tilt so that the tops of the fence and the tops of the trees are in focus but the river isn't. Rethink your plane of focus to perhaps put the fence and the river in focus and rely on the depth of field at greater distances to get the trees in focus.

Thanks Dave. I'll give your suggestion a try next week. I've been getting the

furthest point and the nearest point sharp by tilting etc. and relying on depth of

field to get the "mid"range areas into focus.

Milton, I recall a similar question a while back here, but I can't seem to find it on the search tool. The issue discussed was about mid-distance areas appearing not so sharp as far and near.

 

The consensus reached for this particular writer's picture was that the mid-distance parts of the scene lacked the kind of scene content that contributes to micro-contrast. As I recall, the far distance had trees, whose limbs and leaves contributed to an appearance of sharpness, while the foreground had a similar object with hard edges, such as a fence. The middle ground, however, was just grass, and it just didn't appear as sharp.

 

The other thought that I just had regards film flatness in the holders. Perhaps the middle of the sheet film is buckled or bowed outwards slightly, towards the lens. Most landscape scenes would place the distant areas at the top (bottom of the holder), and the near areas at the bottom (top of the holder). The middle distances would be in the center of the film, where you would most expect film bowing to happen.

Milton - Tilts just adjust the plain of focus, they don't guarantee sharpeness image wide. If you are shooting on the salt flats, yes, you can use a tilt and F8 to get everything sharp. However, let's say you have something at ground level 4 feet from the camera and the infinity focus is on some trees 100 feet away, and the trees are 80 feet tall. The optimum compromise situation in my opinion would be to tilt so the plane of focus cuts from the near to mid-way up the trees. Then you stop down. In this case, the middle of your image is where you'll see the softest focus, but normally stopping down solves the problem.

 

My point is that the tilts alone will not give you uniform sharpness everywhere on your ground glass, there usually needs to be some stopping down. My stuff too often has the mid section a little softer than something right along the plane of focus.

 

Sometimes you make it worse by tilting, other times over tilting will hurt you. It's all about compromise. Remember, you are using a big piece of film, and a so-so 4x5 makes a better print than a perfect 35mm in most cases, im my opinion.

 

RJ

If the near is sharp and the far is sharp the only way the mid can't also be sharp is because something in the mid is sticking up above the plane of focus and you didn't stop down enough to make it sharp.

I echo what the others have said. If you use a tilt, you should visualize the region of sharp focus as a wedge which emanates from a line below the lens. It is centered on the plane of exact focus determine by the tilt, and its angular width depends on how far you stop down. As you focus with the tilt fixed, that wedge rotates on the line.

 

Try to visualize the wedge and see if the midrange region of interest is in it.

I disagree with those who say that this is not a depth of field matter. Because this is exactly what it is. If for instance you focus on a small boulder in the foreground and tilt the rear standard to bring the tops trees in the distance into sharp focus...then you have the distance below that line which must be brought into focus through stopping down the lens. That I believe is the matter called depth of field. I shoot everything from 4X5 to 12X20 and I almost never shoot more wide open then F 22 and more stopped down (if I can help it) beyond F32 on 4X5 for defraction considerations.

As others have said in slightly differing ways, once tilt is introduced, DOF becomes a wedge, extending on either side of the plane of focus, narrow near the camera, and wide at infinity. The farther the elevation of an element in the scene is from the true plane of focus, the softer it will be.

 

However, there is another potential problem - film flatness. A problem with film flatness could make it appear that the area of unsharpness is in the mid-region of the scene. That typically isn't a problem with 4x5, but you might have a faulty or damaged film holder.

Yes, Donald, it is an issue of depth of field. My point was to highlight the misconception that increased depth of field is achieved through tilting the lens. The plane of focus is altered and now the depth of field is not related to distance from the camera as we would usually imagine in a fixed geometry camera, but distance from the plane of focus and distance from the camera.

I think your are doing the right thing by tilting and getting the

foreground and background sharp. Don't just stop there. Get a 4x

loupe it really helps in 4x5, especially if you are enlarging

afterwards. Once you get to that point where you get the far and

the close into sharp focus, it is time to take care of the middle

matters. So, all you do is go back and forth with the rear standard

and looking in the groundglass. You should find a

compromising point between the plane where the background

and foreground are in focus, and the plane where the center of

the negative is in focus. If you go somewhere in between and

then stop down, you should see a great improvement, at least in

most cases it does. That way you are not relying only on shutter

related depth of field, but also in the combination of focus and tilt.

related depth of field.

I hope this helps.

Thanks Christian O. I'ts all a matter of compromise after you get the near and

far points focused with tilt? I have a loupe and will try to get all three in focus

(including mid areas) as best I can. Then I'll stop down to my working aperture

and inspect it all again with the loupe. Maybe there are just some images you

have to stop down to f32 or f45 to get it all tack sharp. I think I have to favor the

near items in the frame as I use them alot as framing devices and need them

tack sharp. 2nd in priority would be the mid items. And lastly the furthest

points, as depth of field should catch the far points by stopping down. Milton.

I think of the plane of sharp focus as a pane of glass. Normally the pane is parallel to the plane of the film. When we use tilt or swing, we reorient the pane. Using tilt to get the foreground and background sharp is like laying the pane flat. Anything not in the flat pane, such as tree branches, will need additional depth of field by stopping down the aperture.

Milton,

 

Last summer, by which time I was fully aware of the problem you've described, we found ourselves shooting on 8x10 a classic near-far looming foreground rear tilt vertical of a recumbent tree stump receding into the mid ground with distant ridge behind. The difficulty was posed by the very tall standing trees which also stood in the mid ground and from the camera's perspective were much taller than that distant ridge.

 

Experience had taught me that there was no way I was going to get everything in focus. The upturned base of the stump, which was just a few feet in front of and below the lens, filled the entire bottom half of the frame, and I had to keep the entire length of the trunk razor sharp all the way down. So I focussed on the ridge, tilted on a near (but not the very nearest) part of the stump, threw in some swing following the line of the trunk, and stopped down to 45 2/3. I sacrificed the tall trees in the midground which no matter what I did were going to poke through the plane/wedge of focus described in the previous posts.

 

I want a 16x20 elargement from this 8x10 negative, so when I printed it yesterday I enlarged it to 20x24 and changed the orientation to horizontal. When I mount, I will cut off the top 8 inches of the print; fortunately, the composition is such that no viewer will note the absence of the tops of the trees, ridge, or sky.

sounds like you are tilting the wrong way. I just set up my camera and got everything from 6 ft from the camera to infinity in focus with the correct tilt direction but reversed gave me out of focus mid distance and everything else in focus (kinda anyway).