Prints out of focusgreenspun.com : LUSENET : Large format photography : One Thread
I made my first contact prints. All prints are out of focus in the top half of the picture. They are landscape black and white. I have been using front tilt only. I focus 1/3 the distance from the foreground to the background. I'm trying to get the look of the entire picture in focus front to back. They seem to be in focus when looking through the camera. Any ideas.
-- tim kimbler (email@example.com), June 01, 1998
Check the negatives. I assume they have the same problem.
The "1/3 distance" is only a rule of thumb. Did you look at the ground-glass through a loupe when you took the photos? It could be that you gave too much or too little tilt to follow the Scheimpflug rule.
-- Alan Gibson (firstname.lastname@example.org), June 02, 1998.
Tim, You stated that your inspection of the groundglass area (center, top and bottom, and all four corners?), after applying front tilt, focusing 1/3 of the way into the scene, and stopping down to an appropriate aperture, reveals a sharp image on your groundglass. I will assume that your set-up, focusing, and stopping down procedures are all correct.
After correctly doing these things, if you are consistently getting contact prints that are out of focus (soft focus) in the top half of the image/negative area, you probably have a mis-alignment of the groundglass/focusing plane and the film plane. That is to say, the groundglass surface (focus plane) is not in the same place as your film surface (film plane). It could be out of alignment in the top half of the image area alone.
There are several easy ways of checking this. I've seen several good responses re: film plane/groundglass alignment on this forum. Do a search, you'll find several postings instructing you how to do this procedure/test. Everyone has their own method. They are all much easier to show than to describe. Briefly, the process is as follows:
Measuring the relative positions of the groundglass surface vs. the film plane surface is best done with the back removed from the camera body.
You will need some method of precisely measuring the distance from a fixed point (a straight metal ruler on edge across the interior surface of the back is good) to the center and all four corners of the groundglass surface. A second ruler, with very fine increments, placed perpendicular to the first ruler, can be used to take measurements at several points across the groundglass focusing plane. I use a vernier caliper measuring device, with a protruding pin to measure the depth of holes, to do this.
Carefully measure the distances to the center and all four corners of the groundglass focusing surface from your fixed point. Now, insert a film holder into the back, WITH a sheet of film in the holder. Repeat the measurements of the distances from the same fixed points to the center and all four corners of the film plane.
I suspect you will notice that the top half of your film surface is out of alignment with your focusing surface. It does not take much mis-alignment, a few 1/1000's in. is enough to cause out-of-focus images.
If so, shim (or otherwise adjust) the groundglass itself so that it corresponds to the film plane surface. I don't know what type of camera you have, but most allow for some type of adjustment of the groundglass itself, in or out. You can usually shim or adjust any of the four corners, or the entire top or bottom half of the glass if necessary.
This test should be done by anyone using a view camera, whether one is experiencing visibly soft negatives or not. Often, a slight mis-alignment of these two surfaces leads to negatives that are not as sharp as they could/should be.
Hope this helps, good luck, Sergio.
-- Sergio Ortega (email@example.com), June 02, 1998.
On the next images you shoot, don't use front tilt unless you actually need it. Most images don't need tilt for a sharp image. Use movements only when you actually need them. Many do use movement because the camera has it, even when it isn't really needed for a good image.
-- Dan Smith (firstname.lastname@example.org), June 03, 1998.
My camera is a Tachihara 4X5 and Nikon 210W. Both are in excellent condition. I may not understand the process of focusing and movement. I do use a Toyo loop. When I focus the entire image is not sharp. Usley most of the foreground and middle of the image are sharp. The background is out of focus. When I stop down to F32 or F64 the image is to dim to tell if it is in focus. Should the entire image be in focus when viewed through the camera if all movements are correct? Would it be better to point the camera down and tilt the back to get the entire image in focus?
-- tim kimbler (email@example.com), June 03, 1998.
When photographing a plane, which long-focus landscapes roughly are, you should be able to get it all in focus, even at maximum aperture. When you use a loupe, you say you can usually get the foreground and middle in focus, but the background is out of focus.
1. With the camera like this, when you adjust the focus, can you get the background in focus? If not, you have a problem, possibly with the lens. If you can, then move to step 2.
2. Increase the tilt. When the middle is in focus, is the background better or worse then before? If worse, then decrease the tilt. If better, then try a little more.
3. Read "The Camera" by Ansel Adams.
-- Alan Gibson (firstname.lastname@example.org), June 04, 1998.
LONG Follow up to Tim: Alan is correct. When composing the average (if there is such a thing) long-focus landscape scene, with the immediate foreground receding into infinity, everything should be in focus across your groundglass, at your widest aperture, when applying the appropriate degree and method of tilt.
While everyone seems to have his/her own method of setting up, applying movements, and achieving adequate focus, you might want to try the following steps to achieve acceptable focus across the groundglass. I will assume that you have only the most basic field camera movements, including both front and rear base tilts. On-axis tilts allow for a different approach to focusing, but most field cameras don't have these movements.
OK Tim, you've lugged your equipment up the mountain, you are set up, and you've pretty much settled on your final composition. Let's say your scene contains important elements in both the foreground and middleground, gradually transitioning into a distant mountain range in the far distance at infinity.
Your rough set up, with both front and rear tilts (as well as all other swings, rise and fall, etc.) set at zero degrees and centered, positions the distant mountain range at the very bottom of your groundglass, and the immediate foreground elements at the very top of your groundglass. Remember, we're seeing upside down and reversed here.
Your pre-visualization of the scene has everything, front to rear, in extremely sharp focus. With your lens at its widest aperture, and all movements at zero and centered, your groundglass shows that when you focus on the near elements (the top of your groundglass), the distant elements fall out of focus. And when you focus on the distant elements (the bottom of your groundglass), the near elements are out of focus. Additionally, if you focus about 1/3 of the way into the scene, somewhere into the middleground (the central area of your groundglass), both near and far elements are now out of focus. How do you achieve your pre-visualized composition?
I suppose you could stop down to f32 or f64, set focus at the hyperfocal distance for your lens, and rely on depth of field. But, let's not do that. Optically, f64 would not be the best choice. And even this aperture might not achieve your pre-visualized DOF. Besides, that's not why you bought a view camera in the first place, with all those wonderful movements.
First, using your loupe, with the focusing track movement, focus on the distant (infinity) portion of the scene, at the bottom of the groundglass, and bring it into sharp focus. Now, while watching the groundglass, slowly apply a tilt movement--either by tilting the front standard forward, or the rear standard backward--till the foreground elements, at the top of the groundglass, gradually fall into focus. Temporarily lock down your tilt movement at this point.
If you were watching your groundgglass, you noticed that as you applied this tilt movement, and saw the foreground elements come into sharp focus at the top of the groundglass, the distant elements, at the bottom of your groundglass, have now fallen slightly out of focus.
Next, using the focusing-track movement, re-focus on the distant (infinity) elements again, at the bottom of your groundglass, carefully bringing it back into sharp focus. You will now notice that the near elements, at the top of the groundglass, have fallen slightly out of focus as you re-focused on the distant mountains. Damn!
Now, unlock your original tilting plane, and apply a little more tilt movement, carefully bringing the near elements, at the top of the groundglass, back into sharp focus. Then, repeat the steps in the last three paragraphs till all areas of your groundglass are in acceptably sharp focus.
These tilt focusing movements are a bit of a juggling act, you will probably have to repeat these steps several times, slowly bringing both the near and far elements into focus. Each movement is inter-related, affecting previous settings. It is simply a process of refining your focus, back and forth between tilt movement and focus track. With experience, it will become automatic, and very quick.
At this point, when both the top and bottom (near and far elements) on your groundglass image appear acceptably sharp, you can lock down the camera movements, choose your best taking aperture, and do a final inspection of the groundglass, with your loupe, before making your exposure. Even if the focus was not previously totally sharp across the entire groundglass, many times stopping down will bring everything into extremely sharp focus.
Knowing when to use either front or rear tilt, or both at the same time, can be confusing. With certain lenses, those having limited image circles for the particular format in question, it is better to use rear tilt. Many LF photographers find that front tilts (and swings) tend to displace the image circle more than rear tilts (and swings) do, sometimes resulting in vignetting. But, if you're photographing architecture, trees, hoodoos, etc., and don't want converging lines, you're better off using front tilt alone, and leveling your rear standard/film plane at vertical.
Also, choosing either a front or a rear tilt will have a marked effect on the "look" of the image. With certain near-far compositional relationships, foreground elements will tend to "loom" (for lack of a better or more descriptive term) more, or less, when choosing either front or rear tilt movements. Try it and see for yourself.
Sorry for the dissertation, guys. I was just intrigued by the question.
Hope this helps. Sergio.
-- Sergio Ortega (email@example.com), June 04, 1998.