Changing depth of fieldgreenspun.com : LUSENET : Large format photography : One Thread
Can anyone help with what is probably a silly question? I understand that I can change the plane of focus by tilting or swinging the front of the camera, I can also get a similar effect by doing the same thing to the back of the camera but that this also changes the shape of the image. 1. What is the effect if I swing or tilt both the front and the back? Is there any advantage in doing this? 2. If the back is straight (to keep the geometry right) and I swing or tilt the front to change the plane of focus) will I still get the geometry right? I have tried to get these answers by experimenting with polaroids but this is very expensive and so would be grateful for any pointers.
-- Joan Roberts (Joanroberts@hotmail.com), February 27, 2000
Joan, tilting the front moves the plane of sharp focus from parallel to the film plane to almost perpendicular to the frame. While tilting the back standard creates image distoration. This is a very difficult subjedt to expalin in a post, however, the best source of information I have found for people to visualize this process is Merklinkers web site, which is linked to this LF home page, I beleive under resorces at the bottom. On his site, he has some short movies that show the relationship to the plane of sharp focus and the front tilt angle, this will really help. Merklinger also has a book called "focussing the view camera", and although it is jammed packed with good information, it is very technical and not well written. However, he does have some incredible information in that book. If you love math, buy the book.
Also any good view camera book will show the basics on movements and the effects on the image. Seeing this will make things clear, trying to explain it is close to impossible... good luck.
-- Bill Glickman (firstname.lastname@example.org), February 27, 2000.
A good book on view camera technique will go a long way - try Stroebel's 'View Camera Technique' or Steve Simmons. Basically, movements (tilts ad swings) at the back control image shape as well as where the plane of focus lies, while movements in front (again swings and tilts) control where the plane of focus lies and leens to subject relationship. Typically, movements at the back are better reserved for keeping your verticals straight etc i.e. to control shape. For controlling the plane of focus, typically one uses the movements on the front, especially when there are image shape considerations as well (which back movements have to be reserved for). Also, remember that back tilts and swings do not place demands on lens coverage whereas front tilts and swings do. The previous reference to Merklinger's site will help you understand how the plane of focus is controlled with tilts and swings. To answer your questions 1/ tilting both front and back will alter both the shape as well as the plane of focus. Sometimes when you do not have shape considerations, this is useful. For example, if your camera is just inches off the ground and you want the plane of focus to lie along the ground (and there are no overwhelming shape considerations i.e., no verticals in the form of trees), you may find mechanical and optical limitations i.e., bellows binding, limited tilt on front standard etc. Then you may well need to use tilt and swing on the rear standard to get your plane of focus where you want it. Hope this helps. DJ
-- N Dhananjay (email@example.com), February 28, 2000.