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07/31/2005 01:50:58 AM · #1 |
What does a tilt shift lens do?
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07/31/2005 01:55:10 AM · #2 |
A lens capable of both tilt and shift movements.
Such lenses permit certain types of lens movements with respect to the body even if the camera does not have a lens separated from the body by a flexible bellows mechanism.
Tilt-shift lenses can be used to correct for the problem of converging verticals, for example. This is lens shifting or perspective control - see the section on perspective control for more details.
The lenses can also tilt, which lets you move the optical axis away from the perpendicular of the film plane. Normally the optical axis of a lens is precisely perpendicular (90°) from the film surface, but tilt lenses let you alter this angle, which is useful for altering what parts of an image are within the depth of field and are thus in focus.
Above was from PhotoNotes.org
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07/31/2005 01:55:13 AM · #3 |
//www.photo.net/equipment/canon/tilt-shift
googled: "what does a tilt shift lens do?"
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07/31/2005 01:59:03 AM · #4 |
Also called a perspective control. Good for shooting buildings to make it look like it's not leaning over.
If you use a shift lense in front of a mirror and shoot at the mirror you can photograph it without appearing in the mirror (like a vampire :P). |
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07/31/2005 02:05:32 AM · #5 |
here's samples...
  
i'm still learning how to use mine :) |
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07/31/2005 02:16:12 AM · #6 |
after reading all that i still dont get it
i would have to look at it through the view finder to understand it
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07/31/2005 02:26:41 AM · #7 |
it's a bit complicated i suppose.. my Arsat shifts 11mm so that means when you're normally shooting, you might end up with tops of cars or people... with the barrel of the lens shifting 11mm, I can get all building and no tops of people or cars... does that make sense?
a tilt on the other hand is great for macro photography or product photography... because the lens can tilt means you can adjust and control your DOF so that the plane of the film is aligned with the plane of your subject...
sounds confusing but it really isn't... it just needs some practice... |
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07/31/2005 06:40:50 AM · #8 |
I did these changes in PS, but I understand the effect is similar.
Look at the line of windows on each edge.
1) Out of the camera
2) With Transform - Skew applied
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07/31/2005 09:44:14 AM · #9 |
Here's a somewhat broader discussion about what these lenses do:
Overview
One of the joys of working with large-format cameras is that the lens and the film plane are mounted independently of each other and connected with a flexible bellows, so it is possible to adjust their positions relative to each other. Large-format camera lenses are designed to throw an "image circle" substantially larger than the size of the film used with them, and the cameras are designed so that the film may be positioned anywhere within that image circle by the photographer; in essence, you can "crop" in the camera. Tilt/shift lenses for SLR cameras are designed to bring this functionality to the smaller format. They are more restricted in their range than a large-format system would be, due to mechanical considerations of the design of the camera body itself, but they are very useful.
How Does "Shift" Work?
All of us have had the experience of trying to photograph a tallish building with our SLR and finding that to include the whole building in the frame we have to point the camera up. When we do so, we get dramatically converging vertical lines, as perspective is introduced and these lines converge towards a common vanishing point. The more "up" we tilt, the more acutely the vertical lines converge.
In practical terms, in order to have parallel vertical lines the film/sensor plane of the camera must be oriented on a true vertical plane. Unfortunately, when we do this we often find that we have too much foreground in our image and do not see all of the building we are shooting; it is cropped at the top. Our only solutions are: use a wider lens, or get further from the subject. In each case, we will have to crop the resultant image to remove unwanted foreground (meaning we use only a portion of the sensor and must accept a loss of image quality), and moving back from the subject is not always an option anyway.
Enter the "shift lens", which throws a larger-than-normal image circle and is shiftable along both a horizontal and a vertical axis, so that we may position our sensor in the portion of the image circle that interests us. These lenses are commonly called "perspective control" lenses, because that's exactly what they are used for. They allow us to position or film plane square to the subject and render it in an accurate manner.
How Does "Tilt" Work?
Besides its shift abilities, the Large Format camera allows the lens and film plane to be "tilted" in relation to each other; for example, the film plane may be vertically oriented (set at 90 degrees to the ground) and the lens may be angled so it is at, say, 60 degrees to the ground (30 degrees of tilt relative to the film plane). Why is this useful? It provides precise control of your depth-of-field.
Depth-of-field is an inherent optical quality of the lens, and it always operates perpindicular to the axis of the lens. If you are focused at, say, 6 feet, your DOF at, say, f/11 might extend from 4 feet to 10 feet with a particular lens. Suppose you are taking an oblique shot of a long fence which extends out of the picture on both sides of the image: the closest portion may be a foot from the camera and the furthest portion may be 100 yards away. The only way to get the entire fence "in focus" without tilt is to stop WAY down, and there are optical considerations that reduce image quality at very small apertures.
Enter the "tilt" lens; it's an optical fact that if the plane of the subject, the plane of the lens, and the plane of the film all intersect at the same point, then if any one point on the subject plane is in focus ALL points on that plane will be in focus. Careful orientation of the camera/subject/lens planes will allow you to precisely control your DOF to a remarkable degree.
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That's it in a nutshell. We hope this program has been useful. Feel free to ask me for more detailed explanations. I don't own a tilt/shift lens for my Canon, so I can't give examples...
Robt.
Message edited by author 2005-07-31 09:45:46.
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07/31/2005 09:59:31 AM · #10 |
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07/31/2005 10:50:19 AM · #11 |
Good diagram of how tilt works, as discussed in my little essay earlier. They misspelled "Scheimpflug" though :-)
R.
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