Tilt-and-shift lens
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A tilt-and-shift lens (also TS lens , T&S lens ) is a special lens for photography or projection , which shifts ( English : Shift ) parallel to its axis and swings (English: Tilt ) of the Lens system compared to the film plane allows. Both changes have different effects, so both need not be possible. There are lenses that only allow shift, for example. As a result, the object level (e.g. the front of a building) can remain parallel to the image level and can be depicted without distortion. Scheimpflug's rule can be applied to tilt , i. H. an inclined object plane can be imaged as sharply as possible.
In the case of large format cameras with bellows ( technical cameras ), the change in position is facilitated by the bellows located between the lens and the film standard , while in the case of special lenses the housing consists of parts that can move relative to one another.
Shift
During projection, shift lenses enable the correct display of the image format if the projector cannot project vertically onto the screen for reasons of space (alternative: electronic keystone correction ). An exact image overlay (cross-fading) of images from two or more projectors, if these are above or next to each other, can also be guaranteed.
Tilt
The plane of focus can be shifted by pivoting the lens system ( Scheimpflug's rule ). The level of focus can be adapted to the desired object level. This can serve technical purposes (continuous sharpness in an inclined plane) as well as image design purposes (working with selective sharpness, is used to simulate a shallower depth of field ).
The additional (selective) blurring, which is occasionally desired in portraits, can be simulated with an image processing program; however, it does not come from depth information, but is determined by the position in the image (e.g. radial distance from the center of the image).
Origins and technical implementation
These recording techniques originate from the field of large format or specialist cameras , where the adjustability of at least the front standard is common. With small and medium format photography , special lenses or special adapters are necessary due to the fixed housing that is customary there.
Special lenses
Shift or tilt / shift lenses from camera manufacturers Canon, Leica and Nikon as well as from third-party manufacturers such as Schneider Kreuznach , Samyang , Venus Optics , Arax or Hartblei from Kiev are currently available for 35mm SLR systems.
- T&S from Canon for small pictures: TS-E 17 mm f / 4, TS-E 24 mm f / 3.5, TS-E 50mm f / 2.8L MACRO, TS-E 90mm f / 2.8L MACRO and TS-E 135mm f / 4L MACRO
- T&S from Hartblei for small pictures: TS-PC Hartblei 35 mm f / 2.8, TS-PC Hartblei 65 mm f / 3.5, TS-PC Hartblei 80 mm f / 2.8, TS-PC Hartblei 120 mm f / 2.8
- T&S from Hartblei for medium format: TS-PC Hartblei 45 mm f / 3.5
- T&S from LEICA for medium format: TS-APO-ELMAR-S 120 mm f / 5.6 ASPH5
- T&S from Nikon for small pictures: Nikkor PC-E 19 mm f4 ED, Nikkor PC-E 24 mm f3.5 D ED, micro-Nikkor PC-E 45 mm f2.8 D ED, micro-Nikkor PC-E 85 mm f2 .8 D ED, micro Nikkor PC 85 mm f2.8 D
- T&S from Samyang for small pictures: TS 24 mm 1: 3.5 with connections for Canon, Nikon, Sony and Pentax
- T&S from Schneider Kreuznach : PC-TS Super-Angulon 4.5 / 28, PC-TS Super-Angulon 2.8 / 50 HM, PC-TS Macro-Symmar 4.5 / 90 HM, PC-TS Apo-Digitar 5 , 6/120 HM Asperic
- T&S from Arax for small pictures: 2.8 / 35mm Tilt & Shift, 2.8 / 80mm Tilt & Shift
- Macro lens from Venus Optics for small images with additional shift function: Laowa 15 mm f / 4 Wide Angle Macro with continuously adjustable ± 6 mm shift function for landscape format shots . There may be shadows in the corners of the image, which is why the manufacturer recommends using the shift function only for recordings in APS-C format. A suitable camera with a lens adapter is required for this.
Some older lenses that are only available second-hand can also be used with current cameras. The older PC Nikkor shift lenses with 28 mm and 35 mm for the Nikon system or the Olympus Zuiko shift lenses should be mentioned in particular.
All of these lenses have no autofocus, and often no automatic iris control either.
Development strategies for T&S lenses
In addition to the complete recalculation of a T&S lens (which, in simplified terms, is a lens with an enlarged image field and additional mechanics), there are various other approaches.
- Adaptation of lenses of the next larger picture format class: For a T&S lens for small format, you take a normal lens for medium format and add additional mechanics. This approach is supported by the larger flange focal length of medium format lenses (Hartblei).
- Adapter without magnification: Similar to adapting, but the adapter mechanism is manufactured as a separate optical component similar to an intermediate ring (?)
- Adapter with magnification: Lenses of the camera itself are used. However, the adapter enlarges the image (typically 1.5 ×), thereby gaining back focal length for a mechanism that allows the enlarged image to be selected (Shift) or can tilt the image (Tilt) (Hasselblad).
- Sensor movement: The lens is not adjusted, but the camera can move and tilt the sensor (TSE adapter).
However, adapting in each of these forms has the disadvantage of not making UWW-T&S lenses possible.
For small picture - SLR different manufacturers currently offer shift and tilt & shift lenses or even shift and tilt adapter.
Some special requirements are placed on the quality of the lens. Compared to non-adjustable lenses, the image circle has to be larger in order not to get any shadows when moving. The edge sharpness must be excellent in order to enable the mentioned advantages when panning at all.
handling
The handling of a T&S lens differs significantly from conventional lenses.
First, the camera is pointed at the subject with the lens not shifted, and the exposure is determined and stored - camera mode M is best suited for this. This first step is important because almost all cameras with TTL exposure metering expose massively incorrectly with the lens adjusted.
Then the camera is aligned so that the plane of the film is parallel to the plane that is to be displayed without distortion; In the case of architecture and landscape photography, this primarily means the precise horizontal alignment of the lens axis. An object at camera level (eye level) can serve as a reference, which must also be in the center of the image in the viewfinder; the center of the image is usually clearly marked in the viewfinder, e.g. B. by AF measuring points. Even better, however, is leveling the camera using additional levels (for example on a tripod ) and the artificial horizon in the camera display and the three spatial axes with fine adjustment of a correspondingly equipped tripod head.
The image section in the viewfinder or display is only then determined by actuating the shift mechanism on the lens.
When using a shift lens, a tripod is almost always used. In this way, not only can the alignment and image section be precisely defined, but an aperture of any size can also be selected to achieve a large depth of field or high edge sharpness without the risk of blurring.
See also
Remarks
- ↑ When shifting, both planes are parallel to each other and to the lens plane ( main plane ), which means that the Scheimpflug condition for maximum sharpness is met when the lens end system is moved in parallel.
Individual evidence
- ↑ Mark Banas: From another planet: Venus LAOWA 15mm F4 Wide Angle Macro quick review , DPRreview, March 13, 2016, accessed November 15, 2019
