photo:lensperspective
perspective control, shift and/or tilt lenses
introduction:
whilst perspective control using shift lenses to correct converging lines can be largely done in post-processing in tools such as Photoshop, the ability to change the plane of focus by using a tilt lens cannot be achieved satisfactorily in PS.
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some
medium format film camera systems (eg. Fuji GX680III, Linhof 679 view, Horseman VR)and practically all large format cameras have tilt and shift capability via use of bellows.
changing the plane of focus using tilt lenses:
the amount and direction of the tilt determines where the Hinge line is.
any movement of the camera back towards or away from the lens (eg. by changing focus ring) causes the plane of sharp focus to rotate about the Hinge Line.
the plane of focus is formed by a line passing through 2 points:
a fixed point (Hinge line) for a given degree of rotation & tilt of the lens located directly below the lens at the intersection of 2 lines:
a line parallel to the film plane at the level of the lens
a line parallel to the lens tilt which lies 1 focal length in front of the lens
to determine which tilt angle to use based on the vertical distance (J in feet) from the lens which this point is placed can be determined by the equation:
tilt angle = arcsin(focal length/J)
if focal length in mm and J in feet this approximates to tilt angle = f/5J.
eg. if using TSE90mm lens with 8mm tilt, this point is ~2.25 feet from lens (4.5 feet if 4mm tilt)
a moving point (Scheimpflug line) along the lens plane which intersects with a line parallel to and intersecting with the film plane
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perspective control using a shift lens:
perspective control in Photoshop:
via Filter:
via Transform:
in either case, this will result in a converging edge to your image which will then require cropping to get back to a rectangular format, thus there is a cost in potentially detail but also in loss of pixels due to cropping.
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pseudo-tilt effect in PS:
perspective control using the LensBaby tilt/shift lens:
these lenses are fairly cheap and can be fitted to most dSLRs to primarily provide creative images rather than technically perfect commercial images as with most other perspective control lenses.
these lenses are NOT true perspective control lenses but just provide a central sharp area with surrounding blur, and the location of this central sharp area can be moved around the frame although it becomes less sharp the further it is moved from the centre - and at its best, its not that sharp.
unfortunately to change aperture you must physically replace the aperture stop
in most cameras, aperture-priority metering works but in some Nikons you must use manual metering.
$US270 for current 3G version & only weighs 162g.
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but you can achieve similar results in Photoshop using radial blur, etc, this lens saves you time on the computer but at a cost of less versatility in changing the end result.
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Micro Four Thirds:
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fortunately with MFT cameras you can buy
tilt or shift adapters which allow you to convert almost any lens designed for 35mm to a tilt or shift lens and you get HD video - and if using an Olympus body, it will be image stabilised - just awesome!!
you can use Canon EF tilt shift lenses via EF adapter but you must change aperture with lens on a Canon body unless you use an adapter which allows aperture control
you can use Nikon PC or Olympus OM shift lenses via adapter as with Four Thirds cameras
Canon dSLR options:
Nikon dSLR options:
Olympus dSLR options:
can use any as listed under Canon except Cambo/Horseman solutions or Canon EF lenses but 2x crop may be an issue.
be aware though that the flash housing on some Olympus dSLRs may get in the way of the knobs on some of these lenses.
photo/lensperspective.txt · Last modified: 2019/06/16 11:41 by gary1