While shift lenses have a clear major advantage in architectural photography, perhaps tilt lenses are particularly useful in close-up work – although we shall see below the benefits of also being able to shift a tilt lens, and others have demonstrated the power of tilt lenses in general photography, both to increase and to decrease depth of field.

• the aperture: the larger the aperture (the smaller the aperture number), the shallower the depth of field;
• the focussing distance: the closer a lens is focussed, the shallower the depth of field;
• the focal length: the longer the focal length, the shallower the depth of field.

The 45mm Hartblei Super-Rotator Tilt/Shift lens has a very short focal length (for Medium Format), and therefore an inherently extended depth of field, so I decided to exploit the other two factors that give a shallow depth of field by taking some close-up pictures and using wide apertures, to see if using the tilt facility of this lens would increase the in-focus range for me.
 

Here is the set-up for the test.
Photographs shot on Fuji NPS 160, which also enabled me to use wider apertures than might have been possible with faster film.  Illumination was provided by natural daylight from a north-facing window on a bright day.

• the intended degree of enlargement
• the intended viewing distance.

That is because there is of course another factor in the first two test shots here: they have been shot at maximum aperture, to enable the effect of tilting the lens to become obvious to the maximum.  No-one would normally shoot an image such as this one at maximum aperture.  In fact, the aperture that gives the sharpest image for the lens would normally be used.  This is normally between f/8 and f/16, depending on the lens.

With any lens, at maximum aperture there is a marked decrease in sharpness away from the centre of the image area, and this is inevitably obvious with this image, too, if we look to the left and right of the in-focus plane.  Note in particular the lack of sharpness of the right-hand part of the red banknote.

Incidentally, the fall-of in brightness at the bottom of the image is a consequence of the set-up and the ambient lighting, as will be observed from the top picture on this page.

In this image, even though the lens is still at its maximum aperture of f/3.5, the tilt has increased the depth of field tremendously, but much more in front of the point of focus than behind it.  I focussed on the central area of the blue banknote, just below the lady’s chin.  I need to re-try, with the focus set further back.  Naturally, the fall-off in resolution towards the edges of the image on each side of the area of acceptable focus has not been changed.

But note that the degree of vignetting that occurs when the lens is fully tilted is massive.  I need to re-run this test, adding an upward shift to see if the vignetting can be eliminated.  This where a tilt and shift lens should score over a lens that only offers a tilt facility.

As a result of running these tests, I would recommend using the magnifier head (scroll down) on the camera, or the angle finder on the prism, as both of these give a magnified image than facilitates the evaluation of the area of sharpest focus.  I do not recommend the use of the “focussing telescope” (scroll down) for use with tilt lenses, as it only magnifies the central area of the image.