Schneider 47mmXL coverage testgreenspun.com : LUSENET : Large format photography : One Thread
I'm not usually a "testy" kind of guy, but. . . .
I've heard many comments over the past few years about the limited coverage of the renowned Schneider 47mmXL lens: that it "just barely" covers 4x5, or even that it's functional primarily for 6x12 and smaller rollfilm formats and of little utility on 4x5. On the other hand, my experience with this lens had indicated that appreciable movements were possible even with 4x5 (though I usually use a 6x12 back on the camera), and I'd heard that Schneider tends to be conservative when listing image circles.
So last week I made a series of photographs with different degrees of movement to discern at what point vignetting begins with the 47mmXL lens and 4x5 film. My Cambo Wide camera has millimeter marks so that as you move the geared rise or shift (you get your choice by rotating the lens panel 90 degrees--and by rotating the camera) you can see exactly how much movement youB re using. I don't usually go to all of this trouble to test a lens, but this is a unique lens.
1. The lens is serial #14583557, manufactured (according to Schneider's website) in late 1995. The lens is in a helical mount, with distance- and depth-of-field markings; I don't know whether Schneider or Cambo does the helical mounting. Other than the helical mount and markings, I believe it is optically identical to the unmounted versions of the 47mmXL.
2. The lens was racked all the way to infinity to provide a "worst case" measurement. (Obviously the image circle would be larger if I'd used hyperfocal options: for instance, according to Schneider's d.o.f. tables, everything from 2.4 feet to infinity is in focus when a 47mm lens set at f16 is focused at 5 feet. The image circle for any lens at the film plane would, of course, be larger at a 5-foot focus distance than it is at the infinity focus distance used in this test.) 3. I set the lens at f16, probably my most commonly-used aperture with this lens and the aperture Schneider uses in its image-circle measurements for this lens. The image circle at the film plane would be slightly smaller with f11, slightly larger at f22 (the lens closes down to a minimum aperture of f32, effectively a pinhole).
4. I used Kodak Readyload E100S 4x5 film in Kodak's (now-discontinued) Readyload holder, with a diagonal of what looks to me like 153.5mm. My Fuji Quickload 4x5 transparencies measure out almost exactly the same, but I didn't have any unexposed Fuji film in the fridge so I didn't use it for this test. I've never used 4x5 film holders or Polaroid, so I don't know what the diagonal is there, but since the 4x5 lens chart on this website lists 153.7mm as the diagonal for 4x5, I assume these kinds of holders are around this figure also.
5. I used Schneider's center filter on the lens during the test. The rear threads of this filter are 67mm and the front are 86mm. I do not believe this filter causes any vignetting, but I wanted it on during the test even if it did cause vignetting because I wouldn't think of using a full rise without it. In other words, a vignetting test of this lens without a center filter wouldn't be a "real-world" test to me.
6. I ran the test "in both directions," i.e., rising to one side of the lens and then inverting the camera 180 degrees and rising in the other direction, just to be sure the lens wasn't mounted off-center on the lens panel (it wasn't, as both sides tested identically). 7. I photographed a blank sky (with skyline at the bottom), overexposing by 2 or 3 stops so I could clearly see any vignetting in the upper corners.
8. The first day I tried rises of 10, 15, and 20 mm, first in landscape (horizontal) mode, then in portrait (vertical) mode (in both directions; see #6 above). After seeing the results of the processed film and estimating at what point vignetting began, the second day I narrowed down the movements, trying 16, 17, 18, and 19mm of rise in landscape mode, then 11, 12, 13, and 14mm of rise in portrait mode.
With 4x5 film (153.5 diagonal), at infinity focus and at f16, the 47mmXL lens apparently allows ~17.5mm of rise in the landscape mode and ~12.5mm of rise in the portrait mode. While this may not sound like much to those accustomed to longer focal length lenses, in light of this lens' focal length and flange focal distance it is quite impressive to me (the rear element is only about an inch in front of the film plane when the lens is focused at infinity). With such a wide-angle lens, even large objects in the image (e.g., buildings on the Chicago skyline in my test) are often only a few millimeters tall on the film, so 17.5 millimeters is significant in my book.
Note that I used the center filter in this test, as I have found that this filter is advisable anytime ANY movements are used (and often when they are not, except when handholding the camera for street-shooting. In those cases the need for 2 extra stops of speed often outweighs light falloff considerations). At full rise without the center filter, it is impossible to judge vignetting even when the center of the image is overexposed 3 or 4 stops, so great is the light falloff at the edge of the image circle. Again, considering the 120-degree coverage of this lens, this light falloff is not surprising. I don't have a way of posting my test photos at the moment, but anyone with questions, comments, criticisms of my test methods, or corroborating/conflicting test results can e-mail me directly or post their remarks here. . . .
|||||||||||||||||| ////////////////// \\\\\\\\\\\\\\\\\\
-- Micah (firstname.lastname@example.org), November 15, 2000
Micah, Thanks for your feedback on your tests. Very interesting. I'm glad I spent the extra money for the 47XL instead of the Grandagon 45 I was proposed. This lens is amazing. I have used it to shoot indoors both in 6x12 and 4x5 and had plenty of rise and fall. As you mention, as little as it can look, 17 mm have huge effects with such a short lens. David Muench in "Plateau Light" has several shots from that lens, mostly rock walls and canyons from within. However, it is not easy to shoot without having to notice distorted objects, especially if they are close to the camera. Squares become rectangles and circles ovals. Even if in nature, such geometric shapes do not appear as easily, I consider the lens a speciality lens and have found few applications to it beyond the 6x12 format so far. But I do not live in the canyons and giant cities country and in fact, this was the kind of shots I had in mind when I purchased it!
-- Paul Schilliger (email@example.com), November 15, 2000.
Micah I had similar results to you but not as accurately achieved. With a Heliopan UV filter in place I managed about 15mm horizontal rise and 10mm vertical before vignetting set-in (this is only approx. has I've not measured rise accurately).
The light fall-off with this lens dosn't bother me. Has I only print b/w, areas can be "held-back" if troublesome. I photographed a scene recently which could only have been made with this lens on 4x5. Having got back as far as I could I used the fall 15/17mm front rise to include the top of a chimney of a derelict brickworks (closed from the early 1900's) on the Isle of Anglesey, North Wales. It's in situations like this when you do appreciate this lens. Prints from this neg. had slight vignetting top L/R corners which were masked off and a "burn-in" of the central sky area to balance things ups was all that was required for a pleasing image.
-- Trevor Crone (firstname.lastname@example.org), November 15, 2000.
Micah, thanks for posting the results of your test!
-- Pete Caluori (email@example.com), November 16, 2000.