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Studio Tests - FX (35mm full-frame) format

The Hartblei Superrotator 120mm F4 Makro TS is a lens which we suspect will be used mainly on high resolution full frame cameras. We've therefore chosen to test it only on the Nikon D3X, and not a DX-sensor body as we usually would. As a start we're showing our conventional test results, covering the central region of the lens's image circle.

The studio data from the Hartblei 120mm F4 shows that the 'Optics by Carl Zeiss' badge is well-earned. The lens exhibits highly desirable characteristics for its intended use - essentially no distortion or chromatic aberration is visible at all, and sharpness is excellent across the frame when stopped down to normal working apertures of F8 - F11 (although the lens is not quite so sharp wide open). This was also probably the most perfectly symmetric lens we've tested so far, giving essentially identical shaprness profiles to all four corners of the frame. Hugely impressive stuff.

Resolution Central sharpness is very high wide open, but the corners are a little soft. Stop down to the sweet spot around F8 - F16 though, and the lens provides excellent results right across the frame; beyond this the image softens progressively due to diffraction. This is all much as we'd expect from a lens designed for a rather larger format than 35mm full frame.
Chromatic Aberration Lateral chromatic aberration is essentially undetectable.
Falloff We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the centre. As we'd expect for a medium format lens used with an FX sensor, falloff is negligible.
Distortion Distortion is to all intents and purposes nonexistent.

Macro Focus

The 'Makro' label on the lens designates that it's optimised for close distance shooting, not that it provides 1:1 magnification. Maximum magnification is still a very respectable 0.24x, at a measured closest focus distance of 76cm which gives a working distance of 55.5cm from the front of the lens to the subject.

Image quality is very good indeed; best results are obtained around F8-F11, at which point the lens is sharp across the frame, and with essentially no geometric distortion or chromatic aberration visible at all.

Performance also holds up well when the lens is shifted - click here for a test chart shot with the lens shifted fully to the right.
Macro - 147 x 98 mm coverage
Distortion: negligible
Corner softness: low
Focal length: 120mm

 

Extended image circle tests

There's little point in testing a tilt and shift lens without measuring its performance at the extremes of shift, so we've extended our usual regime accordingly. However as this data is no longer directly comparable with our normal studio test results, we're chosen to present it in a slightly different form.

Sharpness (MTF-50)

F4
F5.6
F8
F11
F16
F22
F32

This graph shows the sharpness from the centre of the lens's optical axis right to the corner of the image area that is used when full diagonal shift is applied. This therefore corresponds to an image circle approximately 63mm in diameter, as opposed to the 43mm of FX. The exact position of the frame corner on this graph will depend on the amount and direction of shift; full horizontal shift corresponds to 96% and full vertical shift to 90%. (Note that when the lens is shifted, the central sharpest region of the lens will not correspond to the centre of the frame.) The trend observed in the FX area tests continues, with the lens soft wide open but improving dramatically on stopping down; F11 and F16 provide the sharpest results at the extremes of shift.

Distortion

This test represents the recorded FX frame area with the lens shifted by 10mm to the right, and no tilt applied. Distortion is still essentially nonexistant.

Falloff

Again this is the FX image area with the lens shifted 10mm to the right and no tilt applied: only very slight falloff is measurable.

In practical use, however, mechanical vignetting by the lens mount can become an issue when tilt and shift are applied together; this will be more of a problem with relatively small diameter mounts (e.g. Nikon) than with larger ones (e.g. Canon). At large apertures the vignetting effect will appear broad and diffuse, becoming sharper and more defined on stopping down. This can be seen below, using maximum tilt and shift movements combined in the directions indicated. As usual the Nikon D3X is our test body; the exact appearance of the vignetting will vary between camera models.

Mechanical vignetting, Nikon D3X
Left, F4
Left, F8
Left, F16
Left, F32
Down, F4
Down, F8
Down, F16
Down, F32

Checkerboard crops

As a visual illustration of the image quality across the full image circle, here are our familiar checkerboard crops taken from the center and extreme corner of the image circle at F4, F8 and F16 (do bear in mind these are 100% crops from a 24Mp D3X frame). Central sharpness is highest at F8, but the extreme corner improves progressively on stopping down to F16. There's no visible chromatic aberration even in the extreme corner, and the perfect geometry of the corner crops demonstrates the complete lack of distortion of this lens design. Overall pretty impressive stuff.

Lens Center
Extreme Corner
F4
F8
F16

Specific image quality issues

As always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests.

Background Blur ('bokeh')

One genuinely desirable, but difficult to measure aspect of a lens's performance is the ability to deliver smoothly blurred out-of-focus regions when trying to isolate a subject from the background, generally when using a long focal length and large aperture. This is a particularly important attribute of a lens such as this, when it's used creatively for shallow depth of field. The Hartblei 120mm generally gives attractive bokeh, which while not the quite smoothest we've ever seen, never detracts from the subject.

In the two examples below we're looking at bokeh from a distant background with a relatively close subject, and how slightly out-of-focus backgrounds are rendered. On account of the D3X's image size, we're using 25% crops to visualize this. The distant background is rendered with recognisable structure, but without the harsh line-edges sometimes seen in these situations. The close-up is also attractively imaged - transtions from sharp to out-of-focus are smooth, and while there's a slight bright edge to highlights, it's not really distracting.

F4, Nikon D3X F4, Nikon D3X
25% crop, middle left 25% crop, top center

Bokeh Chromatic Aberration

About the only slight hole we could pick in the Hartblei's impressive imaging performance was a slight degree of longitudinal chromatic aberration giving some colour fringing around high-contrast edges in out-of-focus regions. It's not a major flaw by any means (we've had to take 100% crops from 24Mp D3X files to show it) and it's only really visible at F4, but it's there and may well show up when exploiting this lens's selective focus capabilities. The fringing ends to be magenta at high-contrast edges in front of the plane of focus, and green behind the plane of focus; even at its worst it's not particularly broad or intense.

F4, Nikon D3X F4, Nikon D3X
100% crop, in front of plane of focus 100% crop, in front of plane of focus
100% crop, behind plane of focus 100% crop, behind plane of focus
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