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Studio Tests - Leica Elmarit 24mm F2.8 ASPH lens

The fixed Elmarit 24mm F2.8 ASPH lens lies at the heart of the X1's imaging abilities, and its optical quality will necessarily be a key factor in the decision to buy this camera over, for example, a Micro Four Thirds body with the Panasonic Lumix G 20mm F1.7 ASPH. So, unusually for a fixed-lens compact, we've run our full set of optical tests.

The Elmarit 24mm F2.8 ASPH performs very competently in our studio tests. Sharpness is excellent in the center of the frame even wide open, distortion and lateral CA are both well-corrected, and falloff is low. It's a distinctly better performer than the Olympus M Zuiko Digital 17mm F2.8 sold with the E-P1 and E-P2, much sharper across the board and with a lot less lateral chromatic aberration when stopped down. Compared to the Panasonic Lumix G 20mm F1.7 ASPH, though, it doesn't do quite so well, and is measurably softer at larger apertures (however purists may well prefer that, unlike Panasonic and Olympus, Leica doesn't use software distortion correction as an integral part of the system design).

Sharpness Central sharpness is extremely high wide open, but the corners don't match up (although only the extremes are actually 'soft'). However they improve progressively on stopping down, and optimum results are obtained around F8, at which point sharpness is very high right across the frame. Stopping down further results in gradual softening due to diffraction; sensibly Leica hasn't provided settings smaller than F16.
Chromatic Aberration There's a moderate level of lateral CA, which diminishes slightly on stopping down. Wide open there's visible red/cyan fringing across much of the frame; at smaller apertures it tends towards green/magenta in the extreme corners. JPEG shooters won't see this, though, as Leica corrects for it in software.
Falloff We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the center. There's simply nothing to worry about here - just 1 stop wide open, which disappears on stopping down.
Distortion A little barrel distortion is measurable (1.1%), which is high enough to be visible occasionally but shouldn't impact significantly on normal use.

Macro Focus

The X1 is most definitely not going to be the first-choice camera for macro purposes. Its minimum focus distance is a relatively long 30cm, and with its semi-wideangle lens, this gives a minimum image area of about 10.5" x 7" (27 cm x 18 cm). This is can be somewhat limiting in practical use - forget dramatic closeups, they're really not going to happen.

Specific image quality issues

In this section, we're looking in detail specifically at lens-based (as opposed to sensor-related) image quality issues.


The X1 has no easy means for attachment of a lens hood (as there's no filter thread on the lens barrel), so its flare resistance is pretty important. And on the whole it does OK, but there are certain situations under which it's prone to showing problems, and you need to look out for.

Place the sun in the corner of the frame and you'll see flare patterns which become more defined on stopping down - it's probably best to avoid the smallest apertures (F11 - F16). There's also a specific angle to the sun (about 45 degrees) at which the light impinging on the front element gives rise to strong streaks of flare - of course if you're shooting with the LCD you can often spot this, and simply shield the lens with your hand.

F8, sun in corner of frame F9, camera pointing at about 45° to sun

Chromatic aberration

The X1 shows a moderate level of lateral chromatic aberration in our studio tests, in the form of fringing that is mainly red/cyan in color. The good news is that this is corrected automatically in the JPEG files; the bad news, though, is that in many situations where CA would be most visible, those JPEGs show intense purple fringing instead.

Switch to shooting raw, though, and Lightroom will do a much better job of removing purple fringing, and we found that setting the 'Fix Red / Cyan fringe' to -20 in the Lens Corrections tab effectively removed the worst of the CA too (with 'Defringe Highlights' finishing things off when necessary). The examples below show this in action on a couple of typical real-world shots:

1/80 sec, F8, ISO 200 1/500 sec, F5.6, ISO 100
JPEG, 100% crop, upper left
JPEG, 100% crop, lower left
ACR, no lens corrections
ACR, 'Fix Red/Cyan fringe' set to -20
ACR, 'Fix Red/Cyan fringe' as above plus highlight defringe


The X1's fixed 24mm F2.8 lens means that it generally provides lots of depth of field, but if you shoot at close distances with the lens wide open you can achieve quite good separation of subject and background. And in these cases, the rendition of the out-of-focus backgrounds is on the whole very attractive, with no bright edging to out-of-focus highlights. A little bokeh chromatic aberration can be seen, as green/magenta fringing around out-of-focus high contrast edges, but on the whole it's unlikely to spoil your images.

F2.8, distance ~1.5m F2.8, focus distance ~1m.
50% crop 100% crop - green/magenta fringing
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