The Olympus BCL 15mm F8 performs about as well in the studio as its size and price suggest. In fact technically it's just not very good at all, with soft corners, chromatic aberration, vignetting and barrel distortion. Because the lens has no electronics, it can't communicate correction parameters to the camera, so distortion remains visible in the final image.
|Sharpness||Sharpness is decent in the centre of the frame, but drops quickly towards the edges.|
|Chromatic Aberration||Lateral chromatic aberration is quite high, indicating colour fringing will be visible across much of the frame.|
|Vignetting||Vignetting is quite high, at 1.5 stops in the corners, despite this lens being fixed to F8.|
|Distortion||The lens shows moderate barrel distortion, which is likely to be clearly visible in geometric compositions.|
It's slightly difficult to define a clear-cut minimum focus distance for a lens with so much depth of field, but we'd place it around 25cm, a bit closer than Olympus's specified 0.3m might at first suggest. But in a way this is academic; the wide angle of view means that the lens still only covers an area about 25cm across. So while you can shoot reasonably close, this is nowhere near macro - any of the Micro Four Thirds kit zooms will do much better.
In our flat-field chart test, image quality isn't especially good. The centre of the frame is pretty sharp, but the edges are distinctly soft, and red/cyan colour fringing from lateral chromatic aberration is visible across much of the frame. Barrel distortion and vignetting are also both rather pronounced.
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. Obviously the 15mm F8 doesn't look brilliant in the studio, and technically it's not great in real world shooting either. That doesn't mean you can't make nice images with it, but from a purely technical point of view, they'd probably be better with another lens.
Here we're using a detailed landscape shot to see how the 15mm fares in real-world usage. We've taken 100% crops from the marked regions of the frame - centre (at the top), edge, and corner. Exactly as predicted by the studio data, central sharpness is really pretty good, but things fall apart pretty quickly as you move off-centre when you look this close. It's not a lens for making large, detailed prints.
|Olympus Body Cap Lens 15mm F8 on Olympus OM-D-EM5,
ISO 200, 1/320sec. Crop regions are outlined in red.
|100% crops: from top,
centre, edge and corner
The 15mm also shows pretty obvious colour fringing due to lateral chromatic aberration, and unusually it extends quite a long way into the frame, rather than being mainly visible in the corners. Here we're showing 100% crops from two regions of the frame - the corner shows clear green/magenta fringing, while the more central area shows red/cyan fringing. Again, if you're in the habit of looking very closely at your images, the 15mm may disappoint.
|Olympus OM-D-EM5, ISO 640, 1/100sec||100% crops|
The 15mm shows quite obvious barrel distortion, and this results in bowing of straight lines towards the edge of the frame. This is shown in the example below - the lines along to the top and bottom aren't meant to be bent. This kind of distortion is normally corrected automatically in the Micro Four Thirds system, but not in this case as the lens has no built-in chip to store the correction data and pass it to the camera.
|Olympus E-PL2, 1/640 sec ISO 400|
Of course this kind of barrel distortion is only really noticeable in images like this, which have lines running parallel with the long edges of the frame. In most shots you probably won't notice it at all.
The 15mm can also be quite prone to flare in bright light, when the sun is either in the frame or slightly out of it. In the worst case scenario - a bright sun directly in-shot with a dark foreground - it can flare spectacularly, but most of the time it's not too bad. Because it's used on cameras with fully-electronic viewing, of course, you can usually see exactly what's going on, and take steps to compensate such as shading the lens with your hand.
The examples below are fairly typical of how we've found the lens to behave in real-world use. With the sun in the corner of the frame, flare patterns are pretty obvious, but not hugely objectionable. In a backlit shot with the sun outside the frame, there's purple flare at the edge of the frame, which could probably be eliminated by shading the lens or a change in composition.
|Olympus OM-D E-M5||Olympus OM-D E-M5, sun outside frame to the right|
Compared to Panasonic Lumix G 14mm F2.5 ASPH
Here we compare the 15mm to the Panasonic Lumix G 14mm F2.5 ASPH - the smallest autofocus lens for Micro Four Thirds. We've chosen this because of its similar focal length, which means it can be used for much the same purposes. Of course it's rather more expensive too.
In this comparison the camera was placed in a tripod, which means the 14mm shot has a slightly wider view. The aperture was set to F8, to match the 15mm; note that this results in slight diffraction softening, and the 14mm would give sharper results at larger apertures. It's worth pointing out that, in our experience, Micro Four Thirds kit zooms give broadly similar results to the prime at these settings.
Olympus Body Cap Lens 15mm F8
Panasonic Lumix G 14mm F2.5 ASPH
|15mm, F8 on Olympus OM-D E-M5||14mm, F8 on Olympus OM-D E-M5|
100% crop, centre
100% crop, right edge
100% crop, top right
Here we can see how the 15mm compares to a 'proper' lens, and as expected the comparison doesn't greatly flatter it. It's not far off the same sharpness in the center, but renders nothing like as much detail at the edge and corners. We can also see pretty huge coma here (the rendition of point highlights as extended triangular shapes), but then again the 14mm isn't without its own problems on the corner, with equally-strong coma and plenty of chromatic aberration.
Metering and white balance on OM-D E-M5 compared
One point we noticed shooting the 15mm F8 side-by-side with the Panasonic 14mm F2.5 on the Olympus OM-D E-M5 was that the camera showed an occasional tendency to select a cooler white balance and meter slightly brighter. This didn't happen every shot by any means, but meant that images from the Body Cap Lens sometimes came out looking less attractive than they might have done.
Olympus Body Cap Lens 15mm F8
Panasonic Lumix G 14mm F2.5 ASPH
|A mode (F8), -0.7 exp comp, 1/250 sec||A mode, F8, -0.7 exp comp, 1/320 sec|
|A mode (F8), 1/80 sec||A mode, F8, 1/60 sec|
The two examples above, shot in aperture priority mode with Auto white balance, illustrate this pretty well. In both cases the camera has chosen a cooler white balance with the Body Cap Lens, and produced a slightly brighter image. The result is richer and warmer colours in the shots taken with the 14mm. It's not clear why the camera should choose to do this - possibly because it doesn't know anything about the lens it's using.