Boring.

This was never an exciting lens on the M8 or M9 - always very useful, always a little dull. Its virtues are many: it has a reputation for good flare resistance, medium high contrast that can handle a bright day, fairly low distortion, good sharpness, low field curvature and no notable focus shift. For these reasons and for the fact that it has a very reliable placement of DOF in use, and that it is a useful focal length for travel, street and landscape, it was one of my most used lenses. But on the M240 it has gone from 'slightly dull but useful' to 'not as good as it used to be'. Consequently it has also slipped from 'most used' to 'little used'.

Why?

In short, it isn't sharp enough across the frame until F8 to fulfil the 'bigger prints' promise of the M240 sensor. I put this down to the peripheral falloff in the sagittal and tangential MTF 40 even at F5.6. It also seems to lack sparkle and micro-contrast across the frame - a phenomenon that I put down to the wave in tangential MTF 40 and the astigmatism between sagittal and tangential. Also, colour shifts across the frame are evident with current M240 firmware, even when the lens is stopped down. It is still far better than most lenses on most cameras, of course, but it is no longer a must-have, for me at least.

The aperture series tells all: the lens just doesn't get its act together at the edges convincingly until F8 and that is where diffraction is just starting to take the shine of the cherry on centre. Click the image to go to a gallery which has all files from F2 thru 16 and take a look. L1002080

For me, that just isn't interesting enough: it's not as if the lens has enormous character or sparkle to compensate, either. But it does have enough micro-contrast on centre to provoke moire on the M240 - see the following file (click for full size or merely look at the provided crop below).

L1002426 L1002426 As you can see, it is not just the colour artefacts that are clearly evident: there's also the 'maze' shaped pattern moire so familiar from the M9 and so very hard to process away convincingly. I once lost a shot that really mattered to this effect.

On the M9, the lens corrections for the Cron weren't perfect. I don't have test frames from that combination to show a comparison but what matters here is that as a system, the M240/28Cron combo (with current firmware as of March 2013) doesn't do quite well enough and there are some residual shifts, even when stopped down, that will sometimes show up in the sky and possibly in other types of subject. Here is the F2 frame  - click on it to go to the entire series.

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Moving on to distortion - below are uncorrected and corrected frames and for me, they show that this is a non-issue.

L1002512 L1002512-2 Onto flare. Generally, the lens handles it very well if shot with the hood on, but its reputation for being bullet proof in this regard is misplaced: you can provoke it quite easily though I must say that few lenses can cope with having the sun in the frame like this and that generally the lens performs well as long as this situation is avoided. Here's what happens when it goes wrong:

L1002135 On the plus side, it is really very hard to provoke colour aberrations of the fringe variety. The above file, when viewed it a 100%, shows almost no purple problems, when most fast wide lenses would be afflicted.

So there are some moderate problems with the lens but there are also silver linings and they are not to be underestimated. It performs in a generally well-mannered and predictable fashion on the M240 and, unlike with some other lenses, I do not see strange interactions of focus shift and field curvature (despite that mini-tsunami MTF) that can lead to anomalous results when using stop-down EVF focus. Instead I find, as I always previously did, that it lets me very reliably place the field of focus where I want it. That may also partly be a result of my long experience with it but for whatever reason, it is very useful. Scenes such as the following are deceptively difficult to handle with some lenses but with the 28 Cron, you can get pretty much everything, near to far, in great focus handheld and with no sweat, albeit at F8 - click for full size.

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Should you want to do the opposite and explore the lens's bokeh characteristics, a few examples follow. I add more shots than usual here because this is one of the Cron's stronger points: wides often have an obviously 'nervy' bokeh but this one is relatively smooth. Click for larger files. All shot at F2 and F2.8.

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I might have become mildly hooked on tricky lenses (such as the 35 Lux or the Nikkor 28mm F1.8G) because here, with the 28 Cron, I have a solid, reliable lens that doesn't mess me about. With the exception of the potential for some residual colour cast issues and the need to stop down to F8 for certain kinds of scene, it does pretty much what you want pretty much all of the time. But I don't expect it to remain current much longer than the current or next generation M: it needs a makeover at some point. Not urgently, but soon-ish. It should achieve edge sharpness by F5.6 and the colour shifts should be better controlled.

And it's boring.