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Olympus M.Zuiko Digital 45mm 1:1.8 Gordon Laing, Jan 2013
 

Olympus M Zuiko Digital 45mm f1.8 bokeh

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To compare the potential depth-of-field and bokeh effects of the Olympus M Zuiko Digital 45mm f1.8 and Panasonic Leica 45mm f2.8 lenses, I shot two compositions: the first was a traditional head-and-shoulders portrait, and the second was a macro shot taken at the closest focusing distance of the Olympus lens.

In both cases, each lens was fitted to a Panasonic GX1 body, mounted on a tripod. You can see extra results for both lenses from the contents index to the right.
  Olympus M Zuiko Digital 45mm f1.8 results
1 Olympus 45mm f1.8 sharpness
2 Olympus 45mm f1.8 vs Panasonic 45mm f2.8
3 Olympus 45mm f1.8 bokeh
4 Olympus 45mm f1.8 macro
5 Olympus 45mm f1.8 Sample images

I'll start with the portrait shot, a typical head-and-shoulders composition taken from a distance of about 2m with the background mountains about 6km away. This represents pretty much ideal conditions for a portrait with a shallow depth of field and below you can see how the Olympus 45mm f1.8 and Panasonic 45mm 2.8 lenses handle it with their maximum apertures of f1.8 and f2.8 respectively.


Olympus M Zuiko Digital 45mm f1.8 bokeh
 
Panasonic Leica 45mm f2.8 bokeh
Olympus M Zuiko Digital 45mm f1.8 depth of field at f1.8
Panasonic Leica 45mm f2.8 depth of field at f2.8


At first glance the two shots look quite similar, maybe disappointingly so if you expected the Olympus to deliver a significantly shallower depth of field. But look again and you'll see the background details on the Panasonic 45mm sample are noticeably better-defined, from the bushes a few hundred meters away to the hills and mountain ridge beyond. There's no doubt the background on the Olympus 45mm f1.8 sample is softer, less defined and ultimately less distracting, the characteristics most people desire from a portrait shot.

If you're used to shooting with larger formats though, even if it's just APS-C, you may be disappointed by the comparatively large depth of field on these two samples, since both are described as portrait lenses. Fit a 50mm f1.8 to an APS-C camera or an 85mm f1.8 to a full-frame body and you'll enjoy a much shallower depth of field at the same subject and background distances when the aperture is wide open, so what's going on here?

The explanation is the sensor size impacts both the effective field of view and the effective depth of field. In the case of Micro Four Thirds, the sensor effectively reduces the field of view by two times, making a 45mm lens act like a 90mm on a full-frame body. But it also makes the depth of field act like a full-frame aperture that's two stops slower. So when comparing these lenses to a full-frame system, their effective focal lengths may both be 90mm, but their effective apertures become f3.6 on the Olympus and f5.6 on the Panasonic. No wonder the background isn't anywhere near as blurred as an 85mm f1.8 on a full-frame body.

For an effective full-frame aperture of f1.8 on Micro Four Thirds, you'd need an actual aperture of f0.9. While such lenses (or close) do exist, they're not exactly cheap, so anyone wanting a shallower depth of field from Micro Four Thirds without getting closer to their subject will need to increase their focal length instead - the Olympus 75mm f1.8 is the ideal solution for a very shallow depth of field, although with an equivalent focal length of 150mm, you may feel a bit detached from the subject.

Just for reference, I've also included two shots taken with the Panasonic Leica 25mm f1.4 lens below, both at the maximum aperture of f1.4. The first, below left, was taken at the same distance as the two above, so the subject is understandably half the size, but there's still some blurring in the background.



Panasonic Leica 25mm f1.4 bokeh
 
Panasonic Leica 25mm f1.4 bokeh
Panasonic Leica 25mm f1.4 depth of field at f1.4
Taken from same distance as 45mm samples above
Panasonic Leica 25mm f1.4 depth of field at f1.4
Taken from closer distance to match subject size in 45mm samples

Move closer though and you'll see the depth of field reduce, so in the second sample above right I've attempted to match the subject position and size of the 45mm shots by roughly halving my distance. I'm a little too close to the subject now and distortion from the wider focal length is delivering a less flattering result than the longer lenses, but it does illustrate that this shorter lens can still be very useful for portrait work. I actually find it preferable for kids who won't keep sufficiently still for longer focal lengths and who don't seem to mind the closer shooting proximity.

As illustrated above, another way to achieve a more blurred background is simply to get closer to your subject. There's obviously a limit to how close you can get to a person - although the smaller size of kids gives more scope than adults - but if you can get really close in a macro situation, then you can really throw the background out of focus.

To illustrate this in action I lined up a composition of a flower at a distance of half a meter. This is the closest focusing distance of the Olympus lens, although as a dedicated macro model, the Panasonic can focus much, much closer. I'll compare their closest focusing distances on the next page, but here wanted to see how their depth of field compared at the same distance of 0.5 meters.



Olympus M Zuiko Digital 45mm f1.8 bokeh
 
Panasonic Leica 45mm f2.8 bokeh
Olympus M Zuiko Digital 45mm f1.8 depth of field at f1.8
Click image for original at Flickr
Panasonic Leica 45mm f2.8 depth of field at f2.8
Click image for original at Flickr


As with the portrait comparison, there's not immediately a massive difference, but look closer and again you'll notice a much creamier, less defined background on the Olympus at f1.8. It's hard to see exactly what's in the background of the Olympus shot at f1.8, whereas you can begin to make some shapes out on the Panasonic at f2.8. Look closer still and you'll see even some of the leaves and thorns are noticeably less defined on the Olympus version. All of this becomes more obvious at larger reproductions, so I've provided full resolution samples of both at Flickr which you can access by clicking each image above.

As for the actually quality of the bokeh, it's essentially the same on both lenses when shooting at the same distance and focal ratio - both also share a similar diaphragm system with seven rounded blades.

And for all those who yearn for a shallower depth of field, I've included a selection of other images below which attempt to maximize the effect with this lens to illustrate what's possible. It may not be as extreme as a 50mm f1.8 on APS-C or an 85mm f1.8 on full-frame, but as you can see, you can achieve some very nice effects if you minimize the subject distance and maximize the background distance.



Olympus 45mm f1.8 at f1.8
Olympus 45mm f1.8 sample image
Click image to access original at Flickr



Olympus 45mm f1.8 at f1.8
Olympus 45mm f1.8 sample image
Click image to access original at Flickr



Olympus 45mm f1.8 at f1.8
Olympus 45mm f1.8 sample image
Click image to access original at Flickr


Now let's check out their respective close-up capabilities in my Olympus 45mm f1.8 macro results.
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