Monday, 27 September 2010

Bokeh comparison @ 20mm

I have two lenses that can do 20mm, so I thought it would be interesting to compare their bokeh. Both the Panasonic Lumix 20mm f/1.7, and the Panasonic Lumix 14-140mm f/4-5.8 zoom comprise the 20mm focal length. Apart from this, they are of course very different. At f=20mm, the superzoom has a maximum aperture of f/4.4, which is quite a bit smaller than the f/1.7 that the fixed 20mm prime can do.

To compare the lenses, I have taken the same picture with various apertures. The centre region is in focus, and the focus distance is around 60cm, just above the minimum focus distance for the 14-140mm superzoom lens.

First the picture with the Lumix 20mm f/1.7 at maximum aperture. The picture is rescaled and sharpened a bit.


Second, the same image taken with the Lumix 14-140mm at 20mm f/4.4:


Click for larger images.

The make the comparison more sensible, I have looked at 100% crops from the image at various apertures with both lenses (click for larger image):


And here are 100% crops from another region of the image. It was a bit more windy in the second series, so the leaves were not always in the same spot.


Conclusion

It is not surprising that the bokeh for the 20mm prime lens is the best. For out of focus highlights, the bokeh is pretty even, but has hard edges. On the other hand, it is not entirely round, especially when stopping down. All in all, the bokeh is pleasant, and has no significant ringing. The superzoom bokeh is a bit "dirty".

You'll also note some differences in sharpness. Note, however, that a higher ISO value was used for the f/8 and f/11 images for the 20mm prime lens. So some lack of sharpness could be due to using a higher ISO. It can still be noted that the superzoom lens appears very sharp.

The 14-140mm also has more flare, which is due to it's more complicated construction. The 14-140mm lens has 17 lens elements in 13 groups, while the 20mm pancake only has 7 elements in 5 groups. Generally speaking, the less number of lens elements, the less problems with flare you're likely to see. Of course, many other factors also affect flare.

5 comments:

  1. it will be good too, to see the Pana 20mm at f:4,4 ,

    good reviews on the blog, thanks

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  2. Thanks for the article - that's really helpful. I'm struggling with the choices for lenses (and cameras) at the moment. My shortlist is the GF1 with the 20mm pancake + one other lens. Reasonably good Bokeh is on my list of requirements, and this has given me a great comparison.

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  3. The Panasonic Leica 45mm f/2.8 has also got a nice bokeh. But it is pretty expensive, and if you're not into macro, it is not very good value for money.

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  4. I actually do not agree with your result. I am getting "double-vision" in the bokeh in the 20mm @ 1.7. I took a photo of my motorcycle and there was some blades of grass in the background. If you look at it closely, you see each blade is doubled! It's not very nice at all! Disappointed! :(

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  5. Thank you for the article!
    Here is an example of 20 1.7 bokeh on GH3, wide open:
    http://500px.com/photo/54361980
    And this one is at 2.8:
    http://500px.com/photo/54308392

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