Bokeh Comparison - Primes vs Zoom

After I wrote Full Frame vs Crop sensor Depth of field comparison (DoF) I started wondering whether a zoom lens can match the bokeh of a prime lens. So I did a little test where I compared the Nikon 18-200mm VR II with the Nikon 85mm f1.8D and 35mm f1.8G. Before I started the test I realized I needed to use a real world example because those lab test don't always show you what to expect out there in the real world.

First I set up my tripod with the Nikon D300 & Nikon 85mm f1.8D attached. I then took photos at f1.8 through to f5.6. Next I attached the Nikon 18-200mm VR II and tried to find 85mm on the lens which by the way doesn't exist. I only managed to find 82mm and 90mm. So I decided to match the view instead of the focal length which the camera showed as 90mm.

Here are the first batch of photos straight out of the camera. Click to enlarge

It's obvious the 85mm f1.8 wins when it comes to rendering a more beautiful background because of the large aperture. But how does it compare to a consumer zoom lens being shot wide open at the same focal length. That was the question. From the above photos we can see that the zoom actually has more contrast. Whether that is a good thing is actually debatable. Less contrast in my opinion makes for a more harmonious background which focus the viewers attention more to the actual subject. If we remove the contrast we still have two very different backgrounds with the 85mm f1.8D creating a better image in the end.

In the next test we still have the Nikon 18-200mm VRII but against the new Nikon 35mm f1.8G lens. I  expected the 35mm to have superior contrast to the 85mm f1.8 because of all the new technology and that was in fact the case. The 35mm has less contrast when shot wide open but when you stop it down to f4 it actually has better contrast than the 18-200mm VR and still renders a more pleasant background.

I know you can't call this a fair test because these lenses all have different uses. There are however many people who use a zoom as their primary lens and eventually want to experiment with something different. I actually carry my 18-200mm VR everywhere with me but I also have these two primes when I see a really special photo opportunity that need excellent sharpness or very shallow depth of field.

Happy Shooting!