Bokeh comparison @ 200mm

Introduction

I have an old legacy tele lens, the Nikkor 200mm f/4 AIS. It is well suited for use on a Micro Four Thirds camera, since both the focus and aperture are operated manually by twisting the rings on the lens. This is in contrast to Canon EF lenses, in which the aperture is operated electronically, and no adapter is available to control this from a Micro Four Thirds camera.

The lens is pictured here together with the Panasonic Lumix G 45-200mm f/4-5.6 Mega O.I.S. with the zoom extended to 200mm. The Nikon lens is shown with a Nikon-M43 adapter attached.


Nikkor 200mm f/4 AIS

This is a compact and high quality tele lens. The moderate maximum aperture, f/4, makes it less bulky than professional f/2.8 lenses. However, it still gives good quality images already from f/4.

The construction is fairly simple with five lenses in five groups. This is a mature lens design, and gives a good performance overall. It has nine aperture diaphragm blades.

The lens is made of metal, and the focus ring has a well dampened professional feel. The aperture ring can be set at any size, but has click stops at one unit distance, i.e., f/4, f/5.6, f/8, f/11, f/16, f/22 and f/32.

Lumix G 45-200mm f/4-5.6

The Panasonic Lumix G 45-200mm f/4-5.6 Mega O.I.S. is a value tele zoom, often sold with a camera in dual lens kits. For the price, it has a good quality construction, fast autofocus, and good image quality.

Setup

To look examine the bokeh qualities of the lenses, I focused them at their smallest common focus distance, which is 2 meters. The Lumix 45-200mm can focus down to 1 meter. Then I placed some backlit foliage in the background.

Both lenses were focused manually, by using the magnified view on the Lumix GH1. Here are the images at f/5.6 for both lenses:

Nikkor 200mm f/4 @ f/5.6

Lumix 45-200mm @ 200mm f/5.6

Field of view difference

What we can note at once, is that the field of view is not the same. The Nikon gives a closer view of the foreground. This surprised me at once, and I made sure to check the EXIF to see that the Lumix picture was indeed taken at 200mm.

However, we can note that the focal length specification is always given at infinity focus, while in this case I am focusing closer to the minimum focus distance. I did confirm that at infinity focus, the field of view of the two lenses is the same.

The Nikkor lens features a traditional focus assembly, which moved the lens elements forward when focusing closer. The Lumix, on the other hand, features internal focusing. Internal focusing is know to give a change of focal length as the focus is altered. So the effect we are seeing here is not unexpected, and I am guessing the Nikon lens maintains the most correct field of view when focusing closer.

Bokeh

To better compare the bokeh, I am providing 100% crops from the two images above (click to enlarge):

It is pretty difficult to conclude anything from this test. I think I was a bit unlucky with my test subject, it doesn't reveal any bokeh weaknesses that easily. Perhaps we can say that the 45-200mm bokeh at 200mm is a bit more "dirty". But it's hard to point out any significant weakness with any of the bokeh examples.

In the Nikkor 200mm image, it is possible to see the diaphragm blades, since it is stopped down one step. The Lumix bokeh rings, on the other hand, are round, since the lens is not stopped down at all.

The Nikkor could appear to be less affected by flare, which is natural due to it's simpler construction with a much smaller number of lens elements.

Nikon to m4/3 adapter

One of the benefits of the Micro Four Thirds format is the short register distance. Since virtually all other formats have a longer register distance, it is possible to make adapters for other lenses to be used on Micro Four Thirds.

Here is one of many adapters available:

It attaches to the camera just as a Micro Four Thirds lens. Here is a video showing how to attach the adapter to the Panasonic Lumix GH1.

It reads "NIK-M4/3", and can be used to mount Nikon F mount lenses to a Micro Four Thirds camera. These kind of adapters are simple, meaning that they only provide a means to mount the lens, and no control over the aperture or focus is possible from the camera. On the positive side, they are rather inexpensive, and can be purchased for around US$30-40.

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When using a third party adapter like this, the camera has no electronic confirmation that a lens is actually connected. For the camera to still operate, you need to set the menu item "shoot without lens". This is found under the "Custom" menu, indicated by a "C" with a wrench icon. Here is the menu item from the GH2 camera:

In the picture below, the adapter is used to mount a Nikkor 200mm f/4 AIS tele lens to the Panasonic Lumix GH1. When using this legacy lens on a Four Thirds camera, the field of view becomes equivalent to a 400mm lens. With a long tele like this, using a tripod is a necessity. While you can choose fast shutter speeds and capture an image without blurring due to camera shake, framing the subject is very difficult when handholding this combination. Recording video without a tripod is virtually impossible with such a long lens.



This lens has an aperture ring. Since the camera cannot control the aperture, it needs to be set manually. The presence of an aperture ring makes this operation easier. Some more expensive adapters have a means for controlling the aperture also for lenses without the aperture ring, e.g., the Nikon G mount lenses.

Many newer lenses do not have aperture rings, and require an adapters with a lever to stop the lens down. This goes for both Nikon and Pentax lenses.

Focus confirmation

There is some talk on the internet about adapters that provide focus confirmation for legacy lenses. To my knowledge, such a thing is not possible with Micro Four Thirds cameras. The cameras cannot confirm the focus when using non-compatible lenses. In fact, with the current cameras, the only way for the camera to know that the image is in focus, is to use a Micro Four Thirds lens, or one of the CDAF compatible Four Thirds lenses.

To be able to confirm the focus, the camera must jog the focus back and forth to find the optimum contrast. This is not possible with manual focus lenses, of course, since the camera cannot control the focus at all. So focus confirm adapters for Micro Four Thirds simply make no sense at all.

Size

A fun fact is that the adapter is larger than the Panasonic Lumix 20mm f/1.7 pancake lens. (The lens to the right below.)


Example images

Here are two example pictures taken at f/4:



And an example video:



I have also looked into an adapter for Pentax K lenses.