Focus Performance of the E-M1.3 with the 300mm f4 vs. the MC20+300mm.

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drj3 Forum Pro • Posts: 10,918
Focus Performance of the E-M1.3 with the 300mm f4 vs. the MC20+300mm.
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I wanted to do a focus comparison of the E-M1.3 with the 300mm f4 alone vs. the MC20+300mm. Since there were not enough swallows to do a good evaluation, I decided to use the Carpenter bees (3/4 inch bees) that insist on drilling holes in the fascia of my home. Carpenter bees hover in front of the area where they drill their nest, moving back/forth/up/down/around, protecting it from other Carpenter bees.

This comparison was based on using the EVF (necessary to maintain the bee in the frame), the mechanical shutter at 10fps and shutter preferred at 1/800 second shutter speed. I used all focus points, since it was too difficult to keep the bee exactly in the center of the frame, especially with the MC20+300. I pointed the camera at the bee and half pressed the shutter. As soon as the unfocused bee was visible, I fully pressed the shutter, requiring the camera to focus during exposures. This enabled me to evaluate the number of frames required to obtain focus in both conditions.

The other settings were my normal, AF Scanner Mode = 3, C-AF Sensitivity = +2, CAF Release Priority = On, Stabilization On with Image Stabilizer = IS Priority. The lens focus limiter switch was set to 1.4 to 4 meters.

I ran a multiple sequences with each condition with different lighting and backgrounds at different distances. The results were relatively consistent with different illumination and backgrounds as long as the background did not contain too much detail.

Results.

The 300mm alone focused much more quickly and corrected focus more quickly when focus is lost due to bee changes in direction/speed of movement. In general it took 1-3 frames for the camera to focus or regain focus. This was obvious in all the sequences, where even the first frame was often relatively close to correct focus.

The MC20+300mm was slower for both initial focus and focus correction, however, once focus was achieved there was no noticeable difference in maintaining focus as long as the bee did not change direction. The MC20+300mm typically required 3-7 frames to achieve correct initial focus or regain lost focus. I found the same 3-7 frames necessary to achieve focus with the MC20+300mm when I used it photographing flying swallows.

Attached is an example of one of the image sequences with the 300mm (average distance 113 inches – DOF = .61 inches) and one with the MC20+300mm (average distance 127 inches – DOF = .25 inches). The shallow DOF results in only part of the bee being in focus, especially with the MC20+300. All images in each burst are shown. The sequences for both conditions were broken into two files so that the bee images would not require resizing. A single uncropped image from each condition is also attached.

The attached 300mm images were shot in much better lighting than the MC20+300mm images; however, this did not appear to have any important impact on the results. Other sequences with the MC20+300mm were shot in better lighting and other 300mm sequences were shot in poorer illumination.

Both these sequences ended when another bee entered the territory. In the last 300mm image, you can see the increase in wing speed and motion blur caused by the slow shutter speed as the chase begins. The focus performance in these sequences is similar to what I get with the 300mm and the MC20+300 when I am photographing the other type of BIFs.

I chose the specific 300mm sequence since it was photographed with the bee relatively close to a detailed area under the bee. The camera achieved focus by the second frame. There are two examples of serious loss of focus in this series. (#22 - #24 & #40 - #42). Image #28, the full uncropped image for the 300mm shows the background for images 22-24 in the lower part of the frame (end of the boards) and the background for 40-42 in the upper part of the frame (green/brown area). I do not know if the loss of focus was due to the background detail, camera predicted focus error, or photographer back/forth movement, but the focus was corrected within 3 frames in each situation.

The focus performance of the MC20+300mm sequence shown in the attached is typical. The lens focus improves over the first 1-7 frames. In this sequence, focus is relatively good by the sixth frame. Images #7 & #12 are in focus, but show camera/lens movement blurring. I either exceeded the stabilization capacity of the dual stabilization or moved the camera too much during exposure at the relatively low 1/800 second shutter speed with the 600mm focal length.

The shallow DOF (.25 and .61 inches) for targets this close can result in more out of focus images than one should get with birds in flight. Any photographer inconsistent panning movements toward/away from the target cannot be predicted by the focus algorithm and will result in some focus error when the DOF is less than one inch. Such small panning inconsistencies would not affect targets with a greater DOF.

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drj3

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