Low Illumination CAF Performance – E-M1.3 – MC20 + 300mm f4

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drj3 Veteran Member • Posts: 9,865
Low Illumination CAF Performance – E-M1.3 – MC20 + 300mm f4

First the conditions & results for those who want to skip the verbal description and the camera settings.

Time – At Sunset – Sun had set below tree line 18:53:44 – 18:53:51

First sighting of the year of three Sandhill Cranes.

Single Low Sequential Burst of 53 images over 7 seconds – 46 images in focus and 7 out of focus as defined by DOF focus distance limits.

Camera indicated distance for a typical frame 875 feet – my estimate based on the typical bird size and FOV is about 650 feet.

Exposure settings – 1/800, f8, ISO 6400

On a previous post, a DPR member ask, how well the E-M1.3 CAF performed in Low illumination. The attached images may help provide some information. The sun had set below the tree line when three Sandhill Cranes flew over the refuge. I wanted to document their arrival for their second year at the refuge and this also provided me an opportunity for my first long duration test of CAF at low illumination.

I always leave stabilization ON with IS Priority unless I am sure that I will be shooting at 4+ times the focal length. I will often shoot moving birds at far below the recommended shutter speed for a stationary target (1/800 used for these images instead of the minimum recommended 1/1200 for stationary targets without stabilization). I do not recommend such low shutter speeds unless the target is moving parallel to you, so that the distance change during exposure is minimal (essentially like a stationary target when panning). Any variation in your panning rate at slow shutter speeds will result in blurring of the image, since the stabilization (S-IS2) can only compensate for up/down movements and not horizontal movements.

While I normally would not PP images at this ISO (or taken at this distance over a marsh), the images are posted simply as examples of the illumination conditions. The image brightness (exposure) was raised about ½ stop in PP. Seven of the 53 images fell outside the DOF for acceptable sharpness. At least, some, if not all of the unfocused images were a result of my failure to keep any of the three birds near the center of the frame. I tried to vary framing from having one bird centered, to one on each side the frame as the birds moved up/down independently of each other during the burst.

The camera maintained focus very well considering that I used All focus points, CAF Sensitivity +2 and I certainly did not keep the targets centered over the seven second burst. I do have one caution using the Center Start with all focus points. The camera will obtain focus on the target only if the target is in (or very near) the center of the frame. The camera will focus on whatever is in the center or generally fail to focus if the center area is a homogeneous background (sky) even though the target is somewhere within the frame. I currently have one Custom Mode set up with Center Start ALL and one Center Start unchecked and I have a button assigned to each Custom Mode until I decide which setting works best for me.


CAF – All Focus points

Center Start – All

Center Priority – First Three Checked

CAF Sensitivity - +2

C-AF Release Priority = ON

Image Stabilization = S-IS2

Image Stabilization = IS Priority

Low ISO Processing = Detail Priority

Electronic Shutter Low Sequential = 18 fps (actual frame rate with stabilization = 7.57 fps)

EVF Frame Rate = Normal

S – Shutter Priority

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