SAF & CAF: Differences Between the E-M1.3 and the OM1 When Using the Focus Points Instead of Subject

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SAF & CAF: Differences Between the E-M1.3 and the OM1 When Using the Focus Points Instead of Subject
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My Conclusion for those who prefer not to read this rather long post.

SAF focus when using the focus points instead of subject AI on the OM1 is much more selective and better than SAF on the E-M1.3. However, when using CAF with the focus points instead of subject identification for stationary targets, the E-M1.3 is more selective and always as good as or better than the OM1.

The following is based on focus using the focus points instead of the AI subject detection. While it may also have implications for SAF and CAF with subject detection on the OM1, I have not investigated this well enough to draw any conclusions.

Both cameras were set for maximum focus sensitivity: C-AF Sensitivity +2, AF Scanner (On – OM1, Mode 3 – E-M1.3). The AF Area Pointer set to On2 to continually monitor camera focus.

SAF

The SAF focus area of E-M1s (MK2 and later) is considerably larger than that indicated by the focus box. This can lead to the camera focusing on detail in front of or behind the target. The E-M1s will almost always confirm focus in SAF mode, but focus may not be on the target, focus may be on a twig/leaf/branch in front or behind your target.

The SAF focus area for the OM1 is very selective and generally appears to be almost totally within the indicated focus box. If there is not sufficient detail within the box, the camera simply fails to focus without focus confirmation and the camera stops trying to focus.

CAF:

The CAF focus area of the E-M1s is very selective and only slightly larger than the indicated focus box. When there is minimal detail within the focus area, the camera will often focus correctly but fail to give focus confirmation. If you continue to half hold the shutter button while moving the focus point, the camera can often find sufficient detail to confirm correct focus.

The CAF focus area of the OM1 appears to initially be very selective, but if camera does not initially confirm focus, the camera will focus on detail outside the focus box. This is more likely if the focus box has less detail than the surrounding area. The focus may jump to twigs/leaves/branches/distinct detail outside the selected focus box. If you carefully watch what the camera does in this situation, you can often see it initially focus on the target and then refocus on the things outside the focus area before it confirms incorrect focus.

The OM1 also holds the focus on the initial target when the focus point is moved off the target for a much greater distance than the E-M1.3. The E-M1.3 will continue to refocus as the focus point is moved off the target, while the OM1 tends to refocus only when there is very distinct new detail. This probably makes the OM1 somewhat less likely to jump focus to the background for moving targets but makes is less useful for moving the focus point when half holding the shutter button on stationary targets to obtain the best focus balance. This may be caused by the difference in the AF Scanner for the two cameras, but the OM1 does not have an equivalent to the E-M1.3 mode 3.

Setting the larger focus boxes (cross and larger) to Center Priority will limit the initial focus to the area within the focus box for CAF.

CAF Example1

This first test was done only with the OM1 since my subject did not remain at the same location long enough to change the lens to the E-M1.3. However, I always found the E-M1.3 to have no problem focusing accurately with CAF with similar conditions.

I wanted a real wildlife target with little detail located behind a shrub/bush where subject detection was not possible. I found a small Black bear lying close to my bird feeder. She was probably recently separated from her mother and is now looking for a new territory.

There were many twigs in front of the small bear. I alternated using SAF and CAF with the single focus point placed on the fur, between/beside different branches.

The top part first image (camera lcd screen) shows the bear and the placement of the focus point for one of the images using SAF. The white square indicates that I was using the DTC which limits focus to areas within the white square and allows me to easily see if the focus is on the fur or the small branches.

The bottom part of the first image is the unprocessed 100% crop of the SAF image from Work Space, showing that the fur is correctly focused using SAF mode.

In SAF mode the OM1 reliably focused on the fur when the focus point was placed in any of the areas between/around the branches as long as no branch was within the focus box. The E-M1.3 would have focused on the branches in SAF mode.

In CAF mode the OM1 would quickly focus on the fur and then immediately refocus on the branches before confirming the incorrect focus. This was very consistent. The camera would only focus on the fur, if I moved the focus point to the back of the bear away from the branches. It never successfully focused on the fur when the focus box was placed close to any branch. The E-M1.3 would have focused on the fur.

Since the OM1 in CAF mode can focus on the fur with accurate focus when there are no branches close to the focus point, this indicates that very distinct contrast outside the focus box caused the camera to focus outside the focus box and indicates the actual size of the focus box is larger than the indicated focus area in CAF mode.

CAF Example 2

For this I test used both the E-M1.3 and OM1 with the single point focus in CAF mode.

This was a very simple test to check focus change when the focus point is moved. I placed the focus point on the flower (Image #2 and the first section of image #3), and released the shutter. I then placed the focus point at the initial location so that it focused on the first flower and moved the focus point up as I half held the shutter button. I released the shutter as the focus point moved over the rock (middle section of the third image). I repeated this again, placing the focus point on the lower flower and half holding the shutter and releasing it as it reached the upper flower head as indicated in the right section of the third image. I repeated this multiple times with both cameras.

Images #2 and #3 are the E-M1.3 images. The E-M1.3 focused on the initial flower and the focus continually changed to the new location as the focus point was moved.

The OM1 images for the first and third images are like those of the E-M1.3, it focused on the flower heads. However, the OM1 did not refocus as it was moved over the rock, it held focus on the first flower until it reached the second flower head. The first and second CAF OM1 images were identical.

In SAF mode the OM1 easily focused on the two flower heads and the rock, the E-M1.3 focused on the flower heads but would not focus on the rock.

My general conclusion is that SAF focus when using the focus points instead of subject AI on the OM1 is much better than the E-M1.3. However, when using CAF with the focus points instead of subject identification for stationary targets, the E-M1.3 is always as good as or better than the OM1.

Both cameras with firmware 1.2.

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drj3

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