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Olympus OM-D E-M5 The first Micro Four Thirds camera from Olympus with an integrated Electronic Viewfinder

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Old 16th October 2016
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zoom focus speed of focussing

Does your camera focus slowly on zoom focus?

I was running my latest lens aquisition through a quick test to see that all was ok (it was). Then lens was the 7-14mm F/2.8 PRO that I purchased through the forum and I was testing the manual and auto focus. Now it is difficult on a lens of this focal length to get a true estimate of how accurate the focussing is as by its nature almost everything is almost in focus most of the time. To combat this I was using the zoom focus facility with a zoom factor of x8. I was running my tests in the study and as it was dark outside I had the central ceiling light on - so it was not as bright as outside on a sunny day when focussing speeds are very good but it was not dim either.

By pointing the camera at different objects in the room (a picture on the wall, a camera box, my camera bag etc) I noticed that there was a distinct difference in focus speed between having the camera in zoom focus mode with full viewfinder and the zoom box in the middle of the screen (one press of the zoom focus function button) and in zoomed zoom focus mode with the viewfinder showing the zoomed in view where the zoom box fills the viewfinder (a second press of the zoom focus function button). The latter is considerably slower than the former by a factor of 3 or 4.

Now as the image sensor is still subject to the same projected image and the focus area is still the same, why does having the viewfinder zoomed in make such a difference to the focus speed?

I repeated this test this morning with the 12-40mm F/2.8 PRO and got the same results; same room, same subjects , but this time with ambient daylight (not full on direct sunlight so still not overly bright when focus speeds would be extremely fast and any difference would be indetectable).

Anyone any idea as to what is going on and why? Does this happen with all recent Olympus mirroless cameras with the 16MP (or 20MP) sensor?
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Cameras: E-M5, E-PM2, OM40, OM4Ti
Lenses (M.Zuiko Digital): 7-14mm/F2.8, 12-40mm/F2.8, 40-150mm/F2.8+TC1.4x, 12-50mm/F3.5-6.3, 14-42mm/F3.5-5.6 EZ, 75-300mm/F4.8-6.7 Mk1, 12mm/F2, 17mm/F1.8
Lenses (OM Zuiko): 50mm/F1.2, 24mm/F2, 35mm/F2.8 shift
Lenses (OM Fit): Vivitar Series II 28-105mm/F2.8-3.8, Sigma 21-35mm/F3.4-4.2, Sigma 35-70mm/F2.8-4, Sigma 75-200mm/F2.8-3.5, Vivitar Series II 100-500mm/F5.6-8.0, Centon 500mm/F8 Mirror
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Old 3rd November 2016
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Re: zoom focus speed of focussing

Bump. Anyone have any useful insight on the speed of focussing when using zoom focus?
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Cameras: E-M5, E-PM2, OM40, OM4Ti
Lenses (M.Zuiko Digital): 7-14mm/F2.8, 12-40mm/F2.8, 40-150mm/F2.8+TC1.4x, 12-50mm/F3.5-6.3, 14-42mm/F3.5-5.6 EZ, 75-300mm/F4.8-6.7 Mk1, 12mm/F2, 17mm/F1.8
Lenses (OM Zuiko): 50mm/F1.2, 24mm/F2, 35mm/F2.8 shift
Lenses (OM Fit): Vivitar Series II 28-105mm/F2.8-3.8, Sigma 21-35mm/F3.4-4.2, Sigma 35-70mm/F2.8-4, Sigma 75-200mm/F2.8-3.5, Vivitar Series II 100-500mm/F5.6-8.0, Centon 500mm/F8 Mirror
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