Limitations of m43 in bright light. OMD and Leica 25mm f1.4

Started Apr 14, 2013 | Discussions thread
OP Mark Chan Senior Member • Posts: 1,717
Re: Limitations of m43 in bright light. OMD and Leica 25mm f1.4

Anders W wrote:

Mark Chan wrote:

Went to Hong Kong Disneyland yesterday.

Facing the sun around 2:45pm insisted on using larger aperture (against gut feeling)to try and get some background blurring, so used anywhere between f2.0 - 2.8 whilst attempting to keep shutter speed within 1/4000.

Result was lots of CA making pics generally unsharp...I really appreciate the FF in this situ. Need to use zoom and distance with m43 to make up for this somewhat.

What kind of CA (lateral or longitudinal, and if the latter in the in-focus or the out-of-focus area)? Note that CA won't necessarily make an image unsharp once properly corrected in PP (although LoCA in the in-focus area will detract slightly from resolution) and that it does not vary with the brightness of the scene or the exposure. It may become more visible in high-contrast scenes however. Could you post some examples so that we could have a look at what you are talking about?

Anders, I remember you kindly educated me (and other readers) on the same issue with my 75mm f1.8; I believe its LoCA.  I'll try and post later - photos not with me, and time is limited right now...

As a bonus can confirm that my copy of the Leica definitely has af issues. Af somehow extends away from the af box with ONLY this lens. I don't experience this with any of my other 6/7 lens.

What exactly do you mean when you say that "AF somehow extends away from the AF box with ONLY this lens" and how have you tested that? It would surprise me very much if the actual area used for the AF process would differ between lenses even though the box used is exactly the same.

I find it surprising and FRUSTRATING that it occurs.  I have had enough experience with the lens (2 years) to understand that it's not me (the majority of the time).

I don't know why this occurs, but my experience has shown that in spite of having the AF box directly over the subject's head (with sufficient contrast), the final picture that comes out is focused on the background OR somewhere in between.  This occurs when you have a complicated background with shades and what not but ONLY with this lens I have had the most annoying experiences.  The subject / desired focus is often encompassing the entire af box or at least 80% of it.  Yet the initial shot is most often in the background, on a spot that I am sure I did not set focus on, and is at times not within the af box at times.

Redo the whole thing and the shot comes out fine...

I strongly doubt I could rig a test around this.  The only way I have gotten round this is use the small AF box (magnify), which seems to have reduced the 'wrong guessing' significantly.  Unfortunately for me, I forgot to set the fn2 button for thi since the camera was taken in for the lcd bezel fix and came back with the 1.6 firmware and everything reset.

BTW the OMD with the new 1.6 seems a wee bit slower to return from shots...

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