E-M1 Focus problems

Started 8 months ago | Discussions thread
Mark Chan
Senior MemberPosts: 1,711
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Re: E-M1 Focus problems
In reply to lnikj, 8 months ago

Mark Chan wrote:

lnikj wrote:

Mark Chan wrote:

May I suggest overexposure, possibly implicating diffraction?

i try dialing down exposure in strong daylight. The photos I get with positive exposure compensation seem similar and indeed it may be difficult to find where u focused.

I was wondering about whether my practice of ETTR was making it worse.

I don't understand the relationship between overexposure and diffraction though. Can you explain further?

Cheers

PS I have some more test shots to share later. I'm sure now that it is not simply diffraction (though that plays a small part). I am reasonably sure now that shutter speed is the single biggest factor here.

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went back and seeing your aperture it shouldn't be defraction.

by the way, another possible problem will be say shooting in broad daylight with aperture wide open but again that's not your problem.

exposing ETTR is an issue as OLY cameras tend to overexpose in daylight and underexposed indoors. What I do, for my needs, is in outdoor environs I underexpose, and overexpose indoors.

I ETTR for two reasons:

1. The E-M1 is noisy at base ISO.

2. In low contrast scenes outside the E-M1 determinedly sticks the exposure and histogram dead centre when there is often a whole stop of headroom above.

The latter gives more data to work with in the image (you can see this just by looking at the resulting file size).

None of my test shots are ETTR; they are underexposed if anything.

I do feel using ETTR maybe causing the problem.

I am happy to stop ETTRing if it is causing the problem but my (genuine) question as I stated before is: What is the relationship between overexposure and diffraction?

i don't find the focusing issue, and this is with ep-3, ep-5, em-5, em1 and epl-2...but then that's just my perspective.

i do hope you find a fix

Thanks.

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Hiya,

The term shouldn't be diffraction - I kinda messed that term up. It should be 'longitudinal chromatic aberration' i was referring to, but again not in your pics as I experienced this with large aperture lens shot in broad daylight wide open. This caused my images to be very 'unclear'.

Having said that, I would postulate; if diffraction occurs, wouldn't overexposure further reduce sharpness of the image hence you receive an unfocused image?

I would also note of a recent experience; using my EP-5 with 25mmf1.4, I somehow could get the camera to focus on subjects - the background would always be in focus. Ultimately I switched it off pulled batteries and it worked as normal again.

Still miss the no-nonsense cameras of the film era.

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