Why I Prefer the E-5 over the OM-D

Started Mar 27, 2013 | Discussions thread
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Great Bustard Forum Pro • Posts: 36,266
Re: Why I Prefer the E-5 & ISO 100

dave gaines wrote:

The diffraction limit is around f/13 for 4/3.

It depends on what you mean by "diffraction limit".  Let's consider a very sharp lens, like the 50 / 2 macro, and a less stellar lens, like the 14-42 / 3.5-5.6:


As we stop the lens down, we have two competing effects:  lessening lens aberrations that make the lens sharper, and diffraction softening that makes the photo softer.

The break-even point for the 50 / 2 macro is f/4.  That is, it gets sharper as we stop down from f/2 to f/4 since lessening lens aberrations outweigh greater diffraction softening, and then continually gets softer as we stop down further since diffraction outweighs lessening lens aberrations.

The 14-42 / 3.5-5.6, however, is at its peak wide open at 42mm f/5.6 since diffraction is already such a strong player by that aperture, and it's all downhill from there.

In both cases, we can clearly see that f/13 resolves considerably less than the peak aperture.  So, if by "diffraction limited" you mean the point where resolution is no longer acceptable, indeed, one might choose f/13 as the boundary.  But in terms of when the photo begins to lose resolution due to diffraction, that aperture is much wider than f/13.

You need a lower ISO to avoid smaller apertures.

I can't imagine a scene being so bright that f/5.6 1/4000 ISO 200 would be sufficient.

I suspect the OM-D has the same diffraction limits, so why it doesn't have ISO 100 is a mystery to me.

Well, it does have ISO 100, it's just that Olympus calls it ISO 200. 

Most of the lenses are slower so you need a faster ISO to get an equivalent exposure.

The ISO setting is arbitrary, anyway.  What matters is the f-ratio and shutter speed, as those two factors, combined with the scene luminance, determine the exposure.  The ISO setting merely decides how bright the LCD playback and OOC jpg are:


ISO 100 on the E-5 is good for reduced noise, but the DR is less than at ISO 200.

Since ISO 100 on the E5 is simply ISO 200 overexposed by a stop and pulled back a stop for the LCD playback and OOC jpg, it's very possible that highlights could get clipped.

I use it for tripod work where long exposure is not a problem. I use it when I want more detail from the shadows and DR is not an issue due to uniform lighting in the scene.

Exactly.  Overexposing, while running the risk of clipping highlights, reduces overall noise.

Contrary to what some people who've never owned an E-5 want to theorize, the exposure is shifted 1 full stop.

You have to shift exposure 1 stop or you get blacker, less detailed blacks and you won't peg the whites to the right (expose to the right) if you don't adjust exposure, compared to ISO 200 or ISO 400.

For the jpg photographer, it's probably better to use ISO 100 than ISO 200 w/ +1 EC.  However, for the RAW photographer, they would produce the same results.

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