Olympus OM-D E-M1 low light auto focus performance

Started Jan 16, 2014 | Questions
OP msnremea1 New Member • Posts: 14
Re: Olympus OM-D E-M1 low light auto focus performance

Bob_tracks wrote:

msnremea1 wrote:

At the E-M1: Menu -> Cutom Menu -> D (Disp/Tone/PC) -> Frame Rate

This setting significantly affects AF performance in low light. When setting this to "High" the E-M1 is getting nearly as fast at low light as the GH2 and in some cases it matches the GH2 speed. This setting affects EVF and LV the same way.

But there is a drawback. The manual says "Select [High] to reduce frame lag. However, the image quality may drop." I don't see any differences in the pictures taken but the image quality of the EVF and LV gets worse the darker it gets. Worse means: It is loosing more and more colour (I don't care) but at some point with very low ambient light there is nearly no picture visible anymore.

Just to be sure I understand, are you saying that when using High Frame rate:

- your jpg or raw images are NOT impaired

- images in the EVF and monitor go dark

Correct?

Yes, this is what I was trying to say. The live images in the monitor and EVF only go dark(er) in low-light situations though.
I can't see a difference in the RAW output (I never use JPG so haven't tested these).
BUT: I have not done any thorough testing. Just a few hand held shots and I compared them afterwards on the PC.

I will do some more testing over the weekend to see if the quality of the output pictures really stays the same in all situations.

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance
1

I wrote about this several time (including in the DPR E-M5 article and my "Focusing explained" forum thread), here is how I interpret these things.

At "Normal" frame-rate the E-M5 and E-M1 drop the frame-rate of Live View to 30 fps in order to get longer exposure on the sensor. You can see this drop in screen/EVF frame-rate with bare eyes, turning on blinkies while panning makes it even more visible. This has nothing to do with final image exposure (not even with the screen frame-rate), but with how many frames the sensor feeds to the processor/screen per second. And of course your Live View image gets darker in bad light, because there is less exposure (less time per single live frame) with higher frame-rates.

The reason why focusing is slowed down by this is that CD AF needs feedback from the sensor after each movement of the lens AF motor. Lens AF motor is moves -> sensor is read -> contrast is measured -> AF motor keeps moving or is stopped -> if AF motor keeps moving -> sensor is read -> contrast is measured -> etc. pp.

At longer sensor exposure = lower sensor read rate = lower frame-rate the processor needs to wait longer for sensor feedback before it can decide whether to stop the AF motor or keep it moving for further CD measurements.

There is one drawback, in *very* dark light it can happen that AF cannot be acquired at "High" frame-rate where "Normal" is still able to focus due to more light hitting the sensor during AF/Live View.

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rcjim Regular Member • Posts: 318
Re: YES WAY
2

Above you is a good example of the misinformation given out by the Oly fan boys.

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Ray Sachs
Ray Sachs Forum Pro • Posts: 10,580
Way...
6

SaltLakeGuy wrote:

does any of the new Panasonic's focus down to -3EV. I doubt they even go to -2EV.

I have an EM1 and a GX7. While there are things I like more about the EM1 AF (face detection, for example, where the "near eye" focus option is just incredibly effective), the GX7 is notably more sure footed focussing in low light, particularly very low light, where the EM1 gives up well before the GX7. This is assuming the same lenses and apertures of course...

Which is not to say the EM1 is anything other than excellent in low light - I haven't seen anything like the OP on this. But the GX7 is better...

-Ray
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Ray Sachs
Ray Sachs Forum Pro • Posts: 10,580
Re: YES WAY
1

rcjim wrote:

Above you is a good example of the misinformation given out by the Oly fan boys.

Or maybe he just got this one wrong...

-Ray
--------------------------------------
http://www.flickr.com/photos/20889767@N05/

Bob Topp Regular Member • Posts: 481
Re: Olympus OM-D E-M1 low light auto focus performance

Another useful workaround, depending on how fast, and in what direction your subjects move, is to lock focus with the AFL button.  There will still be a slight metering delay with the shutter button, but your lens will no longer rack back and forth until you refocus.  I've had good luck with this approach, but of course, the first focus will still hunt until locking, and is dependent on subject motion.

In the meantime, I'm going to play with display frame rate and see if I can live with degraded viewing performance.  I'd really like to see the EM-1 snap every time in low light.

Bob Topp

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OP msnremea1 New Member • Posts: 14
Re: Olympus OM-D E-M1 low light auto focus performance

Thanks for sharing!
This basically describes what I found out and kind of wrote earlier.

As you seem to have spent time with this topic for a while do you know why Olympus doesn't do it the Panasonic way? Considering the GH2 is three years older than the E-M1 Olympus would have had plenty of time to "copy" that functionality.

Currently it doesn't switch automatically like in Panasonic. It is how it is. But do you know is there any way to have a shortcut to this setting (Frame rate)? That would at least make it easier to use and quickly switch where the situation requires.

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Brian Wadie
Brian Wadie Veteran Member • Posts: 9,080
Re: Olympus OM-D E-M1 low light auto focus performance

Bob, have you tried low light shooting with Live View Boost enabled (+ high frame rate refresh) working with only the EVF?

This is my usual configuration for studio work and as I said earlier in this thread, I have yet to experience a focus delay / miss-focus when working in a blacked out studio lit only by modelling light(s)

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance

Unfortunately I don't own any Panasonic MFT body (only the pocket LF1), so I don't know how they solve the "lack of light vs. AF speed" problem.

As for the shortcut, there are several modes of operation where the frame-rate is automatically switched back to normal even when it's set to fast via menu. "Zoom AF", Art picture modes, iEnhance picture mode, Video mode (can be used for stills shooting with *real* WYSIWYG, but uses 30 fps for Live View constantly). The important part is that frame-rate is only switched back to normal temporarily while you switch the mode, once you switch back frame-rate is switched back to fast, too.

One exception of the latter is when you set focus peaking to any button, this will turn the frame-rate to normal the very moment you change the button, even when focus peaking is switched off.

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance

Brian Wadie wrote:

Bob, have you tried low light shooting with Live View Boost enabled (+ high frame rate refresh) working with only the EVF?

This is my usual configuration for studio work and as I said earlier in this thread, I have yet to experience a focus delay / miss-focus when working in a blacked out studio lit only by modelling light(s)

This should make no difference once you set refresh rate to "High". Live View Boost does little more than turning exposure compensation preview to permanently view +-0 EV, regardless of what exposure settings you use. This can "boost" Live View performance in those instances where 0 EV preview does not need a refresh rate drop to achieve preview, but in dark light it will still drop. "High" refresh rate never drops to 30 fps on the E-M5 and - as far as I can tell yet - the same applies to the E-M1 (even though its high refresh rate mode works somewhat different).

So when you combine both you get the drawbacks of both combined without additional benefit. Just use "High" refresh rate and be good with it, while still being able to get live preview of exposure changes in most situations (albeit not as many as with normal refresh rate).

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Brian Wadie
Brian Wadie Veteran Member • Posts: 9,080
Re: Olympus OM-D E-M1 low light auto focus performance
1

You are probably right Timur but as I have said earlier, all I can base my comments on are my experiences as a photographer. I don't pretend to understand (or care about) the inner workings of my camera, just how it performs for me in my applications.

to repeat - I have never yet missed a shot because of slow focus speed under low light conditions using the EM-1 (nor the EM-5 before) so whether it is slower than the GH2, GX7 or other system is irrelevant to my use (and I suspect to that of  a lot of others)

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OP msnremea1 New Member • Posts: 14
Re: Olympus OM-D E-M1 low light auto focus performance

Just testet. Looks like you are wrong.
Live boost clearly makes the objects my EVF better visible when it's dark and the frame rate set to high. (E-M1, Firmware 1.1)

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OP msnremea1 New Member • Posts: 14
Re: Olympus OM-D E-M1 low light auto focus performance
2

As for the workaround I just learned that enabling "Live view boost" together with "High frame rate" makes a faster AF with still rather good visible picture.

Now, for the shortcut problem I also found a workaround:
I saved "MySet 1" with "Live view boost" = off and "Frame Rate" = normal. I also registered Fn1 button as shortcut to "MySet 2".
Then I saved "MySet 2" with "Live view boost" = on and "Frame Rate" = high.

Now I can quickly switch between fast AF when it's dim and normal AF when there is plenty or basically no light by just pressing the Fn1 button.

Still not Panasonic (does all automatically) but a real good workaround.

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Brian Wadie
Brian Wadie Veteran Member • Posts: 9,080
Re: Olympus OM-D E-M1 low light auto focus performance

just a thought, has anyone seen this effect when shooting using manual exposure (which is the way I shoot in low light situations)?

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance

msnremea1 wrote:

Just testet. Looks like you are wrong.
Live boost clearly makes the objects my EVF better visible when it's dark and the frame rate set to high. (E-M1, Firmware 1.1)

That is because Live View Boost fixes Live View to one exposure preview that is independent of the exposure you set. When you use higher exposure compensation with high refresh rate Live View gets brighter, too. So for exposures where live preview is wrong anyway it can make sense to activate Live View Boost to get a brighter (or darker in bright light) view.

With the E-M5 Live View Boost fixed preview to the equivalent of +-0 EV, with the E-M1 it seems to be different, maybe even dynamic in that it uses a higher value for dark scenes.

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Bob Topp Regular Member • Posts: 481
Re: Olympus OM-D E-M1 low light auto focus performance

Brian,

These days I'm using normal EVF level.  I used boost for a while, and can't remember why I turned it back down (unless possibly thinking this affected battery life).  I'll will try out high boost to see if it helps with the AF speed.  I went looking at frame rate this morning, only to find it grayed out, so I'm still trying to figure out what else I set to affect that.  Info button doesn't say anything.

Thanks, Bob

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Bob Topp Regular Member • Posts: 481
Re: Olympus OM-D E-M1 low light auto focus performance

Yes, Brian,

Slow autofocus affects me in manual mode.

Bob Topp

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance

Bob Topp wrote:

Brian,

These days I'm using normal EVF level. I used boost for a while, and can't remember why I turned it back down (unless possibly thinking this affected battery life). I'll will try out high boost to see if it helps with the AF speed. I went looking at frame rate this morning, only to find it grayed out, so I'm still trying to figure out what else I set to affect that. Info button doesn't say anything.

Thanks, Bob

Focus Peaking set to any Fn button? Using any of the picture modes I listed before?

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Red flash eyes save lives and eye-sight!
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Brian Wadie
Brian Wadie Veteran Member • Posts: 9,080
Re: Olympus OM-D E-M1 low light auto focus performance

check you haven't got Focus peaking on Bob as this blocks high frame rate.

I saw your comment that you are seeing slow focus with manual exposure, its got me beat I must admit.

Maybe my focusing demands aren't so great as others but I have just finished processing another load of Black on Black studio shots and everything is spot on and I shot the session rapidly (>600 shots in 3 hours including many costume and lighting changes ).

It was a pitch black studio lit only by the modelling lights in the flash heads so the exposure meter was, as usual, off the bottom of the under-exposed light-meter scale (so significantly more than -3ev)

A static example (can't show the models as it was a commissioned shoot) but it gives an example of the light levels we were working with, all low key night-club level light shots

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Timur Born
Timur Born Veteran Member • Posts: 4,763
Re: Olympus OM-D E-M1 low light auto focus performance

You will only notice slowdowns in low light with normal refresh-rate, mostly only when AF needs to hunt anyway. If you still got enough light and contrast, like with all the hardware on the drumset, you might not notice the difference (might still be there, but not so relevant).

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