AETTR always way too over-exposed... probably user error?!

[acemonvw]

Hello everyone. I've been using ML for some time (on my 60D), but just updated to the nightly builds a few weeks ago. I'm trying to get some 'holy grail' time-lapses and thought I would use Av mode, Post-deflicker, and AETTR. The AETTR seemed like a good way to bring out the stars at night.

However, it seems that no matter what, AETTR overexposes my image way too much. For example, in my apartment, with the lights on, AETTR 'always on', it sets my shutter speed to 30" (f = 3.5 on my 18-135mm lens)... this blows out the image way too much. Am I just doing something wrong? I'm at work, so I don't have all the settings memorized right now (I can post them at home). It didn't seem like anything I adjusted changed this. I run into the same problem in Manual mode too, so it isn't just an Av mode issue.

Thanks for the help

[dmilligan]

thought I would use Av mode, Post-deflicker, and AETTR.

Don't use AETTR with Av mode, you end up with two competing metering algorithms, it just doesn't make sense, stick with M.

AETTR overexposes my image way too much.

This is not really descriptive/objective enough to provide a good answer. You should probably post some examples and the settings you used. Without that information, there's no telling what could be wrong.

[acemonvw]

Don't use AETTR with Av mode, you end up with two competing metering algorithms, it just doesn't make sense, stick with M.

Ah, cool. When I can't get AETTR to work, I give up with it and move to Av mode plus Deflickering, that's been my best option so far.

This is not really descriptive/objective enough to provide a good answer. You should probably post some examples and the settings you used. Without that information, there's no telling what could be wrong.

Yeah, I was not descriptive enough. I just thought about this while I was at work. When I get home, I'll post some examples and settings so that it's more clear. Thanks very much for the help so far though!

[garry23]

IMHO

I set mid and shadow S/N to zero and use ETTR for highlight exposure control.

If I have a high DR scene I throw in Dual ISO.

Bottom line: play with ETTR without using mid and shadow ETTR, then explore the S/N 'offsets', which I personally think compromise the ETTR value.

[acemonvw]

I couldn't figure out how to put add pictures, so here's my dropbox folder with some of my settings, but I'll explain what was happening:
https://www.dropbox.com/sh/5x585d6xe2q1s6o/AACjR--lN2SRGmygA0IenUsEa?dl=0


I used:
Trigger mode = Always on
Slowest shutter = 32"
Exposure target = -1 EV
Highlight ignore = 2%
Allow clipping = off
Midtone SNR limit = 4 EV
Shadow = 2 EV
Link to Canon Shutter = off
Link to Dual ISO = On
Show metered areas = off (it gets really jittery when I use this)
Show debug info = off

When I use this setting it ALWAYS uses my 'slowest shutter'. That seems illogical, I thought it was a max shutter speed, not ALWAYS used.

Then when I turned: "Link to Canon Shutter = on" THEN I could only change the shutter speed in liveview (which is what it says to do) but it will only use what I set my shutter speed to (if I set it to 1/4, it takes a quick picture, if I set it to 30", it takes a 30" long exposure). So then it just makes it 'manual mode' again and not so much "AETTR" as I thought it should be... As you mentioned earlier, it's a metering formula!

Outside of this menu, I typically set:
Expo Lock = off
Expo Presets = off
Expo Override = off
ExpSim = ON (But I don't notice any effects either with it on or off)!!

So... does AETTR not work properly in a 60D? Or am I just totally stupid when it comes to cameras (it could be very possible and more likely probably as I'm an amateur photographer, doing mostly film type stuff, if anything).

Thanks for the help guys!

garry23, I'll mess with setting the mid/shadow SN to zero as suggested and see if that improves anything. Thanks

[dmilligan]

You need to turn expo override on if you're going to use LV, however, I recommend not using LV for timelapse. Also 2% highlight ignore seems kind of high => 2% of pixels will be allowed to be over exposed.

[acemonvw]

Oh.

I thought you needed to be in LV to use AETTR at all (or post deflicker).

I might have set the 2% highlight ignore high when I was screwing with the settings and forgot what was the original setting.

Thanks

[acemonvw]

Looks like someone else had a similar issue, though turning off the limits doesn't change the results.
http://www.magiclantern.fm/forum/index.php?topic=12700.0

Turning Expo. Override to 'on' doesn't seem to change anything. What I seem to find is this:

1) If 'Link to Canon Shutter' is OFF, then my shutter will ALWAYS be set to the 'slowest shutter' (at night, I assume 20 - 30" is what I'd want for ETTR).

2) If 'Link to Canon Shutter' is ON, then my shutter will ALWAYS be what I set it to...

So there's really no 'metering' going on in either instances.

I turned off Midtone and Shadow SNR limits, which didn't improve my settings, I turned highlight ignore to 0.1% with no effect either.

:/ Thoughts?

[Walter Schulz]

Delete AUTOEXEC.BIN and ML dir from card, copy extracted nightly build content to card and retest.
Results?

[a1ex]

Record a video of what you are doing.

Metering for long exposures in LiveView is likely to give this result, especially on small cameras. If in doubt, get out of LiveView.

Also make sure you don't have some other exposure tools enabled (if in doubt, unload the modules you don't use).

FYI, ETTR will set ExpSim and ExpoOverride as it sees fit, so changing those should have no effect.

[acemonvw]

Good ideas. Thanks! I will give those suggestions a try (but I'll be out of town until Sunday, though perhaps I'll some time to work while I'm away).

@a1ex, I took myself out of liveview and found the same thing happened.

You might be right about other exposure tools enabled, but I don't see any other than the ones on this page of settings.

The one thing I do see is that Exposure compensation in the Canon menu is set to +5 EV, and if I try to decrease this, it just jumps back up to +5 EV every time, unless I turn AETTR off.

I'll delete the AUTOEXEC.BIN and ML dir from the card and replace with the extracted nightly build content and see if that fixes anything.

Thanks

[acemonvw]

I'm still not understanding how AETTR is supposed to be working with the 60D.

I've looked over this guide a few times:
http://www.magiclantern.fm/forum/index.php?topic=8322.0

I've adjusted the Image review up for 8 seconds. I see now that it looks at that result and then says something like this:

ETTR: Next ISO 100 8" (was ISO 800 32")

Then my camera changes the shutter speed to 8" and quickly converts back to 32" (my 'slowest shutter speed'). Something must be taking over and telling the camera to be at that slowest shutter speed.

I've reset the settings in ML a few times, today I deleted the AUTOEXEC.BIN and ML dir and replaced with the extracted nightly build content, but nothing seemed to help. Having 'image review' on for longer does seem to help, now I can see the camera trying to meter down to what it should be, but then it reverts back!

Thoughts?
Thanks!

[Audionut]

Record a video of what you are doing.

[acemonvw]

You should be able to view this. I take a few pictures (which take 32" each, so just skip forward).

I don't talk during the video, but it should be pretty evident. I show the settings my camera had in ML (at least the ones I thought were pertinent, such as my AETTR settings, the modules that were loaded, etc). And then I tried to take a picture. After it was taken, I took another. You'll see that in the image review it says that the shutter should be at 8" instead of 32" and so it changes it, and then quickly reverts back to 32". Maybe you'll see something that stands out. The lighting is bad, but it should still work just fine, I would think...

Let me know if you require more info. Thanks

...just remember that I left the entire shutter release time of 32" in the video (I could have edited it out, but I left it in for clarity).

[Audionut]

http://wiki.magiclantern.fm/userguide#expoverride

edit:  Wait.

FYI, ETTR will set ExpSim and ExpoOverride as it sees fit, so changing those should have no effect.

[acemonvw]

I'll check on 'expoOverride', but with it on or off, there were no differences in what it was doing for the exposure... :S

[a1ex]

Get out of LiveView.

[acemonvw]

Get out of LiveView.

That seems to have worked! Thanks. I didn't see it mentioned in other threads that you couldn't be in liveview... Did I miss something?

Do you have to have image review on and have the LCD facing you (for visual representation)?

Thanks for the help. It must've been that there was some metering going on in liveview that was affecting the metering...

[a1ex]

If your normally exposed picture requires 20 seconds, and you want to meter it from a LiveView frame (1/30 seconds), it's a bit tight (the result will always be "too dark" because ExpSim is already using the highest ISO).

LiveView metering was meant for everyday shooting, not long exposures.