Advice on Auto-ETTR for Sun rise / set Timelapses

[NitromanX]

Hi !

I'm playing with Auto-ETTR for shooting timelapses of sun set / rise and then into night time with stars.

What is the suggested setting for "Highlight Ignore" ?

I normally would asume that 0.1% is best as i want to hold as much highlight detail as i can for sunset ... However, i read somewhere that as much as 5% is needed ... But surely 5% burns out the sun and makes my sunsetting a white blob ? What about at moonrise - should i then use 0.1% to hold the small highlight detail a full moon shows etc ?

Can anyone explain how the "Highlight Ignore" function in practical settings a little more for me please ? Should i also tweak the Midtone SNR & Shadow SNR as not quite sure how this works either as usually leave these at default.

Finally ... are there any instances when i'm best not to use A-ETTR and better to use Aperture Priority AV metering instead ?

Fabulous ! Thanks in advance ...

[NitromanX]

Ah haa ... just found this ... Very helpful.

http://www.magiclantern.fm/forum/index.php?topic=5693.100

[NitromanX]

Oh dear ... back to square one it seems ...

Went out last night and tried an Auto ETTR with Dual ISO on Canon 5D2 using 1.10.15 ML build.

I was anticipating a good sunset (according to forecast) and then a shoot into the dusk ... so i set up my new Edelkrone Slider with Action Module set to Photo Timelapse. 28mm lens F4 100 ISO Manual Exposure Mode. Intervalometer one shot every 16 secs.

ML Settings below :
Trigger Mode - Always On
Slowest Shutter - 16secs
Highlight Ignore = 0.1% (was expecting sun to emerge and wanted as much detail as i could get)
Midtone SNR Limit - 6EV
Shadow SNR Limit - 2EV
Link to Dual ISO - ON
Advanced : Exposure Target -1EV

Dual ISO :
Recovery - ISO 800 (i was certain i'd set)
Dynamic Range Gained - 2.5 Stops (i was certain i'd set)
Midtone Overlapping - 11.2EV

1 ) It seems the Edelkrone Photo Timelapse system will not work with Auto ETTR. It sends signals to the 5D2 to take pics but somehow interferes with the analysis of the raw preview image so Auto ETTR won't work. Shame, so switched to Macro Mode for very slow tracking along slider.

2 ) All my images appear to be badly underexposed - maybe about two stops. I thought this was due to DUAL ISO but when i tried to export the raw files in Lightroom with added Raw cr2hdr plug-in, it told me there was no interlacing so files were not actually DUAL ISO. Is this because there wasn't enough dynamic range in scene to warrant switching on DUAL ISO or did i not lock in DUAL ISO properly (i thought i had double checked this but may have made a mistake) ?

3 ) What else could have caused the underexposure - the Auto-ETTR settings ? The exposures started 1/1600 F4 ISO 100 ... I'm guessing they should have been about 1/500 sec but the Auto-ETTR happily settled on this shutter speed to start sequence.

4 ) Sadly the sun never came out and the sunset flopped ... But all my exposures were underexposed and I'm not sure what i needed to tweak to ensure the raw file had correct exposure. Any ideas what i could have done wrong ?

5 ) Stupid Noob question (forgive me!) ... But how do i upload the image file to show you all ? I just get [IMG][IMG] and can't upload image to Forum.

Here is temporary link to image on one of my websites : www.rodedwardsphoto.co.uk/downloads/IMG_0225.jpg

Thanks in advance ...