Author Topic: EOSM & Timelapse  (Read 2547 times)

garry23

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EOSM & Timelapse
« on: January 17, 2017, 08:35:37 AM »
A potentially dumb question.

Without any Lua scripting, ie using the Canon and ML settings, it it possible to switch off LV when doing a ML Timelapse?

At the moment, the screen seems to stay on all the time.

As I say, a potentially dumb question.

a1ex

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Re: EOSM & Timelapse
« Reply #1 on: January 17, 2017, 09:19:49 AM »
Already answered here, but I'll expand a bit.

Enabling Powersave in LiveView should help, at least a little. However, the camera will still be in LiveView for about 1 second or so before and after taking the picture, which can be significant for battery power.

However, on EOS M, I guess the best way*) is to enable Image Review without time limit; that way, the camera will never return to LiveView. Then, set the display brightness at minimum from Canon menu. This should work, because, at least on other Canons, the biggest power hog is not the display - it's the sensor in LiveView.

At this point, turning off the display from a script is likely to have very little effect on battery life.

*) Just an educated guess, based on how Canon code behaves on all other cameras; I have never had an EOS M in my hands.

garry23

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Re: EOSM & Timelapse
« Reply #2 on: January 17, 2017, 01:48:14 PM »
@A1ex

As usual thanks for the insight. As soon as I am able, I will carry out some experiments and report back anything of ML interest.

BTW, related to the EOSM & Timelapse, so on topic, I'm trying to get a better understanding of the inherent ETTR capabilities by looking at the C code, but this is not always easy.

I'm aiming to see if I can get a more 'intelligent' holy grail script working. At the moment I'm just thinking about it and exploring ideas, ie before any scripting.

My base thoughts (at least day to night TL) go like this:
 - My priority will always be to ensure the highlights are not blown out, or at least not too much. Hence, as a start, I will set both SNRs to zero, highlight ignore to, say, low% and exposure target to 0.5Ev.
- I will set the max shutter speed in ETTR according the 180 deg rules, ie half the interval time.
- ETTR will shift the shutter time from my starting position until the max shutter time is reached, then it will start shifting ISO, but what I'm not sure about yet is, can an ETTR max ISO be set, eg will it pick up on another ML or Canon setting?

My extended thinking goes like this:
- Once I have maxed out the shutter time and ISO, if able, I will open up the aperture until the max aperture is realised.
- Once max aperture condition is met, then I will adjust the ETTR exposure target down to its lowest.
- Finally, once I've 'bottomed out' the exposure target and the script still needs to run, I'll keep all settings the same and (hopefully) push the exposure in post.

If the above is understandable, I would welcome any insight/views before I spend time scripting, eg is/can ETTR linked to a max ISO.

Cheers

Garry

a1ex

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Re: EOSM & Timelapse
« Reply #3 on: January 17, 2017, 03:13:31 PM »
For ETTR, max ISO is taken from Canon menu.

- My priority will always be to ensure the highlights are not blown out, or at least not too much. Hence, as a start, I will set both SNRs to zero, highlight ignore to, say, low% and exposure target to 0.5Ev.

Just be careful with the moon - it might brighter than you expect. I made this mistake a few years ago and ended up with a properly exposed moon, but unusable image otherwise. Had highlight ignore set to 0 and dual iso enabled.



Next image was after I've changed the exposure parameters on the fly (moving the camera in the process, but the timelapse was ruined anyway). Notice the moon is still small, but of course it has no detail (so I'm no longer showing a crop).



Not sure I can actually salvage anything from the footage prior to this frame, but I'm keeping it for future research.

DNG, after processing with cr2hdr (default settings):
3U3B7110.DNG and 3U3B7111.DNG.

BTW, this is one of the reasons ETTR defaults with SNR limits enabled, and with nonzero highlight ignore.

Another thing to keep in mind: metering on midtones (for SNR) is statistically robust (changes very little if things are moving in the image or if specular highlights appear or disappear). Metering on highlights is not - a strong specular highlight that appears out of the blue is enough to underexpose the entire frame.

Quote
- Once max aperture condition is met, then I will adjust the ETTR exposure target down to its lowest.

Not sure what this step is for; once you have reached the max ISO (as set in Canon menu), shutter speed (as set in ETTR menu) and aperture (from your script), the exposure parameters will stay unchanged (until next day).

mothaibaphoto

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Re: EOSM & Timelapse
« Reply #4 on: January 17, 2017, 04:21:27 PM »
This works for me on MKIII:
Code: [Select]
# Config file for module ettr (ettr.mo)

auto.ettr = 1
auto.ettr.ignore = 5
auto.ettr.level = 0
auto.ettr.max.tv = 24
auto.ettr.midtone.snr = 8
auto.ettr.shadow.snr = 3

garry23

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Re: EOSM & Timelapse
« Reply #5 on: January 17, 2017, 04:25:11 PM »
@A1ex

Thanks, first for confirming the ETTR link to canon ISO  :)

The reason I thought I might explore the need for exposure target adjustment was not well thought through by me, but at the back of my mind was the thought I need to ensure the ETTR always finds a solution, as I don't believe I can test the validity of an ETTR solution in. Lua script?

Or maybe I can by assert or something similar. But where or how would I find an ETTR error message that Lua can access?

As I say, I'm trying to see if I can add extra intelligence to the ETTR HG logic.

a1ex

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Re: EOSM & Timelapse
« Reply #6 on: January 17, 2017, 05:16:37 PM »
ETTR messages are not available to Lua, but you could guess its state by looking at ISO. For example, if it's one stop below the maximum limit, I think you can already start opening the aperture (or maybe even earlier).

If it's too dark, the solution will be the ISO and shutter limits.

garry23

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Re: EOSM & Timelapse
« Reply #7 on: January 17, 2017, 05:18:58 PM »
@mothaibaphoto

Many thanks for sharing.

I must say, I have always steered clear of using the SNRs as I wish to 'always' control the highlights not clipping.

However, you and A1ex have given me something to think about and explore  ;)

BTW if there are others who have experience with timelapsing on the EOSM, I would love to hear from them.

Cheers

Garry