Locking Shutter Speed with Auto ETTR

[grodriguez]

Hey guys, just picked up a 5D Mark III and LOVE it! Magic Lantern (1.1.3) is some incredible software. Everything is going perfect except for one issue - I've been using Auto ETTR to ensure proper exposure while shooting, however, and this is just based on the experimenting I've done the past few days, it seems when I use Auto ETTR the aperture stays the same while the ISO and shutter speed are the ones that change.

Since I'm shooting at 24fps with a 180 shutter, I wanted to know if there was any way to set up Auto ETTR to only change aperture and ISO, leaving the shutter angle unchanged? If anyone knows a solution, please let me know 

[justinbacle]

Interested in the answer too.
BTW, you should really download the latest version of Magic Lantern (nightlies)

[Walter Schulz]

BTW, you should really download the latest version of Magic Lantern (nightlies)

?

[a1ex]

Not implemented yet.

Suggestions about what criteria should be used for choosing the aperture (other than measured exposure) are welcome. Also, if all 3 exposure variables are used, it would be nice to know which configuration is the most desirable. From a noise standpoint, the lowest ISO wins because it captures the most photons, but for balancing aperture vs shutter, there doesn't seem to be a clear choice (at least for me).

[grodriguez]

Not implemented yet.

Suggestions about what criteria should be used for choosing the aperture (other than measured exposure) are welcome. Also, if all 3 exposure variables are used, it would be nice to know which configuration is the most desirable. From a noise standpoint, the lowest ISO wins because it captures the most photons, but for balancing aperture vs shutter, there doesn't seem to be a clear choice (at least for me).

Thanks for the response a1ex!

In my case, depth of field is secondary to proper exposure, so I'm biased (especially in the case of full frame where wider apertures have such a narrow plane of focus). But in my current situation if auto ETTR sets it up like - f/4.5, 1/44, ISO 200 - I'll dial down the shutter -1 and up the aperture +1.

Surely either variable could be locked within the software? For all intents and purposes, aperture already is unless the image is massively under/overexposed. I've yet to have the 5D stop down the aperture on auto ETTR in any tame case. It either opens the aperture fully when the meter is starved for light, or stops down a few levels when the image is massively overexposed (I left the ISO set to 12800 the night before). If the exposure is in the ball park of accurate, aperture won't move.

I imagine only two of the three variables are even necessary in any case (that's why we have a P mode!), though if you wanted to write something that considered all three, you could consider the minimum shutter, the lens' widest aperture and the camera's max ISO in an algorithm that maps the values within that subset to their relative stop differences. Sorta like how I've dialed down and up to compensate. I'm probably speaking gibberish, you're the tech wizard here 

[garry23]

@grodriguez

I may have misinterpreted your point, but one way to get the best of both worlds is to focus and exposure stack at the same time or focus stack in dual-ISO mode.

This is why I wrote my Auto Landscape Bravketing script; http://photography.grayheron.net

Cheers

Garry

Ps of course the above is only good for your still photography, not video ;-)