[DONE] Enhanced Exposure Lock in Manual Mode

[meckimac]

Hi folks,

let me first say that I love the ML community and I really enjoy the latest release on my 5DII.

I apologize if this feature has been requested before but I was unable to find anything like that using the search function.

So here is my idea:

I'm shooting sports like soccer and professional Ice Hockey from time to time. I'm mostly shooting in Manual mode since the lighting conditions are really stable and especially for Ice Hockey, the camera meter gets crazy when shooting in either Aperture or Shutter Priority.
What I'm looking for is a feature that would let me dial-in my exposure in M mode and save that exposure using a button. Whenever I decide to change any of the 3 parameters (Aperture, Shutter, ISO), the camera would adjust one or two of the other parameters to keep the same exposure.

Sample:
I'm shooting in M mode at f/2.8, 1/1000 and ISO 1600 (a typical Ice Hockey exposure setting). I suddenly need to get more depth-of -field because there is fight going on very close to me and I want all the fighters in focus. I would like to close-down my aperture to f/5.6 and have the camera adjust either shutter-speed or ISO to reflect the smaller aperture and give me the same exposure as before. So the camera would either slow the shutter speed to 1/250 or it would boost the ISO to 6400 or a combination of both.
Being able to set a range of shutter-speed's and ISO values would be great.
The camera would stay in this enhanced exposure lock until I click a certain button again or until I change to a different program like AV or TV mode.

Am I alone with this or could this be useable for others, too?

If you know a way that we can already achieve this, I'm more than happy to hear your suggestions.

Thanks much for your great work and I can't wait to hear from you.
Cheers
-Ingo

[ilguercio]

I don't see the point.
You have Av and Tv already.

[a1ex]

With Tv/Av you are forced to rely on camera meter (which is far from good IMO).

So, instead of standard ISO/Tv/Av adjustments, one could have ISO/Exposure/DOF. ISO control can't be changed easily, because Canon ISO dialog is locking the other values. So, a easy way to implement this would be to adjust aperture/shutter ratio with back dial, shutter speed with top dial, and ISO unchanged. With this, there's no need for a separate button to enable/disable this, just a menu entry.

Did a quick test and seems to work. Sure, there are quite a few exceptions to take into account, when shutter and ISO get out of range.

[a1ex]

Seems to work quite well, I'll try it when I'll go shooting pics next time.

http://bitbucket.org/hudson/magic-lantern/changeset/191f9e02d2a14317c6e9edb3b71ebc875d226e81

[Greg]

A very interesting feature. The 500D does not seem to work 100%

Example:
Tv ->   : AV,ISO

1/200 F5.6 ISO 100
1/250 F5.0 ISO 100
1/320 F5.0 ISO 100 <- error
1/400 F4.0 ISO 100

[a1ex]

Solved, at least for this particular case.

Canon code expects shutter speeds and apertures to be rounded, otherwise it refuses tiny changes (smaller than 0.5 EV). So ML has to round them in the same way.

Edit: you can see in ML menu the Bv value (that's Tv+Av-Sv). You can compare it with the reference value from expo lock and notice a small difference for 1/320 F5.0(F4.5) ISO 100.

The Bv value should show the brightness of your scene (if the exposure is correct). I'm not sure if I'm using the correct terminology and reference value here - if you have a better documentation than this, please let me know.

[Greg]

Example II :

1/250 F2.0 ISO 1600    Bv = 1.0
1/200 F2.0 ISO 1600    Bv = 0.6
1/160 F2.0 ISO 1600    Bv = 0.3
1/125 F2.0 ISO 1600    Bv = 0.0
1/100 F2.0 ISO 1600    Bv = 0.3  <- error?  correct value = -0.3 ?
1/80   F2.0 ISO 1600    Bv = 0.6  <- error?  correct value = -0.6 ?
1/60   F2.0 ISO 1600    Bv = -1.0

[a1ex]

Good catch. Will push the fix later, since I have some other changes that would break compilation with most cameras.

[ed.jenner]

I have another - not sure if it is related and will be fixed with the current anticipated fix:

5dII, 100L

Expo. Lock
All on
Tv - Av,ISO
Av - Tv,ISO
ISO - Tv, Av

start with f2.8 1/40s iso 100 - increase shutter speed to 1/400 s, ISO increases as expected (except one 'blip' to f3.2).

However, when I reduce shutter speed, aperture keeps decreasing (f number increasing).

I can write out all the combos if necessary.