OK, I promise I'll stop writing blog posts about the EOS 7D shortly, but I've just come across another feature for movie exposure that is really quite interesting.

The camera features auto exposure and manual exposure possibilities when shooting video, but it also features a somewhat half-way house where it makes use of a bit of both technologies. 

A couple of cameras ago we saw the appearance of Auto ISO setting - as in choose a shutter speed and aperture, and the camera will adjust the ISO to suit. And this has been added to the EOS 7D for movie shooting as well. 

This is quite a big deal in some ways as once you start shooting a clip at a particular shutter speed, you won't want to change it. Equally, changing aperture may be undesirable either because you want a specific depth of field, or because turning the dial on the camera will result in noise (as in real, audible noise) coming from the camera dial and aperture diaphragm. By letting the camera choose the ISO, you can have your chosen shutter speed and aperture and still get the right exposure by having the ISO altered - from 100-6400.

Now clearly there are some settings you just can't do, like a fast shutter speed at a small aperture whilst shooting inside, and equally you may well find if you choose to shoot movies at 1/30-1/125 sec that the ISO can't go low enough when shooting with a fairly wide lens in daylight. This is where either extra lighting or ND filters come in. 

It's amazing to think that the EOS 5D Mark II is still making waves like a tsunami this long after launch, but that's really because it is just a very capable camera.

We've talked about the movie mode quite a lot, but looking back through the posts, there's something we haven't mentioned and it might just trip you up...

If you want to get manual movie exposure, you need to put the camera into M mode. Seems logical enough. However, there is a stumbling block - in the Live View/Movie mode settings, you need to make sure you select: Still+movie --> Movie display. If you choose Stills+movie --> exposure simulation, then even in Manual shooting mode, the camera will carry out the exposure adjustments for movies. 

It's one of those quirks that could trip you up if you're not looking for it.  So now you know!

...Well yes, actually.

Having spent some more time playing around with it yesterday, there are a couple of other things in the update that we thought we should expand on. And it all concerns the movie exposure. Who'd have thought it?!

First up the shutter speed. When you go to manual mode in movie shooting, you don't have complete free reign of all shutter speed and ISO settings. While there is full access to the aperture controls, the shutter speed is limited from 1/30sec to 1/4000sec. This makes a lot of sense as you probably won't be wanting settings outside that range anyway.

The ISO speed is also limited. If you set the ISO to a particular speed, you'll be able to choose anything from 100 to 6400 and the H1 setting of 12,800. However, there is also the Auto ISO setting that you can use which will adjust the ISO between 100 and 6400.

One of the downsides of the manual control of exposure in movies is that instead of doing a very smooth transition between different exposures, as the camera does in auto exposure mode, changing the settings (be it shutter speed, aperture or ISO) will result in a step change in the exposure - there will be no smooth transition in brightness. The Auto ISO setting does rectify this by giving you manual control of your shutter speed and aperture but automatically adjusting the ISO to keep the correct exposure - and you get the smooth transition. I'd love to tell you that that's it and all is completely hunky dory on this front. But I can't. While it all works very well, it you use the Auto ISO setting and combine it with manually set shutter speed and aperture, you then can't use the AE Lock button to keep it at a particular setting. It just doesn't work. You can't over-ride what the camera sees as the 'correct' exposure. Yep, no exposure compensation for brighter or darker subjects in Auto ISO. If you change the shutter speed or aperture, the ISO simply changes to keep the exposure the same - right up and down to its limits. So, unless you're filming mid-tone subjects, we'd suggest staying away from Auto ISO in the manual movie mode.