# Tip to use autoISO with fill flash in 5D III



## markojakatri (Dec 9, 2013)

I've find a cool way to use safety shift in 5D. If you use Tv mode and safety shift (ISO), camera will use as high ISO as needed. It actually works identically w/wo flash.

The best thing is that you can use autoISO or set ISO manually. If you set ISO manually, consider your setting as a minimum ISO setting, camera will rise it anyways when needed. This is very nice feature in low light, where fill flash is needed. You can, for example, set high ISO to have f2-2.8, but when it gets darker, f1.2-1.8 are used and if that is not enough, ISO will be risen even more.


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## neuroanatomist (Dec 9, 2013)

Sounds like this feature would work even better on a 1D X. The problem in Tv mode is as the light level drops, the aperture will open up as wide as possible for the lens. In many cases, that yields a depth of field that's too thin (one does not always want to shoot at f/1.2 with the 85L). However, the 1-series bodies allow you to restrict the aperture range used by the camera in Tv mode. Thus, I could try your suggestion, but specify a maximum aperture setting of f/4, for example, even with a faster lens.


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## Marsu42 (Dec 10, 2013)

neuroanatomist said:


> However, the 1-series bodies allow you to restrict the aperture range used by the camera in Tv mode.



I'd like to add that Magic Lantern does the same thing - min. aperture in Tv and min. shutter in Av ... the latter unlimited and not crippled like the Canon implementation, i.e. you can select as fast min. shutter speeds as you like. Personally, I always found "bare" Tv completely unusable as even f4 of my 70-300L is too shallow to many shots, not to speak of faster lenses.

With the said boundaries, I usually use Av for action. For handheld walkaround if I don't want the thinnest dof I use Tv with min. aperture - you can pre-select the shutter speed you think is appropriate, and then the camera selects the lowest iso in range respecing the min. aperture you set. The nice thing: If the iso is at your lower iso limit (selectable on 6d/5d3), it automatically chooses a deeper dof.

The information from the op is a clip from another thread, so just this piece of information if anybody wonders: Magic Lantern's auto iso also works with flash on and doesn't lock you to iso 400, you don't need to use the Tv workaround described.


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## asmundma (Jan 1, 2014)

Does not work on my camera ........ Pls specify more ....


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