Cheat the light meter: under and over exposure in TV & AV cameras

We have already talked about the the Sunny 16 rule that helps us to expose properly without a light meter.

Sometimes, however, a correct exposure is exactly what we do not need: under certain conditions, is very useful to over or under expose.

It is a simple task if you have a fully manual camera, or if you have the opportunity to adjust by 1 or 2 stops via an exposure compensation dial, as for example in many high-end P&S such as the Ricoh GR or Contax T (from T2 onwards).

Problems arise when we have a P&S (like my Yashica T3) because we have absolutely no control, or when we use a rangefinder that works with time or aperture priority (like the Olympus XA)  where we have the control of a parameter and the other is automated to give a perfect exposure.

The classic example is the cover image of this post: to achieve more details when shooting with backlight you need to overexpose of at least 2 stops otherwise you end up with dark shadows and siluettes.

In other situations it may become difficult for “practical” reasons. Take for example the Olympus 35-RC: it has manual adjustment of shutter times and the aperture can be adjusted either automatically or manually (to use with a speedlight). Unfortunately the meter does not work when the camera is completely in manual because, assuming that you are using a flash in the dark, it will not be useful!

To over or under expose is necessary to measure the correct exposure in TV mode, then manually reset it according to our preferences. (This is a little trick that I use occasionally and you can see an example below)

So when a camera works in TV or AV, preventing us from acting effectively on shutter times and apertures, there’s only a parameter that we can adjust: the ISO value! You just have to set this parameter to a higher value to underexpose and vice versa lower it to overexpose! Practically you are fooling the exposure mechanism adjusting it for a more or less sensitive film.

To give you a practical example let’s assume that the proper exposure for our sample scene is 1/200 – f/4 – ISO 400 and we need to underexpose a full stop and that we are using a TV camera
As we all know, if we vary one of this 3 parameters, another one must change to compensate so, in our case, if we raise the ISO of a stop (800) there will be a compensation in the aperture (it will become F/5.6).
Than (we need to understand the following passage) the film will be regularly developed at ISO 400! It follows that the values of the developed film will be 1/200 – F / 5.6 – ISO 400: so we will have an image underexposed by one stop.

Below you can see the two images that inspired this article

This is not really a “secret trick” since many SLR with AV or TV mode have the possibility of over  or under expose and the control is in the ISO dial.

Personally I use this “hack” when I need to have more control of the light in the scene or for the whole roll, because, for example, I like the colors of the Agfa Vista when is a little underexposed.

4 thoughts on “Cheat the light meter: under and over exposure in TV & AV cameras

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