Metering

Whilst I am on this course and learning, I thought I might as well pass on some of my newly gained knowledge. This module is about exposure and metering, and how to calculate the right settings. So that's what you're being treated to today, albeit a much shorter, less technical version!

There are different types of metering that you can use to get the correct exposure. I will explain them briefly here:

Average Reflective Metering

This is where the meter measures the light reflecting off the subject and gives an average reading, which gives the image a mid-tone. The meter will take into account the highlights, mid tones and shadows and give an average of them all. (This sort of metering can also be found integrated in DSLRs). This form of metering is better when there is a good mix of tonal ranges, and not so good for images where the scene has more highlights or more shadows.

Incident Metering

Incident metering is a type of metering that measures the light falling on to the subject. This is a very effective form of metering if you are, for example, shooting with snow. You can use a grey card to take a reading for this sort of metering as long as you ensure you hold the grey card up to the subject and angle it so that the light is falling on it the same as it is the subject or you can use a handheld incident meter.

Spot Metering

With this light meter, an area of the scene is selected and used as the basis for the whole scene and when using a spot meter it is normal practise to take several readings at different points to get the correct exposure. This metering is also another form of reflective metering and whilst very accurate due to taking several readings, it takes practise to master. 

18% Grey card

Camera's have in-built reflective light meters and therefore, any scene it looks at, it assumes are a mid range of 18% grey. This poses a problem if you are in snowy conditions where there are predominantly lots of highlights, as the integrated light meter in the camera will give you a reading based on the highlights but assuming the highlights are 18% grey. So if you follow the meter on the camera, you will get an underexposed image. Similarly, in very shadowy conditions, the reading you get will mean you overexpose the image. Therefore a grey card should be used to calculate the correct exposure. The '18%' refers to the reflective quality of the card and you need to hold the grey card at the same angle as the light falling on the subject to get the reading.

Palm Metering

An excellent string to your bow if you know about palm metering because you literally have it to hand in any given situation, seeing as your palm is attached to your arm! It is similar to grey card metering but you must remember to increase the exposure by one stop (more or less, depending on if you have fairer or darker skin) to compensate for the difference in brightness between your palm and the grey card. And again, you need to angle your palm so that that the light falling on it is the same as the light falling on your subject.

So there you have it! A crash course in the different types of metering to help you get the correct exposure in as little takes as possible.

As part of this learning curve, I was also asked to calculate the dynamic range of my camera* (from darkest to brightest recording of object). Once you know the dynamic range of your camera, you can use this to correctly judge what exposure you will require for your scene but assessing the highlights and shadows and thinking about how much or how little detail you want to keep in the image. After taking lots of images, I was able to see how many 'zones' my camera has and what it's dynamic range is. From that, I was then able to make this I had to come up with a zone ruler which I can now use to help me with future work; I know the settings for the zones below and can use this knowledge when assessing my subject.

*Just FYI, my camera has a dynamic range of 10 and the human eye has a dynamic range of 15!

I hope you have found this post useful. As always, would love to hear your thoughts on it, or suggestions. :-)