Spot Metering
When I wrote my blog piece on June 25 last year about Exposure Compensation (EC) , the penny dropped and I realized I had to increase EC in bright subjects such as snow, and decrease EC in very dark scenes, I thought “well that’s EC cracked then. Onwards!” How naïve, and presumptuous! Hence today’s blog article.
This resulted in me not even thinking about, or trying to discover spot metering at all. It was therefore somewhat of a shock when the A Year With My Camera (AYWMC) online course landscape module popped up in my email, and the lesson was on spot metering. Something I had never done before. I quickly became confused as to where in a scene I placed the spot. I did not appreciate the potential impact it can have to change the exposure in other parts of the frame. I had no clue of the difference in applying spot metering when in manual mode and when in aperture or shutter priority mode.
The spot meter tries to render whatever it is focused on as a mid-tone 18 % grey. So, if you focus the spot meter on the subject which becomes a 18% grey reading that works well. However, if the subject is brighter or darker this can be problematic. The brighter subject will cause the camera to underexpose, the darker subject will cause it to be over exposed, because the camera is always trying to bring the exposure back to 18% grey.
It has been quite a challenging learning curve, prompting me reaching out on the AYWMC course, for advice, which I knew would be excellent.
What is Spot Metering?
Spot metering involves metering off a specific, small area of the frame. Typically, this is 1.5% - 5% of the view finder. On the Sony a6000, I can only spot meter from the center of the frame. There is a small circle, sometimes very faint in some light. On my camera I cannot link the spot meter to the focal point, as you can now on more advanced cameras.
This is my understanding of the workflow to use spot metering:
In Manual mode:
Place the spot. meter on a middle toned area of the scene that's in the same light as your subject or if your subject is actually middle tone then change the shutter speed, ISO, or aperture to get the EC meter to 0 to ensure the image is properly exposed.
If I am happy with the EC reading, I can lock it in using the AEL button. This is usually found on your camera body marked with a symbol that looks like * To use it, press the exposure lock button which will lock the exposure, focus on your subject, press the shutter half way down, You can then recompose if you need to and take the shot.
If there is no mid tone, meter off another area, and use EC knowing you need to add EC to an already bright area, and set the EC to minus 1 or two stops for a dark area.
I have found this to be the most helpful method so far.
Using spot metering, I placed the spot on the subject. This underexposed the shot, EC was -0.7 i could have changed the shutter speed or Aperture, or better still, put the spot on the foliage
In this next image I set the spot meter on the foliage, and the EC meter at 0.
In a priority mode, you have to change the EC reading by using the center dial.
Point the spot meter at a mid-tone area of the photograph, or at the subject if it is already a mid tone.
Choose the aperture or shutter priority you want to use, let the camera choose the rest of the settings, based on where you have centered the spot meter.
Check If the image appears over exposed, change the EC setting to 0, or under expose if that is a preference. Do the opposite if the image appears too under exposed.
Always take a test shot to look at the result of the exposure.
This shot was taken in shutter priority at 1/1000 sec EC -1, f4, ISO 400. It is a little underexposed, the spot meter was placed on the water, and could have been placed on the building.
One thing I have done for some time now is deliberately underexpose some images up to one point or more , as I know I can increase the exposure in post. It is easier to manage an under exposed image in post editing than an over exposed one.
One key take away was how spot metering can impact images more significantly if there are both very bright and very dark parts of the composition. How I set the spot meter can “blow out” bright skies for example, and this needs to be factored in when I am deciding what my exposure level is going to be, and where I will place the spot. It does mean though I am in control and can be creative.
If there is not a middle tone area, use exposure compensation. If we know that a bright scene is going to cause the camera to underexpose, we add one or more stops to the exposure. In an auto exposure mode use EC. In manual mode I can meter to a part of the image that is a mid-tone.
If there is a mixture of tonalities as a group under spot metering, but they are lighter or darker than middle tone, then you need to use EC.
It is worth remembering to change EC back to 0 on the EC meter after taking a shot- otherwise the EC you have set will remain, which may work- but may not, depending on how the light has changed, or where you are when you take your next shot.
When to use spot metering
When the subject is back lit
You can use it in any situation with strong highlights and shadows.
Scenes with a bright subject against a dark background
Setting exposure when the background is very dark.
Spot meter when your subject is wearing very light or very dark clothing.
Shoot in Raw to be able to adjust exposure in post editing. It is hard to use spot metering for moving subjects because the spot meter may miss the subject.
Remember that if you use spot metering, your camera will not measure the light in the rest of the frame. It only concentrates on the small area you choose.
In the course of completing this assignment, I began to learn more about contrast and HDR. HDR stands for high dynamic range. Dynamic range is the range of the lightest tones to the darkest tones within a photo. It’s a measure of the light intensities from the highlights to the shadows.
Knowing this I can now understand how spot metering is useful for these types of scenes, and to be aware of how my metering will impact HDR.
Spot metering is not a default- choosing evaluative or center weighted metering is helpful when wanting to take a broader exposure reading.
Having done somewhat of a deep dive into this during the past few weeks, I can recommend the following links – this You Tube video by Steve Perry is particularly helpful.-
Another good resource is:
This AYWMC lesson was an opportunity to learn more about exposure, remind myself on how the camera exposes to make everything 18% grey, and think more critically about dynamic range.
Another great blog article David - I know that it has taken me a few tries to get my head around EC and metering - and I think that there is still more for me to learn.