How to Use Your In-Camera Spot Meter

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We’ve mentioned in previous posts how in-camera metering can be very unreliable. It can meter the scene differently even if the subject and lighting do not change. In the series of photos below, I left the camera at evaluative mode and took three shots at different focal lengths. I shot in AV mode with the ISO at 400 at f/5.

1/6, f/5 at 30mm

1/8, f/5 at 70mm

1/6, f/5 at 105mm

You can see that the camera’s meter fluctuates depending on the focal length I was shooting in. This should not be the case since I’m shooting the same subject under the same light. You might think that the difference is not that big but I’ve seen cases where the meter will fluctuate to almost a full stop depending on where you zoom in.

The only way to get stable exposures is by shooting in full manual. By how do you know what settings to use? The first thing you need to do is to set your camera’s meter to spot meter mode. You then need to zoom in fully to a part of the scene you want to meter for. In my case, I zoomed into the black lining of the red cup and metered from there.

Since I metered for something black I applied an exposure compensation of -1. I then took note of the readings the camera gave me which were 1/15, f/5 at ISO 400. These were the values I used when I switched to manual mode.

The photo below was taken in full manual with the reading I got from the spot meter. Notice that it is properly exposed. The previous photos, on the other hand, were overexposed. Since I’m already at manual mode, I will get the same exposure no matter how close I zoom in to the subject.

This technique is really useful if you’re planning to take a series of shots since you’ll get the same exposure for all the shots. You only need to use the spot meter again if there is a change in the lighting conditions. If you don’t have a spot meter mode in your camera then you will need to make do with center weighted average or partial metering but you really need to zoom into your target area to get a clean exposure reading.

Related Reading:
When to Use Exposure Compensation
Going Manual: Learning Exposure Basics
Understanding Camera Exposure Modes

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