# Why does my camera give a very different reading from my lightmeter?

I'm new to digital photography.

I start shooting in aperture priority mode, unless some situation require some shutter speed attention. Both ISO and SS is calculated by camera.

I am looking at some landscape right now (cloudy day, no sun, morning), and my camera gives me the following calculation:

F: 5.6 | ISO: 400 | SS: 160


In the same time, using some lightmeter I got the following (for the same F and ISO):

F: 5.6 | ISO: 400 | SS: 640


and if I use formulas, assuming EV=12 then I get (for the same F and ISO):

F: 5.6 | ISO: 400 | SS: 500


So what to trust: camera or formulas?

• I think your question is missing some very important information: what metering/measuring modes are you using on both the camera and light meter? Choosing two dissimilar modes is an easy way to get odd results, and the camera's matrix metering may well be trying to accommodate part of the scene in an unexpected way. Nov 23, 2015 at 14:18

You're probably better off just taking a test shot to begin with then looking at the brightness histogram on the shot you just took to see if you need any adjustments. Generally, you'll want a nice distribution where the graph looks like a bell curve or has a balanced range. This tells you that you have a good distribution of tones, meaning you capture the nuances of the landscape. If you see the graph skewed so much of the weight is one the left or right sides, generally your photo will be under/over exposed depending on which way the graph is skewed.

It looks like the lightmeter and your camera have about a two stop difference, i.e. SS of 1/160th vs 1/640th of a second. There is no "right" answer, but choosing the settings that make the picture more pleasing to you/client/etc. For example, if you took a photo using these settings

F: 5.6 | ISO: 400 | SS: 160


and another using these settings

F: 5.6 | ISO: 400 | SS: 200


I'm pretty sure no one would notice any difference unless you literally had them side by side. So, personally, I would say the answer to your question, whether to trust the camera or formulas, is both and neither. Use them as a starting point, and adjust as necessary. Also, assuming you shoot in raw, or even if you don't, you can always make adjustments to the exposure via post-processing. Obviously, you can't work magic, but as long as you're pretty close it doesn't matter too much in the end.

Since you are a beginner, trust the camera.

The fact that your light meter is 2 stops off means you are doing something wrong or you light meter is faulty.

How did you determine EV-12 ? You are probably estimating the light conditions incorrectly.

Which light meter? Are you using it correctly? If it was an incident meter, it reads the light directly incident on the subject, whereas the camera meter is a reflective meter, reading the light reflected from the subject. Huge difference, with different procedures. The camera Reflective meter is aimed at the subject from camera (affected by subjects colors, often requiring our adjustment), and the incident meter is aimed at the camera from the subject (independent of subjects colors). See http://www.scantips.com/lights/metering.html