Back to the Basics, Again~

myvinyl333 · May 1, 2012

pgriz said:
...I take an incident light reading in the primary light, and in the shadow area. This I do once, unless the light changes. That tells me the range of light I have to work with. I'd do a spot meter on the scene highlights and also in the shadow areas where detail is important. I already tested my camera and know that I have five stops of latitude on the high side, and four on the low side. Say the highlights are at 1/2000 sec at f/8 and ISO 100. If my exposure for the image would be at 1/125 sec at f/8 at ISO 100, then my highlight is 4 stops above that, and is within my 5-stop range. If the image exposure is at, say 1/30 sec, then that is 6 stops difference, and I will definitely lose detail in the highlights. .

Thank you for the information. I do not know the dynamic range of a scene, nor do I know how to get a light reading. That said, I want to learn. I spent last night reading about metering in general and have a better understanding and will do more reading...

pgriz · May 1, 2012

To determine the dynamic range of a scene, you use your spot meter and read the exposure value the camera suggests to you for that spot. Choose the brightest area where you still want detail as the highlight area, and choose the darkest area where you still want detail as your shadow area. Let's say your camera's spotmeter off a highlight reads 1/4000 f/8 Iso 200, your spotmeter off the dark shadow area is 1/4 f/8 Iso 200, then you have a dynamic range of 10 stops. Let's also say that the "average" meter reading of the same scene would be 1/250 sec f/8 Iso 200, then your highlights will be 4 stops above the average, and your shadow will be 6 stops below your average. If your camera has a range of 8 stops (say 4 stops on the high side and 4 stops on the low side), then your highlights will be close to being blown out, and your shadows will definitely be black.

Now let's change the scene a little, and find that the shadow detail comes in at 1/60 (again, f/8 ISO 200), then your overall dynamic range is only 6 stops (shadows 2 below average, highlights 4 above average), and that gives you some leeway - you can under-expose by one stop and have the highlights at 3 above average and the shadows at 3 below average. This will give you plenty of detail in all the important areas and you can use good post-processing technique to extract the maximum info value.

The above meter readings were using the camera's meter in spot-meter and averaging modes. The camera gives reflected light readings. To get incident light readings you either need a incident light meter, or you can use your camera's meter off a grey card.