How do you measure "correct exposure"

[creisinger]

Hmm, when shooting architecture it might get tricky holding up the light meter to the 25th floor to get a "good" reading.

I'd suggest what "pgriz" already wrote: use the histogram. In today's age where an exposure doesn't really cost you anything (besides the time...) you will get an exact result of your exposure looking at the histogram.

Now the trickier part is to be able to read the histogram correctly and to re-check if your desired subject/area is in fact exposed properly.

Besides that, "correct" exposure means not to blow out highlights or to drown areas in 100% black. This is something your histogram will tell you instantly and without a lot of experience it's easy to understand.

Most likely you will have to to some post processing to ensure that your subject "pops" the way you intended it to.

Best of luck. Show us some results.

 

[TCampbell]

The in-camera meter is "usually" good, but it can be fooled based on the reflectivity of your target... white targets reflect a lot of light... black targets don't reflect as much. If the camera s pointed at a scene with lots of middle-gray tones then it'll be accurate. If you notice you're metering a dark scene (night time, evening events, etc.) or a bright scene (snow, etc.) then the meter will be wrong.

A hand-held "incident" meter is spot on accurate and is not thrown by the color/reflectivity of the subject. That's because the meter is telling you how much light is landing on the meter direct from the source of the light... rather than trying to meter light reflections off the subject. You hold the meter in the light where your subject will be located (not where you plan to shoot from.)

A scene may have both highlight and shadowy areas -- even a portrait will usually have a "highlight" side of the face and a "shadow" side of the face. Typically you want to find the limits (darkest point and brightest point) and then find the exposure halfway between those two (the "mean" exposure.) Better light meters do this automatically (you click a button to take readings at multiple points then click another button to display the mean exposure.) This is going to get you the correct and best possible exposure every time BUT... it assumes you CAN hold the meter in the subject light.

If you're shooting architecture or landscape, it may not be practical to walk into the scene and manually meter at the brightest and darkest spots.

To do this you will put your camera's meter (or your handheld meter if equipped with a spot metering feature) into the "spot" metering mode (which uses the narrowest possible area to take a meter reading.) You can use a reflected meter and take several spot meter readings... evaluate the scene (with your eyes) and look for the brightest/whitest point you can find and also look for the darkest/blackest point you can find. Target those two locations and take spot meter readings. Now find the exposure halfway between the two and, assuming the scene doesn't require more dynamic range than your camera can handle, you'll get a good exposure.

BTW, some hand-held meters can be calibrated to your specific camera (you take images of a test target using bracketed exposures and software analyzes the target to find the limits of what your camera can handle.) Once the meter is calibrated, it'll show the range your camera can handle and as you meter multiple points, it'll find the best exposure to keep everything within the dynamic range of your camera or warn you if the image requires more dynamic range than your camera can handle.

When I want accurate metering from a reflected or built-in light meter, I use the spot metering mode because it uses the narrowest area to take the sample reading (it will still be thrown by reflectivity). If you use any other mode, then your camera is doing some averaging (so the metering isn't reporting the exposure for the brightest point... it's reporting the mean exposure based on the total area that it evaluates.)

 

[Dubaiian]

Thank you so much everyone, you have given me a lot of food for thought. I clearly need to get my learning head on in respect of the histogram -it's something I should have done anyway as I am clueless on this subject.

Tcampbelk, thanks for the advise on how to average the metering TTL, this will keep me going until I complete my histogram learning.

Thanks again, you guys rock whenever I travel to the next stage in photography so keep up the good work as I am sure this site is helping so may people to really understand true photography rather than the Instagram and iPhone pictures that litter my Facebook.

 

[timor]

A hand-held "incident" meter is spot on accurate and is not thrown by the color/reflectivity of the subject. That's because the meter is telling you how much light is landing on the meter direct from the source of the light... rather than trying to meter light reflections off the subject. You hold the meter in the light where your subject will be located (not where you plan to shoot from.)

Tim, you started this well, but the ending is confusing. Do you mean: "you point the white half dome in the direction from you will be shooting"?

A scene may have both highlight and shadowy areas -- even a portrait will usually have a "highlight" side of the face and a "shadow" side of the face. Typically you want to find the limits (darkest point and brightest point) and then find the exposure halfway between those two (the "mean" exposure.) Better light meters do this automatically (you click a button to take readings at multiple points then click another button to display the mean exposure.) This is going to get you the correct and best possible exposure every time BUT... it assumes you CAN hold the meter in the subject light.

That's complicated, actually you describe action with a spot, not incident.

If you're shooting architecture or landscape, it may not be practical to walk into the scene and manually meter at the brightest and darkest spots.

A good hand held 1 degree spot can take accurate measurement from the horizon. I think that's far enough for most cases, no need to walk . Cameras spots usually are 6 degrees, a bit wide, but OK for close, big subjects like buildings. Another matter is to decide the exposure from collected data, but than we shoot digital, so the verification will be quick with still time to reshoot.