Exposure levels

[codeglue]

Hi,

Just got back from a vacation in Colorado. I had a great opportunity for mountain flowers and the associated hummingbirds outside the back door in the Betty Ford Flower Gardens at Vail.

I noticed several things with the instant abilities of the 10D that I never would have learned with a film SLR.

A few still puzzle me. Photos of deep blue flowers were often vastly overexposed in the auto or P modes. The camera would expose the blue until it was much lighter than reality. I compensated with the exposure reduction to get the blue back to normal, but then the background was very dark. These results also occured with other colors, notably red, and in a variety of lighting conditions from hot sun to cloudy evening. - Any suggestions?

Another item I found curious was the relative exposure settings between my 28-70 2.8 L and my 200 2.8 L tele. Same subject, say a mountainside covered with evergreens, same time, same light, but the 200 telephoto was much brighter than the 28-70. Both are 2.8. Anybody feel like explaining this? I thought that as both were 2.8, the relative "brightness" would be similar....

TIA

Lee
Overland Park, KS, USA

[Jeppe]

Well yes, dark colurs like deep blue and strong red is nearly a full stop from 18% gray. Therefore, when metering those colours this will result in that the camera will try and make them 18% gray, wich they are not.

So, therfore you need to compensate, maybe 2/3 or as much as 1 stop, depending on the colour. This will ofcours set back the darker tones even more. This is a thing that you must take in calculation when exposing the picture. What is most important ? the flower or the background.

It all comes down to one thing. How to measure the ligth correctly.

[Motorsports Photo]

I've had lots of trouble with exposure as well. The same scene taken in the same light using Tv will have different f-stops recorded, and at least one of the pics is overexposed.

Right now I shoot ant 1/2 or 1 stop under to compensate for this problem.

I use the histogram to tell if the exposure is off, not the cameras LCD.

-PS

[scottbergerphoto]

Jeppe's response is right on the money. Your camera's meter is set for 18% grey. Objects lighter then that will be underexposed and objects darker then that will be overexposed, because your meter is trying to make them look 18% grey. Consider reading "The Confused Photographers Guide To The Zone System" by Farzad, for an easy to understand explanation of exposure issues(available at Amazon). Another issue is that your meter can be fooled by a very dark or very bright backround. In the abscence of spot metering, you can check your exposure by putting a zoom lens on the camera and zooming in so that the subject fills the viewfinder. Check the camera's exposure setting and then recompose the picture by zooming out to where you want it. Check to see if the camera is giving you the same readings. If not, shift to manual exposure and dial in what you got when you zoomed in. You could also zoom in, hit exposure lock, and then zoom out. You will still have to correct for very light or very dark objects because of the 18% grey issues mentioned above. Camera light meters(reflected light meters) are accurate for images of average tonality. They get into trouble at extremes of light and dark (eg. snow, black objects).