A few years ago, I was told that there were a lot of dental photography experts who were suggesting that dentists use "TTL" (Through The Lens) metering for their cameras. I was not a fan of TTL to begin with because I felt that it left too many decisions up to the camera, so I continued shooting and teaching non-TTL, histogram based dental photography.
The primary perceived value of TTL is that it's easy to use. In my opinion, based upon my experience and side by side comparisons, nothing could be farther from the truth. You see, SLR cameras weren't specifically designed for the very rigid demands of dental photography. We shoot images from about 1 foot away with the majority of the image being white and pink. Because our use is so far outside of the normal macro photography, the metering system just doesn't work right in the TTL mode. As a matter of fact, after learning how to properly use histogram based capture, most students have an "AHA!" moment related to a variety of close up images that they previously couldn't capture using TTL.
It doesn't seem to matter what camera system is being used, or whether one is using "E"TTL or "i"TTL. In either case, the images just don't compare to the beauty and sophistication of non-TTL photography.
When I changed from Nikon D-100 cameras to D-200 cameras, I figured that I would give the newest Nikon TTL system a chance. For over 2 months I actually tried everything in my power to give TTL a chance. Unfortunately, I could rarely capture an image that was even close to what I was getting with the non-TTL shots. To this day, I look back at the images I took during that period and cringe.
If you think that your camera and TTL are different, please feel free to look at the histogram. I virtually guarantee you that changing to a non-TTL image capture workflow will give you a far better result.
Have a fun time capturing some great images!!!