Mirror is a good reflective material. Glasses are another good example. Water also reflects light quite well. If you do not believe me, try looking at a pool of water for the reflection of the sunlight. Please remember to protect yourself with good sunglasses before you do that. Sunglasses are also another example of good reflective materials.
Good reflective materials reflect light very well. They reflect so well that they can spoil your photos! Usually, you will not take notice of them until you have seen those photos that you have taken earlier. You will realize that the photos have bright spots due to the strong reflection of the reflective materials in the background.
You can conduct a simple experiment for yourself. Go to a mirror and try to take a photo of your image in the mirror. Take one photo with a flash light and the other without the flash light. After taking the photos, examine them.
For the photo taken with a flash light, you will notice there is a bright spot in the photo representing the reflection. This is so significant that it commands the main attention instead of your subject. The bright spot ended up as the main focus instead of your subject.
For the photo taken without a flash light, you may notice other possible bright spots. For example, the sunlight through the windows may have caused multiple reflections in the mirror, thus creating the bright spots in the photo. And bright spots distract the attention from the main subject. In short, they spoil the photo.
From the experiment, we can conclude two things. Firstly, please do not use a flash light or any strong light source directly at the reflective material. The reflection will create bright spot that will destroy the photo. Secondly, avoid taking a photo of the subject where the background contains reflective materials. This is equivalent to shooting directly at reflective materials.
We can extend the experiment further by taking a photo of the mirror at various angle. Instead of taking directly or 90 degrees, we can take the photo from any angle varying between 10 to 80 degrees. Try to take the photos with and without flash light. Examine the photos after the shooting experiment.
For photos taken with flash light, you will notice that there are certain angles where the bright spot are much darker. For photos taken without flash light, you will notice that there are certain angles where there is almost no bright spots. In conclusion, if you want to take a photo of reflective material as a subject, you will have to find a suitable angle to reduce the bright spots issue.
In short, the simple idea that I will like to share with you is:
Avoid shooting directly at reflective materials.