Our brains are much cleverer than most of us think. Walking along the high street we look in shop windows and only see what’s inside them, despite the fact there are huge reflections of the shops opposite, cars and people passing and even reflections of ourselves. The reason is that our brain is filtering the unwanted information and our eyes are focussing beyond the glass to help ignore the reflections.
The trouble is that, clever though cameras are, they’re not that clever, so need a lot of help. A number of factors come in to play. Firstly, how bright is the scene beyond the glass compared to the reflection? Ideally you want a lot more light on the scene than behind the camera and this is where a professional photographer can overcome the problems by using specialised polarising filters and choosing angles carefully. Shooting at about 56 degrees to the glass, with a polarising filter, will almost eliminate the reflections. The same applies to photographing water, only the perfect angle for that is 53 degrees, so you eliminate the reflection of the sky.
Another aspect of using a polarising filter is to avoid using a wide angle lens, as the polarising effect diminishes as the angle varies so much.
Choosing the right time of day also helps. If the sun is shining directly on objects opposite the glass they will reflect more strongly, so choose a time when the buildings opposite are in shade. A professional photographer taking architectural photography would choose his time carefully as a matter of course and may even take the shots at night so the interior is at it’s clearest. This adds another problem, if there are street lights or car headlights, and a large black cloth on stands may be used by the professional photographer to mask off bright reflections.
In the studio, glass is sometimes used as a base or background for some objects and, once again, the professional photographer will be adept at lighting from the best angles to avoid reflections. This can also be helped by putting more light on the background behind the glass, to overpower reflections on the front.
Taking photographs out of a window has similar problems of reflections from items near or on the camera, but this is fairly easily rectified by covering the area the camera can see reflected, with black cloth or card. The closer that is to the glass, the smaller it needs to be.
Next time you don’t notice a reflection, just think how clever your brain is.