Look at that title - normally photographers are trying to do just the opposite - use glass to tame light. But there are times when you need to go at it the other way around.
We've all been to museums, shops, and galleries where interesting things are displayed under glass. It is under there to prevent you from getting your grubby hands on it and degrading it - or to create a sense of wonder and desire on your part. The awkward part comes when you want to take a picture of it.
Sometimes the people selling or displaying the things won't let you do it - for fear of breaking some law or giving away some advantage. Sometimes it is to allow them to sell their own pictures of the objects in their own bookshop - this is a classic ploy for some museums. No good you taking your own pics when there are postcards to be sold!
Even if you are allowed to shoot photos, you frequently fall foul of the way the goods are displayed:
1. The items may be behind tinted glass.
2. The glass surface may be dirty - filthy dirty in some cases.
3. There may be dodgy lighting in the display case. Dodgy in positioning and intensity and definitely dodgy in white balance. Some lights do not have a colour temperature - they have a colour fever.
4. Strong lighting outside the display case may reflect on the glass surface and obscure the contents.
Oddly enough, this is exactly the situation that pertains to outside displays at one of my favourite events - the car show. If a car owner chooses to wind up the window and it is dim inside while bright outside you cannot get a good picture of the interior of the car.
This happened so often that I evolved a way to deal with it that can be applied equally to the museum or shop.
First - if you are not allowed to use flash you can't do this. Likewise if your camera can never come off of an "automatic" sort of setting, you are stuck. But if you are not so restricted, here's what you do:
1. Put the ISO up to 400-800.
2. Put the camera in Manual mode.
3. Set the shutter speed to 1/125 or 1/180.
4. Set the aperture to something between f:4 and f:11. You'll be experimenting with the first couple of shots and can dial yourself into the correct exposure after you see the results.
5. Set the flash to manual as well and try your first shot at 1/2 power.
What you are doing is making your camera's sensor blind to the ambient light but sensitive to the powerful blast of light from the flash. If you are careful to keep the camera and flash pointed at an angle away from where the light hits the glass, it'll go though to the subject and not come back as a reflected blast onto the camera. The depth of field being shallow at close ranges means your camera won't effectively see the surface of the glass - it will see through it.
You may also have to take your camera off AF to do this as it may insist upon focusing on the surface of the glass - and you want to select the subject yourself.
Fussy readers will please excuse the slight over-exposure on the grey Leica camera but note how much better it is than the ambient-light shot at seeing past the obstructions.
The car interior is also through a full side glass window.