I usually advise most photographers to avoid taking pictures from outside through windows. The glare tends to distract the eye from what's going on inside, and the dust on the window can lessen the image quality. Nevertheless, there are some cases where shooting through a window can help you get the shot. Sometimes you want a more candid image or perhaps a unique perspective on a familiar scene. In other cases, like shooting from inside an airplane, you have no other option but to shoot through a window. If you need to look through a piece of glass other than your lens, here's what you have to do.
Get a Polarizing Filter
Polarizing filters cut out the extra sunlight that causes glare. They are sort of like sunglasses for your camera. With a polarizing filter (and a few minor adjustments), you can get rid of nearly all of the reflections on the glass you're shooting.
When using your polarized filter, it helps to look through the viewfinder and twist the polarizer until you get rid of as much glare as possible. By twisting the polarizer, you are lining it up with the angle of the glare and blocking it (while keeping the light coming through the glass).
Polarizers work because most of the light comes into your camera from two different angles. The angle of the light coming through the glass is always different from the angle of the light reflected from outside. A polarizer allows you to block one without blocking the other. In this case, we are blocking the reflections by twisting the polarizer until they are gone. The rest of the light still comes through.
Now I know what some of you are thinking. "I don't own a fancy digital SLR camera that lets me use polarizing filters." No problem. You can still get rid of glare by holding a pair of polarizing sunglasses in front of your lens and twisting them. This isn't as precise as using a digital SLR, but it still works.
If you can’t block the reflections, blur them out
Here’s something digital SLR owners can do when a polarizing filter just isn’t doing the job. You can widen your camera’s aperture to blur out the reflections still present in your image. Here’s how it works.
When you increase the size of the aperture, you limit what is known as the depth of field of your image. In basic terms, the depth of field is how far you can see into an image. If the background is blurry, you have a smaller depth of field. If you can see everything in the background, you have a very large depth of field. As f-numbers go down, the depth of field goes down too, so to pull this off you’ll need to pick aperture values near F4.
You’ll probably want to go with manual focus when you use this technique. It’s too easy for your camera to get “confused” from the reflections. Manual focus also gives you more control over the final product. You can see exactly what will be in focus before you take the picture (though there’s no harm in double checking afterwards!).
This is the quintessential if-you-can’t-beat-em-join-em-technique. A third option requires a little more gear, but it will definitely give you the results you want.
The cloth technique (assistant or duct tape needed)
This trick will definitely make your presence as a street photographer known, but it is really useful for taking photos in aquariums or out of airplane windows. Go buy yourself a nice big piece of black felt cloth and a cut a lens-sized hole in the middle of it.
The next time you need to take a picture through some glass, simply poke your lens through the hole in the cloth and press your lens up to the glass. Now drape the cloth over the lens and the glass to block out the light from behind you that's causing all of the reflections.
It almost goes without saying that you will need some tape or an assistant when you do this. You need something to hold the cloth up to the glass.
It also helps to have absolutely zero concern for what random passersby might think of you. Pressing anything up to glass looks pretty weird (especially out in public), so smile and act like you were the one hired to photograph the patrons in the café today.
Flash is a definite no-no. You're trying to prevent outside light from entering into your photo, so it doesn't make a lot of sense to add in more outside light (especially of the highly intense pinpoint variety your onboard flash makes). It doesn't matter if you use a polarizer or not. It probably won't be strong enough to block out the flash.
You should also consider the lighting inside of the place you're trying to shoot. Is it strong enough? Most indoor spaces (aside from aquariums designed to grab your attention) aren't lit well enough for cameras. You might need to consider using a tripod to keep your camera stable. This allows you to use slower shutter speeds and capture more light coming in from the other side of the glass.
Once again, the tripod solution probably isn't ideal for candid photography (you'll get discovered while you’re setting up shop), but it's fine for aquarium photography and other purposes. If you want to do something similar, and you are going for a candid shot, increase your ISO speed in conjunction with using the polarizing filter. A slight ISO speed increase will make your camera more sensitive to light, letting you see more of what's on the other side of the glass (but do be aware that it also makes your images a little more grainy).
Other uses for these techniques
Glass isn't the only reflective surface. You can also use a polarizing filter to get rid of reflections on shiny metal objects and water. Just remember to look through your camera's viewfinder and twist the filter until you've gotten rid of as much glare as you can. Every surface is a little bit different in the way it reflects light. Keep adjusting your polarizing filter until it's just right.
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