It's cold outside. I know, I know that comes with living in Minnesota and our winters can be brutal, but the weather forecast for this week into next week is for below 0F degrees and that includes our high temperatures. I may have to go for a walk today in the snowy woods below our house just so I will better appreciate the hot summer days that we'll get here next summer, providing summer ever comes.

I get a bit stymied about my usual daily hike when it is this cold, but I also want to take some photos. Just a few minutes ago a coyote loped through my backyard. I missed him, but now a cardinal is sitting on the bush just outside the patio door and that is an excellent opportunity to get in a few shots and practice some processing and maybe even writing a quick blog article about shooting through window glass. I'll do that....

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Window glass does not posses lens-quality optical characteristics. It would be nice if it did, but that would be a bit expensive. In fact, in my past I worked for a telephone engineering company at about the time that we began designing for fiber optics. We think of glass as being clear but go to your local big box hardware store and take a look at several sheets of glass stacked together and you'll realize looking through that blue-green mess that it doesn't take very many sheets of glass before you can only see vague shapes moving on the other side. Now imagine shooting a light signal through thousands of feet of fiber optics versus a couple of inches. The nearly perfect optical clarity and lack of imperfections in fiber optic filaments is an engineering marvel. Yes, the messenger light is laser but even a laser won't sufficiently penetrate several sheets of window glass in good enough shape to carry a reliable signal. That window glass quality creates a problem for photographers who are used to lens-glass-quality sharpness in their photos. We need to find ways to minimize the loss of sharpness without opening the window which would, of course, cause us to freeze in the weather that would give pause to a caribou.

All the usual stuff still applies: interesting subject, good lighting, good composition, steady holding of the camera, shutter speed, etc. Once all of that is taken care of we need to think about that darn multi-paned, double or triple insulated window glass. Of course, the glass should be clean as possible, but eliminating reflections, shooting perpendicular to the glass, and not being right up against the glass are three things I keep in mind when shooting through glass. 

Cleaning the glass is important, but maybe not as important as some might think. I've not cleaned the patio door through which I took this photo since last fall. The above photo is pretty sharp. Not as sharp as if I had slid the door open, but then the cardinal probably wouldn't have stuck around for the photo if I had done that. But, yeah, keep the window as clean as possible, or whenever you think of it.

Eliminate reflections. Reflections on the glass are distractingly awful and degrade contrast and sharpness. If I flip off the lights in my office to shoot through the patio door I don't have reflections but my office doesn't have any windows that would throw light on me from behind or to the sides that would cause me and other items in the room that would cause reflections. It also helps if the inside is darker than the outside so I always turn off the lights in the office when shooting through glass. Some people put rubber hoods on their camera lens and press it up to the glass. That works, too, but read the next paragraph. Oh, and don't use flash. that creates an enormous reflection--this is all natural light technique unless you rig up a wireless flash outside and control it from your camera inside where it is warm and cozy.

Because I can control the reflections in my particular situation, I like to stand back several feet from the window when shooting through it. Shooting close to a window, I believe, can work, but if there is an imperfection in the glass between you and the subject it your photo will tend to blur and lose contrast and definition. Standing back further, for me at least, seems to reduce that issue as glass blemishes are likely to cover a smaller area in relation to the photo's frame. It also gets me away from the window where my subject may spot me.

Photos will be their sharpest if you are shooting perpendicular to the glass. Light rays must pass through more glass as the angle increases. Remember what I wrote above about several thicknesses of window glass? Window glass, even the best window glass, gets more opaque as it gets thicker and if you are shooting at an angle through glass there will be more glass in the way. When the amount of glass increases through which you are shooting, the more likely there will be blemishes as well with which to contend. And, of course, the light will have to pass through more dirt, if you've forgotten to clean the window in the last year, or more. 

Lastly, be sure to open up your aperture to reduce depth-of-field. Doing so will reduce the impact of blemishes in the glass. And be sure to move around a bit to shoot through different spots on the glass as glass imperfections are not always obvious through the viewfinder. 

What do you think? Do you have other ideas for managing sharpness when shooting through window glass?