An Open Door Lens Sharpness Discussion.

The three images below show the effect of shooting through an open door when the inside temperature is 70 degrees and the outside temperature is 20 degrees.

The first and last photos were taken through regular somewhat dirty window glass immediately before and immediately after the door was opened and closed.  The middle photo was the best of several taken with the door open and only clean air between the camera and hawk.

The open door had some advantages.  The auto-exposure increased from 1/500 to 1/1000.  A slight green color cast is noticeable in the photos taken through the window glass.

After taking a number of photos through my kitchen window,  I decided to risk a shot from outside.  I moved my camera to my unheated sun porch and shot through the open screen door.  As careful as I was, one of the two hawks was spooked and flew away.  Its partner was disturbed but remained long enough for a couple of photos.

The shot on the left was taken through window glass and the shot on the right was taken in the cold air. 

The three photos above are a 300x closeup view of the differences in sharpness in the unsharpened raw files.  The image on the right was taken in 20 degree air - it is the sharpest.  The image on the left was taken in a 70 degree room with ordinary window glass between the camera and hawk.  It isn't as sharp but could be sharpened in Photoshop.  The image in the center was taken through a door that was opened in a 70 degree room.  It is unusable mush.

When I photograph Sandhill Cranes, I usually use my vehicle as a blind.  It is often very cold and I close the windows when I'm not shooting.  These images illustrate why it is better to stay warm with a jacket instead of using the heater in the car. 

I've seen many discussions comparing lens sharpness.  The differences are usually barely perceptible.  The shots above show that even the best lens will produce unacceptable results when the air between the lens and subject is distorted.