N00b Incoming!

[Andy Perrin]

The leaf problem, to me, is probably just the typical lack of fine detail in IR because most leafy foliage does not differ greatly in its IR reflectivity. We should look up that value. I used to know it, but it escapes me at the moment.

The issue isn't that the foliage differences in IR reflectivity, it's when you have, say, a car and a tree in the same scene next to each other with a 550nm long pass filter. You focus on the car (reflecting visible red at 600nm, cause it's a Miata), but the trees are reflecting 700-1000nm. So you get a nice sharp Miata and a blurry tree.

 

Of course in addition to this you have diffraction in both.

[nfoto]

This scenario will play out only if the lens fails to keep its focus shift under sufficient tight control across the spectral range used for the capture.

[dabateman]

 

The issue isn't that the foliage differences in IR reflectivity, it's when you have, say, a car and a tree in the same scene next to each other with a 550nm long pass filter. You focus on the car (reflecting visible red at 600nm, cause it's a Miata), but the trees are reflecting 700-1000nm. So you get a nice sharp Miata and a blurry tree.

 

Of course in addition to this you have diffraction in both.

 

But isn't that how you make the car look to be moving faster than it really is?

Parked cars aren't always so interesting.