Infrared

I bought an infrared filter ($10 on eBay, direct from China) and because my camera doesn't have threads for filters I had to buy an adapter which fit over the lens barrel ($15?). Looks impressive but it's mostly a big empty aluminum tube. I don't know why they made it so long, I can't use anything approaching wide angle with it, I have to stay zoomed in or I get rounded corners. Focusing infrared is weird because it behaves differently than visible light going through lenses. You can't see through the filter because it blocks most visible light. Don't even think of doing this without a tripod because these are mostly like 1 second exposures.

I'm having fun with it, I just haven't learned to predict what it's going to do yet. Tree leaves are white and when they're in focus the tree takes on a lacy aspect. Clouds are white also so a tree against clouds gets lost. Focusing is getting better with experimentation. The filter just blocks visible light, most digital cameras already show infrared. Point a remote control at yours and watch through the viewfinder while you push a button on the remote, you'll probably see something.

The reason I bought this is that some nights when I go out to take sunset pictures the viewfinder just comes alive with color, most nights it doesn't. I wonder if some infrared is getting through on the good nights. It might also be able to see heat leaks around windows, doors, etc. like they show on TV when they advertise energy audits of houses, but I'll have to wait for winter to see those. They make UV filters that work the same way.

There are 2 versions of all these pictures. The first is a scaled-down picture as it came out of the camera. The second one I did a simple histogram stretch on to improve the contrast. In Photoshop or Gimp or whatever you have go into levels and move the black and white sliders to where the lumps end in the histogram. That sets the black and white points to what the extremes of the data in your actual picture are. The same thing works for normal color pictures, I do it to most of mine when I remember. Watch the picture while it's happening because you may not want the full effect so stop dragging partway.

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filter stretching
Filter Stretching
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Infrared Landscape   Enough experimentation, back to work. Histogram stretched, focus at plain old infinity. Most of a familiar landscape by infrared. This is as far as I can zoom out with the filter adapter barrel on there. Tried an umbrella for shading the viewfinder so I could see it but what works better is the way I was doing it years ago. Take a flannel shirt and put part of it over the camera and part of it over your head. It gets hot in there though. 7/24/2013 dscn8541.jpg

Another section. I've made some advances in reliable focusing and I started experimenting with a retinex (software) filter on these images. Look it up at wikipedia but this one's built into Gimp. There are several settings which I left set at the last thing I used it for. There are places it introduces false color, I think that can be tuned out.

I hit 10,000 pictures on my camera and the counter wrapped around in the middle of this, that's why the numbers are strange. I almost like the vignetting or having the corners rounded. Here I didn't mount the filter adapter on the camera with setscrews, I just slid it over the lens barrel and it slipped a little on the first one.

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