Water Meadow VI

Eventually I have managed to get the complete picture. The main

problem was that the tripod I was using has seen a lot of hard use,

and its joints are loose. The problem was solved by buying a heavy

duty carbon fibre tripod.

 

It is interesting what you can see with NIR. The wispy clouds were

not visible to the naked eye. The sycamore behind the cottage is very

healthy, but the one just visible on the right is not. It is

recovering from a serious road traffic accident. The bright pink

trees are beeches.

 

Professionally, I run a company that produces bespoke industrial

software for intelligent processing of IR images, so this is a bit of

a busmans holiday for me.

Wonderful, it seems IR is making a comeback and rightly so. You have hadled it extremely well, does the focusing shift with digital cameras?

Hi Richard. The focussing does shift at NIR with any lens. Camera lenses are corrected for chromatic aberration at optical wavelengths, so you can expect them to behave differently outside the visible spectrum. Good lenses should have an IR focussing index mark to help you. Unfortunately, none of my AF lenses have such a mark, so it is a matter of experience just where you set the focus. Professionally, I recently measured the focal length of C mount lenses used on IR TV cameras, and I found that they were about 10% longer than their marked focal length at 800 nm.

 

Obviously you cannot focus the lens through the viewfinder with an 87 filter on the filter blocks all visible light, and you cannot see the light that comes through. What you can do with the S2 Pro, however, is to turn off automatic focussing, and do test shots, zooming in on the LCD display to get the sharpest setting. That setting would be out of focus at visible wavelengths. Fortunately, the camera comes to the rescue itself. In IR it gives an exposure of about 1/15 at f/3.5. When you take the filter off it stops the lens right down, so you get an acceptably sharp optical image at infinity, even though the lens might be set to 10 feet, without resetting the focus (which you do not want to do, because the images would not be exactly registered).

 

Great!

I see more and more IR shots. This one is a good one

Thanks Antonio for the explanation, it was very informative and has given me an insight into the IR field. I will one day have a try, at the moment I only have a compact type Olympus C5050, but I will aspire to this someday, again many thanks - Richard.