Alternative Infrared Filters
It is time to return to the roots of this BLOG! Enough (for now!) with the touchy, feelie posts and back to the technical discussion of Infrared Photography!
If you have a Full Spectrum Infrared converted camera (like the Olympus E-PL1) that has an electronic based viewfinder then you have the ability to photograph with Infrared filters that are opaque to normal human sight. What this means is that you can see through the filter by using the cameras electronic viewfinder. This is a VERY important distinction. There are a lot of really unique filters out there that cannot easily be used on any other type of IR conversion.
I am going to discuss the B+W 403 (UG-1) dual band (UV/IR) filter today. This filter is a lot like LDP’s XDP filter but slightly narrower on the UV side. If you take a look at the frequency response chart on the right (a comparison of the most common IR filters) for the UG-1 filter (dark purple) you will see that the filter passes light energy in the UV end from 300nm to 375nm that is very sensitive (allows a LOT of light in that frequency range to pass through). This is dark blue/purple colored light. It also allows a little light (less sensitive) from 710nm to 775nm before it falls off to nothing. This end is in the Near Infrared end of the spectrum but at a much reduced amount. In fact, compared to the rest of the normal IR filters shown in the chart, the UG-1 does not allow much light through it at all!
What this means to us is that with this filter you will get VERY dark blue/purple skies and very white foliage. This filter was NOT designed for Infrared photography in mind, but pay that no head. It will generate very ethereal images that have a dark blue sky and very white leaves and takes full advantage of the Wood effect! Take a closer look at the response line on the chart to the left. Only what is above the blue line is actually recorded on your camera! This means that the leaves will be stark white and seem to be surrounded by a slight halo! This makes for very pleasing images that really draw the viewer into the image. Most of the image will be monochromatic except for the sky and sky reflections in water.
To make good use of this you need to concentrate on compositions that have a good sky with scattered clouds, lots of leaves and hopefully a little water for reflections. Remember, leaves are the primary subject of interest for this filter. The sky will give a good contrasting area of dark blue and the rest of the normal 720nm compositional items will add supporting structure.
There will be very little to NO red information in your LCD display if you have properly white balanced your camera with the filter installed. In fact it should be totally monochromatic except for a beautiful blue sky!
White Balance is extremely important in order to get good images here. I suggest that you try different targets for WB. Green grass or leaves, the sky and so on. Experiment until you find what works well for you and your equipment. The image to the right and above had its WB set on the leaves on the left side of the picture.
I will talk about this filter a lot more in the future. But for now I want to leave you with the following points for your consideration if you decide to try this filter:
- There is about a 4 stop loss of light when using this filter. This means that you will have longer shutter speeds.
- There will be no reds recorded that will be usable for Faux Color Post Processing.
- There is NO CHANNEL SWAP needed to use this filter. The image (above) is basically what you get right out of the camera!
- Compositions with lots of green plants, blue sky and water will generate a very ethereal image that makes full use of the desired Wood Effect.
- This filter B+W 403 is on the expensive side (as are all opaque filters).
Obviously, this filter would not be your normal choice for normal (is there such a thing?) Infrared photography. BUT it does have a place in your bag of tricks. If you do decide to give it a try, please come back and let me know what you think!