We’ve been testing the E-3 (among others) for infrared photography suitability and to discover the best ways to use it.
The Olympus E-3 digital camera is an impressive unit. It has a decent resolution of 10Mpixels, LivePreview using the shooting sensor, a swing and tilt LCD screen and excellent ergonomics and weather proofing. The weather proofing I can testify to after getting soaked when a bigger than expected wave broke over me and the camera.
For infrared shooting there were a number of things I wanted to have a good look at. One was whether the LivePreview would give a useful image for composing. Sadly this is not the case, since it uses the same sensor that takes the picture. The sensor has a fairly strong IR blocking filter. This means that while there is a faint image visible it is not enough for careful composition. The other thing to look at has just how strong this IR blocking filter is, since the trend has been for this to get more effective at blockign IR with each camera generation. Here, as you will see, we are lucky.
The RAW image straight from the camera when using a Hoya R-72 IR filters is as below:
The individual channels are as follows,
and here is the red channel image after processing:
As you can see, there is quite a difference between the three channels.
So now let’s look at the exposure issue. I shot a sequence of images, starting at 2 second, f4 and 100ISO:
As you can see from examining the histograms, 4 seconds is a good exposure if you are only using the red channel, 8 seconds if you want the green and 15 seconds for the blue. The difference in exposure is showing that the green and blue Bayer filters are progressively cutting off more parts of the spectrum and so we will get a slightly different look from channel to channel.
Here we have an image from the red channel of an image exposed correctly for the red:
and here from the blue channel when exposed for that:
Now let’s look at noise. This sequence was shot starting at 4 seconds and 100ISO, keeping the aperture fixed, and we have taken the red channel only. This is a 100% crop from the center of the images:
Overall, noise is pretty good with this camera, especially given the small sensor size. However given that even if you raise the ISO you will still be in the tripod range there is not a lot of reason to raise the ISO.
The above shot is taken from the blue channel.
The Olympus E-3 is a lovely camera and is very capable of excellent quality, long exposure infrared images.