Wednesday, July 1, 2009

Photoshop Infrared compared to Digital Camera Infrared

We asked Mark Soares, Professional Services Representative from Precision Camera, to help explain the difference between Infrared (IR) photography done in Photoshop as compared to converting a digital camera to do infrared capture.

Here is how he explained it to us:

"There are a few differences between the real thing and a Photoshop filter applied in post processing. When you use an in-camera high pass filter you are only allowing the camera to expose for the infrared wavelengths, which means your image will be free of most visible light. This may not seem like a big deal to some people but the fact is, when shooting a true IR picture you want to have an image that is as true to that wavelength as possible. Just like the manufacturer's applied a lowpass filter to block IR light from affecting the image, you should block out everything else when shooting an IR picture.

When using a camera that is converted to expose for the full spectrum, your camera will expose for all the wavelengths. This causes the image to be soft by nature because the IR focal plane is behind the visible light plane, and the UV plane in turn is in front of the visible light plane - when you sandwich all those wavelengths into one flat image, because they have different focal planes the image will be softer.

The other issue with using a full spectrum camera and performing adjustments in postprocessing is that Photoshop will usually perform an adjustment where one of the channels (green usually) is copied, then blurred on purpose (to create the softness which is natural in IR photo) and overlayed on top of the image. The file is then converted to B&W and the contrast punched up. There is some deterioration of the image there since you are manipulating it to the point of losing detail in the highlights. The end result will not look like a 100% true IR image because the postprocessing is dependent on the amount of green in the image, whereas the IR image will factor in the actual IR light from the subject being photographed.

The best analogy I can come up with is comparing it to music.
An image captured with a full spectrum camera is like listening to the whole song (guitar, bass, drums, vocals). If you wanted to remove all the instruments and just listen to the vocals, it would be very difficult because all the information is intertwined and embedded with each other. Basically, the instruments and vocals have combined to create one song which cannot be broken down to its basic elements (unless you have the original tracks of course).

An image captured with an infrared camera is like a song with just the vocals (for example), and all the drums, bass and guitar are not audible, in fact, they have never been recorded. The sound will be nice and clear without any distortion because you are not manipulating it to get the vocals out, like you would if you wanted just the vocals from the full song.
A dedicated IR camera is a very limited device, however, it is very good at what it does. It allows for the isolation of a wavelength range with minimal deterioration of the image.

That's my take on it!

Mark Soares - Precision Camera

© Ron Rosenstock

Great description, Mark! If you're looking to have your camera converted, Digital Silver Imaging has partnered with Precision to bring you the absolute best Digital IR conversions at a very competitive price.
Click here for more details about our IR conversions.

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