Infrared camera conversion

About IR-Basics

What is Infrared Photography?
In infrared photography, the image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). (“Infrared filter” may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.)

Converted Digital Cameras vs External filter (Infrared camera conversion)
Infrared images taken with a none converted camera and external (lens) infrared filter will require extreme long exposures and in the higher wavelength even be blocked. To better use the complete spectrum of infrared the camera sensor need to be converted to full spectrum. The sensor is now sensitive to the complete spectrum up to 1000nm and in some cases above this. So i n short, you always need to modify your camera to full spectrum to record Infrared light.

Why convert to full spectrum?
In a full spectrum conversion, the camera’s sensor mounted hot mirror is removed and replaced with a clear glass filter or no filter at all. This makes the camera sensitive to UV, visible, and IR light. This gives you the flexibity for various external filters, the camera can take pictures of regular light, infrared light, UV light, or any other combination of these. Most hot mirrors also have an anti-aliasing filter built in, so by removing this filter pictures will be sharper. Big advantage of full spectrum is flexibity in the spectrum. But be carefull in SLR camera’s full spectrum have the disadvantage of looking through the lens, so with lens mounted filters like a 920nnm filter, you will see NOTHING through the eyepiece. You must use the camera’s build in live view function. This disadvantage is not present in system camera’s for both the eyepiece as the display you will look at a picture that is recorded by the sensor.

Uses of Infrared and Full Spectrum Photography
Infrared will enable you to take pictures of landscapes, people or other objects that will turn your images in fine art. The full spectrum also let’s you image the nightsky, like for example the galaxies or nebula but also Ultraviolet images that will enable you to image the skin defects or sunscream effectiveness, but also the old wet colodian photo’s. [/vc_column_text]

Choosing a Camera

Which camera best suits my needs?

You first have to decide what are your requirements. To do that make a short list of the main primairy goals like: i want to use my camera for daytime normal photography or strictly for the purpose of IR and do you want to stay flexible in which IR you want to image etc. The second main descission you have to make is do i want to have a SLR or system camera. System camera’s can be used in combination with a full spectrum sensor which gives you much flexibilty. A stated earlier a SLR camera in full spectrum in combination with lens filter blocks the use of the eyepiece viewer (human eye does not record IR, the image sensor of the camera does). Dutch Digital Works will be happy to advise you on which camera best suits your needs.

The DSLR

DSLRs enables you to shoot very good IR images and even old camera’s can be used for this purpose.

The Pros:

DSLRs give you high flexibilty in use. they offer a wide range of options from the menu’s en great fexibility in which lens you use.

The Cons:

Image quality overall is better, but you need to have an build-in IR filter to enable you to look through the eyepiece viewer to actually see what you are recording. This build-in filter will also maximise the risk of trapping dust between filter and sensor, which in turn you can not remove yourself.  Different companies offer IR sensor filters for your camera but this ends up in 70-80% of the cases in some dust spots in your images. Best way to use the SLR camera with IR and still maintain flexibity and dust is full spectrum in combination with the liveview function and lens filters. Big advantage is that you will still be able to use your camera daytime photography.

The Mirrorless Camera

Mirrorless cameras like Sony A series or the Panasonic camera are very good camera’s for the infrared photography. They come in full format 4/3 or other sizes and offer wide range of lenses.

The Pros:

System SLR’s enable you to use the sensor in full spectrum mode and with the use of lens filters take pictures in incredible details. During conversion no other filter is placed in front of the sensor and the risk of dust trapped between sensor and filter is prevented.

The Cons:

The flexibility that you have with lens choices is most of the time limited.

Summary

Infrared camera conversion

Choosing a Filter

Which filter?

IR 590nm Gives you high flexibilty. Images are still color rich.

IR 665nm produces more vibrant colors than the 720nm for pale yellow leaves and brighter blue skies.

IR 720nm Most used in the IR field. restricts the visible enough to get the beautifull snow like effect but still contains enough color information to play with.

IR 850nm Produces Black and white images in IR. The camera produces bright whites and pronounced darks.

IR 920nm like the 850nm but even more extreme.

clear glass makes the camera sensitive to UV, visible, and IR light, allowing switching between various external filters to achieve the desired effect, this allows going between infrared and regular shooting.

DAW Conversion IR sensitive but also enables you to do daytime photography. Blocks UV spectrum (Below 400nm)

Focus Calibration

Removing filters requires focus calibration

For the IR conversion, filters need to be removed in front of the sensor. Removing these filters will impact the lightpath. Every glass has it’s infuence on the lightpath in what is called breaking index. In most camera’s there are two filters in front of the sensor. Dependent on the type of modification these two filters are replaced by 1 filter. This will require recalibration of the camera’s optical path. [/vc_column_text]

Problem with IR

Common problems with infrared and how to avoid them

Hotspot

A number of the commercial available lenses have what is called “hotspot” in the central part of the optical path. Those artifacts can be removed from your picture with a good software package. But better is to prevent them. from the database above you can determine if you lens is prone to these artifacts.

Sensor Cleaning

Build in sensor clean function.

When converting a camera for whatever reason, the build in sensor clean function is disabled picture. For this purpose Dutch Digital Works has developed a filter that preserves the sensor clean function, the so called DAW conversion which only applies to the full spectrum conversion. For infrared conversions this will not work. In these cases the build in sensor clean function is lost.