The first step in choosing a camera is deciding what type of camera is best for you. There are three major varieties of digital cameras, point and shoots (pocket and fixed lens type), DSLRs, and mirrorless cameras. Recently some manufacturers have started making fixed lens cameras with APS-C or similar size sensors, such as the Sony R1, Fujifilm X100, Sigma DP1, and Canon G1X. In this discussion they will be included in the same group as mirrorless cameras, because they have the same benefits except with a fixed lens.
You can scroll to the bottom for a consise summary.
The point and shoot camera is a great starting point for infrared. They are small and cheap, a perfect secondary camera for someone starting out with infrared, or who will only shoot infrared occasionally. They are ideal for keeping in a pocket or along a bigger camera in an equipment bag.
With an infrared converted point and shoot, the camera will have accurate autofocus through the entire zoom range of the lens. Since the camera uses just one sensor, it will expose properly, every time. You can also preview the way the scene will look directly in infrared on the viewfinder. Another benefit is that adding another infrared filter in front of the lens still allows you to compose, focus, and get proper exposures, even if the filter is visually opaque.
The biggest downside to a point and shoot camera is their small sensor, and with it smaller pixels. These small pixels have higher noise levels and smaller maximum true resultion. Infrared photography can have increased noise, which will be more evident with a point and shoot. Below is a 100% crop from a point and shoot left (Lumix FH20) and a DSLR right (Nikon D40x). Both were taken at base ISO in bright sunlight.
Another issue with point and shoots is the resolution. While manufacturers advertise a larger megapixel count, it is important to understand that this is only a measure of the total pixels, not the resolution. At the size pixels need to be to fit on a tiny sensor, they are smaller than the photons available. There are only so many light photons that can fit per sensor area, giving a limit on resultion possible, regardless of number of pixels there to record the information. A more in depth explanation of this phenomenom can be found at Snapsort. That site also provides the true resolution for many camera models so you can get an idea of what resolution you will actually get.
So, why is this important for infrared? Infrared light has a longer wavelength than visible light, so the amount of infrared information available is even less per a given area. In some compact cameras, this will result in a slight decrease in real resolution when shooting infrared. The cameras that will have this effect are those that already have a smaller true resolution than the advertised MP rating, otherwise the pixels will likely be big enough to accomodate the larger size of IR light.
Point and shoot sensors can also have reduced color sensitivity for infrared compared to larger sensor cameras.
Many do not come with filter threads to mount external filters, requiring adapters to do so.
DSLRs can produce very good IR images and converting a DSLR can be a very good way to bring new life into an old camera.
DSLRs produce very high quality infrared images. They do not have the resolution or noise issues of point and shoots and can be used for very vivid color infrared. They offer the flexibility of using multiple lenses and more manual control options.
While image quality is better, they have their own set of problems for infrared that stem from using a seperate sensor for autofocus and exposure, and imaging. Glass will bend different wavelengths of light different amounts, so consequently when shooting in the infrared wavelengths lenses will exhibit a focus shift. For a camera to autofocus properly in infrared , we use replacement glass filters with a thickness to compensate for the infrared focus shift. While this works very well for point and shoots and mirrorless cameras, it does not work for all lenses in an IR converted DSLR. The reason for this is that because different lenses use different numbers of glass elements and different types of glass, they will not all have the same degree of focus shift between visible and infrared light. Since DSLRs focus with a different sensor than the imaging sensor (which still focuses to visible light after a conversion) the camera has no way to compensate for a lens with an irregular IR focus shift. Using this lens would then require stepping up the aperture, manual focusing, or having the camera calibrated for that lenses focus shift.
DSLRs additionally use this secondary sensor for exposure controls. The 720nm filter usually requires an exposure consistent with visible light, and provides properly exposed images. Sometimes, particulary with other filters, the visible and infrared light in a scene isn't the same, and an exposure value (EV) has to be dialed in to compensate.
Yet another problem is using an opaque filter on the lens. This prevents the use of the viewfinder and causes problems with auto exposure and autofocus, which all utilize visible light.
If the DSLR has live view though, all of these problems can be avoided. When using live view, the camera uses the imaging sensor for autofocus, exposure, and preview, resulting in flawless performance.
Mirrorless cameras like the Micro 4/3 system and Sony NEX system combine the best features of point and shoots and DSLRs for infrared. Very large sensor point and shoots share these same benefits.
The camera will autofocus and expose pictures accurately. External IR filters can be used on the lens without affecting any of these features. Additionally, these cameras use a large sensor which do not have the noise or resolution problems that some point and shoots have.
One of the drawbacks of these systems are in the fact that they are new formats, and have less lenses that work natively with them. Certain models also do not have sensors that are quite as large as DSLRs, and may also not have as good color performance as DSLRs.
|Point and Shoot||DSLR||Mirrorless|
|Autofocus Issues?||No||Some lenses (when not using Live View)||No|
|Exposure Issues?||No||Occasionally (when not using Live View)||No|
|Noise Performance||Can be poor||Good||Good|
|Reduced True Resolution?||Sometimes||No||No|
|Can use external IR filters easily?||Yes, if they can be mounted||No (unless using Live View)||Yes|
|Color IR performance?||Poor to Very Good||Good to Very Good||Good to Very Good|