As stated previous normal photographic lenses are designed for visible light photography and can sometimes behave quite strangely in infrared light. This page covers the most common lens problems when photographing in IR light. Just something for you to think about and be aware of when working in infrared.
Lens Hot Spots
Lens hot spots is the most common problem encountered when shooting infrared light. They usually manifest in the form of a bright circle, sometimes in the shape of aperture leaves directly in the center of the image. The problem is exaggerated as you stop down (increase f stop number), with the spot becoming more prominent and defined.
Hot spots can be caused for a variety of reasons, the most common of which is the coating on the inside of the lens barrel being reflective in IR light. Another frequent reason is light interaction between the coatings of the lens elements. A less common reason is light interaction between the lens elements and the imaging sensor (usually the micro-lenses) in the camera. In this case using the lens on one camera model may have no hot spot issues and on another model there could be prominent hot spots.
Unfortunately, if your lens has this issue the
only solution (NEW! – our AR Filter Coating Upgrade may help to reduce or eliminate this issue) is to simply use a different lens altogether. Fortunately the majority of lenses don’t have this problem or the problem is very minor and normally not visible in images. We are compiling a list of lenses we recommend people avoid as they have been proven to have hot spots with every model and lens copy below.
|16-35mm 2.8 II|
|24-70mm 2.8 II|
|24-85mm AF-S 3.5-4.5G ED VR|
|E PZ 16-50mm F3.5-5.6 OSS Power Zoom|
|Sonnar T FE 35mm f/2.8 ZA|
|FE 28-70mm f3.5/-5.6 OSS|
|Sony 85mm f/1.4 GM stopped down past f/4|
|7-14mm (Bad distortion between 7-10mm)|
|XF 10-24mm f/4 R OIS Lens|
With this upgrade we would use a new type of internal filter in your camera conversion service. Our Advanced Multi-Layer Anti-Reflection (AR) Filter Coating is applied to both sides of the glass filters we use for camera conversions and would serve to significantly reduce, if not entirely eliminate the majority of lens hot spot issues when shooting infrared light.
With uncoated optical glass you have 2 surfaces, one on each side of the filter, each surface reflects about 4% of light for a total of about 8%. This reflected light bounces around the various optical surfaces inside the camera, leading to hot spots on lenses prone to this issue. The AR or Anti-Reflection coatings reduce the amount of surface reflections from 8% to less than 1% on average. Lenses that have hotspots due to this reason would be helped significantly with our AR Coated filters. Of course in some cases as explained above in the hotspots section, the reasons for the hotspots are numerous, so it’s still possible that your lens may not be helped by this upgrade, it’s all still lens specific.
Fortunately, the AR coatings server other beneficial purposes aside from helping with hot spots. When less light is reflected off the filter surface, more light is actually reaching the sensor and helping to increase light sensitivity and shortening exposure times. Also, AR coatings help improve the overall image quality, with less light bouncing the overall contrast and fine detail are improved.
Point & Shoot Camera Hot Spots
Since on point and shoots the lens is a permanently attached part of the camera if there is a hot spot you pretty much have to rule out using that camera model. This is the main reason we only convert a limited range of point and shoot models. Below is a list of known P&S camera models to have a hotspot:
|CANON P&S CAMERAS|
|NIKON P&S CAMERAS|
|SONY P&S CAMERAS|
|RX100, RX100 II and RX100 III: Detected hot spot only at telephoto portion of lens (zoomed all the way in) at smaller apertures. Increasing ISO further defined the hot spot.|
|OLYMPUS P&S CAMERAS|
|PANASONIC P&S CAMERAS|
|FUJIFILM P&S CAMERAS|
Wide Angle Distortion
You may have noticed in your images of buildings that sometimes the vertical or horizontal lines seem bent, especially at the edges of the image, this is barrel distortion and is present to some degree in all wide angle lenses. As a rule of thumb the wider the angle, the more distorted the image.
These distortions are also present in IR and in some cases are more pronounced due to the longer wavelengths.
Let’s proceed to the next section: