How an astro camera can be used for normal photography during the day

You often read that a camera that has been modified for astrophotography cannot be used for normal daytime photography. Such a general statement is too undifferentiated and almost wrong - the daytime suitability depends on the type of modification and can be dramatically improved with an additional filter, depending on the type of camera.

Basically, the red sensitivity or, depending on the modification, the infrared sensitivity of the camera has been greatly increased. As a result, a modified camera produces a distinct red cast under sunlight, which does not look good at first. As with an infrared camera, the camera's automatic white balance is unable to cope with this color cast and will always produce a red cast. However, with a manual white balance on a gray card or a white sheet of paper, the red cast can be effectively counteracted and an image with a balanced color mood can be created. However, it is important to note that the white balance is fixed and must be adjusted depending on the lighting situation by re-measuring a gray card or a white sheet of paper. Alternatively, the white balance can of course also be fine-tuned afterwards from a RAW file.

Using a full spectrum camera during the day

With a full spectrum camera, UV and especially infrared light hit the sensor in addition to visible light, which leads to a very strong red cast. As already described, a manual white balance can eliminate this red cast and deliver a neutral image result. However, this does not mean that the resulting colors are "accurate" and true to life. A full spectrum camera always shows an extreme color cast under sunlight, which mainly affects plant foliage and dark synthetic materials.

The color quality can be drastically improved with a full spectrum camera if an additional filter is used. Our Normal Plus screw-in filter are attached directly to the lens and improve the color reproduction to a level that is almost indistinguishable from the original. A major additional advantage is that the camera's automatic white balance can be used again.

However, small color differences in the final image between an unmodified camera and a full spectrum camera with a Normal Plus filter cannot be completely ruled out. The differences are usually very small and subtle, without a trained eye the differences are hardly noticeable. However, there are three situations in particular where the differences are more noticeable:

1. Objects with a high IR reflectance can exhibit a greater color shift than usual. These include, for example, foliage and black synthetic clothing.
2. If you are in a forest, you will notice a muddy color under the trees due to the very high IR content.
3. In backlit situations, you will notice more problems and light reflections.

Important note for DSLRs: A Normal Plus filter is screwed onto the lens, which means that you will see a cyan-colored image when looking through the optical viewfinder of an SLR camera. Experience has shown that autofocus and exposure metering work very well, but the eye can be irritated by the color cast and working with a screw-on filter is therefore somewhat more awkward.

Using an astro camera during the day

In a camera with a "real" astro filter, the red sensitivity is greatly increased, but both UV and infrared light are largely blocked. Images from such a camera show a slight red cast under sunlight, but this is not quite as extreme as with a full spectrum camera. Here too, a manual white balance as described above is necessary to compensate for the red cast. At first glance, the result is a natural image with relatively good colors. However, this filter shows a few slight weaknesses, especially under direct sunlight: objects with a high IR reflectance (especially plant foliage and dark synthetic materials) can show a slight color deviation

Similar to the full spectrum filter, the color quality can be improved by using an additional filter. Our Normal Plus screw-in filter are attached directly to the lens and improve the color reproduction to a level that is de facto indistinguishable from the original. Although the difference is no longer as extreme as with a full-spectrum camera, the result is as good as perfect - with green foliage, synthetic materials and in the forest, a color deviation is only measurable and has no relevant influence on the image. And, of course, with the additional filter you can easily fall back on the camera's automatic white balance.

Important note for DSLRs: A Normal Plus filter is screwed onto the lens, which means that you will see a cyan-colored image when looking through the optical viewfinder of an SLR camera. Experience has shown that autofocus and exposure metering work very well, but the eye can be irritated by the color cast and working with a screw-on filter is therefore somewhat more awkward.