Comparison between CCD Chip size and Eyepiece Focal Length
When using a C-mount adapter in combination with one of our eyepieces, the resulting magnification has an effect on the image field on a CCD chip. For example, a combination with an eyepiece with a focal length of 10 mm produces a strongly magnified image of the eyepiece reticle, so that with a 4.8x6.4 mm "½" chip only 30% of the height and 40% of the width of the reticle structure are imaged on the chip. If almost the entire reticle structure is to be imaged, the eyepiece with a focal length of 25 mm must be selected. Then 75% of the height and 100% of the width of the reticle image are displayed on the same chip size. Therefore, the eyepiece should always be selected to match the selected application. Similar effects occur when interacting with the human eye. However, these depend strongly on the user and cannot be specified exactly.
Left you will find exemplary illustrations of the image field used for different CCD chip sizes and corresponding eyepieces.