Adjusting Window Width And Level for images with a VOI LUT

Width and Level properties for windowing normally have no effect on images which contains a "Values of Interest Look up Table" ( VOI_LUT)

If the image contains, in attribute (0x28, 0x3010), a "Values of Interest Look up Table" ( VOI_LUT), which is defined by the DICOM standard as a replacement for windowing, then Window Width and Level are normally ignored as required by DICOM. If you wish to revert to using conventional width/level, you may set the image's VOILUT property to 0, which inactivates the VOI LUT. Inactivating the VOI lUT is technically in contravention of the DICOM rules, but it is commonly requested by users!

A similar issue (non-active Width and Level properties) can occur if a Presentation_State is applied, as that also explicitly over-rides the chosen values.