Hi @tuncaemre ,
Please note that you cannot simply take the pixel value as radiance.
Sequoia only produces raw data accompanied by the required metadata to perform the needed corrections.
It never performs any corrections by itself.
Therefore, as @kikislater has pointed out, corrections for things like vignetting need to be accounted for.
Please refer to this thread and ask there if you still have questions regarding estimation of reflectance using Sequoia (for any of its monochrome bands):