I just bought the tamron 17-70 2.8 for my apsc camera and when I photograph the stars I notice some weird artifacts.
When I up the dehaze to exadurate them the lens loses contrast in like a semi circle pattern at the bottom of a vertical image aswell as it seems like the lens isn’t covering the full apsc image circle. There corners seem to be experiencing some sort of darkness because of that. It’s not any filter that I had on because even with and without filter the bad vignetting is still there.
Does anyone know if this is like a know defect of the lens, or if my particular lens has a defect?
The bright center and darker corners you showed in the image is lens vignetting.
The circle may be worsened by a filter. Interference filters permit light to enter perpendicularly, so you can get artifacts around the edges. The issue may be a combination of the filter and vignette.
For now you can manually correct for this in Lightroom: raise the corners, lower the exposure overall, crush the shadows, and increase the contrast until the sky appears even. There is also specialty software for this correction as many lenses suffer from it.
Next time try stopping down the lens one or two stops and make sure lens corrections are turned off.
As I said in the post, this was taken without a filter