On Wed, Nov 13, 2013 at 6:14 PM, Darren Addy <[email protected]> wrote:
> But this problem? The mirror is UP, during the exposure. So that > implies that the mirror does not fully cover the screen on the bottom > of the pentaprism. Light, coming from the viewfinder (crack between > the mirror and the screen???) must reflect off the back lens element > (or goes through the lens reflects off the dark filter and comes back > at the sensor?). That's the only thing that I can picture. If someone > has an alternative explanation, I'm all ears. Yeah, there's gaps around the mirror. If you take the lens off and fire a long exposure, and hold a flashlight to the viewfinder, you can see quite a bit of light getting past the edges of the mirror (at least on the K-5 II). The biggest streak of light was at the bottom of the photograph, which would correspond to the top edge of the sensor (due to the inverted image). I would guess that comes from light getting past the mirror along the back edge (closest to the sensor) and hitting the sensor pretty directly. Control of scattered light is a pretty big factor in things like telescope design. Since you're getting into astrophotography, keep an eye on your screwheads! -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
