[Snydly]

I have a quick question about DFS.

When I first got my k7 I took some 25 second exposures in full moonlight of the houses behind mine. I couldn't believe the detail and color from something I could barely see. The roofs are silver tin, so it made an interesting exposure. I'm sorry I don't have them to upload right now, I'm still struggling a little with the upload process.

Anyway, I've searched and read a lot about DFS, but don't understand it as it relates to long exposures specifically on the k7. I know what DFS is (I think), but don't know what it means when someone says you can disable it on the k7 at exposures below 30 seconds. Is this done by disabling noise reduction?

Then, how do you make the DFS to stack or subtract later?

If this is too deep to cover here I understand, and would be grateful if someone could point me towards a book or web article.

Thanks,

Bill

[MPrince]

Page 92 of the manual answers your first question. In custom menu setting 3 item 18 you can choose to turn on or turn off slow shutter speed NR. If you turn NR off, then noise is reduced only when shooting in Bulb mode and the shutter is open for 30 seconds or longer.

I don't understand your second question so I can't help with that.

[Snydly]

Page 92 of the manual answers your first question. In custom menu setting 3 item 18 you can choose to turn on or turn off slow shutter speed NR. If you turn NR off, then noise is reduced only when shooting in Bulb mode and the shutter is open for 30 seconds or longer.

I don't understand your second question so I can't help with that.

Thanks MPrince, that's what I thought. So the 'Slow Shutter Speed NR' is DFS.

My second question resulted from other posts I was reading where some people were putting their lens caps on after a series of photographs and then taking a photo 'In the Dark' to later 'subtract' from their images to reduce noise. I'm trying to learn about that function.

thanks again,

Bill

[JeffJS]

Take a 5 minute exposure and you'll understand why it's desirable to turn off DFS. Up to 30 seconds on the K7 you can turn it off. After that, no, it's on automatically. It takes just as long to work as your exposure. So if you want to do 2x 5 minute exposures, one right after the other, you'll have to wait 5 minutes before taking the second one.

I don't know what others do but I just use noise reduction software to kill any noise that shows in such an exposure (DFS can be turned off in the K5).

[Ex Finn.]

Dark' to later 'subtract' from their images to reduce noise

They are taking a "dark frame" ( an exposure that contains the noise signal from sensor and related electronics) to be used later in software like Deep sky stacker.
It can get complicated, here is the link.DeepSkyStacker - Free

[Snydly]

Thanks for the help everyone.