Long Exposure degrades quality?

[manaheim]

Right, it won't kill the detail in RAW (because RAW is not processed at all) but I wanted to add that in-camera NR for very noisy images will just destroy image detail and leave the photo looking muddy and dull (as in not crisp & sharp!). It depends on the amount of noise it has to remove.

Unless I'm mistaken, I do think the long exposure noise reduction on-cam still occurs on the RAW images...

 

[Garbz]

Indeed manaheim you are right, but both of you are talking about a different type of noise reduction. Bifurcator is describing standard NR which would be present in any frame and even more so in high-ISO frames when the camera processes to JPEG (however slight the effect may be).

manaheim is talking about long exposure NR, where a second image is taken with the shutter closed (which is why it takes as long as the original exposure and chews batteries). This will bring up only dead pixels and a logical subtraction will eliminate them. It does nothing for the standard Gaussian noise distribution though, just eliminates those pesky dead pixels, and leaves detail intact.

 

[manaheim]

manaheim is talking about long exposure NR, where a second image is taken with the shutter closed (which is why it takes as long as the original exposure and chews batteries). This will bring up only dead pixels and a logical subtraction will eliminate them. It does nothing for the standard Gaussian noise distribution though, just eliminates those pesky dead pixels, and leaves detail intact.

Not to make myself wrong in the end, but I was actually talking about the algorythm built into the camera to reduce the noise. I thought it was on even during RAW captures on my D300... it never occurred to me what a silly idea that was.

This does 2 things. First it explains why that one day, all my pictures were noisy, and second it reinforces the method I was using when I took this picture (and was amazed at how little noise there was).

Oh yeah and it also makes me feel like a raging idiot.



Ah well, it wouldn't be a normal day if I didn't learn something new on TPF. Thanks guys, for setting me straight.

 

[potownrob]

Because of this, RAW files usually need some post-processing done to make them look their best, but when it is done (well ), the results are better than a JPG.

Probably very true (not that it'd make my pics look much better ) but I personally hate post-editing .

Another option, if you want to keep shooting JPGs, is to turn off any kind of noise reduction in your camera. I've read somewhere that you can individually turn off both high-ISO noise reduction and/or slow shutter speed noise reduction in a Nikon D200, although I'm not sure about other cameras.

Yeah!! Ken Rockwell taught us noobs how to do that with our D40s!! :thumbup:

Although like I said, it shouldn't make a massive difference. I've done 30-second long exposures which are nice and sharp.

Not the same as on a dSLR but I read a review on the Panasonic FX-500 where they tested it with and without noise reduction (it allows you to turn it off, unlike on my FX-35) and they found it to perform practically the same with NR on and off (and that was supposed to be one of the selling points for the FX-500 over the FX-35...).

 

[Bifurcator]

Unless I'm mistaken, I do think the long exposure noise reduction on-cam still occurs on the RAW images...

Indeed manaheim you are right, but both of you are talking about a different type of noise reduction. Bifurcator is describing standard NR which would be present in any frame and even more so in high-ISO frames when the camera processes to JPEG (however slight the effect may be).

manaheim is talking about long exposure NR, where a second image is taken with the shutter closed (which is why it takes as long as the original exposure and chews batteries). This will bring up only dead pixels and a logical subtraction will eliminate them. It does nothing for the standard Gaussian noise distribution though, just eliminates those pesky dead pixels, and leaves detail intact.

Aw... I see. Yup, my mistake. I should have read it more thoroughly. My bad.

 

[Alpha]

In my experience, long exposure problems much more often boil down to lens construction than film or sensor reciprocity failure. Engineering flaws in lenses are often negligibly apparent when shooting at normal speeds. But when you leave the shutter open for extended periods of time, these flaws become greatly exacerbated. In zoom lenses, in particular, I've seen a remarkably strange halo occur around light sources (no, not the same halo you'd see around a street lamp).