A lot of noise in night sky photos

[Mateo1041]

Hi,

I've been trying to get into night sky photography and just did my first star trail shot this weekend. While it turned out pretty neat, I've been having a lot of trouble with noise and it's been pretty frustrating when loading the RAW images onto my computer here at home. I just took a batch of photos last night and even the lower ISO stuff had considerable noise to the point of being unusable. I've read I'm supposed to shoot in ISO 800/1600 or even higher. Anything lower and it was a challenge to really see anything. Any ideas? Is it possible my sensor could be going bad?

Thanks!

 

[Theo2]

What camera and lens combo are you using? The higher your ISO the more grain. If you want star trails you can usually shoot pretty low ISO, I go for 400-800. You just have to open up your aperture and lower the shutter speed. If your camera supports it you can also try long exposure noise reduction (your camera takes a second exposure with the shutter closed and subtracts the noise, aka a dark frame) or ISO noise reduction.

 

[Mateo1041]

Here's an example I was able to get uploaded to kind of show what I mean. And that's only F2.8, 17mm, 30s, 1600 ISO.

 

[Mateo1041]

Another example, this one F2.8, 17mm, 30s, ISO 800. I'm shooting in RAW. I tried three software programs to see if it was that, but it doesn't seem to be.

 

[Mateo1041]

Here's the one that did turn out better, but still plenty of noise.

 

[KmH]

Digital photos don't have 'grain'.
A higher ISO setting adds more amplification to the the voltage the pixels develop.
That higher amplification introduces more image noise.

The darkest portion of a digital photo has the lease image information, which is why image noise is usually more visible in the dark oarts of a digital photo.
http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf

Top an extent it also depends on the image sensor in your camera and the 'noise floor' the sensor has.
http://www.lumita.com/site_media/work/whitepapers/files/pscs3_rendering_image.pdf
See page 6 of the PDF linked to above.

 

[Mateo1041]

What camera and lens combo are you using? The higher your ISO the more grain. If you want star trails you can usually shoot pretty low ISO, I go for 400-800. You just have to open up your aperture and lower the shutter speed. If your camera supports it you can also try long exposure noise reduction (your camera takes a second exposure with the shutter closed and subtracts the noise, aka a dark frame) or ISO noise reduction.

Sony A55V. Lens is a Tamron 17-50mm XR DiII SP lens. Goes to F2.8. I posted a few examples above. I just see all these amazing photos in the blogs and tutorials and would love to get to that point, but I'm honestly not sure how they do it without all the noise I'm getting, even with similar settings.

Thanks. Just frustrated is all.

 

[Theo2]

Digital photos don't have 'grain'.
A higher ISO setting adds more amplification to the the voltage the pixels develop.
That higher amplification introduces more image noise.

The darkest portion of a digital photo has the lease image information, which is why image noise is usually more visible in the dark oarts of a digital photo.
http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf

Top an extent it also depends on the image sensor in your camera and the 'noise floor' the sensor has.
http://www.lumita.com/site_media/work/whitepapers/files/pscs3_rendering_image.pdf
See page 6 of the PDF linked to above.

Woah. I meant noise, don't know why I said grain.

 

[PaintBrightStudios]

try shooting with longer shutter, and lower iso. goodluck!

 

[Braineack]

stop shooting at f/2.8 and a very high ISO

 

[jsecordphoto]

For all of my night sky photos I start at ISO3200, f2.8, 30 seconds and adjust from there. I know in the past with film people would shoot at iso100 and shoot for hours to get star trails, but now it's much easier to shoot 100+ frames and do the star trails in post with StarStax or photoshop. I don't know anything about that camera you are using, and how it performs at high ISOs, but iso800 is pretty low. It seems like there is some pretty significant light pollution where you are shooting too.

 

[TCampbell]

Astrophotography images are normally "stretched" (not the dimensions... the tonality).

Imagine splitting the image into tonal zones... very dark, dark, mid-tones, brights.

There will be some dingy dark stuff which contains a lot of noise as well muddy light pollution. Most of the noise will be in that dark data. We like to push that down toward the blacks. There will be the bright points of stars and we like to pull them up toward the whites. That's what I mean by "stretching".

 

[Mateo1041]

Thanks! I think it's just been somewhat confusing to me as I've read articles that say both higher (1600+) and lower ISO. I can definitely try very low with a longer shutter time and see if that helps.

 

[Mateo1041]

For the purposes of ISO, what is generally considered high and low? I've primarily been trying 400-800, but I guess it just surprised me that even those turned out grainier. I'll try some more experimentation soon and post results.

 

[shaylou]

Noise is one of those things that comes down to personal preference. We know that lower iso gives less noise than high iso. So if you do not like the amount of noise you are ending up with the obvious solution is to lower your iso till you find a noise level you like. Of course you will need a longer shutter speed to make up for the lower iso but with a tripod and cable release you will be fine. It's really that simple.