Low light. Higher ISO vs Longer exposures

[peatoire]

I've noticed that when shooting low light with my 350d if you set a low ISO, say 200 to minimize digital noise, the fact that it reqires a much longer exposure than say 1600 seems to create noise produced purely because of the exposure length and not the ISO. Is this normal, and if it is, does anyone know of any tips to get nice clean long exposures.

[JohnnyBlood]

Use a tripod.

[peatoire]

I always use a tripod for lowlight, I'm referring to noise not camera shake.

[ijohnson]

Noise reducing software or one of the cameras that have noise reduction for long exposures. (5d, I think 20d, more I'm sure.)

The former is much cheaper.

[convergent]

High ISO causes more noise in digital images, just like it causes more grain in film. I believe this is caused by the ISO, not the exposure. There is a different effect caused by very long exposures that some of the cameras have a setting to help clean up... not sure if the 350D does or not. About the only thing you can do to minimize high ISO noise is to a) make sure the exposure is dead on accurate as this will decrease noise in most situations... underexposure causes more noise to be revealed when you correct it, and b) use noise reduction software like Noise Ninja or Neat Image.

[peatoire]

Thanks for the replies guys.
I do understand how ISO noise is generated. I avoid high ISO's at all costs usually unless absolutely neccessary, I particularly hate digital noise. But even when on a tripod at say iso 100 with a good exposure, setting a low ISO (theoretically reducing noise) noise reduction is actually offset by the noise produced by the longer exposure required by the low ISO value.
There is a correction facility on the 350d for this but it only works on exposures over 30 secs on ISO 100-800. ISO 1600 its 1 sec or longer.
I beleive there is a technique of subtracting a dark frame whci you can do in PS which replicates the function in the camera.
I thought someone may know of a 'Happy medium' ISO/exposure to minimize the two types of noise

[Andrew Khan]

All my long night exposures, and lightning more that 300 seconds have unacceptable noise...I do not use noise ninja, I just live with it.....why is this happen?

[peatoire]

All my long night exposures, and lightning more that 300 seconds have unacceptable noise...I do not use noise ninja, I just live with it.....why is this happen?
I'm lead to believe that long exposure noise is created by the sensitivity of certain pixels on the sensor (leakage current in CCD well).
Not normally noticable, the 'hot' pixels are accentuated with longer exposures.

[JohnnyBlood]

My point was that if you used a tripod you could lower the ISO, which in turn results in higher noise. The other option is to enable Custom Function 2 on your camera, which is will reduce noise on long exposures (I think the 350 has that feature).

[peatoire]

My point was that if you used a tripod you could lower the ISO, which in turn results in higher noise. The other option is to enable Custom Function 2 on your camera, which is will reduce noise on long exposures (I think the 350 has that feature).

Sorry but I'm getting mixed messages from you. I want less noise. Your first post stated to use a tripod (which I do) and your second states that by using a tripod I could lower ISO giving more noise.
Noise reduction function will only work on exposures over 30 secs for anything but ISO 1600.

ISO noise is created by amplifying a weak light signal from the sensor
Long exposure noise is created by inconsistancy in the cells on the sensor which are accentuated by a long exposure
Two totally separate things.

[JohnnyBlood]

I know they are two totally different options...hence the phrase "the other option is to..." And according to my manual Custom Function 2 will reduce noise whenever exposures exceed 1 second. That is a far cry from the 30 seconds you cite above.

By the way, your other option is to get a Canon 5D. Probably what you didn't want to hear, though.

[Juan Zas]

I think your two assesment are correct:

"Digital images shot in low light or with a high ISO setting are often very grainy, with flecks of color "noise" in areas that should have smooth color"

One is caused by the sensor resolution, highing the sensitivity increase the noise; and the other it´s also true, light are electrons and few electrons (low light) arriving to the sensor also produce noise (poor sensor activation) over longer times of exposition.

In this link you will find more details & noise definitions:

http://www.stonepages.com/darclean/

[peatoire]

I know they are two totally different options...hence the phrase "the other option is to..." And according to my manual Custom Function 2 will reduce noise whenever exposures exceed 1 second. That is a far cry from the 30 seconds you cite above.

By the way, your other option is to get a Canon 5D. Probably what you didn't want to hear, though.


Custom Function 2 Noise reduction only takes place after 30seconds with ISO 100-800.
Then for ISO 1600 (in my opinion not an option) Custom Function 2 works after 1 second.
The 5D is certainly on my wish list but I think I'll have to wait a while. BTW I appeciate your input.

Thanks for the link Juan. I was after that last week.

[Juan Zas]

What do you think about this shot (Look EXIF, please):

http://personal.telefonica.terra.es/web/juanzas/IMG_4211f_M2.jpg


Canon 350D + Sigma 24-70 f/2.8 EX DG Macro

[Ricko of Fla]

I faster lens like Jaun Zas 2.8, 1.8 will help with less noies and shorter shutter time

[JohnnyBlood]

Hmmm...then your Custom Function 2 on the 350 is different than the Custom Function 2 on my 20D. Do you suppose there is some benefit in trying it on exposures between 1 second and 30 seconds in length? How different can the firmware be between the 350 and the 20D?

[MagentaJoe]

I take a ton of night shots with my 350d. Most are no longer than 20-25 seconds and the noise is very very low at 100 iso. This was 13 seconds.

http://ceretti.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=1141&g2_serialNumber=2

[Phtographr Extraordinaire]

I find the 350D great for noise. I try to use ISO100 if I can use a tripod for night shots. I also often use a small aperture. Take a look at this shot I took last year: http://www.deviantart.com/view/24506083/ It was a 4 minute exposure with f22 and 100ISO.

[peatoire]

Thanks for the replies, all the shots posted look great to me. Although mine are greatly improved when scaled down. I think it will be a case of trying a few diffrent things.
I will definitely give the dark frame subtraction a go though.

[Juan Zas]

Thanks for the replies, all the shots posted look great to me. Although mine are greatly improved when scaled down. I think it will be a case of trying a few diffrent things.
I will definitely give the dark frame subtraction a go though.

Sure !! at 100% you see more the noise , defects and unsharpen things.

So, try to increase the ISO, use fast o wide apertures up to where you can (my photo was wide open, at f/2.8, so my lens is enough sharp), try to avoid in this way very long exposure times (way to ensure enough electron power to activate sensor) and USE NOISE REDUCTION SOFTWARE TO GET RID OF THE NOISE. So use Post Processing ...

[peatoire]

Thanks Juan :-)