Long Exposure Noise Reduction

danny_bhoy

danny_bhoy

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Danny
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Hi all,

I'm off out later tonight to shoot some long exposure stuff.

I've come across a setting on my camera (Canon 40D) that allows for automatic noise reduction on long exposure shots. There's also one with the option to reduce the noise at high ISO, which is something I find the 40D really tends to struggle with.

My question is, if I choose to enable one or both automatic noise reduction features will I lose quality/sharpness or suffer any other side effects?

Surely if there was no drawback it'd be something that the camera just did automatically.

Any advice is appreciated,

Cheers,

Danny.
 
Long exposure NR usually involves a "dark exposure" where the sensor records an image of the same duration as the original one without opening the shutter, thereby having only the image of the "overexcitable" pixels (in other words, pure noise). It then subtracts the dark image from the photograph leaving a cleaner image. The major downside is that the camera is tied up for the same length of time as the original exposure while the dark exposure is made and for a short while afterwards while the software does its thing.

High ISO reduction usually involves a loss of fine detail as it applies a small amount of blur to hide the noisy pixels, ie it does involve a slight loss of sharpness. Whether that loss is enough to spoil the shot is a matter of taste - shoot the same subject at the same settings with it on and off, see which you find better at final use. If the noise bugs you more than the slight loss of sharpness, keep the NR switched on. IMO, NR is best applied in PP rather than in camera, in PP you have control over the level of NR/blurring applied. Plenty of NR software available, including some free.
 
No problem, hope the shots came out how you wanted them too, or at least help you for next time!
 
You can't do the long exposure dark image correction in PP, as You would not have captured the data to do it.
As NOD mentioned it is done as a pair of shots of eqial length.
 
Very nice shot Danny.
Looked at your Flickr stream and you have some cracking work on there too.
Well done.
I noticed from the exif that it was a 128 sec exposure @ ISO 100.
How much noise was there before you cleaned it up, out of interest?
 
That is a very nice image Danny, give yourself a pat on the back. Was it taken with a Tamron 17-50, if so, VC or none VC?
 
GHP said:
Very nice shot Danny.
Looked at your Flickr stream and you have some cracking work on there too.
Well done.
I noticed from the exif that it was a 128 sec exposure @ ISO 100.
How much noise was there before you cleaned it up, out of interest?
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Thank you very much!

There wasn't a huge amount to be honest. Only had to remove a touch in PP - only a couple of notches on the slider in LR4.

To be honest it's probably me being paranoid and looking for issues that aren't really there :)

The 40D struggles badly with noise at anything about 400 ISO in my opinion but what can you expect from a camera of its age.
 
killwilly said:
That is a very nice image Danny, give yourself a pat on the back. Was it taken with a Tamron 17-50, if so, VC or none VC?
Click to expand...

Thanks!

It's the non VC version. If I remember rightly it was a few hundred quid cheaper than the VC model. It's a cracking lens though, the constant 2.8 makes all the difference and for what I paid (about 280 quid) you can't get better for cheaper in my opinion.
 
That is an excellent shot,i would be very happy with that one,well done.:)(y)
 
Excellent for a 40D. Though I have never used mine at night.

Great shot.
 
danny_bhoy said:
Thanks!

It's the non VC version. If I remember rightly it was a few hundred quid cheaper than the VC model. It's a cracking lens though, the constant 2.8 makes all the difference and for what I paid (about 280 quid) you can't get better for cheaper in my opinion.
Click to expand...

Thanks Danny. I had the none VC version on my Christmas list to replace my 18-55 kit lens, but then saw the 7D and 15-85 for sale with Argos for an unmissable price, so went for that kit, which I have no regrets in buying. I still might get the Tamron some time in the future. :)

My next purchase will be a macro lens. I'm still using my 100 mm FD macro lens I bought 40 years ago with an adapter on my EOS camera.:shake:
 
You're welcome to the advice Danny - if that shot's a result, you're more than welcome to it! If it was one of mine, it would get printed as big as it can stand and hung in pride of place!
 
danny_bhoy said:
Thanks for that Nod, just what I was after.

Think I'll stick to Lightroom for eliminating or reducing noise. My patience is stretched during the 2-3 minutes of a normal long exposure without adding on the same time again and then some :)

Thanks again for the advice.
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May I ask what you are shooting that needs 2 or 3 minutes of exposure?
 
shaylou said:
May I ask what you are shooting that needs 2 or 3 minutes of exposure?
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Hi.

Off the top of my head I think the shot I took and posted above was maybe two and a half (ish) minutes long. The main reason was obviously because it was pitch black so I switched to bulb mode and used trial and error to get the exposure right but secondary to that I wanted to capture the movement of the traffic on the left as well.
 
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wow , that picture is really good .i would be so pleased to get that sort of picture .There is so much to see in the picture .Great capture .
 
As been said, excellent shot.

So many colours - just calls out to be mounted on a very large wall.
 
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danny_bhoy said:
Thanks for all the positivity everyone. Makes freezing my extremities off in the middle of the night worth while! :)
Click to expand...

Yeah I tried my first night shots the other day in Llangollen and I actually lost my thumb and right index!
 
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