Long Exposure Noise Reduction

Simon_Hill

Simon_Hill

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What do you guys do when shooting bulb exposures? Do you have this option turned on or leave it off and handle any noise in PP?

Am especially interested as considering getting a 10 stop grad and this could lead to some very long exposure times. As I understand things, if the option is turned on the camera will create a second exposure of the same length and write that to your card and use it to reduce noise. As I shoot raw all of the time, do I really need this overhead?
 
I shoot ISO100, and low noise reduction for long exposures, my 7D only takes one shot maybe a 5D thing
 
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Dave, I suspect your camera is doing it, you just don't realise it (check your manual for the setting info), it doesnt prevent you taking another image as long as the buffer can cope.

My point is really whether or not it is worthwhile or if you can do the same or better in PP?
 
Try taking a time exposure with the lens cap on. If no hot spots show up on the image then LENR shouldn't be necessary.
 
Simon_Hill said:
Dave, I suspect your camera is doing it, you just don't realise it (check your manual for the setting info), it doesnt prevent you taking another image as long as the buffer can cope.

My point is really whether or not it is worthwhile or if you can do the same or better in PP?
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No mine only makes one CR file, per exposure not 2, 5D may be different, I dont remember seeing that option, Im off to check the custom functions :thumbs:
 
Dave you dont actually get to see the exposure, it's just something the camera does before saving your image to the card. I'm pretty confident your 7D will do it, my old 500D did exactly the same thing.

As I understand things, it takes a second exposure (albeit without the lens open) for the same duration while the sensor is at the same temperature and then uses this data to perform the NR. Once done, it discards the second image and saves your one to the card.
 
Simon_Hill said:
Dave you dont actually get to see the exposure, it's just something the camera does before saving your image to the card. I'm pretty confident your 7D will do it, my old 500D did exactly the same thing.

As I understand things, it takes a second exposure (albeit without the lens open) for the same duration while the sensor is at the same temperature and then uses this data to perform the NR. Once done, it discards the second image and saves your one to the card.
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Well Im being educated here as Ive never heard of it but will look into it :thumbs::thumbs:
 
Off for night-time work. Can't startrail with LENR on and for anything else (light painting for example) you lose the fluidity of the capture process waiting for a NR file to complete.

Never bothered with NR in PP either, fwiw.
 
I tried it out for the first time last night. Didn't like it but I will see what the results on the screen say when I get a chance to look at them.
 
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Just Dave said:
I shoot ISO100, and low noise reduction for long exposures, my 7D only takes one shot maybe a 5D thing
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If your 7D is only taking one exposure then it's not doing Long Exposure Noise Reduction. Stick the lens cap on, set the exposure for 10s, ensure LENR is on, take a photo. You should hear the shutter open, close 10s later, open again, close 10s later.

Simon_Hill said:
Dave, I suspect your camera is doing it, you just don't realise it (check your manual for the setting info), it doesnt prevent you taking another image as long as the buffer can cope.
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The LENR exposure does prevent you taking another image until that second exposure is complete.

Try p.208 of the manual.
 
hollis_f said:
If your 7D is only taking one exposure then it's not doing Long Exposure Noise Reduction. Stick the lens cap on, set the exposure for 10s, ensure LENR is on, take a photo. You should hear the shutter open, close 10s later, open again, close 10s later.



The LENR exposure does prevent you taking another image until that second exposure is complete.

Try p.208 of the manual.
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Why would it bother opening the shutter? :thinking: Not sure mine does (50D) as I can't remember and I thought it took the second shot almost immediately afterwards? I guess I'll have to have a play. :)
 
Splog said:
Why would it bother opening the shutter? :thinking: Not sure mine does (50D) as I can't remember and I thought it took the second shot almost immediately afterwards? I guess I'll have to have a play. :)
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Yes, that makes sense. I may have got that bit wrong.
 
Second frame is with shutter closed. It's basically running the sensor to see what noise occurs 'naturally' over the same exposure duration without any photography taking place.

This gives a slight positive that the viewfinder remains usable so whilst you're killing time you can set up your next shot... if you're brave enough - there's always a chance the NR will stop and you'll realise your first shot was toilet and needs reshooting.
 
So does anyone have an opinion on whether it is better to let the camera do its LENR or switch it off and try to fix in PP?
 
I switched it off last night to try some firework shots as it takes too long to write to the cf card with it on.
Then just run the shots through a noiseware programme.:)
 
eccles said:
Try taking a time exposure with the lens cap on. If no hot spots show up on the image then LENR shouldn't be necessary.
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If shooting RAW, most modern RAW processors (well, to my knowledge Canon DPP and Adobe Camera RAW / Lightroom) silently remove hotspots that they find in the image before you ever get to see it.

Hotspot removal is slightly different to LENR with a dark frame capture, though.
 
i never have my LENR turned on, taking long exposures with 10 stop filters the big stopper and the b+w nd110
im sure you'll not notice any hot spots plus it save on battery life as the LENR runs it down pretty quick.
 
Musicman said:
If shooting RAW, most modern RAW processors (well, to my knowledge Canon DPP and Adobe Camera RAW / Lightroom) silently remove hotspots that they find in the image before you ever get to see it.

Hotspot removal is slightly different to LENR with a dark frame capture, though.
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Really? I can see hot pixels from RAW files in DPP, LR and PS. Is it an option somewhere?
 
ifine said:
it doesnt prevent you taking another image as long as the buffer can cope.
g.php
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:bang::bang::bang:

Let me try this again....

The LENR exposure does prevent you taking another image until that second exposure is complete.

Try p.208 of the manual.

Look, this bit....

LENR.jpg
 
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jimmyriddle said:
Really? I can see hot pixels from RAW files in DPP, LR and PS. Is it an option somewhere?
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AFAIK, there's no way to turn it off in Lightroom or ACR. Haven't used DPP in ages, so I don't know.

Can you post an example?
 
Musicman said:
AFAIK, there's no way to turn it off in Lightroom or ACR. Haven't used DPP in ages, so I don't know.

Can you post an example?
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I will have a look for some on my PC when I get back (Im away for a few days), just had a quick read on the net, and it seems the JPEG preview in LR wills still show hot pixels, so maybe it was there that I saw them.
 
hollis_f said:
Look, this bit....

LENR.jpg
Click to expand...

This is clearly camera specific as my manual says...

"shooting is still possible as long as the maximum burst indicator in the viewfinder shows "1" or higher"

the comment with regard to Live View shooting is the same though.
 
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Simon_Hill said:
This is clearly camera specific as my manual says...

"shooting is still possible as long as the maximum burst indicator in the viewfinder shows "1" or higher"

the comment with regard to Live View shooting is the same though.
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Well, I'll be ...... Every camera I've owned with LENR has been the same as the 7D.

How on Earth do they do that? Unless they do the dark frame in multi-parts.

It would be really interesting is somebody with a 5D MkII would take a 30s exposure with LENR on. Then, 15s after the end of the initial exposure, take an ordinary image (1/100s or so) and see what happens.
 
OK. Done some googling and found that Scott Martin has looked into this - LINK. Yup, the 5D (c and MkII) have a buffer for the LENR dark frame acquisition. Damn, I wish my 60D had the same - would be great for star pics.
 
hollis_f said:
OK. Done some googling and found that Scott Martin has looked into this - LINK. Yup, the 5D (c and MkII) have a buffer for the LENR dark frame acquisition. Damn, I wish my 60D had the same - would be great for star pics.
Click to expand...

Fascinating article. Thanks for posting the link to that.
 
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