looooong saving process due to long exposure?

[mentos_007]

yesterday I was taking long exposures at night (up to 10 minutes). I had Long Exposure noise reduction option turned on (in custom functions in my rebel xt/350d). and when the camera ended exposing I had to wait a long time for the photo to be saved on my memory card. the slower I was exposing the photo (a few sec) the shorter the time of saving was. I suppose it was caused by this custom funcion, am I right? Or it is something wrong with my memory card? (It is SanDisk standard card )

 

[Orgnoi1]

Nope its a normal thing on dSLRs that if you are running the noise reduction feature on long exposures that the write time to card is incredibly long... sometimes (most of the time) almost as long as the exposure itself.... I actually had to turn off my 1D Mark II one time because I thought something was wrong... I had taken a >5min exposure and it was over 10 minutes to process it to card...

 

[Big Mike]

That's correct, the noise reduction function takes about about as long as the exposure. Kind of a pain in the but...if you ask me.

 

[JTHphoto]

i recently had the same problem taking firework pics, mentos... but i didn't remember turning on the NR. by the time i realized what was going on, the firworks were almost done... now i will have to wait until next year... =(

 

[mentos_007]

I turned it off... I think that software like Neat Image may do the job as well... but... I was trying my attempts at star trails and of course the stars... moved out after a few minutes ... dang... I need to wait for another beautiful night

 

[hovis]

You might want to try Noise Ninja for post processing noise out - works like a charm...

 

[boris152]

The long exposure noise reduction option on Canon SLRs uses an extra exposure to cancel out sensor related noise in the picture. As in, once the exposure is completed, the camera takes an identical exposure with the shutter closed, and then uses the second one to map out and cancel noisy pixels in the photo. The actual write time isn't any longer than taking a normal picture, it's that pesky second exposure that's to blame. It's certainly up to you whether you want to deal with the added time or simply use a software tool to do the job.

 

[Alex_B]

I was shocked too when first I got this ultra long processing
but when i saw the wonderful job it did I was quite happy.

prefer neatimage over noise ninja a great deal. but that is maybe just personal preference.

works PERFECTLY for film grain as well

 

[rmh159]

Does NR of any type (in camera, software, etc) blur the pic at all? I thought there was a trade off to it but can't remember the details.

 

[Alex_B]

well, at least the noise due to very long exposures is different from the totally random noise you get at sort exposures as I understand. long exposure noise is not totally random as it also includes actual physical variation of different pixels on the sensor (hot pixels etc.).

Anyway, to my experience blur with in-camera long-exposure compensation is minimal, better to say i never saw any beyond my focus and lens blur . nut then again I did not play alot with long exposure yet.

As far as software noise reduction goes, there certainly is blur. The worst blur you get when you use noise/grain reduction from scanning software (e.g. GEM).

Noise Ninja and Neat Image are really good. And if you profile them to your camera or if you fine tune with respect to the image, you have almost no loss of information in the resulting image. But to achieve this, you have to go to pro-mode and play with lots of sliders

Anyway, if you do not overdo the noise reduction, results will be fine (similar with sharpening). Oh and always do noise reduction first, sharpening second. That means you best switch off any in-camera sharpening and do it after or with the noise reduction.

 

[Arch]

i found the best method is to duplicate your final image, use neat image or other, then add a layer mask and take it away from highly detailed areas. This way the important things are still in focus, the most noticable areas of noise are in open areas like skies.

 

[hovis]

. But to achieve this, you have to go to pro-mode and play with lots of sliders .

That depends on what camera you are using - there is a looooong list of camera profiles readily available, so you could get the right profile loaded real quick.......

 

[Alex_B]

true.. there are profiles for my camera. but also every image is different so you might want to tune sometimes.

Anyway, Archangel is right about the layers, that can save a lot of hassle and improve the result alot.

 

[fotogenik]

Nikon DSLR's do the exact same thing. They take an exposure of the ccd with the lens closed to compare to the image you exposed. What it is looking for is a hot pixel and drops it or changes it in some way to compensate for it.

You are not actually having a long save time (time it spends saving to the card is exactly the same)

What your seeing is two identical exposures. So if you take a 5 minute exposure with in Camera NR turned on your actually going to take 10 minutes (plus a couple seconds) per shot.

Cheers,