Hello everybody!



I've just had two weeks of vacations. I had the time to rest, and finally get more than 4-5 hours of sleep per night. Unfortunately, the weather has been TERRIBLE, and by terrible I mean LOTS of SUN, and NO CLOUDS at all! It's a landscape photographer's nightmare...



On to photography topics... I have been investigating on the topic of the need, or not, for the boring in-camera long exposure noise reduction feature. For long I have wondered if I really had to have this thing turned on, while I was freezing out there and waiting for the noise reduction to accomplish his job. Read on to find out...





First of all, a bit of explanation. For the ones who don't usually shoot long exposures, the in-camera long exposure noise reduction function is a feature where, after shooting a long exposure shot, the camera automatically closes the shutter, and then takes another photo with exactly the same exposure time. Why? Because with long exposures the sensor generates quite a lot of heat-generated "hot pixels" (red, yellow or white single pixels scattered all over the image), which you obviously don't want appearing on your photo. As such, the camera developers created a feature, available in most dSLRs, where the camera will take a 2nd long exposure shot right after the first one, this time with the shutter closed, so that it can detect those hot pixels, and then subtract them from the original image, cleaning up all of them in the right spots.


The problem is that, if it is a pain in the ass to wait 2 minutes out there in the cold, with your feet and tripod soaked in water, then imagine what it its to still have to wait two aditional minutes (where the camera is locked and unusable), while it generates the shutter-closed long exposure, to apply the mentioned noise reduction. Considering that the "golden hour", where the light is at it's best with the sun touching the horizon, last about 15-30 minutes, if you are using 2+2minute exposures, you will be shooting half the photos you could shoot in this critical moment... and all of you know as sometimes long exposures come wrong, due to exposure misjudgements.





So I finally had the time to start searching for this subject on google, and found that there are many people who don't use this function. I learned that this feature was mainly developed for astrophotography, where long exposures sometimes reach hours, where lot's of noise is generated due to the sensor heating. There were even some photographers stating that long exposure landscape photos taken with this feature turned off, had better detail (even though this last one is quite controversial). Finally, some photographers also said that the landscape long exposure photos did HAVE hot pixels, but that lightroom and adobe camera raw automatically cleaned them as soon as the raw file was opened. This last one sounded too good to be true...

Since I would love to be able to turn this function off, I did my own tests in the last week. I seized the only day that had a few clouds and went out to shoot with my full ND filter, and made about 30 long-exposure sunset photos, with the long exposure noise reduction turned off...





As I arrived home, I uploaded the photos. On the preview windows on Adobe Bridge, I could clearly see about 50 hot pixels per photo, perfectly visible and disturbing... then I opened one of the images in Adobe Camera Raw, et voila, all the hot pixels instantly dissapeared as soon as the image opened! :-D Adobe Camera Raw automatically cleaned every single hot pixel of each image!


As such... from now on... Long-exposure noise reduction TURNED OFF! :-D






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