Hot Pixels On Long Exposures

I take a lot of long exposures of seascapes and landscapes and anything above 30 seconds(when I get in to minutes) I tend to get hot pixels mostly around the corners of the image.
Very noticeable when you zoom in 100% and there are literally dozens of the little deckers in various colours. They only appear in the longer exposures but they are really annoying me now.

I`m shooting with a Nikon D3200, more often than not use the lowest ISO setting(100) and use a 10 stop filter and sometimes a 2 stop grad as well.

The camera is only 7 months old and there is no issue with 30 second exposures or less.

Is this a common problem? Is it specific to some models? The only cure Ive found is the heal brush in LR(Don't have PhotoShop) but its time consuming going through them all and I`d prefer my camera not to have the issue at all.

Am I alone with this problem? The group I shoot with are all Canon users so I have no one to consult and compare with and none of them seem to have the issue.

Its a bit disheartening as I feel I am really starting to find my photography feet and have invested a couple of grand on gear.

​Any help/opinion would be greatly appreciated.

It's very common for hot pixels to show up during long exposures.

And one thread is more than enough.

I think it is a common issue with almost all the digital cameras. Take a look what the Canonians say about their cameras (some of these being even full frame models):
Flickr: Discussing Understanding dead/hot/stuck pixels in Canon EOS 5D Mark II and EOS 5D Mark III Group

Dumb question - are you sure you're not seeing color noise instead a true "hot" pixel? Because a hot pixel will show at the same place in all your photos, both long and short exposure images.

Dave_W said:

Dumb question - are you sure you're not seeing color noise instead a true "hot" pixel? Because a hot pixel will show at the same place in all your photos, both long and short exposure images.

Click to expand...

Hi Dave,

​Perhaps it is colour noise rather than hot pixels. It's certainly not prevalent at exposures of 30 seconds or less. I'll try and get an image up to show what I mean.

Ice Blue by adox66, on Flickr

On the above image you can see them in the top right of the image and also on the left at the darker rock.
I know its a processed shot but they are the same as I am getting on some other images unedited(shooting raw). Also its probably at the extreme end of my shooting time(15 minutes) so they are probably more noticeable.

Hard to see in this photo but I am guessing that it is noise and not hot pixels. I would bet that Nik Define 2 would go a long way in cleaning it up.

If you click on the image name it will bring you to the Flickr image where you can see it at a larger size.

Yup, definitely color noise...not hot pixels. Believe me, you'll know when they're hot pixels! VERY noticeable! And always in the same place.

I see red spots in the top left without even enlarging it.

That ain't noise.

Nikon promises a firmware fix for the D7000 hot pixels issue | Nikon Rumors

And read this: http://www.mediachance.com/digicam/hotpixels.htm

This will probably come in handy for you, too: http://www.pixelfixer.org/

I too think these are the hot ones (though mixed with the regular color noise). Here is a nice review on the topic:
Dead vs Stuck vs Hot Pixels

Thanks for the links, make interesting reading. I`m pretty sure its Hot Pixels going by those articles.

One thing I`m confused about. It says that Lightroom will automatically take care of them if you are shooting RAW but its not doing anything to them for me?

​Also I`m presuming its not something to be overly worried about and common enough?

Yes, common enough (unfortunately)...

Definitely sensor noise.

Looking at the EXIF data in this picture, I see that it was an exposure of more than fifteen minutes. To have that long an exposure, and not completely wash out the picture, there had to be very, very little light actually reaching the sensor.

There's always going to be at least a little bit of noise in the sensor, but under more normal exposure conditions, it will be insignificant compared to the actual light that is being recorded. But here, you've got very little light, so the noise is more significant.

Think of it as being like trying to watch a distant, weak station on an analog television. You get a lot of “noise”—hiss and static and “snow”. The same amount of noise is always there, but the stronger the signal, the less significant the noise appears.

Here, you're intentionally giving your camera's sensor a very weak signal, and then wondering why you see so much noise.

See also: Signal-to-noise ratio

Bob Blaylock said:

Definitely sensor noise.

Looking at the EXIF data in this picture, I see that it was an exposure of more than fifteen minutes. To have that long an exposure, and not completely wash out the picture, there had to be very, very little light actually reaching the sensor.

There's always going to be at least a little bit of noise in the sensor, but under more normal exposure conditions, it will be insignificant compared to the actual light that is being recorded. But here, you've got very little light, so the noise is more significant.

Think of it as being like trying to watch a distant, weak station on an analog television. You get a lot of “noise”—hiss and static and “snow”. The same amount of noise is always there, but the stronger the signal, the less significant the noise appears.

Here, you're intentionally giving your camera's sensor a very weak signal, and then wondering why you see so much noise.

See also: Signal-to-noise ratio

Click to expand...

Thanks for that. Yeah it was one of the extreme examples I posted but I am getting it with shots 30 seconds and above.
Being relatively new to photography(7 months of owning a DSLR) I was wondering if it was something to be concerned about. Im starting to zoom to 100% and 200% now on Lightroom and removing them with the healing tool! Taking an age to do and probably totally over the top.

Just trying to clarify if i have a problem with my camera and if others suffer with the same problem too. Also if there is anything I should do or if it is a normal enough thing?

i can definitely see the issue here. and it only shows in the corners, so i doubt its a typical color noise. but then, i'm not familiar enough with nikon sensors to make a clear statement

one easy way to fix that in post is by color cloning, but that will only be possible in shots with a dominant color through the entire image, like the one in the sample, otherwise it could really take some effort

Lightroom has a colour noise slider. Turn it up and see if it goes away.

I developed a hot pixel when shooting with my D90. It either came from using ISO 3200 with shutter speeds of only 1/15 over a 2-hour time frame or from taking ISO 100 shots at @5-8 seconds. Either way, I am now left with a hot pixel that shows up whenever I shoot at ISO 400 or higher. It's easy to remove the hot pixel during post processing, but now I try to take precautions so the issue doesn't get worse. Sure Nikon can do some type of remapping so the hot pixel doesn't appear, but I'd rather not send in my camera for repair for something so minor.

My point is if you do wind up with a hot pixel, most likely it will always appear in every photo at higher ISOs regardless of your shutter speed. Like I said, mine now appears in every photo at ISO 400 even with faster shutter speeds. It doesn't mean it will happen to you, but now I try to avoid shooting where the sensor will get so hot.

I know of no "automatic fix" in Lightroom for noise, and I wouldn't expect or want it as I'd want to be able to adjust for noise on a photo by photo basis. They do have both Color and Luminance Noise adjustment sliders.

According to the EXIF data this is a 923 second exposure. That's a LONG time - over 15 minutes. That's plenty of time for the sensor to heat up and produce hot pixels and general sensor noise. What you can do is produce a similar black image by covering both the lens and the eyepiece and shoot a 923 second black exposure, which should theoretically produce the same level of sensor noise in the same areas. You can then use that image with the original RAW file to subtract out the noise. This is the same methodology that the camera uses with Long Exposure NR without having to wait out in the field for a second 15 minute period while the camera produces the black image and then does the subtraction in-camera.

There's a difference between hot sensor noise and hot pixels. As @hark stated, a hot pixel is always hot, regardless of exposure times. What you have is evidence of an overheated sensor. And a lovely shot, btw. If you wanted, you can desaturate your reds, magentas and purples in LR without impacting the overall color of the photo - at least not to my eyes. The spots are still there, but they're white instead of hot pink. Or, if you prefer, after doing basic adjustments in LR you can send it to Photoshop and use color-specific noise reduction. I did 100% NR on the red and green channels, reducing details to 0%. This took out a ton of noise, and was very effective given that you're image is almost all shades of blue (i.e. this may not have worked as well on a more color-full image). From there it was just a matter of using the spot healing brush to take out the white flecks that were left. Harder to see on a 1000px upload, but I can shoot you the full size image if you'd like. You definitely loose some sharpness on the rocks, but again this was done quickly and on a JPEG and not the RAW file.

Lots of options available to you.