Pink dots EVERYWHERE!?? please HELP.

tron76 · Feb 2, 2014

hi....i was taking a long 4 min exposure tonight.....
everything looked fine till i got home a viewed it at 100%....pink dots everywhere apart from the sky.....
i use a 5d II 24-105mm lens..i have processed this through lightroom with noise reduction...but it didnt help at all
it was a hot night tonight....can this be hot pixels??
how can i remove them from the entire photo...is there a way...?? in photoshop?? what a nightmare...

if u can tell me how to remove all these dots....id be really thankful

kel

ann · Feb 2, 2014

looks like noise, what iso did you use?

tron76 · Feb 2, 2014

ISO was 100 and i used noise reduction in LR....80% luminance 50% color....ive never had noise before at iso 100....even in 30 second esp....but this 4 min exp....i have pink and green dots everywhere...thousand of them but strangely enough not in the sky....

Overread · Feb 2, 2014

Noise on the sensor is increased when the cameras sensor gets hot. This is why people doing hour long exposures for astrophotography will often use a series of shorter exposures and blend them together to keep the sensor cool instead of one long exposure. The other option is that they break out liquid nitrogen and supercool the camera via custom setup.

You can use long-exposure-noise reduction in the camera menu. What this does it take a second photo for the same exposure time as the first, but with the shutter blades shut. This results in a second exposure that has detail only where sensor noise has appeared; it then subtracts that from the first shot.

The shot youve shown here is also underexposed which will further increase noise levels; especially if you brighten it to a normal exposure appearance. If you use a higher ISO but expose correctly for the scene you will get less noise than if you expose incorrectly at a lower ISO and then bump up the brightness.

KmH · Feb 2, 2014

FWIW.

The under exposure Overread mentions is readily apparent from the Histogram LR is displaying in the screen shot you posted.

To minimize noise, digital images have to be exposed to the right (ETTR) side of the histogram.
Digital Camera Image Noise: Concept and Types
Optimizing Exposure
ETTR - The guy that wrote this ETTR article - Jeff Schewe - is one of the guys that wrote the software that is LR's sharpening and Noise Reduction panel. Note that Sharpening and Noise Reduction are on the same panel. That's because they're directly related. Reducing noise makes photos less sharp. Sharpening photos makes image noise more visible.
Jeff has written or helped write several books:
Real World Image Sharpening with Adobe Photoshop, Camera Raw, and Lightroom (2nd Edition)
The Digital Negative: Raw Image Processing in Lightroom, Camera Raw, and Photoshop
The Digital Print: Preparing Images in Lightroom and Photoshop for Printing

tron76 · Feb 2, 2014

thanks for the info...hmmm
yeah i was exposing for the sky, i wanted the sky to be bright and the foreground i could bring back in LR with the shadows, i was also using a black glass to get the 4 min exp to make the clouds streak....
sadly today in melbourne it was 44 degrees....so..not only was the camera hot but the weather was a killer...
is there any way to fix it in post?? or is it just dead?

Overread · Feb 2, 2014

Next time consider taking two (or more) exposures and then blending them in editing either manually with layer masks or using some HDR software. The idea there is to take advantage of a correct exposure for each area of the photo whilst at the same time overcoming the cameras limitations.

You can use noise reduction software on the photo now, although you'll find it hard to remove noise that strong, esp if you want to both brighten and retain detail. You might find resizing and displaying online/printing might also hide some of the noise present although its pretty strong so likely you'll still see its effect somewhat.