Go Back   Steve's Digicams Forums > Digital Cameras (Point and Shoot) > Fujifilm

Reply
 
Thread Tools Search this Thread
Old Apr 26, 2010, 5:40 AM   #1
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default Dark noise in F70EXR photographs

I can see some dark noise or sparking effect in long exposure photographs of F70. Is there any way to remove it?
you may see it in the 100 % crop.

Aperture value: 4.8
Brightness:-3.73
Exif color space: sRGB
Compressed bits per pixel: 4
Exposure time: 5 sec
F stop: 5.3
Focal length: 16.8
ISO speed ratings: 400
Shutter speed: 4.92458 sec
Attached Images
 
arena is offline   Reply With Quote
Sponsored Links
Old Apr 26, 2010, 5:42 AM   #2
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default

After Noise reduction
Attached Images
 
arena is offline   Reply With Quote
Old Apr 27, 2010, 12:32 AM   #3
Member
 
Join Date: Aug 2005
Posts: 70
Default

by sparkling white noise are you referring to the white spots in the upper center of the black background?
archish is offline   Reply With Quote
Old Apr 27, 2010, 12:52 AM   #4
Senior Member
 
Hawgwild's Avatar
 
Join Date: Mar 2006
Location: Pensacola, Florida
Posts: 3,525
Default

Hot Pixels?
__________________
Always use tasteful words - you may have to eat them.
You cannot find knowledge by rearranging your ignorance.

My Flickr
-Robert-


Hawgwild is offline   Reply With Quote
Old Apr 27, 2010, 2:43 AM   #5
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default

Yes Ofcourse,

I tried to change and reduce ISO to 200 but still white spots were there. In black background it is clearer.
arena is offline   Reply With Quote
Old Apr 27, 2010, 7:05 AM   #6
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Those are hot pixels, and you'll probably need to use software to remove them. I see that the manual for your camera says this on page 38:

Quote:
Noise in the forum of randomly spaced bright pixels may occur on long exposures
http://www.fujifilm.com/support/digi..._manual_01.pdf

That tells me that it probably doesn't have a Long Exposure Noise Reduction feature to remove hot pixels. Basically, some (if not most) cameras have what is known as Dark Frame Subtraction Noise Reduction for use with longer exposures. That's not the same as high ISO noise reduction.

With some non-dSLR models, it's not uncommon to see hundreds of them on exposures much over a second if long exposure NR is turned off. Most dSLR models do better. Virtually all sensors will have them in some conditions. The longer the shutter is open, the more likely a photosite won't be linear with it's fill factor, and it will record a higher value faster than it should.

You just don't see them with many newer cameras because of built in dark frame noise reduction to subtract them out on longer exposures (if you have it turned on), since the ones that occur at typical shutter speeds have already been mapped out at the factory. With most cameras, it only engages on photos taken longer than 1 second (where hot pixels usually show up).

The way it works is by taking two photos. The first photo is of your subject. Then the camera automatically takes a second image using the same settings with the shutter closed.

The camera then notes the positions of any hot (bright) pixels in the "dark frame" (second) exposure, and maps them out of the actual exposure by interpolating values from surrounding pixels to replace the hot ones.

It knows where to find them because the dark frame exposure was taken at the same time, using the same settings, with the camera at the same temperature. In most cases the hot pixel locations will be the same in both images using this technique (so those will be the only pixels it sees in the dark frame exposure and can record their locations for use in mapping them out of the actual exposure). But, the longer the exposure, the greater the chance it will miss some of them.

But, your camera doesn't look like it has that feature (or if it does, I can't find any mention of it in the manual).

So, you'll probably need to use software to remove them. Here's one program that's been around for a long time:

http://www.tawbaware.com/pixelzap.htm

Here's another one I just found with a quick google search:

http://www.mediachance.com/digicam/hotpixels.htm

If you search for hot pixel removal using google, you'll see many hits.
JimC is offline   Reply With Quote
Old Apr 28, 2010, 12:52 AM   #7
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default

Many thanks Jim
arena is offline   Reply With Quote
Old Apr 28, 2010, 4:05 AM   #8
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default

After Hotpixel removal process by hotpx-xtr stand-alone I got better results.as you may see in the samples.

Before process:
Attached Images
  

Last edited by arena; Apr 28, 2010 at 4:10 AM.
arena is offline   Reply With Quote
Old Apr 28, 2010, 4:07 AM   #9
Junior Member
 
Join Date: Mar 2010
Posts: 13
Default

After process:
Attached Images
  

Last edited by arena; Apr 28, 2010 at 4:10 AM.
arena is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 2:10 AM.