Night shots with 6500FD

[daniellyt]

Took a few night shots using the 6500fd. When i upload to the PC i found there are quite a number of dust like white spots on the pics when viewing with actual size.
Initially i thought it was dust so i blow the lens using a lens blowing kit. But the problem still persists. But there is no problem with day shots.
Anyone has this problem??

[Clockunder]

Originally Posted by daniellyt Took a few night shots using the 6500fd. When i upload to the PC i found there are quite a number of dust like white spots on the pics when viewing with actual size. Initially i thought it was dust so i blow the lens using a lens blowing kit. But the problem still persists. But there is no problem with day shots. Anyone has this problem??

Can you show a sample of the night shots ..... with full EXIF intact so that we can see your exposure time etc.?

I guess it could possibly be hot pixels noise which is normal with long exposure.

[daniellyt]

how to post the full size pics with full exif data? Pls pardon me for the question

[Clockunder]

Originally Posted by daniellyt how to post the full size pics with full exif data? Pls pardon me for the question

Ok, you may just downsize your picture and then upload to imageshack and then post the link or use[img][/img]to post the picture up. The EXIF info should be intact unless you've saved the image by discarding the EXIF info. Alternatively, just state the aperture, shutter speed and ISO used.

http://www.imageshack.us/

[daniellyt]

the link is here. When u zoom in, u will see the dust like spots clearly

http://img220.imageshack.us/my.php?i...1150025ep3.jpg

[Swordwindsg]

hmm...don't seems like dust spots to me leh...the "spots" seem to be spreaded out too evenly and there R soooo many of them! tt's if i'm referring to the same "things" as u lah...

[daniellyt]

i think both of us are refering to the same 'thing'.
Was just wondering what is it & any of you encounter it b4?

[michhy]

i suspect hot pixels.... coz u using ISO 200 for 15 seconds exposure...

[Moonstone]

You have to turn on the NR function (Noise Reduction) when using shutter speed of 15 sec or longer time exposure.

[daniellyt]

i think u guys are correct.
Tried using shorter exposure timing & the "spots" disappear.

[Reno]

Originally Posted by michhy i suspect hot pixels.... coz u using ISO 200 for 15 seconds exposure...

agree with you.....

[Clockunder]

A hot pixel is usually red or blue or green (the 3 primary colours of the pixel array) or a combination of the 3 colours (such as purple etc.).

Those here seems to be unusual and could be a combination of long exposure (15 secs here) and high ISO (200 here)

Try to use ISO 100 or below (if available) for long exposure night shots to avoid random noise.

To prevent/reduce hot pixels for long exposure, turn on the NR (noise reduction. The tradeoff is loss of some details) or use de-speckle in photoshop (sometimes, duplicating a layer, apply some noise reduction, change the blending mode to luminosity or overlay and adjust the opacity may do a better job in reducing the noise without losing too much details).

For prosumer cameras, no need to go smaller than F/8 for night landscape unless you're going after a really starry effect of bright light spots. This is because, due to the small image sensor, diffraction usually becomes evident starting from as big as F/5.6 (unlike an APS sensor DSLR where diffraction usually becomes perceptible only beyond F/13) and a starry effect can also be achieved with F/8 which is actually very small already due to the short actual focal length (remember that the F numbers for aperture is measured vis-a-vis the focal length. F/8 at 8mm is actually physically half the size of F/8 at 16mm).

Alternatively, use a bigger aperture and thereby reduce the exposure time. Using F/5.6 and exposure of 4 second at ISO 100 should be able to get the necessary Depth of Field, sharpness and exposure for most night landscape. The general guideline for 35mm format nigth landscape is 888 .......ISO 80, F/8 and 8 seconds. For prosumer cameras, a bigger aperture such as F/5.6 should still be ok as the actual focal length is shorter (meaning the actual aperture is already very small at F/5.6) and the sensor is much smaller (meaning that shorter exposure is desired to avoid hot pixels and random noise).

For some good examples of noise, go to the Olympus forum and look for threads such as this : http://forums.clubsnap.org/showthread.php?t=217199

[daniellyt]

Tks Clockunder, points noted.

[cutypuppy]

Just want to ask something out of this topic, will the S6500fd camera date & time reset after remove the battery for some time like the F420? this seem abit disturt everytime when replacing the battery.