[hinyeung_leo]

Most of the sales and even staffs in Nikon CS said dust doesn't really matter in image, I am really in doubt if that's the case

[peterchan04]

Why did they say that?

Dust on the sensors...? or dust on the lenses...?

.

[Obi-Wan]

the dust on low pass filter above the CMOS can only been seen in photos with small aperture, e.g. f11, f16 etc. AND pointed to plain color such as the sky. BUT how frequent do u take photo in this way???

my D200 has many dust particles and even 1 dead dot in the sensor. I still use it on jobs for clients who like Nikon more than Canon.

[pigpig2000]

>>>I still use it on jobs for clients who like Nikon more than Canon.
=====================================================

very selective customer ^_^

[Obi-Wan]

pigpig2000

"very selective customer ^_^", some clients who know something about camera have special request to use Nikon rather than Canon, I really don't know why. Some clients even teach me how to shoot! =.=

[hinyeung_leo]

I see..
So dust within the lens or even on the low pass filter should be acceptable then..
Would like to know whether photoshop can test whether there is dust or dead dot, or if there is better software for testing

[Obi-Wan]

very simple method to test dust on CMOS or dead dot on CMOS

check bright dot
1. use manual mode, ISO 100, NO AF
2. with the cap on the lens, set 1/1000", f11
3. take a photo, a total dark photo is recorded
4. check whether any bright dots is present

check black dot & dust
1. use A mode, ISO 200 or above, NO AF
2. use a well lighted paper (indoor or outdoor ok), point the camera to the white paper, set AV value to f4 or below
3. set +/- AV value to +2 or +3
4. take a photo, a total white photo is recorded
5. repeat the experiment with AV value to f22 or above

if there is dark dot, the same dark dot appear in the white photo
if there is dust, the dust will appear in f22 but not in f4

[hinyeung_leo]

Thanks Obi for the detail explanation.