Dust on sensors - at different apertures

[Leicakillen]

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Inspired by the recent dust postings I did the following experiment with a well used M8 (my M9 is on a rangefinder adjustment trip to Solms);

- I inspected the sensor with a magnifier - I could see a lot of dust particles.

- I took images of the sky at normal exposures at different apertures from 2 to 16 and with 35, 50 and 90 mm lenses.

- Inspected the images at 1:1 in Lightroom. At small apertures (11-16) I could see maybe about 50 spots. If I darken the image I can see even more. This is a dusty sensor!

- I could see no difference between the lenses, I expected to see more dust on 35 mm compared to 90 mm due to bigger DOF - but I cannot see this.

- Very big difference when comparing images at different apertures. On f2 I can see no dust at all - even when I now where to look. At f8 I can see a hint of dust, and at f16 I can see it quite clearly.

- Then I printed these images on Epson Matte paper A3 size (the sky is white on the print ,RGB 98-99). The dust is then even more difficult to see. The f8 print is clean, no dust spots on the print - even if I can see hints on the screen.

 

As some of you have pointed out - don´t panic re dust on sensors, I now fully agree. Very good if we could agree on the best cleaning method of course, but I can be waiting on this without any problem!

 

Regards

Anders

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[RSL]

If you really want to see the dust: (1) Set the lens to minimum aperture (smallest hole). (2) De-focus to the minimum distance the lens is capable of. (3) Make a shot of a blank, blue sky and bring the file into Photoshop. (4) Bring up Levels. (5) Click the Auto button.

 

Depth of field has nothing to do with it.

[zlatkob]

This was a good article on the subject, especially the "Testing" paragraph:

Sensor Cleaning