mysterious dust

Heterop · Oktober 15, 2021, 17:08:58 NACHMITTAGS

Hi,
I'm playing with my microscope trying different ways to photo with my DSL but encounter a strange dust problem.

Test 1: For base line image I used my Canon 50D with 100mm prime len and raynox dcr-150. This would allow me to compare it with the result of the microscope photos.

Test 2: Attach my DSL over Zeiss universal compact camera adapter (2.6X) with 50mm fix focus len. Image was fine but the problem has black dust stains all over the image. Since I didn't saw any stains in test-1 I assume the adapter is dirty and I tried to wipe it gently with cotton ball but without success so I did another test.

Test 3: Attached my DSL to the Eye Piece port with cheap adapter. Again I see the exactly same stains. See red arrows in the attached photo they are exactly in the same location. So the only two components which where use in both Test-1 and Test-2 are the DSL sensor and the microscope internal optical system.

And here is the strange part. in Test-1 I didn't saw any stains so it can't be the DSL sensor and in previous post https://www.mikroskopie-forum.de/index.php?topic=42163.0 I already use Canon G5 to take photo with the microscope and also no stains appear? So were are those stains come from?

Best regard,
Heterop

sushidelic · Oktober 15, 2021, 17:19:24 NACHMITTAGS

Hey Heterop,

those are tiny dust particles on the sensor. They become the more visible, the smaller the effective aperture becomes (the more parallel the light beams hit the sensor).

Best regards,
Michael

Heterop · Oktober 15, 2021, 19:03:10 NACHMITTAGS

Zitat von: sushidelic in Oktober 15, 2021, 17:19:24 NACHMITTAGS
Hey Heterop,

those are tiny dust particles on the sensor. They become the more visible, the smaller the effective aperture becomes (the more parallel the light beams hit the sensor).

Best regards,
Michael

Thanks, it helped me a lot

I didn't realized that lower aperture make the dust more visible. Here are two photos: in F22 you can see the dust and in F10 nothing at all. When I checked my previous tests I saw that both Test-1 (expose 1/250 with flash) and Test-2 (expose 1/40 with nature light) where photo with F10 but only one show dust stains. So to explain it I can assume that expose time also effect the visibility of the dust?
What is the best way to increase the light reaching to my camera? I tried to illuminate the object but that doesn't really help.