Strange lense issue

[Sebastian]

Hello,

I am the new owner of a Nikon D70 body and a Tamron 28-75mm XR Di lense.

After a night shot session (at dawn...) earlier this week I have noticed a small circular bluried shadow in the upper right corner of the frame that showed on some pictures (while some other pictures appeared to be flawless). I have looked at the front element of the lense which appeared to be perfectly clean and I cleaned it anyway as a safety procedure. I wasnt too bothered by this event as it seemed to have happened randomly on some pictures and I have tought that it might have been some dust on the front element that fell off itself.

Last night, I went for a similar night shot session and tried my lense at all apertures and the same problem happened yet I have discovered that this blury dot appears arround f/5.6 and keep getting darker and more precise (less blury) as the aperture get smaller. At f/32 it is actually a tiny black dot.. After that, I have looked at (and cleaned) both the front and the rear element of my lense (who both appeared to be clean) and I gave a look at the camera sensor which appeared perfectly clean as well. I also blowed some air on the sensor just in case...

Now I havent shot since then but I am seriously wondering what is going on. That problem never showed up while shooting things that are near me (and thus not focusing at infinite).

Does anyone ever experienced something similar??

thanks

Seb

Dust on the sensor. Get a Giotto blower of sensor swabs, do NOT use canned air.

Learn to live with it, film would move to a new frame with each shot, our sensors go nowehre, and bing electrically charged attract boatloads of this stuff. Nothing we can do about it.

[Trevor Ash]

Learn to live with it...

Although I think Sebastion is getting ahead of himself a little; his great advice is best taken now if you're able

[Asylum Steve]

"our sensors go nowhere..."

I'll have you know MY sensor goes everywhere I go...

[Seb]

I am both annoyed but relieved to know that this is the problem. In theory things should be fine as I did blowed air on the sensor (with an air blower that is) last night.

Just for the records could somebody explain me the link betwen aperture and the way dust actually appears on pictures?

thanks again

Seb

[Trevor Ash]

I am both annoyed but relieved to know that this is the problem. In theory things should be fine as I did blowed air on the sensor (with an air blower that is) last night.

Just for the records could somebody explain me the link betwen aperture and the way dust actually appears on pictures?

thanks again

Seb

Aperture affects how much light is scattering on the back side of the lens. The larger the hole (like f/2.8) the more the scatter and thus the more the blur of the dust. When you have a small aperture (like f/32) the light is more finely focused and scatters less so the dust is blurred less and it become more obvious.

Think of it this way......hold your finger a few inches in front of your eyes. Look directly at it for a second. Now look past your finger at your monitor without moving your finger or head. Although not quite the same effect, it's very similar in the way it works.

[Seb]

Hey guys,

After several unsuccesful attemps to get rid of the dust with my (little) air blower I went back to the store as I started to wonder if it truly was only dust but it was. The technician spent something like 30 minutes to get rid of it with a "monstro" air blower. There truly is a whole lot of static electricity on the sensor!

Anyway, the camera is now perfect and I have bought the same air blower the technician used. I now realize that there was strictly no way I could have removed the dust with my small blower.

Just for the records, I have just tried few flower shots with the aperture set at f/9 as I have heard that the Tamron give its very best arround f/10. I obviously dont get the nice blur I achieved arround f/3.2 but the sharpness of the flower cores is literally stunning.

I'll post an example on the viewfinder later on.

regards

Seb

[Sebastian]

Hey guys,

After several unsuccesful attemps to get rid of the dust with my (little) air blower I went back to the store as I started to wonder if it truly was only dust but it was. The technician spent something like 30 minutes to get rid of it with a "monstro" air blower. There truly is a whole lot of static electricity on the sensor!

Anyway, the camera is now perfect and I have bought the same air blower the technician used. I now realize that there was strictly no way I could have removed the dust with my small blower.

Just for the records, I have just tried few flower shots with the aperture set at f/9 as I have heard that the Tamron give its very best arround f/10. I obviously dont get the nice blur I achieved arround f/3.2 but the sharpness of the flower cores is literally stunning.

I'll post an example on the viewfinder later on.

regards

Seb

What blower did you get?

Glad it's better.

[Seb]

Hello Sebastian,

Sorry for the delay...

Actually, it's a brandless blower but it appears to be equal in size (and price) to the Giotto.
It's way more powerful than the tiny blower I used to have.

regards

Seb