Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-16-2008, 10:20 AM   #1
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Can anyone tell me what these circles are?

I may be showing my digital ignorance here, but can anyone tell me what those two circled darker spots in the blue sky area are? The most noticeable one is just inside the palm tree trunk on the right. They appear, if at all, regardless of the lens.


12-16-2008, 10:25 AM   #2
Senior Member




Join Date: Aug 2007
Location: San Jose, CA
Posts: 281
Dust

That is dust on your sensor. Time to try sensor shake cleaning, rocket blower, etc to try and dislodge it.
12-16-2008, 10:29 AM   #3
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Original Poster
Thanks. That was my initial thought.
12-16-2008, 11:36 AM   #4
Junior Member
tbone-ike's Avatar

Join Date: Apr 2008
Location: West Michigan
Posts: 38
I thought they were UFO's in the sky. Glad to hear it's only dust!

12-16-2008, 12:32 PM   #5
Moderator PEG Judges
Kerrowdown's Avatar

Join Date: Aug 2008
Location: Highlands of Scotland.
Photos: Gallery
Posts: 32,801
Only dust I'm afraid, a bit of blowing or photoshop sorts 'em out.

Had they really been UFO's, that shot would have been worth big money.
12-16-2008, 12:45 PM   #6
Pentaxian
dosdan's Avatar

Join Date: Dec 2007
Location: Brisbane, Australia
Photos: Gallery | Albums
Posts: 1,699
They seem a bit large for dust. I had similar spots on my K100D Super after I changed lenses in slight rain and I believe they were caused by dried rain drops (the rain is not pure water).

See the example I posted a bit down in this thread compared to a dusty sensor example:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/30901-k100d-sensor-dirt.html


I was able to finally remove it by using a Pentax sensor cleaning kit (expensive but effective). I described how to fix up affected photos in the healing section of this tutorial:

https://www.pentaxforums.com/forums/post-processing-software/29978-gimp-photo...-cropping.html


The following video shows someone using the Pentax O-ICK1 Image Sensor Cleaning Kit to clean a Nikon sensor. It helps to see it in action to learn how to use it properly:

YouTube - Pentax O-ICK1 Image Sensor Cleaning Kit

Dan.

Last edited by dosdan; 12-17-2008 at 12:26 PM.
12-17-2008, 07:43 AM   #7
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Original Poster
QuoteOriginally posted by dosdan Quote
They seem a bit large for dust. I had similar spots on my K100D Super after I changed lenses in slight rain and I believe they were caused either by dried rain drops (the rain is not pure water).

See the example I posted a bit down in this thread compared to a dusty sensor example:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/30901-k100d-sensor-dirt.html


I was able to finally remove it by using a Pentax sensor cleaning kit (expensive but effective). I described how to fix up affected photos in the healing section of this tutorial:

https://www.pentaxforums.com/forums/post-processing-software/29978-gimp-photo...-cropping.html


The following video shows someone using the Pentax O-ICK1 Image Sensor Cleaning Kit to clean a Nikon sensor. It helps to see it in action to learn how to use it properly:

YouTube - Pentax O-ICK1 Image Sensor Cleaning Kit

Dan.
Your shots do look closer to mine, though what is different about my spots is that they appear to be perfect circles rather than flecks or blobs. I gave it a shot of air, and i don't seem to see them now, though I need a clear blue sky (it's snowing here) to give it the acid test.
12-17-2008, 08:15 AM   #8
Veteran Member
mysterick's Avatar

Join Date: Oct 2006
Location: 44266
Photos: Gallery | Albums
Posts: 428
Shoot a white sheet of paper and see if...

12-17-2008, 08:28 AM   #9
Veteran Member
ManuH's Avatar

Join Date: Dec 2007
Location: Montreal
Photos: Gallery | Albums
Posts: 1,209
Shoot at f22 a wall or a sky, unfocussed and SR off (the more the blurr the better, if there is dust on the sensor, it will stand out). Even with the K20D I do that (the dust alert doesn't work that well IMHO).

What I do to clean: a rocket blower first. If this doesn't work, the Pentax O-ICK1 kit, very effective for sticky dust.
12-17-2008, 10:46 AM   #10
Junior Member




Join Date: Nov 2008
Location: Taunton, UK
Posts: 48
People keep recommending rocket blowers but every time I use one I end up with more dust on the sensor than when I started. I guess it shifts all the dust in the body, not just that on the sensor.

The picture shown looks just like the dust I have seen and the only way I could remove it was with a chamois pad on a stick (designed for cleaning video recorders) and isopropyl alcohol. It's a bit scary especially doing it the first time. First time I tried, some of the dust must have been a bit greasy and it smeared all over the sensor. After repeatedly cleaning, the smears went away and it ended up clean.

I have found that with a strong bright light at an angle and good reading glasses, you can see the actual dust on the sensor without having to take test pictures just to see if you have successfully cleaned it.

Incidentally does anyone know if the shake reduction mechanism on the latest cameras makes this cleaning more likely to do damage? Hopefully it is required less anyway.
12-17-2008, 12:22 PM   #11
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Original Poster
The weather finally cooperated and I got this shot. It looks like my blast of air got them. I've goosed the contrast way up, which is how they showed up most in my shots from Florida.

12-18-2008, 12:16 AM   #12
Veteran Member
pop4's Avatar

Join Date: Aug 2007
Location: YMML
Photos: Gallery
Posts: 1,877
Looking good, now try a shoot at say F/11 and then F/22. The above shot was taken at F/5.6, but your original shot was taken at F/8, and smaller apertures will tend to show up dust bunnies a lot more.

Personally, if my sensor looks clean at F/11, then I'm happy; I don't bother trying to get a clean sensor at F/22, since I rarely shoot at more than F/11 anyway.
12-18-2008, 05:56 AM   #13
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,775
Original Poster
QuoteOriginally posted by pop4 Quote
Looking good, now try a shoot at say F/11 and then F/22. The above shot was taken at F/5.6, but your original shot was taken at F/8, and smaller apertures will tend to show up dust bunnies a lot more.

Personally, if my sensor looks clean at F/11, then I'm happy; I don't bother trying to get a clean sensor at F/22, since I rarely shoot at more than F/11 anyway.
Interesting observation about the aperture. I hadn't thought that would matter, but now that you mention it, my program line on the day that I noticed all these circles was for MTF, and that seems to mean my K10d tries to maintain F/8 about 90% of the time. I've gone over the raw shots again, and the circles are, in fact, much more visible at F/11 and much fainter, though still discernible, at 5.6. (All the shots with the circles in the sky were at F/5.6-11)

I'll see if the weather cooperates again today for another test.

Last edited by GeneV; 12-18-2008 at 06:06 AM. Reason: additional info
12-18-2008, 07:16 AM   #14
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
QuoteOriginally posted by GeneV Quote
Interesting observation about the aperture. I hadn't thought that would matter, but now that you mention it, my program line on the day that I noticed all these circles was for MTF, and that seems to mean my K10d tries to maintain F/8 about 90% of the time. I've gone over the raw shots again, and the circles are, in fact, much more visible at F/11 and much fainter, though still discernible, at 5.6. (All the shots with the circles in the sky were at F/5.6-11)

I'll see if the weather cooperates again today for another test.
They will be much better focused as you close down the aperture. Shooting at f/22 will usually allow you to see the exact shape of the dust (in the case of hair and fibers).

Remember that the sensor is inverted horizontally and vertically from what we see, so if you are trying to clean a particular spot, you'll need to account for the flip.
12-18-2008, 09:33 AM   #15
Veteran Member
pop4's Avatar

Join Date: Aug 2007
Location: YMML
Photos: Gallery
Posts: 1,877
QuoteOriginally posted by GeneV Quote
I'll see if the weather cooperates again today for another test.
You don't necessarily need to wait for clear blue skies for the test. Any bright, even coloured surface should work; I use my computer monitor set to display all white (I open up Paint, set the Width and Height in Attributes to bigger than my desktop resolution, and then go to View Bitmap). Just make sure that you've got it on manual focus so that the monitor/surface is not in focus when you take the test shot. Moving the camera around, whilst keeping it pointed at the test surface, also helps.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Concentric circles in viewfinder? jds Troubleshooting and Beginner Help 5 10-02-2009 04:42 PM
Project 52, Week 40 - Concentric Circles - Winners! jezza323 Weekly Photo Challenges 5 03-29-2009 04:19 AM
Project 52, Week 40 - Concentric Circles DanLoc78 Weekly Photo Challenges 13 03-24-2009 05:43 PM
Circles & Lines shiner Post Your Photos! 1 01-23-2009 04:40 AM
Color Cloth Circles Eastern Shore Charlie Monthly Photo Contests 0 04-27-2008 03:37 PM



All times are GMT -7. The time now is 01:21 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top