[Scot628]

Hi, I have started to see these annoying circular blemishes on photographs taken with my K5. Strangely they don't appear in the same place every time; in some pictures they appear at the top in others further down (I've cropped a couple of examples to show how the pesky things seem to move around!) - in fact fairly randomly but with a tendency to the top of pictures (although maybe they are only more noticeable because the top of most of my pictures tends to be the sky and lighter?). I assumed they must be dust specks, and have used a manual blower and brush to no avail. A sensor check for dust doesn't reveal anything. Are these dusty specks or something else? Help!

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Last edited by Scot628; 07-22-2013 at 03:24 PM.

[VisualDarkness]

Looks like dust probably on the sensor and maybe on the rear element of the lens.

[Scot628]

Looks like dust probably on the sensor and maybe on the rear element of the lens.

Thanks VisualDarkness, I thought dust, I'm just puzzled by why it doesn't show up on a sensor check.

[VisualDarkness]

It's quite many of them though and I agree that they look a bit odd. Check the lens first at least. Are there any spots from some kind of fluid on either the sensor or the rear of the lens?

[Scot628]

It's quite many of them though and I agree that they look a bit odd. Check the lens first at least. Are there any spots from some kind of fluid on either the sensor or the rear of the lens?

I had a look a the lens (da18-135) and it looks clean. I did a sensor check for dust and it comes back blank (attached - although it looks like its not attached because its so white!). No obvious signs of anything on the sensor - am stumped!

[VisualDarkness]

That's weird, upload a bunch of pics where the spots shows.

[kiwi_jono]

Don't rely on sensor dust check - mine often comes up blank when there is dust.

Ideally try another lens. In any case take some pictures of the sky using a very small aperture (like f22 - f32 or what ever the smallest aperture is for the lens) because this shows up sensor dust more clearly. You may need to use a Rocket blower to clear the dust.

[Scot628]

That's weird, upload a bunch of pics where the spots shows.

Thanks for the help, here are a selection with the spots appearing in them.

[jatrax]

That is a lot of dust. Do you have the dust shake mechanism set to run at start up? That has helped me a lot. Try running it manually several times and then take another picture, blue sky at f/22 and see if anything changes.

[Scot628]

That is a lot of dust. Do you have the dust shake mechanism set to run at start up? That has helped me a lot. Try running it manually several times and then take another picture, blue sky at f/22 and see if anything changes.

Thanks to all - i have the dust shake set to run at set up. I think i'm going to need to work at shaking out whatever has got lodged in there!

[DeadJohn]

Use a rocket blower to clean the mirror box and sensor. The camera menu has a function to lift the mirror for cleaning. Do not use canned propellant or a brush because that can cause more problems.

You mentioned the 18-135 lens looking clean. Do you have another lens? If yes use it for a while to confirm a camera vs lens issue.

If dust remains and you've confirmed it's not the lens, get a special sesnor cleaning kit and use it carefully. I've never had to resort to that but there are other threads with details.

[Mutters]

I'm wondering if it's not oil or some other substance, rather than dust, as they're all fairly consistent in size.

Maybe you could do a visual inspection with a loupe and torch?

With the dust sensor, I've found it more reliable if you can point the camera at an even light source - like a blank computer screen.

Good hunting.

AB

[jatrax]

Dust removal procedure in order:

1) Use the camera dust removal system (shaker) There is a menu setting to turn on/off. If you have dust run this several times in a row and then check for dust again. I leave mine on "run on startup" and think that is best so you don't have to worry about it.
2) Use a 'rocket blower' or equivalent to blow off anything the shaker will not get rid of. Do not use compressed air or canned air. Some folks report it is OK to use canned air if you are careful, personally I'm not taking any chances.
3) Use a wet cleaning kit. This is the last resort, and on two cameras with over 25,000 actuations in all kinds of environments I've never had to use one yet. Get this if all else fails but don't go there unless you are sure you need it.
4) Send in for professional cleaning. Pentax extended warranty (in the US) includes one 'free' cleaning. Not sure about anywhere else.

[IchabodCrane]

Those look exactly like a dust spot I recently had. I couldn't blow it out so I ordered the Sensor Swab Plus (pre-moistened four-pack) from B&H. Very easy to use and worked perfectly. Just make sure you order the correct size. I think it's Size 2 (APS-C).... but check.

[Scot628]

Thank you to everyone who replied, very useful and I will work my way through the advice - fingers crossed!