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01-08-2012, 12:03 PM   #1
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Spots coming and going on K20D sensor

I took some photos with my K20D on long exposure settings, max 30 sec

First one came out fine with some dust on sensor, but a day or so afterwards I tried it on a wreck close to the shore and, horrors of horrors, it came out as on the photo with blobs and spots all over. Pity, becasue it would have been a great photo. It also looked as if there were fog between me and the wreck, but there were none, It was latish in the afternoon and I used a ND filter. I had the lens before I left the car and I was worried that the sensor was totalled from whatever, condensation or something horrible. After a sleepless night I took a normal photo the day after and only some dust on the sensor again, but no spots. So I could sleep again at least.

Any ideas as to what it was and even more important, how to prevent


Last edited by Basie; 04-12-2015 at 12:56 PM.
01-08-2012, 12:12 PM   #2
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I'd expect that you used a small aperture for that second shot? There's no EXIF on the images, if you could let us know the basic EXIF for each shot, it would likely explain this.

Dust is always more apparent with a small aperture, and often invisible with a large one. Looks like you need to clean your sensor.
01-08-2012, 12:22 PM   #3
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That's definitely dust- you've got quite a dirty sensor!

If you don't already have one of these, it works great in removing dust:
AA1900 Giottos Rocket Air Blaster, Manual Air Blower with Extra-Large Rubber Bulb - 7.5" Long

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01-08-2012, 03:49 PM   #4
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You probably would benefit if you gave some thought to how the dust got into the body so that you can avoid the situation the next time around.

If you bought the camera used, then just blame it on the previous owner

I have a nephew that used to just stuff extra lenses into his jacket pocket without covering the back side of the lens. Dust gets into the lens backside, then gets into the camera the next time around.

Dust is constantly falling out of the air in our houses and outdoors. Don't keep the body uncovered for any more time than absolutely necessary, plus try not to point the open mount upwards - better to point it horizontal .

Don't change lenses if there is dirt in the air from road work, a strong wind, or whatever - common sense applies - dirty air means dirty sensor if its open.

best of luck!

01-09-2012, 02:31 AM   #5
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Hi

Goodness gracious, I have only once seen a sensor with such a heavy load of dust and that was when a friend of mine left his cam body sans lens pointing up on the table over night in his workshop.

Your cam is in desperate need of a thorough sensor clean. But whatever you do, do not use a rocket blower. The reason is simple. Firstly, it will not remove all the dust, and secondly, because of the quantity of crap that is on the sensor the amount the blower will shift, the majority if not all, will be blown inside the mirror chamber where it will reappear back on the sensor in a matter of hours. The turbulence created by zoom lenses and mirror slap will see to it.

Rather buy a very soft, say 10mm wide wide, nylon brush from your local art supply shop (it must be unsized) and wipe it gently over the sensor. The light static charge will pick up most of the dust, then flick the brush sharply over the edge of a pencil to dislodge the dust from the brush and repeat the process.

The reminder of dust that cannot be removed that way; Purchase the "Pentax O-ICK1 Digital camera sensor cleaning kit" and finish off with it.

And finally, proceed with care but please remember the sensor is more robust then people let you to believe. After all manufacturers of cameras know that this is a user service part because dust is an ever prevailing problem that cannot be prevented. And please clean your sensor more frequently, don't let it come to this. The amount of crap on your sensor is simply shocking.

Good luck

Greetings
01-09-2012, 12:25 PM   #6
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Ouch!!

It has been at least four decades since I was reprimanded like this, but I will take it on the chin, Looks like I deserved it.

The first two photos were both taken at highest F stop for the focal length of about 55 mm and that would be about f37. I took some without the filters of the wreck with more normal settings of about F8 and it showed the same spots. So not only f stop related, but even with dust detect it is not so obvious. I still wonder about condensation as well

I do use the camera a lot outdoors, that why I bought a Pentax, I grew up with a K1000 and it never needed cleaning, but do take care when changing lenses with the K20

Problem is I live about 1000 miles from nearest service centre and a commercial sensorcleaning is not practical, because it will probably recur. This is desert with lots and lots of dust and that it where I go to take photographs.

I will try to use the sensor shake and use the small brush method in the meanwhile until I can order the sensor cleaning kit. Seems to be the way to go

Thanks a lot for all your input. I am continually amazed by the depth of knowledge on this forum. And I am sure I can use the good wishes
01-09-2012, 12:55 PM   #7
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I find that using a brush, followed by a blower, repeating if necessary, works quite well. I use soft artist's brushes, sable and such, and keep them exclusively for this purpose (they've never been near paint nor artist). It definitely does more than the blower alone, as it loosens any stuck particles, which the blower can then remove.
01-09-2012, 02:21 PM   #8
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QuoteOriginally posted by Basie Quote

Any ideas as to what it was and even more important, how to prevent
I had the same issue for a long time and finaly got tired of constantly cleaning sensor. i tend to get myself into extemely dusty enviroments ( windy beaches and worse when travell out west, Birdsville, Camrons Corner desert country). Here is a tip it might be helpful or not.
I rummaged through my old film gear and pulled out my Dark Bag, it was used for preparing film for development without the need for a darkroom.
If I think I'm going to be in a dusty location I now carry this with me. Put Camera and lens into bag, zip it up and change lens in bag. My one is large
enough I can swap out a sigma 120-400mm in it. I seem to get less dust now.
hope I have been helpful.

01-10-2012, 12:27 PM   #9
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Hi my bovine friend

I never used a dark bag, but used a thick jacket folded over and putting arms through the sleeves for an impromptu darkroom ( mostly when an unused 35 mm film swallowed the film tip before I put in the camera) but that was always a dusty and hairy affair.

I walk a lot with my k20 and three lenses and do have to change it outside. The Toyota is usually more dusty inside than out on the plains. Maybe I should get a k5 as well so that the lens changes is at less. Problem is it is not available even at the wholesalers in South Africa, which is my nearest place

Thanks again for all the really helpful suggestions
01-11-2012, 05:22 AM   #10
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QuoteOriginally posted by Basie Quote
Hi my bovine friend

I never used a dark bag, but used a thick jacket folded over and putting arms through the sleeves for an impromptu darkroom ( mostly when an unused 35 mm film swallowed the film tip before I put in the camera) but that was always a dusty and hairy affair.

I walk a lot with my k20 and three lenses and do have to change it outside. The Toyota is usually more dusty inside than out on the plains. Maybe I should get a k5 as well so that the lens changes is at less. Problem is it is not available even at the wholesalers in South Africa, which is my nearest place

Thanks again for all the really helpful suggestions
Hi

Look, the whole business with dust is really elevated to a bigger problem than it needs be. Sure, it is a pain in the derriere but it is ever present and one has to learn to live with it. In the old film days where I grew up certainly dust was around just the same but by transporting a new stretch of film in front of the focal plane, it meant the problem was less apparent. However the digital age has changed all this and "dust management" is now a discipline to be learned.

I for one do not get overly paranoid about dust. I recognize the problem but won't let it spoil my day. While the above mentioned suggestions to affect a lens change inside a bag is a good one, the reality is it's not practical in the field. Sooner or later dust and fluff will find itself inside the bag as well and for all you afford you will probably not be better off.

So my approach to the problem is to do a lens change as quickly as possible and by assessing the prevailing conditions try to modify this activity as best as I can. I also have come to recognize that, despite everything that has been said about sensor cleaning, this is a simple and none destructive activity. These sensors are quite robust little buggers and only the most talented person will find them easy to destroy.

This means when I shoot (and change lenses) in unusually dusty places I simply clean the sensor more often and in particular at the end of the shoot. I use now exclusively a soft artist's nylon brush and just brush the sensor clean. By doing it often there is never a buildup of dust to worry about. I can tell you the soft nylon brush with its light static charge picks up dust that has settled on the sensor surface nicely. After all you just wipe a soft brush over a small "glass" area, how difficvult is this? If you do this at the end of the day after a dusty shoot there is never a chance any of the crap will weld itself onto the sensors AA filter's surface through condensation.

My K-5 is now pretty well 12 months old and I have lost count of how often I have used the nylon brush on the sensor. I can guaranty you the sensor is in absolute perfect condition. Companies that sell sensor cleaning gear at prices which return them a 2000% margin hate guys like me.

So, as they say in the classics, people get "their knickers in a knot" for nothing (Or not much anyway)

Greetings
01-11-2012, 06:24 AM   #11
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Hi Schraubstock

Thanks for your rational reply. It is obvious that I totally underestimated the problem of dust and was thinking about a pro clean every year. Amazon does not support sending to a Namibian address, but I will eventually get the Pentax cleaning kit and a few nylon brushes. The brushes I can get here. I do enjoy the camera a lot and will not feel it a waste of time to lavish some TLC on the sensor on a evening after a shoot

Thanks again
01-12-2012, 09:08 AM   #12
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QuoteOriginally posted by Basie Quote
I walk a lot with my k20 and three lenses and do have to change it outside.
Looks to me like a good excuse to buy 2 more bodies.
One for each lens and you won't have to change them.
01-12-2012, 11:14 PM   #13
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Hi Parallax With you being a senior moderator I will use it as an authoritative to show to my other half as to why I need a k5 as well. I am on my way there, bit carrying three bodies? I will just cleaning more regularly

Cheers
01-16-2012, 06:12 AM   #14
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I'm on the same boat, but for a much sillier reason.





I saw a lonely spot on a sky picture and somehow formulated the brilliant idea of wiping the sensor with a t-shirt. No before picture though and I think I saw particles on the sensor before my blunder so some of it might have been there beforehand.

Running the sensor shake a few dozen times got rid of a single grain. I also tried using a synthetic brush as per this site with the blowerless method. First bunch of swipes removed a small number and shifted around some of the rest, second go moved some around but didn't make any immediately noticeable difference to quantity (I didn't attempt to count them).

I'll be getting a Giottos and trying that either directly or by charging the brush. Somehow I doubt that that it will be enough so I hope I haven't inflicted any damage that can't be undone by a professional clean.

Also, hi!

Last edited by Tycn; 01-16-2012 at 06:26 AM.
01-16-2012, 07:09 AM   #15
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LOL, well welcome to the forum! That's quite an entrance.

You may need to do a wet clean, swabs and solution, to fix that up. You might get away with the way I do it, brush, blower, repeat, but it may take quite a few repeats, judging from that pic.

On the upside, it just looks like dust and fibers, not scratches, so I think it's unlikely you've done any permanent harm.
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