Something to Try (Only for the Brave)

Hi All,

I think I've discovered a sure-fire way to see all the crud on your sensor.

Not for the faint of heart - like moi - I'm still depressed..

Wait for a blue sky - or use a well-lit, clean sheet of blue paper.

Set your lens for its absolute minimum aperture, completely de-focus and shoot the sky. I find zooms show most at their longest setting.

Dump onto your computer and enlarge.

Ick.

I have about 25 UFOs, but I can't see them when looking at my sensor under bright lights with a magnifying glass. Took many blasts with a large bulb blower - no improvement.

With my 31mm at f22, they're all there. Fainter at f16, just about gone at f11. Seem not to show at f8 and larger.

Now the dumb question - (hey, it's ME after all)

Why do the little beggars show up most at minimum aperture? Is this some DOF side effect?

The dirt is actually on the glass cover of the sensor, so a little in front of the sensor itself. Wider apertures mean the light can 'go around' the dirt, a small aperture means the light is coming from more of a point source, so the dirt gives a more defined shadow.

Bit like the difference between a grey sky giving no shadows, and a bright sun giving harsh ones.

Does that make sense? I could draw a picture, but hope you don't need it.

Dan

Gotcha Dan!

Great explanation, and I didn't realize there was a glass cover on the sensor either. Good to know.

See, this is something us old film dawgs ain't used to.

We used to get 36 brand new, clean sensors per roll

Looks like I'll be tracking down an Artic Butterfly as the next big ticket purchase. Still kinda chicken to use the wet swabs.

Thanks again Dan!

Don't be, sensors are tougher than we're led to believe I reckon. See my comment on this thread.

As I say there, not something I'd recommend doing, but it did at least prove that the sensor is not some fragile, delicate thing never to be touched.

The arctic butterfly things do seem popular and effective though, if you didn't want to mess with the wet stuff.

Dan

If I can put my 3p into the 'discovering sensor dust' fun .
I have possibly better way, manual focus (and whatever focus setting), take a picture of a white/gray (best - uniform) wall, or piece of white paper, you can boots exposure a bit to get that white/gray object more white than gray . Load picture into gimp, and use function called 'equalize' (menu: colors->auto->equalize), and here you have all the spots clearly visible. Actually 'equalize' function shows dust well with most photos, but uniform, white picture just make it easier to spot the dust.

Dan, ol' Buddy,

You've instilled confidence in this ol' chicken.

And:

You might have just saved me a ton 'o' money.

I think Artic Butterfly's cost as much as my camera. Certainly more than many of them.

SRS has a Pentax wand-type thingy. You press it on the dust or whatever and then clean the wand's sticky tip with their special paper.

Anyone had experience with this? Looks kinda different.

And, Piotro's found an even better high-tech way to chase down the UFO's!

A whole new passtime for me and other obsessives!

Wheeeeeee!

Cheers,

A better way still!,,,,,,,,,,,,treat yourself to a K20D!...it has a built in programme to show you where the dust is...clever little camera it is!.............Ken

Beat me to it, and it puts a picture into a folder called 'Dust' as well!

Does it make tea in the mornings too?

Kris,

We gotta go there - the camera that dust built!

Thanks Beginner and Unlocker!

That's UNBELIEVABLE! It tries to shake it off and tells you when it can't:

Maybe K20D firmware version 1.02 will analyse the dust particles and tell us what they're made of.

We can have a competition !....the best "DUST!" shot!.......extra points for distribution of particals..........

A couple of years ago, on the morning of the southerners PU meet in St. Albans, I used this technique to make sure my *istD sensor was spotless.

Sat in my lounge, pointing the camera at the blue sky through the window, I took a snap, and there was dust. So I tried the rocket blower, took another snap, still dust, but it had moved a bit. Another go with the blower, no good, just shifting the dust about.

So onto the wet wipes, normally sorts it first time. This time? NO! Still just shifted the dust about, plenty of spots all over the sensor. So after several more wet wipes and test shots, I'm thinking "what on Earth's going on here?"

Then it dawns on me. I've defocused the lens. But inadvertently focused on the window instead. I've been busy taking photos of my dirty lounge window for the last half hour.

Didn't do that again!

Dan

Another forensic show for television. We have three in North America - various iterations of Crime Scene Investigation or CSI. Mannesty will like this.

This forum is world wide, so how about Cruddy Sensor International for a contest name?

'Course only K20's could enter, ANOTHER reason to upgrade!

Ha! A plot by Pentax! There must be a spy among us! A mole!!

I blame Chris personally, this stuff always shows up just when he gets more stock.



Know what, Dan?

I did EXACTY the same thing last weekend! Fortunately I caught on before I "scrubbed" my sensor - had only used the bulb blower a few times.

Lesson learned - shoot the sky outside, or use piotro's technique.

Cheers

You know, the K200D also has the built-in dust detection. So no reason to limit a competition to the K20D

Btw, I have used the Sensor Swab on my K100D with good results. Just make sure you get the right fluid, there are two types. And I believe that cameras up to K100D inclusive use the Eclipse variant, while the K10D, K20D and K200D use the E2 fluid.