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Numpty photo question


Boonie Hound

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Calling photographers

 

An annoying black dot has appeared on my pics when I use my 70 to 300 lens. Looked at the lens and camera and had a bit of a wipe around but the bl *mad* *mad*dy thing is still there and I can't see what it could be.

 

Not too keen on wraggling finger/ cloth in my digital SLR without having an idea what I'm trying to do.

 

Any cleaning suggestions for lens etc or should I just take it down the camera shop and say fix it.... I know this is something simple but as I spent most of my bonus on this camera and lens I really don't want to hurt it by scratching something etc.

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Boonie

 

Do not stick your finger nor any sort of cloth inside your camera body

 

It may be the lens or it still could be your camera sensor - different lenses can display different symptoms due to their differing focal lenghs etc

 

I'll post more later

 

Paul

 

Supercheese R250

 

Caterham pictures here 😬

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It's quite easy to test and diagnose - if it's dust on the sensor...

 

Take a lens, set the camera to Aperture-priority ('Av') mode, set the aperture as high (numerically) as you can (f/22 being common), point at a blank bit of sky/cloud or a bright but plain painted wall (etc.), take pic. Point somewhere else (similar) take pic.

 

Now set the aperture as wide (lowest number) as possible - repeat above.

 

Load them into the camera and zoom in to where the spot is. If it's always in the same place - and worse at f/22 than f3.5 (or whatever), then it's almost certainly dust on the sensor. You can triple-check this with another lens, but I suspect that's your problem.

 

Do not poke anything in there - find the manual and work out how to get the camera into manual-cleaning mode (it flips the mirror up) - then use an approved blower thingy (not compressed 'air' in a can - use a Rocket Blower or similar). Give it all a good blast with the camera inverted - being careful not to trigger the mirror back down, trapping the blower.

 

Now repeat the tests (you'll need to perform a sweep-scan of the image at high magnification) and repeat the cleaning if necessary until you're satisfied.

 

The effect of sensor dust is greatest with small (i.e. high numerical number) apertures and shouldn't be *much* of a problem below f/8, say (esp. if it's not in an area commonly taken up with bits of sky).

 

I've still got some dust that I can't get rid of in my £3k Canon 1d mk III body - despite it having an anti-dust feature. It's not an issue in normal use though (motorsport with little - if any - sky)

 

If none of that works/tracks then let us know... *wink*

 

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Alcester Racing

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Dead/hot-pixel will be obvious - dust ain't a perfect rectangle.

 

Canon will allegedly clean mine once for free - but then I'd have to post my monster to them with all the attendant risks. I think I'll wait until the 'off' season.

 

I'm very wary of letting anyone other than Canon at it while it's still within warranty. Still, at least it's not the 1Ds mk III (22 MP full-frame anyone? By inference, the sensor must cost as much as my 1D mk III alone... *eek*)

 

 

          🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

Alcester Racing

7s Equipe™

🙆🏻 🙆🏻 🙆🏻 🙆🏻 🙆🏻

 

Alcester-Racing-Sevens.com


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It is possible for non weather proof lenses to ingest dust i.e. they have dust size gaps betwixt the moving parts (zoom & focus)

Not quite true... it's also perfectly possible for 'weatherproof' lenses to ingest dust if a zoom. Both my 17-55 2.8 and 70-200 2.8 have a few dust specks in them. C'est la vie... as they say.

 

 

Not a good advert for the anti-dust-vibrate-self-clean-itself thingy on dSLRs, Myles *eek* Personally, I find it's all about equipment management... ie. in 1.5 yrs use I still have had zero dust on sensor issue with my D200. That includes changes on windy beaches, up mountains, etc. I just give oral blow ( *eek* *tongue*) around the mount before lens-changing and always keep the body face-down.

 

[of course... this posting has guaranteed I'll get dust on me sensor now! *rolleyes* *tongue*]

 

 

 

 

 

Edited by - jason liddell on 2 Sep 2007 11:32:42

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Have you tried taking an f/22 pic of a clear sky recently, Jason? *tongue*

Heh heh - not since that last posting *tongue* (Seriously, I have no dust. Careful when changing lenses and occasional Rocket Blower puffs on teh sensor).

 

Boring bit warning... why does the aperture affect the reveal of sensor dust? If the dust is against the sensor then it's on the 'focal plane' of the sensor and focussing/aperture DOF etc aint gonna make any difference. Surely a wide open aperture reduces the chance of lens dust confusing the issue?

 

 

 

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I know you probably have been all losing sleep over my dust dilemma but I can put your minds at rest.

 

The speck was indeed on the sensor and together, with a very nice man in a camera shop, we solved the problme and it is now dust free.

 

Thanks for all those who helped as always it was much appreciated and did indeed stop me from putting my finger in places that would have got me shouted at.

 

However, I am now tempted to buy a doubler instead of thousands on a new big lens...ideas on a postcard

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