Help!! need investigation

Hi ,everyone

I have a problem with my second hand SD14.
As you see in the picture
the first shot use f 9.0 there are blur spot around the picture

the second shot use f 32 there are very sharp spot around picture too,at the same
position as the first one.
i don't sure is it about sensor or lens or etc.
both are blur picture but spots are sharp and still.
really have no idea.
if anyone know what is it and how to fix ,please
i need your help
thanks a lot

It looks like sensor dust to me, the thing to do would be to get a really complete cleaning.

You can do a search here for "sensor cleaning" for more details. I like the Visible Dust cleaning products, the sensor swab is nice because it makes wet cleaning (which you probably need) easier to get right. But others work just as well, it's just a matter of finding a system that you are comfortable with.

If you're really not comfortable with cleaning the sensor yourself, you could send the camera to Sigma for a cleaning. There may also be local stores willing to do the cleaning but they might not be familiar with how to replace the dust protector, so you'd want to at least learn how to do that to show them (it's a bit delicate).

--
---> Kendall
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These spots are certainly dust on the sensor !!

How to clean your sensor :

1 Insert a FULLY charged battery .. be 100 % sure it will last as long as it takes you to clean the sensor

2 Remove the lens and the dust protector

3 follow instructions in the manual to raise the mirror.

4 use a piece of Pec-Pad lens paper or similar, wrapped around a suitable rubber or soft plastic spatula... add one drop of EXLIPSE or similar PURE alcohol.

5 wipe the sensor ONCE with the paper.. take another piece and wipe it clean.
Never use the same surface more than once.

6 mount the dust-protector and lens ..take a few test-shots at a small aperture.

7 if there are still dust-spots .. repeat all the above untill its completely gone.

Well ... its much easier to do it, than to write how to do it
Good Luck
--
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Hi and
thank you very much

in fact i used to send it to local store once,they have free cleaning service.
and it get better (before that is terrible)
maybe it's time to do it myself.

thanks very much for the suggestion again

Just one more thing to remember - installing dust/IR filter must be done carefully, without force, without touching filter glass and without any bending of filter.

--
Arvo
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FritsThomsen said:

These spots are certainly dust on the sensor !!

Click to expand...

They certainly are and you will have noticed that they becaome more visible the more you stop down the lens aperture...By using fast lenses at wide apertures you wont even see them when pixel peeping. In any case, you should'nt need to stop down to more than f5.6 with the SD14 to get a deep enough depth of field for most shots unless your taking macro shots, so stay at f5.6 or wider and your dustpots will cease to be a problem, and the quality of your photos will be better too as most lenses peak in sharpness between f4-f5.6.

FritsThomsen said:

How to clean your sensor :

1 Insert a FULLY charged battery .. be 100 % sure it will last as long as it takes you to clean the sensor

2 Remove the lens and the dust protector

3 follow instructions in the manual to raise the mirror.

4 use a piece of Pec-Pad lens paper or similar, wrapped around a suitable rubber or soft plastic spatula... add one drop of EXLIPSE or similar PURE alcohol.

5 wipe the sensor ONCE with the paper.. take another piece and wipe it clean.
Never use the same surface more than once.

6 mount the dust-protector and lens ..take a few test-shots at a small aperture.

7 if there are still dust-spots .. repeat all the above untill its completely gone.

Well ... its much easier to do it, than to write how to do it
Good Luck

Click to expand...

Or you could simply just dry-brush the dust off the sensor with a soft lens brush, whilst holding the end of a vacuum cleaner hose near the mount to suck out the displaced dust. Wet cleaning is a difficult process to get right...get it wrong and you could leave water marks on the sensor which can be visible in your images, or worse still permanent scratches on your sensor as the liquid can trap tiny abrasive particles which are then dragged across the sensor as you try to clean it. Dry brushing is much easier, safer and much cheaper to do too because lens brushes cost a lot less than a wet cleaning kit.
Heres one type of lensbrush that is suitable for the job:

http://i.ebayimg.com/01/ !B-!B7rQ!mk~$(KGrHqV,!icEzN7Zi)eTBM7YYso15! 12.JPG

You can remove the brush from the "puffer" and use the brush on its own.

This is something I don't understand : how can changing the aperture - in the lens - have an impact on how the sensor records dust - on its surface ?

It would make more sense if it is dust in the lens that comes into focus because of the using large f-stops.

best regards ... jef

JefDeC said:

This is something I don't understand : how can changing the aperture - in the lens - have an impact on how the sensor records dust - on its surface ?

Click to expand...

Because DOF increases the more you stop down, bringing stuff close to the sensor that is normally OOF into focus. At f16 dustpots are sharp looking black blobs, which can be any shape depending on the shape of the dust particles themselves but at f4 they can be OOF enough to not be noticable most of the time (This is subject dependant though...Taking a picture of a white painted wall or the sky may make them noticable.)

--
DSG
--



--
http://sigmasd10.fotopic.net/

Because the dust isn't on the sensor itself but on the cover glass.

As such it's a slight distance away from the sensor, and if you can imagine the difference in light coming from a tight angle as with a small aperture as opposed to a wide angle, as with the lens fully open, you will see why the smaller aperture causes a smaller but more sharply defined shadow.

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Thanks,
Gary.

Gary,

I agree totaly with your expanation, this afternoon I was pondering the question and made the following 2 rudimentary - not to scale - pictures to illustrate the issue.

First with a small blob on the sensor - blob size a few pixels max.





This is how I believe the phenomenon occurs.

IMO It is not like to often quoted 'because of the bigger DOF' as that would effectively mean that the DOF would extend behind the lens itself.

A big blob - covering many pixel - will be visible regardless of the f-stop :





Open for discussion off course ...

best regards ... jef

ps. for those who would like to ponder further don't forget that there is always a plane in focus on the sensor except when the focus is further than the infinity mark.

gbainbridge said:

Because the dust isn't on the sensor itself but on the cover glass.

As such it's a slight distance away from the sensor, and if you can imagine the difference in light coming from a tight angle as with a small aperture as opposed to a wide angle, as with the lens fully open, you will see why the smaller aperture causes a smaller but more sharply defined shadow.

--
Thanks,
Gary.

Click to expand...

Thanks to everyone
already took it for cleaning
and the result is very goood
(still have some but very little dot)
thanks again

... an internal vacuum of the camera interior.

I use a small vacuum cleaner and have (made it) a bung in the end of the flexible tubing, through the middle of which is the body of a cheap ballpoint pen (i.e. has central small diameter hole) and I marked the casing to indicate when almost touching the sensor surface (thus cannot touch it in use).

Use this to vacuum around inside the mirror chamber (being careful to not touch the surfaces of the mirror or focus screen), then follow the Sigma instructions for setting the camera open (mirror up & shutter open) for cleaning and then vacuuming around the inside. That is the only way to really ensure no dust remains to re-deposit itself again on the sensor surface.

It takes less time to do than to write about. One tip is to have the vacuum cleaner outside the room, so any dust passing through does not enter the room, as the hose can come through the slightly open doorway.

Otherwise, plenty of advice around for actual cleaning.

--
Zone8

The photograph isolates and perpetuates a moment of time: an important and revealing moment, or an unimportant and meaningless one, depending upon the photographer's understanding of his subject and mastery of his process. -Edward Weston
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