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originalgum
4 Feb 2013 - 4:55 AM

On some pictures that I have taken with my Canon, I can see a " ୮ " on the photo after I transfer it over to my computer. It appears in particular in the cloudy, overcast days. I has appeared several times over the last few weeks. Not in every shot, but in a few. If you look in my portfolio picture of the deer in the fog, you can see this obstruction in the right of the frame, mid way up. I have tried to replicate it by using the same settings as the shots it appears in, but it does not show up. Tonight I used a silicon dust cleaner made specifically to clean the image sensor glass, and tried to replicate again. It does not appear, and the sensor looks free of dust. I am hoping that I have been successful in removing what ever had been an obstruction, but I was wondering if someone more experienced than I has some kind of clue as to what this may be... is it anything that I should be concerned about beyond what I have already done...? I appreciate your help. Mike

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brian1208
brian1208 e2 Member 1110369 forum postsbrian1208 vcard United Kingdom12 Constructive Critique Points
4 Feb 2013 - 6:59 AM

looks like sensor much to me, a small fibre at a guess.

Seems to be in the same position in the shot and the fact that you were able to remove it by cleaning would clinch it.

I've never yet had a sensor that didn't need a good clean now and then

lobsterboy
lobsterboy Site Moderator 1014171 forum postslobsterboy vcard United Kingdom13 Constructive Critique Points
4 Feb 2013 - 7:03 AM

That looks like dust on the sensor to me. It would be tiny, so you might not see it by eye and you may not see it at low f numbers.
There are details at the bottom of this page as to how to take a test shot to see if your sensor is clear.

Chris

rogerfry
rogerfry e2 Member 9509 forum postsrogerfry vcard United Kingdom
4 Feb 2013 - 9:44 AM

Definitely dust on the sensor.
I noticed that a lot of your shots are taken at f22, and wondered why you are using such a small aperture. You wind up with 2 disadvantages doing this...firstly, you have very long exposure times, and secondly, you will be suffering from the effects of diffraction. This will occur after about f11 or f16 and your pictures will actually be less sharp than if you used a wider aperture. You might be interested to look at this article.

Focus_Man
Focus_Man  4481 forum posts United Kingdom631 Constructive Critique Points
4 Feb 2013 - 9:51 AM

Without wishing to create an argument, I would say not to worry about diffraction at f11 at all, and very little at f16, but beware at f22 and smaller. I say that because if you use no smaller than f8 and you need to rule out your maximum aperture as well (except for special circumstances as per f22, f32 etc) then with some lenses you will be restricted to f5.6 and f8 only.

So generally beware at maximum and minimum apertures and use what is between.

Last Modified By Focus_Man at 4 Feb 2013 - 9:51 AM
adrian_w
adrian_w e2 Member 73373 forum postsadrian_w vcard Scotland4 Constructive Critique Points
4 Feb 2013 - 5:15 PM

Is this f/22 diffraction thingy a consequence of digital? I only ask because in the days of film I regularly used f/22 or smaller on Olympus lenses without an issue.
Also remembering back to my physics days diffraction only becomes an issue when the aperture is of the same order of magnitude as the wavelength of the light. No way is an f/22 aperture close to that .

Confused of Glasgow.

rogerfry
rogerfry e2 Member 9509 forum postsrogerfry vcard United Kingdom
4 Feb 2013 - 5:28 PM


Quote: Is this f/22 diffraction thingy a consequence of digital? I only ask because in the days of film I regularly used f/22 or smaller on Olympus lenses without an issue.
Also remembering back to my physics days diffraction only becomes an issue when the aperture is of the same order of magnitude as the wavelength of the light. No way is an f/22 aperture close to that .

Confused of Glasgow.

.
Have a look at the article referred to above.

keith selmes
4 Feb 2013 - 6:40 PM


Quote: not to worry about diffraction at f11 at all, and very little at f16, but beware at f22 and smaller.

agreed

originalgum
5 Feb 2013 - 2:02 AM

I want to thank everyone for helping me with this... I did not expect such a big response... thanks! I appreciated the links to the articles, which I have read, and will make application of what was reported on here... thanks again. Mike

originalgum
6 Feb 2013 - 5:56 AM

img-1447.jpg
Hello, everyone... I followed the instructions that appeared in the article that lobsterboy so kindly provided... here is the image I came up with. I understand the dark spots are sensor dust. I am a NEWB... what I would like to know, based on every ones experience with this problem, what level of sensor dust am I experiencing here? Does it warrant sending in to a dealer to be cleaned? I have tried using Dust-Aid silicon sensor cleaner... how do I look here? I really appreciate everyone's opinion... Mike

digicammad
digicammad  1121988 forum posts United Kingdom37 Constructive Critique Points
6 Feb 2013 - 8:42 AM

Looks like a job for an Arctic Monkey to me. I wouldn't send your camera off to a dealer unless you are really ham fisted or your sensor looks like the surface of the moon.

Avoid wet cleaning if at all possible, the Arctic Monkey gets rid of dust spots no problem.

Ian

mikehit
mikehit  56692 forum posts United Kingdom11 Constructive Critique Points
6 Feb 2013 - 9:02 AM


Quote: Looks like a job for an Arctic Monkey to me.

Nah. The guitar strings will scratch the sensor.

User_Removed
6 Feb 2013 - 9:03 AM

What about the group Blur? They could help hide it?

AlexandraSD
6 Feb 2013 - 1:35 PM

Erasure would remove it completely Grin

User_Removed
6 Feb 2013 - 10:25 PM

OriginalGum get one of these so you can see the dust then it's easy to get rid of it with a blower or careful swab.

The one I linked to is a cheap one there are more expensive ones. I wasted loads of money on fancy brushes, swabs and fluids then got one of those and no more dust problems ever.

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