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