Alley in Pisa, Italy

by Lars Kotthoff

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I'm fairly new here and fairly new to photography too. So I'm hoping someone can help me out here. You see, there is this white spot that appears in my photos and I don't know what causes it. It doesn't appear all the time but only sometimes, but when it does appear, it appears roughly on the same area. It's the spot slightly to the left around the middle of the photo. The first photo was taken 2 days after I bought my DSLR. Thanks in advance for the help!

http://farm9.staticflickr.com/8321/8070288693_8eea4b9ac2_z.jpg

http://farm9.staticflickr.com/8461/8070286963_977f5906a3_z.jpg

________

Extra information provided elsewhere by Apathy:

  • I have only one lens at the moment so I can't test it out with another lens.
    I attached that lens to my DSLR since the first day I bought them and have never removed them once. So I'm quite sure that the problem does not lie within the rear of the lens.

  • Upon checking the images, I found that the white spots indeed do appear at smaller apertures of f8 and above.

  • Thirdly, I checked the front part of the lens and found something like a small mark around the middle. So that could be what's causing it. I'm a total beginner at this and I'm scared of damaging my lens if I decide to clean it by myself. So I shall get this cleaned at a photographic shop sometime soon and I'll see what happens.


FOLLOW UP:

thank for all the input you've given me.

Firstly, I have only one lens at the moment so I can't test it out with another lens. And I attached that lens to my DSLR since the first day I bought them and have never removed them once. So I'm quite sure that the problem does not lie within the rear of the lens.

Secondly, upon checking the images, I found that the white spots indeed do appear at smaller apertures of f8 and above.

Thirdly, I checked the front part of the lens and found something like a small mark around the middle. So that could be what's causing it. I'm a total beginner at this and I'm scared of damaging my lens if I decide to clean it by myself. So I shall get this cleaned at a photographic shop sometime soon and I'll see what happens.

Anyway, thank you for the help guys, really appreciate it!

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2  
Do you have a UV or protective filter on your lens? –  mattdm Oct 9 '12 at 11:12
    
Do you get this issue when you change lenses as well? Or is it specific to a lens? –  AJ. Oct 9 '12 at 11:18
    
Now that you have a little bit of reputation on the site, you can post images here using the upload image button when you edit a post. This is advantageous because Stack Exchange has an agreement with an imaging hosting provider so the links will not go dead in the future. –  mattdm Oct 9 '12 at 12:22

3 Answers 3

I don't think this looks like dust or a smudge on the lens. Generally, smudges on the front of the lens will simply result in loss of sharpness and not be clearly defined.

It could very well be flare due to light bouncing off of a UV filter. That's my top guess.

However, I could also be wrong -- the two smudges do appear to be in the same place. What aperture were the two images taken with? Probably the one with the more-defined smudge (prickly-looking dome) is taken with a smaller (higher-numbered) aperture.

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Having the original images available and the EXIF would help, but, it does seem to be a "real" object. Knowing if this is cropped (I'm assuming not) and aperture would help in analysis. Knowing the lens type and settings would be valuable. New or used equipment?

The simplest explanation (which Occam says is the preferred one, even though it may be wrong :-)) is that you have a mark on your lens or filter or an especially severe piece of fungus or similar inside the lens and that how it appears depends on degree of zoom and on aperture. If this explanation was correct I'd expect it to be worse at smaller apertures (larger f numbers) and at longer zooms.
In the two example images I'd expect that the blur on palm tree on roof photo had been shot at a longer focal length (although focus point also affects this. So

Inspect front of lens or filter.
Clean if dirty. Report.

Check lens for fungus or similar. This would be near the front of the lens to do this. Remove lens from camera. Zoom to minimum focal length.
Open aperture iris using lever at camera end of lens.
View towards a bright light (NOT THE SUN) through lens looking in front with light off axis. Move lens around and note that you can see surfaces etc withing lens once you know what to look for. Fungus comes as clumps or fine filaments.

Gross dust can be umped into lenses on occasion but this size would be rare.

The camera will only image objects that are a substantial part of the lenses focal length away from the optical centre of the lens. As they approach the optical centre their image will be increasingly spread across the whole image and will become invisible.

Proof of concept:

Focus point will also affect result.
In a quick test I was able to image a scrap of paper on the lens front element (with lens pointing vertically upwards) at some camera settings and not at others. This provides a proof of concept if not proof of reality of the above as the reason for your problem.


Accessing Facebook photo albums:

The original question pointed to images oin a Facebook page. To provide access to Facebook albums for all viewers, including those without a Facebook account follow the instructions given here

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It seems as though it might be a smush on your lens? The reason you only see it sometimes may be due to focal length excluding it from the image, or focussing straight past it. Alternatively, it might be the camera sensor is dirty.

To identify which it is, I would try taking pictures with a different lens. Does that exhibit the same problem?? If not, it is probably the lens at fault.

I would suggest removing the lens from the camera body, taking care to cover the exposed hole of the camera. Inspect the front glass of the lens carefully in good light. Using a lint-free, microfibre cloth (inexpensive, available in any photographic shop), carefully wipe off any marks using a circular, from middle-to-outer motion, until you are happy the front lens element is clean.

Next, look at the rear of the lens. You should be able to see the rear element. Again try to remove any marks with the lint free cloth. If you can't access it (if it is recessed into the lens body, use a rocket blower to try to dislodge it. Do not force your way into the lens to clean it!!!

If, upon using another lens, the problem remains, you might need to look at your sensor. Most DSLR's have some sort of sensor clean function that you can use to flip up the mirror and open the shutter so you can see the heart of your camera -- the sensor itself. In as clean-an-environment as possible, activate this feature and examine with the help of a small torch, the sensor and clear covering... Try not to spend too long with the shutter open! As much as we are looking for dirt or dust, leaving it exposed too long could attract additional dust to it! If you see any dust or blemishes on the sensor, take it to a local camera shop to be properly cleaned. Although there are products out there for doing this yourself, I would advise against it.

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