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Old Jul 19, 2009, 7:08 AM   #1
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Default Spots on the lense

Gday

Everyday before I head out for a shoot I clean my lense. I have a small glass cover on it and clean it front and back along with my lense glass. So last weekend I was at go karts shooting away no worries. After taking over 1000 shots I packed up and headed home.

I loaded up my photos and begun looking at what I got. After the first 100 I noticed black spots that seemed to be little dirty spots on the lense. I checked the lense in the light and everything seemed to be fine so I checked my cap which was good. I cleaned my gear and put it away.

So this weekend I went out again to a motorbike event. The racing was fierce and I was taking some cracking shots. During the first race I decided to check my photos on my camera to make sure everything was ok... so far so good. After a while I decided to go somewhere and just clean my lense to make sure everything was ok.

I went back shooting away and didnt touch my lense for the rest of the day. Then this evening when checking over the photos I noticed the following... First few photos before cleaning the lense the photos have the spots on them... after I cleaned the lense they went away for 100 or so shots before coming back again... and then my last 3 shots of the day CRYSTAL CLEAR PERFECT SHOTS...

SO I ask myself WHAT IS GOING ON?

Can anyone help?

My gear is clean and I just got no idea whats going on!
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Old Jul 19, 2009, 8:06 AM   #2
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My guess would be a dirty sensor. Make an exposure of the clear sky and change the lens and shoot another. If you find the culprit in the same place on both it will be due to dirt or dust on the sensor or mirror. Cleaning of both has been covered many times and you'll find it here through the search. Seldom does dirt on a lens show up on photos. One reason you may not have noticed the spot after cleaning could have been the stop you were using. Dust on a sensor is more noticeable the furthur you stop down.
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Old Jul 19, 2009, 8:20 AM   #3
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Ive done that as well still no improvement. The spots are there unless Im at full extension (300mm) where they can be slightly seen

See below of 2 different photos. First is the spots and second is the last shot of the day.


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Old Jul 19, 2009, 12:45 PM   #4
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You are almost certainly seeing dust on the sensor.

Spots on your lens surface emphatically do not make your pictures look like that. In fact you can't see them at all, they only affect the overall sharpness and contrast.

If you don't believe me check out this link:

http://www.lensrentals.com/news/2008...ment-scratches

You may not realise that the aperture you are shooting at plays a very big role in whether you can see sensor dust or not. At wide apertures it's mostly invisible, it is only visible at small apertures.

To do a check set your lens to f22 and shoot a well-exposed shot at a white wall. Then open up your lens as far as it will go and shoot the wall. Chances are you will not see the dust spots at the wider apertures, or they will be much less noticable.

You may need to wet-clean your sensor. Do not do this without knowing what you are doing and with the right equipment as you can destroy your camera.
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Old Jul 24, 2009, 12:41 AM   #5
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If have a second lens, you can repeat the test shots and compare. If the dirt are in the same spot, then it is most likely you have dust on your sensor.
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Old Jul 24, 2009, 7:51 AM   #6
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That first shot was at f/25 according to the EXIF information I see for it in your album:

http://www.flickr.com/photos/3007259...34423361/meta/

Trying to stop down the aperture that much is going to make any dust on your sensor visible, as Tomsch and peripatetic mentioned. It looks like your other shot was probably at f/10 (which is why you don't see the issue).

Note that if you stop down the aperture that much, you're also going to get softer images from diffraction (as well as some degradation of image quality from using ISO 800). See this page for more information on how diffraction plays a role in image sharpness.

http://www.cambridgeincolour.com/tut...hotography.htm

I can understand that you wanted to keep shutter speeds slower to highlight the sense of motion when panning, versus freezing the subject, wheels and background. But, you may want to consider using lower ISO speeds versus stopping down the aperture down that far.
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Old Jul 24, 2009, 7:57 AM   #7
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Upon closer examination, I see you were using Shutter Priority to keep the shutter speed at 1/200.

The problem is that the camera had no choice but to stop down the aperture to f/25 to prevent overexposure since you had it set to ISO 800. IOW, you may want to keep an eye on the aperture the camera is selecting, and lower your ISO speed when needed so that it doesn't need to stop it down that far.
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Old Jul 27, 2009, 8:17 AM   #8
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Thanks for your comments guys.

I sent the camera in for a clean today (went on holidays so had no time before i left) so Ill check it out this weekend.

Thanks for your advise on shutter speeds etc Jim. I plan to work towards more keepers this weekend at set my shutter speed at 1/1000 and adjust my ISO up to 1600 (using a 20D). The motion shots were good and look good but due to my lense and body the shots just aint good enough.
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