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Dark patches in images: sensor problem?

At the end of today's shoot, I noticed two dark circular marks on an image, one on the top right and the second just above the centre. I did some tests and was concerned to find that the marks appear on every image, regardless of the lens I'm using. They are very noticeable in even toned areas, such as a blue sky, when viewed at 100%. Does anyone know what causes this and how to fix it?
Posted: 1 minute ago
Could be dust on the sensor. Use mirror lockup on your camera, turn it upside down, and use some air to blow the dust out (DO NOT USE CANNED AIR) - use an air rocket or something similar that doesn't propel a liquid.
Posted: 1 minute ago
is it hot pixels?, is blue or red color?

Posted: 1 minute ago
Almost shore is dust particles on sensor. If you don't have experience cleaning the sensor i recommend to find somebody who haze....
100mm f/2.8 USM, Quad core Workstation PC with 8Gb of RAM and Nvidia ...
Posted: 1 minute ago
That is a dust. You can use air blower.
Pentax K-X, Wacom Intuos3
Edited: 1 minute ago
Thanks, eveyone. From what you all say, I think it's dust. I've tried cleaning the sensor using my Canon 40D "clean sensor now" setting, but it hasn't worked. I'm away on holiday at the moment and don't have an air blower with me. I'll try to clean it manually when I get home. Looks like the next few days are an opportunity for me to put my new Canon S95 through its paces as a back-up!
Posted: 06/23/2011, 03:16:33 AM

When I cleaned my sensor the first time I read lot of articles on the Internet on cleaning. Unfortunatelly, I used russian sources, so I can not share with you but for sure you can fild lot of text on the subject in English, as well.

In principle, there is ALWAYS some dust on the sensor (it is not avoidable) and there is no too much harm due to it. It is visible only if aperture is strongly closed (f/16, f/22. ...) and in any case it is easy to remove these spots using PhotoShop tools.
7d + lenses: Canon EF-S 15-85mm/3.5-5.6 IS USM & EF 100mm/2.8 USM Mac...
Posted: 06/23/2011, 03:27:59 AM
Strange, the dust made two rings... It more like lens flare. Did not you shoot directly to sun or close it in last shoots ( it can damage sensor) ?
Posted: 06/23/2011, 03:47:10 AM
@Igor: I've already started researching methods of cleaning - there's loads of info out there. I'll be very careful! Unfortunately the marks are large and visible with the lens wide open.

@Linda81: I've taken several test shots since first noticing the marks, using plain backgrounds, and they appear in the same place each time. I didn't shoot into the sun.
Posted: 06/23/2011, 05:09:15 AM
I had the same problem a few weeks ago with my Nikon D40.

You should do exactly as Wysiwygfoto said.

1. Purchase an air blower at a pharmacy for ~$10

   Blue air blower   

This is meant to be used for cleaning certain body parts.

Make sure you you use it on the camera before. :)

2. Use the mirror lockup of the camera (don't use bulb). Read the manual how to do this.

3. Hold the camera with the sensor facing down.

4. CAREFULLY insert to air blower nozzle into the sensor housing.

Use you fingers to support the nozzle so it won't touch anything!

5. Squeeze the blower a few times.

To check success, take a picture of the blue sky at f22.

If this doesn't work, take it to a shop for a wet cleaning method.

Good luck!

Nikon D90, Nikon D40, Canon S95, Various Nikon Lenses
Edited: 06/23/2011, 07:30:27 AM
My local camera shop has experienced technicians who blow the dust off at no cost--cleaning it on my own gets me nervous. If you live near a camera shop, you might ask.
Currently my primary cameras are a Fuji X-T2 and a Fuji X100F.
Posted: 06/23/2011, 11:05:47 AM
@ Adeliepenguin. Unfortunately, I don't know of a camera shop near me that offers this service. I live in Shropshire in the UK. Does anyone out there know of a shop within 50 miles of Birmingham that does?
Posted: 1 minute ago
@Hugoht: Thanks for the detailed instructions. I've just ordered a Giotto air rocket (good reviews from several photographers on Amazon UK) and will try this out when I get home
Posted: 1 minute ago
Get a hurricane blower. It puts out a lot of air volume without using compressed air. Each time you change your lens, blow out the end of the lens that connects to the camera, as well as the cameras chamber. It also helps to lift up the mirror and blow the area around the sensor (do not touch the sensor just blow it off). This method should only be done in a dust free or low dust environment (not outside with the wind blowing by any means), but preferably inside a room or the interior of your vehicle.

I've used this method for years and have had to have the sensor cleaned professionally very few times. This method was recommended by my local camera shop repair and sensor cleaning guy. Works great.
IS, Canon 17-40mm L, Canon 100mm F/2.8 Macro, and, occassionally, a C...
Posted: 1 minute ago
Thanks, Lightart - a good tip!
Posted: 06/24/2011, 04:02:07 AM
I have a few dark spots too. Thank you for the suggestions and I will by trying out what you've said.
Posted: 1 minute ago