Is this a dirty sensor?

Is this pattern that I see at high image magnification, which looks almost like reticulation, the result of a dirty sensor on the 20D?
This example is a 200% crop with some over sharpening to show the detail. Thanks for your help.

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Best way is to focus to infinity, aim at a blue sky, set at f/22 and shoot while moving the camera in a circle. The only things left in focus at that point is junk on the filter covering the sensor. I don't think you are not going to see sensor dust at F/4.

# Exposure Time (1 / Shutter Speed) = 1/250 second = 0.00400 second
# Lens F-Number/F-Stop = 4/1 = F4.00
# Exposure Program = aperture priority (3)
# ISO Speed Ratings = 400

That doesn't look like dust on the sensor. I'm not sure what it is, but sensor dust would look like irregular shadows in the image.

Mark

Hard to tell. Try this instead:
Take a pic at ISO 100 f/22 or higher of a very evenly lit area. A cloudless blue sky works well. A blank word document on your monitor works well also.
Make the pic as out of focus as you can. If taking the sky, focus near and if taking a monitor, focus to infinity. Introduce some motion blur as well for good measure. You want only stuff on the sensor to be in focus.
In photoshop or image processor of you choosing, bump the contrast and over sharpen. The "Auto Levels" works great in photoshop.
The dust bunnies should pop right out. It should look like this.

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Thanks for your response. I'm aware of looking for dust with the method you describe above. But I'm interested in knowing what this noise-like pattern is that I'm seeing on my images.

What is the original picture, and what are you zoomed on?

Here's the original and a 100% crop. But all my images are showing this pattern.

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Let me correct that to, "my images are showing this lately."

Pinto wrote in post #3385843
Let me correct that to, "my images are showing this lately."

Those are really interesting patterns; have you been doing closeups/macros of plants lately. A lot?

What I see are the three textures (and colours) of the plant as revealed up close by magnification.

I note that there are three different textures - the white, the off-white of interior of the "hood", and the green exterior of the "hood" of the plant.

Do you have a closeup of someone's skin or a smooth painted surface?

Do you have a shot of the clear blue sky with the lens focused at minimum?


EDIT:

The EXIF data indicates that the shot was with your 24/105L lens - and at f/4.

May I suggest that you have a really good copy of this lens - the detail of the surface texture of the plant is really quite good.

It doesn't look to me like there is anything wrong with your sensor - there are three distinct patterns and they are quite visible.

Maybe I'm missing something but the pic looks normal to me. I do see a little digital noise in the photo (normal for ISO 400) but not enough to even worry about IMO.

I don't think I see sensor dust.

Just looks like a combination of noise and sharpening to me! Nothing really wrong there.

Thanks for your responses. I'll post some other examples of images later today. Yes, Glen NK, I do love the 24-105.