Dark speck in image

M

madaload

New member
Hi, I'm having a strange problem with my Nikon D7100.

There is a dark speck near the centre of the image. I've cleaned the mirror and the sensor, but the speck remains.

I have three different lenses and the speck shows in the exact same spot with all of them, so it's definitely not a lens problem. Also, when I take a picture without a lens attached, there is no speck.

Does anyone know what may be causing this?
 
BackdoorArts

BackdoorArts

Senior Member
Need to see an image or two. Could be a dead pixel. Could be dirt. Have you used a loupe or magnifier to really look at the sensor? Either way, post a couple images.
 
M

madaload

New member
Hello,

Sorry for the delay and thank you for your replies.

I'll try to attach some images. The spec is actually most prominent at smallest aperture, so it seems the mirror or the sensor are still dirty. At F3.5 you can barely see it and it's larger, while at F22 it's small and very visible along with a few other specs. I'll have to do a better cleaning job I suppose.

UPDATE:
I've been trying to upload three sample images to my gallery without success. They seem to upload fine, but afterwards the gallery is empty. I'll just clean the mirror again. Thanks for everyones help.
 
Last edited:
Bob Blaylock

Bob Blaylock

Senior Member
madaload said:
Hello,

Sorry for the delay and thank you for your replies.

I'll try to attach some images. The spec is actually most prominent at smallest aperture, so it seems the mirror or the sensor are still dirty. At F3.5 you can barely see it and it's larger, while at F22 it's small and very visible along with a few other specs. I'll have to do a better cleaning job I suppose.

UPDATE:
I've been trying to upload three sample images to my gallery without success. They seem to upload fine, but afterwards the gallery is empty. I'll just clean the mirror again. Thanks for everyones [sic] help.
Click to expand...

It's on your sensor. If it was on your mirror, then you would see it in the viewfinder, but it would not show up in the images. And yes, contamination on the sensor shows up better, the smaller the aperture you use.
 
B

Bill16

Senior Member
The forum is not uploading right for a several of us at least. You can only upload one photo each time or they don't show up.

The other method that works, is to upload them as attachments. :)

madaload said:
Hello,

Sorry for the delay and thank you for your replies.

I'll try to attach some images. The spec is actually most prominent at smallest aperture, so it seems the mirror or the sensor are still dirty. At F3.5 you can barely see it and it's larger, while at F22 it's small and very visible along with a few other specs. I'll have to do a better cleaning job I suppose.

UPDATE:
I've been trying to upload three sample images to my gallery without success. They seem to upload fine, but afterwards the gallery is empty. I'll just clean the mirror again. Thanks for everyones help.
Click to expand...
 
M

madaload

New member
Blacktop said:
Would be interesting to know how you did that.
Click to expand...

I used a new lint-free lens cloth from my optician. Wrapped it around the tip of a cotton bud stick and dipped it in LCD cleaning solution for the first pass. Then used a dry one for the second pass. NASA couldn't have cleaned it better and safer.

I only gently touched the sensor to wipe off the dust, but it had no effect. I also used compressed air, but that didn't change anything either. I am a bit afraid to properly rub the sensor. It doesn't seem to have a smooth surface. It has kind of a fingerprint texture to it, only much finer.

Attempting to attach sample images again (f/3.5, f/11, f/22):
F3.5.jpgF11.jpgF22.jpg
 
4

480sparky

Senior Member
Get yourself a proper sensor cleaning kit and stop risking damage to your sensor by being cheap and attempting home-grown solutions.

A good, commerically-available cleaning kit will take care of your sensor dust bunnies.
 
Bob Blaylock

Bob Blaylock

Senior Member
madaload said:
I've cleaned the mirror and the sensor, but the speck remains.

I have three different lenses and the speck shows in the exact same spot with all of them, so it's definitely not a lens problem. Also, when I take a picture without a lens attached, there is no speck.

Does anyone know what may be causing this?
Click to expand...

Blacktop said:
Would be interesting to know how you did that.
Click to expand...

madaload said:
I used a new lint-free lens cloth from my optician. Wrapped it around the tip of a cotton bud stick and dipped it in LCD cleaning solution for the first pass. Then used a dry one for the second pass. NASA couldn't have cleaned it better and safer.
Click to expand...

It's not on the mirror. The mirror only affects the view through your viewfinder, and not what actually gets recorded as an image. When you take a picture, the mirror flips up out of the way, allowing light from the lens to get directly to the sensor. Your mirror could be so filthy or so damaged that you can't even see through the viewfinder, and it still wouldn't affect the picture that gets recorded.

By the way, you do understand that this is a first-surface mirror, and that first-surface mirrors are very delicate, right?


madaload said:
I only gently touched the sensor to wipe off the dust, but it had no effect. I also used compressed air, but that didn't change anything either. I am a bit afraid to properly rub the sensor. It doesn't seem to have a smooth surface. It has kind of a fingerprint texture to it, only much finer.

Attempting to attach sample images again (f/3.5, f/11, f/22):
…View attachment 111770
Click to expand...

Yes, you've definitely got some dirt on your sensor. If compressed air doesn't do the trick, the next thing to try is this brush; buy it, read the instructions carefully, and follow them. If that doesn't do it, then you need to get a wet-cleaning kit, such as this one.

It is one of the unfortunate facts of life about DSLRs (probably equally with MILC/EVIL cameras as well) that dirt does eventually get on the sensor, and you need to know how to clean it and be equipped to do so.
 
M

madaload

New member
480sparky said:
Get yourself a proper sensor cleaning kit and stop risking damage to your sensor by being cheap and attempting home-grown solutions.

A good, commerically-available cleaning kit will take care of your sensor dust bunnies.
Click to expand...

Thanks for inspiring my new signature, lol
 
L

Lawrence

Senior Member
Definitely sensor spots. I know because I had this exact same issue a couple of weeks ago.
I got myself a sensor cleaning kit and watched lots of videos before attempting to clean the sensor.
Compressed air is a risky method (according to what I read and watched) so don't do it.
Mine was so bad I had to traverse the sensor three times but in the end it is spotless and I am nows much more aware of holding my camera opening down when changing lenses.
Prevention is better than cure.
 
Bob Blaylock

Bob Blaylock

Senior Member
madaload said:
Attempting to attach sample images again…
Click to expand...

By the way, here's how best to take an image that will show up the dust on your sensor…

  1. You've got the 18-55mm “kit lens” that is standard with this camera, right? Mount that lens.
  2. Set the autofucuts switch on the lens to “M”, and manually focus it to infinity
  3. Set the zoom to its longest focal length, 55mm.
  4. Set your camera to aperture-priority mode.
  5. Set the aperture to its largest number (smallest aperture) which will be ƒ36 with this lens.
  6. Set your camera's ISO setting to its lowest value.
  7. Bring up a browser or some other application on your computer's screen with a blank page/document, so that you just have a big expanse of plain white on your screen.
  8. Holding the camera an inch or two away from the screen, take a picture. Move the camera around a bit during the several seconds of the exposure.

The idea here is to not really take a picture of anything outside of the camera, but to evenly and narrowly illuminate the sensor, record what the sensor is seeing. The point of using the smallest possible aperture is to provide the narrowest possible light source. A narrower light source makes for sharper shadows, which is why, in the pictures you've taken so far, the dirt shows up more prominently the smaller the aperture you use.

If your sensor was perfectly clean, and perfectly free of any noise, any unevenness, or any other possible imperfections, then you would just get a picture that contained nothing but the same uniform solid shade of grey. Nobody's sensor is that perfect. If there is any dust, dirt, or foreign material on your sensor, then that is what will show up most prominently.
 
M

madaload

New member
photogramps said:
Doesn't sound to me like you are cleaning the sensor at all ... sounds like you are cleaning the focusing screen!
Click to expand...


Spot on, mate! Lifted the mirror (via camera menu), used compressed air and the speck is gone.

Now I know a little more about how my camera works. Turns out the sensor is hidden behind a plastic shutter that's shut by default when you lift the mirror manually. I didn't expect that, so I assumed the sensor was above the mirror. Silly me.

BTW, the video keeps cutting off for me with the message "An error occurred..."

This thread can be closed. Home-grown solutions do work and pay off!
 
M

madaload

New member
Thanks Bob, I understand how optics work (not so much how the mechanics inside my camera do).

I just wanted to show the big nasty speck near the center in those pictures. Now that you've pointed me to the proper cleaning gear and photogramps told me I was cleaning the wrong thing, I can take it from here.

Thank you guys and have a good night, unless you're in Sacramento, in which case have a nice day. At a sunny 29°C there's no other choice ;)
 
Bob Blaylock

Bob Blaylock

Senior Member
madaload said:
Spot on, mate! Lifted the mirror (via camera menu), used compressed air and the speck is gone.

Now I know a little more about how my camera works. Turns out the sensor is hidden behind a plastic shutter that's shut by default when you lift the mirror manually. I didn't expect that, so I assumed the sensor was above the mirror. Silly me.
Click to expand...

It would definitely be to your advantage to gain at least a basic understanding of the mechanics and operation of an SLR. If you can get your hands on an old, film-based SLR—the older and simpler the better, and spend some time playing around with it, you'll surely get a much better understanding of how the thing works.


madaload said:
Thanks Bob, I understand how optics work (not so much how the mechanics inside my camera do).

I just wanted to show the big nasty speck near the center in those pictures. Now that you've pointed me to the proper cleaning gear and photogramps told me I was cleaning the wrong thing, I can take it from here.

Thank you guys and have a good night, unless you're in Sacramento, in which case have a nice day. At a sunny 29°C there's no other choice ;)
Click to expand...

Yes, Sacramento is where I am.
 
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