spot on lens

peter.roberts

peter.roberts

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Name
peter
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hi there I purchased this 18-70mm lens of ebay and ive run some test shots and I'm getting what look like sensor dust spots but when I swap back lenses they disappear ive taken a shot of the lens is this possible for lens dust to show in images
 

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No. :D. It's highly unlikely.
It's more likely on the rear element than anywhere in between.
 
I assume you've given both front and rear elements a thorough clean? Can you post samples to see if we can determine what it is?
 
And you've checked the shots from both lenses (yours and this new purchase) are the settings ? As you say the apparent dust spots disappear with the new lens....
 
peter.roberts said:
thanks for reply would you return lens for this issue or just live with it
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I've never had a problem with a lens, yet.
Normally you just clean them. If it is inside, it is unlikely to cause a problem.
If there is a problem it would seem to be caused by something else - maybe :)

I have a lot of lenses, some going back to the 70's. I have more problems with sensor dust than anything else.
 
Looks like sensor needing a clean to me :thinking:
 
Looks like sensor dust.
 
I'm only on the phone but they look very much like dust spots on the sensor to me. Are you sure you're using the same aperture when you're shooting as this image was at f22 and dust spots only tend to show at small apertures. If you shoot at around f5.6 and wider I'd expect these wouldn't show.

Edit just seen you've posted they were both at f22, you posted as I was typing ;)
 
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Yep looks like a dirty sensor to me as well. You shot that at f22 - just the kind of aperture you'd see the dust spots in your photos.
 
Why is one picture bright white and one dark grey? The white one doesn't look like a photo, odd. What are you shooting when checking for the spots?

I would try again and try to get the exposures matched. That second one looks so overexposed it might be masking any spots.
 
Your settings on both images are wildly different - ISO and shutter speeds - you need to take an identical image using identical settings - then you can make a fair comparison.
 
So set the camera on MANUAL - to the settings in the grey shot - then take one photograph with each lens of the same wall.

Don't let the camera change anything.

You want two identical shots - different lenses.

Then we can compare without you being bamboozled :)
 
peter.roberts said:
DSC_0006 by peter.roberts2011, on Flickr
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Regardless of ISO and shutter I'd expect those dust shots to show on this pic.

Two things spring to mind, either something on the rear element or that the other lens isn't stopping down when you take the shot. Have you got another lens to try, and have you cleaned the rear element of the eBay lens?
 
peter.roberts said:
I don't have another lens yet no what do you mean by stopping down
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Stopping down is making the aperture smaller eg going from f5.6 to f8, or f16 to f22. When a lens focuses it does so wide open (largest aperture the lens has) and it is only when the shutter is pressed that the aperture stops down to the aperture you've selected, f22 in this case.

A simple way to check is take a shot of a close up subject (but not filling the frame) at the widest aperture, and then take it at f22 and see if the depth of field changes.
 
Aside from posting random photos on both lenses at different settings - I would sit down - take a breath - and do what I mentioned above. Same settings - same wall - same lighting - same everything. Then compare.
 
cymruchris said:
Aside from posting random photos on both lenses at different settings - I would sit down - take a breath - and do what I mentioned above. Same settings - same wall - same lighting - same everything. Then compare.
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And ensure the other lens is stopping down when it takes the pic ;)
 
peter.roberts said:
(snip) ... but when I swap back lenses they disappear ive taken a shot of the lens is this possible for lens dust to show in images
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peter.roberts said:
I don't have another lens yet no what do you mean by stopping down
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Your OP states that they disappear when you swap lenses? Or did you mean a third lens?

Anyway, academic as problem solved!
 
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OK, this is so confusing. Peter, you need to slow down, take one step at a time, and tell us EXACTLY what you're doing each step. Otherwise nobody can help you.

So far you have posted three pictures which might or might not illustrate these spots.
  • in post #5, the link to image DSC_0001 on Flickr (the grey image): 18-70mm lens @ 70mm, manual exposure, f/22, 1/125th, ISO 2200
  • in post #16, image DSC_0006 (the blue image): 18-55mm lens @ 29mm, aperture priority, f/22, 1/640th, ISO 640
  • in post #21, image DSC_0002 (the white image), 18-55mm lens @ 55mm, manual exposure, f/22, 1/125th, ISO 2500
(The blue image in post #23 is exactly the same image as in post #16.) Your settings are all over the place and you don'y have a uniform blank target, so that makes comparisons very difficult.

Here's what we do at Lenses For Hire when we want to test a camera sensor. Follow these steps exactly and you'll be able to tell whether the problem is with the sensor (as everybody here suspects) or with your lens.
  1. Find a blank, uniformly lit wall to use as your target.
  2. Mount the 18-70mm lens that you want to test.
  3. Set the camera/lens to manual focus, and manually turn the focus ring to infinity. We want the wall to be out of focus.
  4. Set the camera to aperture priority, f/22.
  5. If you know how to, dial in 1 stop of positive exposure compensation. This is not essential but will help give you more contrast on your test shots.
  6. Zoom the lens to its widest setting (18mm), point the camera at the wall and take a shot. Make sure the area of wall in the frame is uniformly lit, no shadows.
  7. Zoom the lens to its longest setting (70mm), point the camera at the wall and take a shot. Make sure the area of wall in the frame is uniformly lit, no shadows.
  8. Mount the 18-55mm lens, or any other lens, and repeat from step 3.
  9. Compare and contrast:
  • Any spots which are in the same place in all pictures are caused by dust or marks on the sensor.
  • Any spots which are only in the pictures taken with one lens, and are in the same place in both pictures, are caused by dust or marks on the rear element of the lens.
  • Any spots which are only in the pictures taken with one lens, but are not in both picture or not in the same place in both pictures, are caused by dust inside the lens.
Please report back when you have some data.
 
thanks for your help guys got hold of a third lens today same spots so it is my sensor and shows my 18-55mm is broken Ive tried cleaning with eyelead gel sensor stick no joy anyone know a good place in uk to get my sensor cleaned
 
Don't know if West Yorkshire Cameras in Leeds would, close to you. :)
 
odd jim said:
It wouldn't stop down during the test.
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??
StewartR said:
  • in post #5, the link to image DSC_0001 on Flickr (the grey image): 18-70mm lens @ 70mm, manual exposure, f/22, 1/125th, ISO 2200
  • in post #16, image DSC_0006 (the blue image): 18-55mm lens @ 29mm, aperture priority, f/22, 1/640th, ISO 640
  • in post #21, image DSC_0002 (the white image), 18-55mm lens @ 55mm, manual exposure, f/22, 1/125th, ISO 2500
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sk66 said:
??
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The camera was set to f22 but the lens did not stop down when the picture was taken. The EXIF registers the aperture the camera was set to.
 
snerkler said:
The camera was set to f22 but the lens did not stop down when the picture was taken. The EXIF registers the aperture the camera was set to.
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Still not seeing it...
The "proper exposure" (blue sky) was f/22, 1/640, 640. The overexposed image was f/22, 1/125, 2500... a bit over 4 stops brighter. It seems to me that it *was* at f/22 for both images and the "issue" was manual vs A/Av.
 
sk66 said:
Still not seeing it...
The "proper exposure" (blue sky) was f/22, 1/640, 640. The overexposed image was f/22, 1/125, 2500... a bit over 4 stops brighter. It seems to me that it *was* at f/22 for both images and the "issue" was manual vs A/Av.
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As I'm sure you know a lens is at its max aperture until the shot is taken, therefore if an f5.6 lens is stuck it will stay at f5.6 rather than stopping down to f22.

To check for this I suggested the OP take a pic of a close up subject (not filling the frame) and take a shot at f5.6 and f22 and see if the DOF changes. He came back saying it doesn't stop down so I assume the DOF didn't change.
 
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