Is it possible for a lens's internal dust to appear in an image?

gatorguy · 01-03-2020, 11:08 AM - **1 Like**

Originally posted by clickclick

Regrading not using walls etc., while perhaps not ideal, it may be the easiest option. I'm in a highly wooded area, and it can be a real pain trying to get the perfect piece of sky. Take multiple shots and see what moves and what doesn't. I've found it pretty easy to figure out what's dust on my sensor versus a blemish on my test background.

With multiple images that would work too.

**DeepThrob** · 01-03-2020, 11:41 AM

I use this, seems to work just fine.

gatorguy · 01-03-2020, 01:09 PM

Originally posted by DeepThrob

I use this, seems to work just fine.

LOL! Perfect. Now if we could only find some way of selling those.

Bertrand3000 · 01-03-2020, 01:22 PM

Regarding dust on lens affecting image, the only way I could see happen would be (much) dust on the rear element. Could you post shot of lens front and rear element please?.

**kiwi_jono** · 01-03-2020, 01:25 PM

Sounds like its pretty much been covered by other posters but my thoughts are:
1. Yes its possible for dust in a lens to show up in an image BUT in most cases its likely the dust is actually on the sensor.
2. The most common scenario to see dust in a lens is in out of focus (bokeh) highlights. Its quite common to see annoying blobs in bokeh balls - often cleaning the front element(s) will help.
3. Its also possible if you have a dusty lens - for dust in the lens mount area to find its way on the sensor. I had a lens (I don't use now) that would end up depositing dust in my camera every time I used it. Something to be aware of if you have a second hand lens been had been left lying without a rear cap on. Blowing out the rear of the lens can help though.
4. When you do test for sensor dust make sure you close down the aperture to something like f22+ and point the lens at uniformly lit subject (ideally deliberately out of focus) such as blue sky.
5. To look for lens dust (once sensor dust eliminated), select fastest aperture and take a very out of focus shot of some highlights (like lights) - how clean do the bokeh balls look?

**Tonytee** · 01-03-2020, 02:59 PM

Okay, I will now post three images. The first image you can see the speck on the jar and some debris in the lower right corner. Please keep in mind that these images were taken after the third

sensor cleaning. The second image will show the same speck in a different position along with the same crap in the lower right corner. The third image was taken with a different lens, the Takumar

F 70~200mm and as you can plainly see, there are no dust issues, so that tells me that the sensor is very clean. The 80~320mm lens has to be the problem. Thnx, Tony

**Tonytee** · 01-03-2020, 03:00 PM

Number 2.

Attached Images

View Picture EXIF

**Tonytee** · 01-03-2020, 03:01 PM

Number 3. Spotless with the Takumar F 70~200mm lens.

---------- Post added 01-03-20 at 03:03 PM ----------

I do have different images available, but the end result is the same. I did shine a flashlight up into the lens from both ends and could locate any dust particles. Thnx again. TT

**PJ1** · 01-03-2020, 03:59 PM

You have made your point very well, Tony. It has to be something on or in the lens. Wherever it is, it hits the sensor as a focused object. Some experimentation is called for. Bear in mind that bottom right on the sensor could be top left on the rear element.

**BigMackCam** · 01-03-2020, 04:02 PM

Originally posted by Tonytee

Okay, I will now post three images. The first image you can see the speck on the jar and some debris in the lower right corner. Please keep in mind that these images were taken after the third

sensor cleaning. The second image will show the same speck in a different position along with the same crap in the lower right corner. The third image was taken with a different lens, the Takumar

F 70~200mm and as you can plainly see, there are no dust issues, so that tells me that the sensor is very clean. The 80~320mm lens has to be the problem. Thnx, Tony

Originally posted by PJ1

You have made your point very well, Tony. It has to be something on or in the lens. Wherever it is, it hits the sensor as a focused object. Some experimentation is called for. Bear in mind that bottom right on the sensor could be top left on the rear element.

The first two shots appear to have been taken at narrow apertures, given the considerable depth of field (the background wall isn't especially blurred). The third shot - the one taken with a different lens, that doesn't show debris - is taken at f/8 according to the EXIF data. At f/8, it's unlikely that very fine debris would show up clearly.

Here's a brief article explaining why dust only shows up at narrow apertures:

https://photographylife.com/why-sensor-dust-is-more-visible-at-small-apertures

From that article, you can surmise why folks shooting fast lenses wide open rarely (if ever) see the effects of dust on their sensors, whilst landscape photographers (for example) - shooting at narrow apertures for maximum depth of field - are much more likely to see dust...

So, to test conclusively, you need to take two photos - one with lens "A", the other with lens "B". Both photos should be taken at the same narrow aperture (such as f/22). If you can see the debris on both of those images, it's on the sensor. My guess is, it's on the sensor - especially in one of the corners, which can be hard to reach when cleaning

If you'd like to post your results again, we can investigate further...

**Tonytee** · 01-03-2020, 04:53 PM

Originally posted by BigMackCam

The first two shots appear to have been taken at narrow apertures, given the considerable depth of field (the background wall isn't especially blurred). The third shot - the one taken with a different lens, that doesn't show debris - is taken at f/8 according to the EXIF data. At f/8, it's unlikely that very fine debris would show up clearly.

Here's a brief article explaining why dust only shows up at narrow apertures:

https://photographylife.com/why-sensor-dust-is-more-visible-at-small-apertures

From that article, you can surmise why folks shooting fast lenses wide open rarely (if ever) see the effects of dust on their sensors, whilst landscape photographers (for example) - shooting at narrow apertures for maximum depth of field - are much more likely to see dust...

So, to test conclusively, you need to take two photos - one with lens "A", the other with lens "B". Both photos should be taken at the same narrow aperture (such as f/22). If you can see the debris on both of those images, it's on the sensor. My guess is, it's on the sensor - especially in one of the corners, which can be hard to reach when cleaning

If you'd like to post your results again, we can investigate further...

Yes, but it plainly evident in the third photo where the speck on the jar is not there. The debris to the right is also not there. However, since you need more proof, I will upload more images taken with higher exposure levels where the debris does in fact appear. Thnks. Tonytee.

**BigMackCam** · 01-03-2020, 05:02 PM - **1 Like**

Originally posted by Tonytee

Yes, but it plainly evident in the third photo where the speck on the jar is not there. The debris to the right is also not there. However, since you need more proof, I will upload more images taken with higher exposure levels where the debris does in fact appear. Thnks. Tonytee.

Hi Tony

It's not that I need more proof... I'm attempting (poorly, perhaps) to explain that any debris on the sensor - anywhere within the image frame, corners or otherwise (and, therefore, including the speck over the jar) - will be clearly visible at a small aperture such as f/22, but much, much less visible (if at all) at a wider aperture such as f/8. As such, for the comparison of images from two different lenses to have any meaning at all in this test, the photos from each need to be taken at the same small aperture (such as f/22). If one or the other is at a different, wider aperture like f/8 (as in your third image), you're not comparing like for like. Both must be taken at the same small aperture to conclusively prove if this is dust on the sensor.

I hope that makes sense, and my apologies if it seems that I'm being difficult... My motive is only to ensure a controlled test that gives you the information you need to conclude whether or not the debris is on your sensor, or in your lens

**Tonytee** · 01-03-2020, 05:21 PM

Man, is my face red. I took several photos with the Takumar F 70~200mm lens and the speck and the debris show up in the images. I'm practically speechless since I cleaned the sensor three

times. Is it possible I may have in some way damaged the sensor while cleaning it ? I will give it another go at cleaning and see what transpires. I will go ahead and upload the images for everyone's scrutiny.

TT

**Tonytee** · 01-03-2020, 05:24 PM

Image #2, same camera body, lens and settings.

TT

swanlefitte · 01-03-2020, 05:41 PM

If the sensor is dirty the whole inside is too. So it is easy to clean the sensor only to knock the dust around the sensor on to it. I clean the box with a brush several times before I work on the sensor.

01-03-2020, 11:41 AM	#17
DeepThrob Site Supporter Join Date: Nov 2012 Location: Taos, New Mexico Posts: 295	I use this, seems to work just fine. Attached Images

01-03-2020, 04:02 PM	#25
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by Tonytee Okay, I will now post three images. The first image you can see the speck on the jar and some debris in the lower right corner. Please keep in mind that these images were taken after the third sensor cleaning. The second image will show the same speck in a different position along with the same crap in the lower right corner. The third image was taken with a different lens, the Takumar F 70~200mm and as you can plainly see, there are no dust issues, so that tells me that the sensor is very clean. The 80~320mm lens has to be the problem. Thnx, Tony Originally posted by PJ1 You have made your point very well, Tony. It has to be something on or in the lens. Wherever it is, it hits the sensor as a focused object. Some experimentation is called for. Bear in mind that bottom right on the sensor could be top left on the rear element. The first two shots appear to have been taken at narrow apertures, given the considerable depth of field (the background wall isn't especially blurred). The third shot - the one taken with a different lens, that doesn't show debris - is taken at f/8 according to the EXIF data. At f/8, it's unlikely that very fine debris would show up clearly. Here's a brief article explaining why dust only shows up at narrow apertures: https://photographylife.com/why-sensor-dust-is-more-visible-at-small-apertures From that article, you can surmise why folks shooting fast lenses wide open rarely (if ever) see the effects of dust on their sensors, whilst landscape photographers (for example) - shooting at narrow apertures for maximum depth of field - are much more likely to see dust... So, to test conclusively, you need to take two photos - one with lens "A", the other with lens "B". Both photos should be taken at the same narrow aperture (such as f/22). If you can see the debris on both of those images, it's on the sensor. My guess is, it's on the sensor - especially in one of the corners, which can be hard to reach when cleaning If you'd like to post your results again, we can investigate further... Last edited by BigMackCam; 01-03-2020 at 04:23 PM.

01-03-2020, 04:53 PM	#26
Tonytee Loyal Site Supporter Join Date: Jul 2012 Photos: Gallery \| Albums Posts: 21,452 Original Poster	Originally posted by BigMackCam The first two shots appear to have been taken at narrow apertures, given the considerable depth of field (the background wall isn't especially blurred). The third shot - the one taken with a different lens, that doesn't show debris - is taken at f/8 according to the EXIF data. At f/8, it's unlikely that very fine debris would show up clearly. Here's a brief article explaining why dust only shows up at narrow apertures: https://photographylife.com/why-sensor-dust-is-more-visible-at-small-apertures From that article, you can surmise why folks shooting fast lenses wide open rarely (if ever) see the effects of dust on their sensors, whilst landscape photographers (for example) - shooting at narrow apertures for maximum depth of field - are much more likely to see dust... So, to test conclusively, you need to take two photos - one with lens "A", the other with lens "B". Both photos should be taken at the same narrow aperture (such as f/22). If you can see the debris on both of those images, it's on the sensor. My guess is, it's on the sensor - especially in one of the corners, which can be hard to reach when cleaning If you'd like to post your results again, we can investigate further... Yes, but it plainly evident in the third photo where the speck on the jar is not there. The debris to the right is also not there. However, since you need more proof, I will upload more images taken with higher exposure levels where the debris does in fact appear. Thnks. Tonytee.

01-03-2020, 05:02 PM - 1 Like	#27
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by Tonytee Yes, but it plainly evident in the third photo where the speck on the jar is not there. The debris to the right is also not there. However, since you need more proof, I will upload more images taken with higher exposure levels where the debris does in fact appear. Thnks. Tonytee. Hi Tony It's not that I need more proof... I'm attempting (poorly, perhaps) to explain that any debris on the sensor - anywhere within the image frame, corners or otherwise (and, therefore, including the speck over the jar) - will be clearly visible at a small aperture such as f/22, but much, much less visible (if at all) at a wider aperture such as f/8. As such, for the comparison of images from two different lenses to have any meaning at all in this test, the photos from each need to be taken at the same small aperture (such as f/22). If one or the other is at a different, wider aperture like f/8 (as in your third image), you're not comparing like for like. Both must be taken at the same small aperture to conclusively prove if this is dust on the sensor. I hope that makes sense, and my apologies if it seems that I'm being difficult... My motive is only to ensure a controlled test that gives you the information you need to conclude whether or not the debris is on your sensor, or in your lens Last edited by BigMackCam; 01-03-2020 at 05:15 PM.

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01-03-2020, 11:08 AM - 1 Like	#16
gatorguy Moderator Join Date: Feb 2015 Location: Central Florida Photos: Gallery Posts: 6,092	Originally posted by clickclick Regrading not using walls etc., while perhaps not ideal, it may be the easiest option. I'm in a highly wooded area, and it can be a real pain trying to get the perfect piece of sky. Take multiple shots and see what moves and what doesn't. I've found it pretty easy to figure out what's dust on my sensor versus a blemish on my test background. With multiple images that would work too.

01-03-2020, 01:09 PM	#18
gatorguy Moderator Join Date: Feb 2015 Location: Central Florida Photos: Gallery Posts: 6,092	Originally posted by DeepThrob I use this, seems to work just fine. LOL! Perfect. Now if we could only find some way of selling those.

01-03-2020, 01:22 PM	#19
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	Regarding dust on lens affecting image, the only way I could see happen would be (much) dust on the rear element. Could you post shot of lens front and rear element please?.

01-03-2020, 01:25 PM	#20
kiwi_jono Loyal Site Supporter Join Date: Dec 2009 Location: Christchurch, New Zealand Photos: Gallery \| Albums Posts: 2,437	Sounds like its pretty much been covered by other posters but my thoughts are: 1. Yes its possible for dust in a lens to show up in an image BUT in most cases its likely the dust is actually on the sensor. 2. The most common scenario to see dust in a lens is in out of focus (bokeh) highlights. Its quite common to see annoying blobs in bokeh balls - often cleaning the front element(s) will help. 3. Its also possible if you have a dusty lens - for dust in the lens mount area to find its way on the sensor. I had a lens (I don't use now) that would end up depositing dust in my camera every time I used it. Something to be aware of if you have a second hand lens been had been left lying without a rear cap on. Blowing out the rear of the lens can help though. 4. When you do test for sensor dust make sure you close down the aperture to something like f22+ and point the lens at uniformly lit subject (ideally deliberately out of focus) such as blue sky. 5. To look for lens dust (once sensor dust eliminated), select fastest aperture and take a very out of focus shot of some highlights (like lights) - how clean do the bokeh balls look?

01-03-2020, 03:59 PM	#24
PJ1 Loyal Site Supporter Join Date: Jul 2012 Location: Toowoomba, Australia Photos: Gallery \| Albums Posts: 5,484	You have made your point very well, Tony. It has to be something on or in the lens. Wherever it is, it hits the sensor as a focused object. Some experimentation is called for. Bear in mind that bottom right on the sensor could be top left on the rear element.

01-03-2020, 05:41 PM	#30
swanlefitte Pentaxian Join Date: May 2015 Location: Minneapolis Photos: Gallery Posts: 4,068	If the sensor is dirty the whole inside is too. So it is easy to clean the sensor only to knock the dust around the sensor on to it. I clean the box with a brush several times before I work on the sensor.