A lot of dust inside the Pentax SMC-M 35mm/2.8 I just bought second hand, what to do?

elena_ · 12-20-2022, 07:29 AM

Hi! I'm not sure if I should post it here or in the general Repair section.

I just bought a Pentax SMC-M 35mm/2.8 lens online from a private seller, second hand. The ad said it was in good state, nothing specified.
I received it and immediately noticed that it has a lot of dust inside the lens, kind of halfway between the front and back lens.
See photo attached; if you zoom in, you'll see all the particles that are more than 10-15 and spread all over the surface.

I read a lot and always read that dust inside the lens doesn't show in the final image, unless you shoot a white wall at f/22, but is it true for a lens that has this amount of dust particles? In the discussions I found, people are talking about 1, 2 particles, not this amount. I also read a lot that "anyway even if you get a clean lens dust will eventually go inside", but I have several lenses from my dad and uncle that have been at home since the 70s and they are perfectly clean inside, as are two other lenses I just bought second hand from other sellers, so I don't feel I should consider this inevitable.

My second question is: even if I won't see the particles, because they are way distant from the area in focus, will the sharpness of the image be affected? I paid 110€ for this lens and chose it after reading a lot of reviews for all the positive feedbacks about its sharpness and image quality, and I bought it to use as primary lens on my Pentax ME super and always take it with me, so I want to be sure it will perform as it should.
I feel I should send it back, but I want to hear some thoughts related to the specific condition of the lens in the attached photo and also consider middle-way options since the seller is open to dialogue (see below) and it's not a lens that is so easy to find (at least in the UE, from what I could see in the past month of Ad monitoring).

EDIT: I add that I can't verify the image quality myself because I only have an analog Pentax and I would have to shoot some photos on a film and have it develop. Also, if particles don't show but the overall image quality/sharpness is affected, I wouldn't be able to tell it because I don't know how this lens should perform. I'd like some "theorical input".

The seller seems very nice. He is selling a few old items and seems honest, although of course he should have checked the lens more thoroughly and mention the condition in the ad. He even told me since it's Christmas time and post service is super busy he will reimburse me the lens and I may even keep it. Now I am honest too and I'm considering these options:.

1) This lens will not perform and having it cleaned at a repair shop is something it's better to avoid > I will take the whole reimbursement and ship it back to him after Christmas, and hopefully find another one to buy around the same price soon.

2) This lens will not perform perfectly, but it's safe to have it cleaned at a repair shop > I will ask him to reimburse the cost of the cleaning service (should be around 50€)

3) This lens will perform perfectly, that amount of dust will not affect the image in any way, not even sharpness and contrast wise > I keep it as is, I don't get it cleaned, I just ask him for a discount given this issue and the fact I will probably won't be able to resell it at the same price, if one day I sell it.

Thank you for any suggestion!

Attached Images

Last edited by elena_; 12-20-2022 at 09:45 AM. Reason: SMC M and not A

**pepperberry farm** · 12-20-2022, 07:32 AM

have you tried/tested the lens yet?

ah - I noticed your edit...

elena_ · 12-20-2022, 07:41 AM - **1 Like**

Originally posted by pepperberry farm

have you tried/tested the lens yet?

ah - I noticed your edit...

Yes, sorry, I added that after posting because I realized that would be the first thing to suggest

**pepperberry farm** · 12-20-2022, 08:15 AM - **1 Like**

Originally posted by elena_

Yes, sorry, I added that after posting because I realized that would be the first thing to suggest

no worries...

it's difficult to see the dust from my phone...

Fogel70 · 12-20-2022, 08:18 AM - **1 Like**

You can even capture usable images with a large crack on a lens element. (but you can see the effect of the crack in the bokeh balls)
Taking Pictures Using a Lens With a Smashed Middle Element | Fstoppers

AfterPentax Mark II · 12-20-2022, 09:04 AM

Are you sure that it is an SMC Pentax-A?

elena_ · 12-20-2022, 09:43 AM - **1 Like**

Originally posted by AfterPentax Mark II

Are you sure that it is an SMC Pentax-A?

M, sorry

I'm editing the title (seems like I can't but I'm editing content of the first post)

Not a Number · 12-20-2022, 10:12 AM - **2 Likes**

I edited the title for you. Normally you should be able to edit the title, though there may be some limitations for members.

Depending on the terms of sales (As-is or not) the seller may be willing to refund some or all the cleaning amount. It really depends on the seller and your negotiation skills.

The closer the dust is to the rear of the camera the more impact it potentially have but most likely it will have negligible or not noticeable effect on the image.

**Just1MoreDave** · 12-20-2022, 10:17 AM - **1 Like**

I know the Pentax-M 35mm f2.8 is prone to having a sticky aperture. A repair shop could clean the dust and make sure the aperture works well in the same visit, so you could rely on it working in the future. I don't think the dust will affect images enough to measure. It will affect resale price a little, if you were going to sell the lens.

elena_ · 12-20-2022, 10:57 AM

Originally posted by Just1MoreDave

I know the Pentax-M 35mm f2.8 is prone to having a sticky aperture. A repair shop could clean the dust and make sure the aperture works well in the same visit, so you could rely on it working in the future. I don't think the dust will affect images enough to measure. It will affect resale price a little, if you were going to sell the lens.

Thank you Not a Number for editing the title and for the suggestion. The seller seems really sad about not noticing the issue and open to any solution I offer, I just want to make something that is hones and also practical for me, as in: if this lens will work perfectly, I have no reason to send it back or have it clean.

Just1MoreDave: Thank you for your reply too! I had read about the sticky aperture and my copy does have that, but if I understood correctly it just slows down the process of closing the curtain, which is not immediate? If so, it won't be a problem for me, since I don't shoot in conditions where I need it to react fast. If it implies other problems I will for sure have it checked for both issues. I thought it was a characteristic of this lens that could not be corrected.

Not a Number · 12-20-2022, 11:10 AM - **1 Like**

It is easy to check for sticky aperture blades. Dismount the lens, stop the aperture ring down, actuate the aperture lever on the back and release it quickly observing the action of the diaphragm. It should close down and open quickly. If it gets stuck or hesitates or is slow to open/close then there is probably oil on the blades and needs cleaning.

**MossyRocks** · 12-20-2022, 11:23 AM - **1 Like**

Depending on the lens (I don't own that one) and where the dust is it may be an easy resolution. I have had some sticky aperture blades on lens and one had a huge piece of dust in it. It was between groups so when I took the mount off to clean the migrated grease I just unscrewed the rear element group and dumped it out. Screwed it back together and put the mount back on and it has worked just fine. If the dust wasn't there or behind the front element group (another one that likely just can be unscrewed out) I probably wouldn't have tried cleaning it as I would have ended up with a pile of glass elements covered in finger prints. If I did manage to get a mess like that back together I would probably put more dust in it than I removed.

**UncleVanya** · 12-20-2022, 11:28 AM - **2 Likes**

Originally posted by elena_

M, sorry

I'm editing the title (seems like I can't but I'm editing content of the first post)

You have to edit in desktop not Mobil and switch to advanced mode in the editor. At that point the title shows up in post number 1. I realize this is already fixed but it may help for future.

Not a Number · 12-20-2022, 01:04 PM

Originally posted by UncleVanya

and switch to advanced mode in the editor

Right, you need to go into the advanced editing mode to edit the title. Only the thread starter or moderator/administrator can edit titles.

**Just1MoreDave** · 12-20-2022, 01:36 PM - **1 Like**

Originally posted by elena_

Just1MoreDave: Thank you for your reply too! I had read about the sticky aperture and my copy does have that, but if I understood correctly it just slows down the process of closing the curtain, which is not immediate? If so, it won't be a problem for me, since I don't shoot in conditions where I need it to react fast. If it implies other problems I will for sure have it checked for both issues. I thought it was a characteristic of this lens that could not be corrected.

I fixed mine so it is correctable. In this lens it is not the blades that stick, it's the mechanism that moves them. I removed that, used solvent to dissolve old lube, added a drop of new lube and put it back together. You probably need to fix that because the camera holds the lens fully open for focusing. Then when you shoot, the aperture closes to your setting before the shutter opens. A slow aperture will not close in time, so you'll get overexposure unless your shutter time is really long.

12-20-2022, 07:29 AM	#1
elena_ New Member Join Date: Dec 2022 Location: North-west of Italy Posts: 11	A lot of dust inside the Pentax SMC-M 35mm/2.8 I just bought second hand, what to do? Hi! I'm not sure if I should post it here or in the general Repair section. I just bought a Pentax SMC-M 35mm/2.8 lens online from a private seller, second hand. The ad said it was in good state, nothing specified. I received it and immediately noticed that it has a lot of dust inside the lens, kind of halfway between the front and back lens. See photo attached; if you zoom in, you'll see all the particles that are more than 10-15 and spread all over the surface. I read a lot and always read that dust inside the lens doesn't show in the final image, unless you shoot a white wall at f/22, but is it true for a lens that has this amount of dust particles? In the discussions I found, people are talking about 1, 2 particles, not this amount. I also read a lot that "anyway even if you get a clean lens dust will eventually go inside", but I have several lenses from my dad and uncle that have been at home since the 70s and they are perfectly clean inside, as are two other lenses I just bought second hand from other sellers, so I don't feel I should consider this inevitable. My second question is: even if I won't see the particles, because they are way distant from the area in focus, will the sharpness of the image be affected? I paid 110€ for this lens and chose it after reading a lot of reviews for all the positive feedbacks about its sharpness and image quality, and I bought it to use as primary lens on my Pentax ME super and always take it with me, so I want to be sure it will perform as it should. I feel I should send it back, but I want to hear some thoughts related to the specific condition of the lens in the attached photo and also consider middle-way options since the seller is open to dialogue (see below) and it's not a lens that is so easy to find (at least in the UE, from what I could see in the past month of Ad monitoring). EDIT: I add that I can't verify the image quality myself because I only have an analog Pentax and I would have to shoot some photos on a film and have it develop. Also, if particles don't show but the overall image quality/sharpness is affected, I wouldn't be able to tell it because I don't know how this lens should perform. I'd like some "theorical input". The seller seems very nice. He is selling a few old items and seems honest, although of course he should have checked the lens more thoroughly and mention the condition in the ad. He even told me since it's Christmas time and post service is super busy he will reimburse me the lens and I may even keep it. Now I am honest too and I'm considering these options:. 1) This lens will not perform and having it cleaned at a repair shop is something it's better to avoid > I will take the whole reimbursement and ship it back to him after Christmas, and hopefully find another one to buy around the same price soon. 2) This lens will not perform perfectly, but it's safe to have it cleaned at a repair shop > I will ask him to reimburse the cost of the cleaning service (should be around 50€) 3) This lens will perform perfectly, that amount of dust will not affect the image in any way, not even sharpness and contrast wise > I keep it as is, I don't get it cleaned, I just ask him for a discount given this issue and the fact I will probably won't be able to resell it at the same price, if one day I sell it. Thank you for any suggestion! Attached Images Last edited by elena_; 12-20-2022 at 09:45 AM. Reason: SMC M and not A

12-20-2022, 10:12 AM - 2 Likes	#8
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	I edited the title for you. Normally you should be able to edit the title, though there may be some limitations for members. Depending on the terms of sales (As-is or not) the seller may be willing to refund some or all the cleaning amount. It really depends on the seller and your negotiation skills. The closer the dust is to the rear of the camera the more impact it potentially have but most likely it will have negligible or not noticeable effect on the image. Last edited by Not a Number; 12-20-2022 at 10:20 AM.

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12-20-2022, 07:32 AM	#2
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,766	have you tried/tested the lens yet? ah - I noticed your edit...

12-20-2022, 07:41 AM - 1 Like	#3
elena_ New Member Join Date: Dec 2022 Location: North-west of Italy Posts: 11 Original Poster	Originally posted by pepperberry farm have you tried/tested the lens yet? ah - I noticed your edit... Yes, sorry, I added that after posting because I realized that would be the first thing to suggest

12-20-2022, 08:15 AM - 1 Like	#4
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,766	Originally posted by elena_ Yes, sorry, I added that after posting because I realized that would be the first thing to suggest no worries... it's difficult to see the dust from my phone...

12-20-2022, 08:18 AM - 1 Like	#5
Fogel70 Pentaxian Join Date: Sep 2009 Location: Stockholm, Sweden Photos: Albums Posts: 3,062	You can even capture usable images with a large crack on a lens element. (but you can see the effect of the crack in the bokeh balls) Taking Pictures Using a Lens With a Smashed Middle Element \| Fstoppers

12-20-2022, 09:04 AM	#6
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Are you sure that it is an SMC Pentax-A?

12-20-2022, 09:43 AM - 1 Like	#7
elena_ New Member Join Date: Dec 2022 Location: North-west of Italy Posts: 11 Original Poster	Originally posted by AfterPentax Mark II Are you sure that it is an SMC Pentax-A? M, sorry I'm editing the title (seems like I can't but I'm editing content of the first post)

12-20-2022, 10:17 AM - 1 Like	#9
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	I know the Pentax-M 35mm f2.8 is prone to having a sticky aperture. A repair shop could clean the dust and make sure the aperture works well in the same visit, so you could rely on it working in the future. I don't think the dust will affect images enough to measure. It will affect resale price a little, if you were going to sell the lens.

12-20-2022, 10:57 AM	#10
elena_ New Member Join Date: Dec 2022 Location: North-west of Italy Posts: 11 Original Poster	Originally posted by Just1MoreDave I know the Pentax-M 35mm f2.8 is prone to having a sticky aperture. A repair shop could clean the dust and make sure the aperture works well in the same visit, so you could rely on it working in the future. I don't think the dust will affect images enough to measure. It will affect resale price a little, if you were going to sell the lens. Thank you Not a Number for editing the title and for the suggestion. The seller seems really sad about not noticing the issue and open to any solution I offer, I just want to make something that is hones and also practical for me, as in: if this lens will work perfectly, I have no reason to send it back or have it clean. Just1MoreDave: Thank you for your reply too! I had read about the sticky aperture and my copy does have that, but if I understood correctly it just slows down the process of closing the curtain, which is not immediate? If so, it won't be a problem for me, since I don't shoot in conditions where I need it to react fast. If it implies other problems I will for sure have it checked for both issues. I thought it was a characteristic of this lens that could not be corrected.

12-20-2022, 11:10 AM - 1 Like	#11
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	It is easy to check for sticky aperture blades. Dismount the lens, stop the aperture ring down, actuate the aperture lever on the back and release it quickly observing the action of the diaphragm. It should close down and open quickly. If it gets stuck or hesitates or is slow to open/close then there is probably oil on the blades and needs cleaning.

12-20-2022, 11:23 AM - 1 Like	#12
MossyRocks Loyal Site Supporter Join Date: Nov 2017 Location: Minnesota Photos: Gallery \| Albums Posts: 2,982	Depending on the lens (I don't own that one) and where the dust is it may be an easy resolution. I have had some sticky aperture blades on lens and one had a huge piece of dust in it. It was between groups so when I took the mount off to clean the migrated grease I just unscrewed the rear element group and dumped it out. Screwed it back together and put the mount back on and it has worked just fine. If the dust wasn't there or behind the front element group (another one that likely just can be unscrewed out) I probably wouldn't have tried cleaning it as I would have ended up with a pile of glass elements covered in finger prints. If I did manage to get a mess like that back together I would probably put more dust in it than I removed.

12-20-2022, 11:28 AM - 2 Likes	#13
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,460	Originally posted by elena_ M, sorry I'm editing the title (seems like I can't but I'm editing content of the first post) You have to edit in desktop not Mobil and switch to advanced mode in the editor. At that point the title shows up in post number 1. I realize this is already fixed but it may help for future.

12-20-2022, 01:04 PM	#14
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Originally posted by UncleVanya and switch to advanced mode in the editor Right, you need to go into the advanced editing mode to edit the title. Only the thread starter or moderator/administrator can edit titles.

12-20-2022, 01:36 PM - 1 Like	#15
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Originally posted by elena_ Just1MoreDave: Thank you for your reply too! I had read about the sticky aperture and my copy does have that, but if I understood correctly it just slows down the process of closing the curtain, which is not immediate? If so, it won't be a problem for me, since I don't shoot in conditions where I need it to react fast. If it implies other problems I will for sure have it checked for both issues. I thought it was a characteristic of this lens that could not be corrected. I fixed mine so it is correctable. In this lens it is not the blades that stick, it's the mechanism that moves them. I removed that, used solvent to dissolve old lube, added a drop of new lube and put it back together. You probably need to fix that because the camera holds the lens fully open for focusing. Then when you shoot, the aperture closes to your setting before the shutter opens. A slow aperture will not close in time, so you'll get overexposure unless your shutter time is really long.