What would you consider an "acceptable" dust partical count in your new lens?

As the title states. You spend 1,2, maybe 3 grand on a lens. You see dust particles behind the front element. You count 1..2..3.. what number do you get up to before you decide to send it for exchange or repair? I know some of you will say, "Well, if you don't see it on final result.." That statement aside, this ain't a cheap hobby or career for that matter.

Zero

For me the test would be: "do the dust particles affect image quality?"

When someone looked at one of Carl Zeiss's lens and noted a tiny air bubble in one of the elements he reportedly replied, "My lenses are made to be looked through not at"

Isn't it funny that people say dust in a lens will not affect IQ, but dust on the sensor does? I always found that amusing.

Anyway... How much dust do I consider an acceptable amount to be in my lens?

If I spent...

$1k- some...maybe 15-20 specks. (not that much, really)

$2k- better be none.

$3k+ - You can go RIGHT to hell if you think I'm gonna put up with dust in my weathersealed lens.

Glenn NK wrote in post #3218856
For me the test would be: "do the dust particles affect image quality?"

When someone looked at one of Carl Zeiss's lens and noted a tiny air bubble in one of the elements he reportedly replied, "My lenses are made to be looked through not at"

Couldn't/wouldn't air bubbles in one of the elments directly impact flare resistance, though?

Glenn NK wrote in post #3218856
For me the test would be: "do the dust particles affect image quality?"

When someone looked at one of Carl Zeiss's lens and noted a tiny air bubble in one of the elements he reportedly replied, "My lenses are made to be looked through not at"

But on a new lens ? I think zero on a new one. After some use, I would agree.

Arguably, there isn't a 'threshold' limit on dust particle count. Furthermore, as I age, my eyesight is going to deteriorate and I'm going to see less dust in any lens.

When I still used to buy brand-new lenses in the past, it was common to get lenses in absolutely pristine condition, with just one or two specks of dust out of the box. With a blower I'd easily remove them as well since they were invariably on the front element.

Now I've begun to buy used and it's normal to see a good amount of dust in a lens...twenty-odd specks maybe? I'm sure it'll affect IQ to some degree, but I've got too many things to worry about to care about a bit of atmospheric dust. Size matters also of course. If it's a mighty big piece of felt then it means much more to me.

Ronald S. Jr. wrote in post #3218980
Isn't it funny that people say dust in a lens will not affect IQ, but dust on the sensor does? I always found that amusing.

It might in fact be true (if my reasoning is correct):

Suppose you take a picture of a white dot on a black background. Light rays from the dot not only travel parallel to each other, they travel from the dot in all directions (if they didn't then standing at a 45 degree angle from the lens axis, one wouldn't see the dot). Some light rays hit the centre of the lens, some hit the edges, etc. The ones that encounter the dust or hair particle may not get through, but all the others do. Result - the dot is rendered quite visibly.

On the other hand, the dust spot or hair on the sensor is immediately in front of the pixels - light has been focused by the lens and for the dot, the light rays hit only one tiny spot (the same size as the dot for a 1:1 macro). If the dust or hair particle is right where the dot is supposed to be, the light rays are disrupted and one gets the image of the dust or hair, superimposed on the dot.

Dust on the sensor is far more serious than dust on a lens.

I tried it by mistake myself a few days ago - something got onto my UV filter - and it was really ugly - worse than a hair. I had taken a few pics when I noticed it. Looking back at the images on the screen, I couldn't tell which ones were taken with the spot on the filter.

The same spot on the sensor would have been a disaster - in fact spots on the sensor that can hardly be seen with the naked eye can be quite problematic at f/16 or f/22.

I think Carl Zeiss was correct - small imperfections in a lens (such as a dust particle) aren't terribly troublesome.

Oh man ... I better go check ... this is something else to get paraniod about. If 15-20 is Ok for Ronald then maybe I better hope for just 10-15. But what if there's 16? Now I can't sleep. I can't shoot ... what if I get flare through that 16th spec and spoil my shot? Man ... help me????!!!!!!

Personally, I really don't care unless it affects my prints or it affects how the camera functions. I bought my gear to make photos, so that is my primary concern.

I do definitely understand that it can be a bit irritating to have dust on the lens but some lenses like the 100-400 do suck in air and dust and it is an inevitable part of life. If it's a sealed lens like the 70-200mmf2.8, then you may consider sending it back and getting another one though.

But having said all that, I don't worry about dust on elements b/c 99.9% don't affect the photos I make.

Good luck

condyk wrote in post #3219310
Oh man ... I better go check ... this is something else to get paraniod about. If 15-20 is Ok for Ronald then maybe I better hope for just 10-15. But what if there's 16? Now I can't sleep. I can't shoot ... what if I get flare through that 16th spec and spoil my shot? Man ... help me????!!!!!!

Do I detect a very small amount of sacasm in your post Dave?

(I only have 13 so I'm sleeping tonight)

Ronald S. Jr. wrote in post #3218980
Isn't it funny that people say dust in a lens will not affect IQ, but dust on the sensor does? I always found that amusing.

maybe i am slow (well, not maybe) but i don't get how is that funny? i have some visible dust in one of my lenses and it never showed in any of the images but every time i have dust on my sensor, i have to clone crap out and clean my sensor. maybe if you explain the joke to me i will be able to join in on the fun

Glenn NK wrote in post #3219232
It might in fact be true (if my reasoning is correct):

Bingo. A dust particle will go unnoticed inside the lens, or on a lens surface. Its real easy to test. Take an old filter and put some dust on it, and go shoot. Then take the filter off, and shoot some more. You won't be able to tell which had the dust, and which didn't. The only time dust particles become an issue is where there is a huge amount.

Technically, I don't know exactly why, but its the same reason you can take a couple pieces of thread and dangle them in front of the lens and barely see it in the image, if at all.

Would I return it, yes. Its not about the existing flakes, but how or why they are there in the first place. Is it the inside paint failing, wasn't assembled properly (assembled in a clean room they should be dust free), was something dislodged, and so on? I'd worry about finding even more as time goes on and the lens gets knocked around and used more. If you get more and more, eventually it will cause problems.

blonde wrote in post #3222435
maybe i am slow (well, not maybe) but i don't get how is that funny? i have some visible dust in one of my lenses and it never showed in any of the images but every time i have dust on my sensor, i have to clone crap out and clean my sensor. maybe if you explain the joke to me i will be able to join in on the fun

I just meant funny, odd, queer, etc. I just kind of assume that if dust on the sensor is visible at even f/8, then it seems like dust in the lens would have an impact at one aperture or another.

kevin_c wrote in post #3222320
Do I detect a very small amount of sacasm in your post Dave? (I only have 13 so I'm sleeping tonight)

I have a t-shirt that says 'fluent in sarcasm' ... so I think you may be correct. I also have one that says 'chaos, panic, disorder ... my work here is done'.