Dust question Canon EF 100-400mm f/4.5-5.6 L IS II USM

[Redhead-Husker]

I'm looking to buy a used EF 100-400mm lens. The one I found at a local camera store is in like new condition with one exception. It has quite a few dust spots behind the front lens and on the second lens from the front.  I've been told this won't effect the images, but before I invest $1600 I'd love to know what others might think. The dust spots are very small,  but there are quite a few. Maybe 20 or more. 

Also,  any particular methods to test if they will affect the images?

[normadel · Accepted solution]

Dust and other artifacts (fingerprints, smudges, water spots, even scratches)  on the front, rear or inside of a lens do not show up in images. They are so far from being focused-on that they are invisible. An EXTREME amount can cause loss of contrast, but it'd take a lot. You don't see them in the viewfinder, do you?

You test a lens for problems in this regard by taking picture and looking at them.

[March411]

KEH and MPB have a real good rating system. The gear meets or exceeds the rating displayed for items I have purchased from them and the bonus is the return/exchange policy.

And like John mentioned, that price does seem a bit excessive.

[Redhead-Husker]

To be clear,  this is a version II and other than the dust is in near mint condition. From my research the price isn't my concern, I'm wondering if dust in the objective end of the lens will present issues with the image.

[jrhoffman75]

Just take some test photos. It is rare not to find some dust in a lens. While the general consensus will be that it is unlikely to see an effect only you are actually seeing the lens. 

[Ron888]

That many dust specs cant affect the optical performance much,if at all.If compared to a perfect lens i'd be surprised if it can be measured (see below).
However it will affect resale value so make sure the price is good! (i'm unfamiliar with prices for that model)

DPreview did a video where they tested for dust and also damage to the front element.It's shocking how much damage can be done without it showing in the images! Contrast is first thing to be affected,then resolution.
DPREVIEW damage testing

 

[March411]

Hey Husker,

Historically this lens has had challenges with dust and those who discuss it state that has not cause problems with there images. It's very widely talked about and the conclusion seems no be no impact. If you do a search on EF 100-400mm II you will see what I mean, discussions as far back as 2016.

[Waddizzle]

Over priced.  You could pay half that amount for a dusty Mark II on eBay.

[ebiggs1]

"Over priced.  You could pay half that amount for a dusty Mark II on eBay."

Absolutely, way too much money for that lens probably by double.

"Historically this lens has had challenges with dust and those who discuss it state that has not cause problems with there images."

While this is true but I doubt it is fact.  I've owned two of them if we are speaking the old push-pull zoom(?) All zoom lenses, well they zoom. They move in and out it really doesn't matter if it is a rotating dial or a push-pull the movement is still there. The exception might be the internal zooms.

Excuse me if we are not talking the push-pull model. But the reports and discussions about it are simply not true, IMHO..Unless you know the history and how the lens, any lens, was used and treated, no factual bottom line can be made. It's possible to get dust inside any lens zoom or prime.

But to the OP, pass on this one unless the store comes down by a lot, a whole lot.

[March411]

At it again I see Ernie.

"Historically this lens has had challenges with dust and those who discuss it state that has not cause problems with there images."

"While this is true but I doubt it is fact."

Interesting, I never saw that I used the word fact in the post you quoted, seems like a bit of a misrepresentation.

[Waddizzle]

I believe the OP said it is a Mark II.  Reports and complaints about this model being prone to collecting dust are few.  It uses internal focusing and not the pump action for zooming. 

So a copy that exhibits such issues is a major red flag in my book.