lawny13
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Veteran Member
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Posts: 3,132
Re: That tried and true "air pump" design
ZX11 wrote:
ThePointblank wrote:
ZX11 wrote:
ThePointblank wrote:
ZX11 wrote:
RDKirk wrote:
ZX11 wrote:
I don't like the air pump design of the new RF 70-200 and its far higher price for the same image quality. To me, the EF 70-200 on the EOS R is a better choice. To each their own.
Interestingly, nobody seems to be reporting problems with the "air pump" design for the 24-70 or the 24-105...and it hasn't been a problem for decades. It appears to be a design Canon perfected a long time ago.
After reading Roger Cicala's disassembly report on the RF 70-200, I have no reason to doubt its solid mechanical prowess.
https://www.lensrentals.com/blog/2019/12/the-not-very-long-awaited-teardown-of-the-canon-rf-70-200mm-f2-8-is/
I have seen the video on youtube.
Hasn't been a problem for decades? The EF-S 17-55 f/2.8 does have a problem with dust getting in it due to the huge volume of air it pumps in and out as it zooms. It is not a decades old design. Similar dust with the EF 24-105.
No other air pump lenses get dust in them? Seems there are plenty of youtube videos about getting dust back out of Canon's air pumps.
I do not have to like the RF's air pump design just because it is the newest greatest hip thing. I do not think Canon was mistaken when they designed the all internal design on the EF 70-200 f2.8 and the EF 70-200 f/4.
I don't like fiddling with the lock on the RF 24-105 that is necessary for its air pump design. Do I have to like it too? I don't like the extra rotation range the RF 70-200's zoom ring has. The extra rotation needed to move the RF 70-200's large front element, entire barrel, hood, and the kitchen sink, forward and back.
I like the non-pumping, non-moving inner barrel, and thinner design of the EF 70-200. The EF is solid, sealed, and proven reliable. My choice. To each their own.
Read what Roger Cicala says in the comments:
OK, I'm not commenting on 'will it resolve' because I'll go on a 20 minute rant. Of course it will resolve.
Biggest dusters: 85 f1.2, 105mm f1.4s, 70-200 f/2.8s, 150-600s are fast horses. The biggest variable to 'how dusty is it' is probably 'how much do the front and rear elements magnify it'.
To be fair, in olden times some extending barrel zooms (Canon 100-400 old version, Sigma Bigma) were the dustiest. Like so many things, progress was made. I believe that progress is more like "we know the front element is going to magnify, we know there is air flow, let's design the air flow so it doesn't pool under the front element", but I don't know for sure.
Here's what I know for sure:
Every lens has air flowing through it, there are no air-tight lenses.
Air has dust in it.
Dust in air likes to settle on solid objects.
That glass stuff in your lens makes things look bigger, smaller, sharply in focus and sharply out of focus. Including what's inside the lens.
When you take a lens apart to clean out dust it's interesting how the horrid dust you saw on the second element almost disappears when you take the first element off.
When you take apart a lens to not clean out dust it's interesting how dusty the inside might be even though you didn't really see it.
There is generally less dust (not no dust) in lenses that we just opened new in box, too.
I sum this up in Roger's Rule #63: If you don't see dust in your lens, you don't have a bright enough light.
Per what he sees, the current crop of non-pumping 70-200 f/2.8's are already gathering a lot of dust inside. He also listed a a couple of large prime lenses (which don't zoom at all) and the 150-600's as among the worst.
All lenses will get dust inside. The issue is how much the front and rear elements in a lens magnify the dust.
You appear to say but don't say, the EF 70-200 pumps as much air through it, air with dust, as the RF 70-200. I don't think that is true. I don't want an air pump if given a choice.
I don't see dust in my EF 70-200 and still think it is a solid, sealed, and proven lens. Regardless of R forum attempt to say it isn't the lens it was before the RF was introduced. The EF isn't air tight and water proof but it doesn't exactly flow air through it. The new RF is an air pump, abet an air pump with air filters. It flows air through it like nobody's business.
My comment was to the replier who said "no one" was reporting problems with the air pump design. When you see a video on cleaning dust out of a lens, it invariably is an extending zoom design.
People like the compact collapsing design of the new lens. Good for them. I don't need that and am happier with the solid EF version.
You are moving lens elements inside a lens. Don't think for a second that there isn't air movement in and out of the lens.
And Roger Cicala has far more experience tearing apart lenses than either one of us, and has seen the 70-200's from all vendors. He's saying that once you tear apart the lenses for cleaning, the worst offenders for dust accumulation are the current crop of non-pumping 70-200's, and a number of large primes. While some pump-design lenses do make it on his list of worst offenders (namely the old 100-400 and the 150-600's), his opinion is that they have gotten a lot better over the years with better lens designs.
It is his belief based upon experience cleaning thousands of lenses that the biggest issue is how much does the front and rear elements magnify the dust. You can have an incredibly dusty lens on the inside, but don't notice it until you tear the lens apart for a cleaning, or you can have a lens with noticeable dust spots, which disappear when the front and rear elements are removed for cleaning.
Interesting that he finds internal designs pumping more air in and out. Or, enough air that they get dustier than extending barrel designs. I thought they would just pump air around inside them, from front to back, with very little external air movement. The extending lens designs double their internal volume and then half their volume with each zoom change.
I think there must be more to Cicala's story than what he is telling us. Those EF 70-200's used in dustier conditions, for longer, because they are sealed? Used in harsher conditions than the new RF 70-200 he tore down? I will stick with reviews of internal lens designs without moving front elements and what they say are its advantages than go this one guy.
Or, do we need to go comment on the plethora of old videos about the EF 70-200's and correct their comments on the internal design. Correct them due to this one guy, Cicala's video. I'm pretty sure I can find a video about the earth being flat or the sun rising in the west so I watch lots of reviews on the lenses before I decide.
I think you are going through logic because of your initial assumption that if the lens telescopes it must pump dust in and out of it and it is therefore worse than non telescoping glass.
Perhaps the initial question should be... do lenses get dust in them? There answer there is yes. Primes, zooms, both get dust in them over time. The following question should be how do telescoping lenses compare with their internal dust acquisition over time with the other lenses.
So though I am certain that telescoping lenses do end up with dust with them over time, it seems that if you look at the real world reports from places such as lens rentals, is that ALL lenses get dust in them over time. I have had dust in zooms and primes. And I have not noticed any significant difference between them nor any impact on the resulting images.
So you find people on youtube finding dust in their telescoping lens. Big woop. If I search on youtube "internal dust prime lens" I find vids on that as well, and instructions for opening up and cleaning that dust. So what does that tell us??
So if at lensrentals they state that in their experience they find more dust in primes than zooms, should I right off primes? Nope. dust is a fact of life.
