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Old Feb 22, 2006, 12:20 AM   #1
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i've heard complaints about some lenses sucking in dust during AF operation -how big a problem is this really? i live in the Pacific NW, not exactly a "dusty" climate, but i really don't like the idea of spending a grand or more on a couple of lenses if they're going to need to be sent off for expensive cleaning procedures because they ingest dust out of thin air... is this a real problem, or is it just a couple of instances where lenses havehad problems because they wereused in dusty conditions?


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Old Feb 22, 2006, 9:45 AM   #2
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Hi squirl033...

This is quite an unlikely problem for most DSLR lenses. Not an impossibility. I've read on many forums and reviews many more people WORRIED about dust getting in than actually people saying that they had it. That is (from my experience), one can read MANY people say: "I'm worried about dust getting in my lens" - but very FEW people saying: "I have dust in my lens which is ruining my photos"!

Sure, there is a possibility with some lenses "sucking in dust" through gaps between the lens barrels, etc. One lens I own (the Canon 28-135mm lens) has the reputation for this being a possible problem. I've taken over 6000 photos, quite a number of them in fairly dusty locations (I live in Romania, which can be a bit dusty in the rural countryside) - but I don't have ANY dust that I see / notice in my lens. And anyway, most people who have even got dust or a small something in their lens don't see it in photos.

Of course I don't purposely subject my camera or lenses to dust (keep it in the bag and have lens cover and rear cap on whenever not in use, etc).

If I remember well you are soon or about now getting a Digital SLR camera? Well, I would say that changing lenses (if you are going to get and use more than 1 DSLR lens) is going to be your biggest worry related to dust- where possibly (flying / floating) particles of dust might land on the sensor (well actualy on the thin cover in front of the sensor) which DO show up much easier in photos (as contrary to if that same dust was in / on your lens). Dust on the sensor is especially noticeable at higher f values (e.g. f16 and above).

I have cleaned mysensor 2 times with a "blower" hand pump (don't use compressed gas) when I could see one or two specs of dust in photos. Check this website out for good advice on the whole topic. http://www.cleaningdigitalcameras.com The bulb cleaning method has worked good enough for me (so far)!

So when I change lenses I try to do it in a clean place, (not outside unless absolutely necessary) and not leave the camera sensor (it's "insides") exposed for too long. (that is change lenses quickly, and use the camera / lens caps!) Also some advice don't do things that might make dust in the air before, or during the procedure of "changing lenses" (e.g. don't play with hair, bed linen, clothes, etc...) Use a clean table surface (don't shake the tablecloth!) :-)

I think you'll find 99% of lenses are fairly okand will NOT have a dust sucking problem. That's my 2 cents worth (or maybe it's up to 5 cents!) Hope it's helpful squirl033!

Paul

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Old Feb 22, 2006, 10:39 AM   #3
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It's not really the AF which 'sucks' in the air...

Most lenses draw in the air because of the zoom operation (not the primes) - i.e. the bellowing (or accordeon) effect of the lens barrel changing its length is what displaced the air column.

This is why zoom lenses with internal zooming are better designed:
1. Their lenght remains constant throughout the zoom range (and do not draw air)
2. The lenses balance the same when zooming instead of shifting weight as they extend in/out
3. Internal zooming mechanisms are also smoother/faster in operation (forces do not vary as the zoom ring is turned)

But the worst offender is the AF not staying in focus when zooming - 3rd party lenses and especially Nikon zooms are better at this than most if not all Canon zooms: The Canon EF loses focus when the focal lenght is changed including the L's :evil:


-> You also want internal focusing - i.e. the front element do not rotate when AF -> this will help with the polarizer...
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Old Feb 22, 2006, 11:49 AM   #4
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thanks, guys.

Paul - yes, i'm looking into stepping up to a 20D... i've been impressed with the image quality it produces, and while my FZ20 is exceptionally good for what it is, it's still a small-sensor digicam with some significant limitations. i'll probably only be getting a couple of lenses to start with - the Canon EF 17-85 IS USMto use asa general-purpose "walkabout" lens for flowers, landscapes and the like, and a long zoom for wildlife and distance shots. i probably won't be changing lenses all that often, since i usually know beforehand where i'm going and what kind of shots i'll be looking to take.

NHL - considering your comments on long zooms, what's your opinion of the Sigma APO 80-400mm F4.5-5.6 EX OS lens? non-rotating front end, so polarizers will work, but i'm not sure about internal zoom. it's a fairly new lens, so it might have that feature. seems to me it would be comparable to the 100-400L, though perhaps not quite as fast (especially at max zoom), but it's also agood $400 cheaper... i know you're a fan of fast lenses - and if i had the cash to drop on a 400mm f2.8 lens (which my FZ20 has, by the way! it needs it, to compensate for the low ISO limits), i'd be all over it. but budget constraints do come into play, and i just can't swing $2000+ for one lens at this point...
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Old Feb 22, 2006, 5:45 PM   #5
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I found this site quite helpful: http://www.pbase.com/fstopjojo/tests
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Old Feb 22, 2006, 6:11 PM   #6
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Yes NHL is right, sorry I didn't mention before - that it isn't the AF mechanism but the zooming part of some lenses that might draw in dust (but it's not really a problem on 99% of lenses, as I said!) - even those without internal zooming.

Many people have used the 28-135mm or 17-85mm lenses for thousands and thousands of shots in dusty place with no dust problems. though of course there might be the "bad copy" with bad quality control that DOES create a dust problem.

Wishing you all the best squirl033 for your D20 purchase, I think you'll be very happy with it and with the intended lens/es you hope to get.

Paul
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Old Feb 22, 2006, 7:26 PM   #7
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thanks, Paul...

as if the choices weren't complicated enough, now there's the 30D, which is only a marginal improvement over the 20, by all accounts, but if the price isn't appreciably higher, it does have a couple of features i'd like, such as selectable frame rates in continuous mode, a larger LCD, and the ability to switch ISO settings if need be without taking the camera from your eye... ahhh, decisions, decisions! :-?
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Old Feb 26, 2006, 4:03 PM   #8
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ok, my suggestion for difficult decision dilemma ....

1. cut2 small pieces of paper, on one write 20D and the other 30D.

2. Place them about 50cm apart. Place an emptybottle (side down) between them.

3. Spin bottle.

4. Wherever the bottle neck points to, get that camera! (.... OR spin bottle repeatedly till it lands at the one you want!) :-)

I'd probably go for the 30D and try to save up some money somewhere else in the personal funds to justify it!! :-) However I wouldn't skimp out on lenses (as I think you know!)

Hope your decision making and purchasing goes well. Lookin' forward to your posts from your new camera in time...

Paul




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