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  1. #1
    Join Date
    Nov 2006
    Location
    Cerritos, CA
    Posts
    66

    TAMRON 28-80mm F3.5~5.6 | Isn't it asking for dust trouble?

    Hey Sony folk.

    I just had to scoop up the following lens on eBay:



    For $13 shipped (I guess no one wanted to bid) I thought it'd be a great "F-it" lens for less than ideal situations. Surprisingly, I'm liking the pictures so much better than the kit that it's spending more time as my everyday BS lens.

    Thing is, I never noticed until I was playing around with it that on its rear mount the lens element hollows out while you zoom. I think this is one of those cheap "push/pull" zooming mechanisms that people talk about when dealing with budget lensing:



    Holy smokes! I don't even want to think of what could be in there that is just waiting to get blown forcefully into the open cavity that is my 5D's mirror and CCD sensor cavity. Sure, I take the usual cautions such as not zooming the lens unless it's mounted on the camera or with the rear cap on, but still, am I the only one concerned with it?

    -Brian
    grip: KM Maxxum 5D | Minolta 50mm f1.4 neck: Sony A200 | Minolta 70-210mm f4
    backup: Fuji s6000fd | pocket: Fuji F20SE
    sentimental: Sony DSC-S85
    wife: Canon s800IS | 9yo daughter: Canon s410

  2. #2
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,560

    Red face Blow hard!

    Quote Originally Posted by unclebrudy View Post
    Hey Sony folk.

    I just had to scoop up the following lens on eBay:



    For $13 shipped (I guess no one wanted to bid) I thought it'd be a great "F-it" lens for less than ideal situations. Surprisingly, I'm liking the pictures so much better than the kit that it's spending more time as my everyday BS lens.

    Thing is, I never noticed until I was playing around with it that on its rear mount the lens element hollows out while you zoom. I think this is one of those cheap "push/pull" zooming mechanisms that people talk about when dealing with budget lensing:



    Holy smokes! I don't even want to think of what could be in there that is just waiting to get blown forcefully into the open cavity that is my 5D's mirror and CCD sensor cavity. Sure, I take the usual cautions such as not zooming the lens unless it's mounted on the camera or with the rear cap on, but still, am I the only one concerned with it?

    -Brian
    I believe you will find that many lenses do this. I may even have this happening with my incredibly expensive Canon EF 70-200mm f/2.8L IS USM, but I will need to look closer. (EDIT: After closer inspectection, the 70-200 lens is totally self-contained and does not move any rear elements.) I suppose we could examine how all our lenses "breathe" and be horrified.

    The SONY A100 has the dust-reduction feature, which occasionally shakes the sensor free of dust particles. Does it work well? Well, I guess so ... I haven't had to clean the sensor yet, unlike the fixed sensor of the Canon EOS 20D I have.

    Remember, the air inside your camera body should be as well protected as you can make it (Keep the Body cover in place, when no lens is on the unit ... also cover the rear of the lens to protect it from injesting "bad air", when it isn't mounted.) It's a relatively easy process to mitigate the average dust exposure and your concerns, while interesting, may not be as bad you you may think they are.

    You should also take into account that the lens you are using was not designed for use on the digital SLR. Sure, you CAN use it on the DSLR, but when originally designed, it was for the standard SLR ... which has no real dust concerns. So ... you have to ask ... aren't we expecting a little too much, in this case?

    I mean ... a non-DSLR lens on a DSLR ... caution dictates that it definite might have some issues. The choice to use this type of lens is, of course ... YOURS.

    EDIT:
    Here is the rear of a Canon EF 75-300mm f/4-5.6 III ... it does the same thing
    Name:  rear-75-300.jpg
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Size:  229.5 KB

    Here's the rear of the TAMRON SP AF28-75mm f/2.8 XR Di LD Aspherical (IF)
    Name:  2875-f28.jpg
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Size:  222.9 KB
    Last edited by DonSchap; 04-23-2007 at 07:29 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

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