extension tube help

Discussion in 'Beyond the Basics' started by jocose, Feb 28, 2006.

  1. jocose

    jocose TPF Noob!

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    Hey folks.

    I did a quick search and couldn't find anything, so I apologize if this has already been answered.

    I just bought a set of 3 extension tubes: 12mm, 20mm, and 36mm. The first thing I discovered to my dismay is that they will only work on my lensed that have manual f-stops (so my 18-70mm is out...).

    Anyway, here's my question. I threw them on my camera with my 50mm. I can get amazingly close, which is, of course, great and the point, but I notice that everything looks like those lensbabies...that is, the center is in focus but nothing else is. Is this normal? Is it because I'm using my 50mm (I also have a 70-300mm, which I haven't tried yet)? Am I doing something wrong?

    Also, can someone explain the numbers to me? Is it if I use the 12mm with my 50, it's like having a 62mm lens? That doesn't sound right...but I'm still not really getting the mm thing (I mean, I understand that with a 50mm lens, the light all comes to the point at 50mm from the lens to the sensor/film [and let's not get into digi/film conversion right now if we can avoid it]).

    Thanks.
     
  2. MommyOf4Boys

    MommyOf4Boys TPF Noob!

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    I dont know much about the tubes, Joe would be a good one to ask. I use the lens filters that screw onto the front. They work very well for me.
     
  3. jocose

    jocose TPF Noob!

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    you can use filters to do macro stuff?
     
  4. JonK

    JonK I want MORE!!

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    mommy is talking about close-up filters that screw into the front of the lens. In reality the tubes are better as there is no optical degradation. the filters are more convenient tho.

    Did you get the Kenko extension tubes? they do make them for AF and manual lenses andyou have to specify which you want... I would try to exchange them if possible.

    as for the focus issue...the closer you get the less DOF that is available to you. I suspect you're confusing lack of focus with shallow depth-of-field.
    The 'mm' delineation on the tubes just refers to how much more extension you get from the film/sensor plane.
    Also you may find that if you are too close you cannot focus at all and you may have to physically move the tripod back (assuming you're using one which is a good idea in these cases) in order to find your close focus distance.

    I would deffo try these with the zoom as you not only have the focus as an option but also the zoom ability...the combos can make for some cool abstract close-ups if you stack all three tubes and play around zooming and focussing/defocussing.

    I used 3 tubes and my 70-200 lens to get this shot:

    [​IMG]
     
  5. jocose

    jocose TPF Noob!

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    Jon,

    Yea, I was talking DOF...but it's still out of focus on the edges :mrgreen: BUt yes, very very very very shallow DOF.

    Nice pic...what is it exactly?

    When I get home tonight, I will try the zoom...unfortunately, right now, I'm limited to my film cam, no digi at the moment.

    No, I can't return them...eBay aution. They are vivatar. I think they are pretty old. They have these little rabbit ear extensions that connect to each other and to (I'm assuming, but my cam doesn't have it) a prong on the cam that controls the f-stop. They were $47, so it's no great loss...they will work fine until I can buy some new ones :)

    Thanks.
     
  6. woodsac

    woodsac TPF Noob!

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    Not much to add. It sounds like you got the wrong tubes Jo? MF instead of AF.
    Really close your aperture down. Take the same shot at f/4 and f/22. You might not notice any difference while shooting the image, but the outcome will be a very noticeable.
    What works for me, is to first adjust how close my lens is to the object. I watch through the viewfinder until my object is coming into focus as I move the camera closer. That gives me a basic distance. Now you can start to fine tune your focus with the lens.

    We were typing at the same time :)

    Here's what you want:
    http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=375238&is=REG&addedTroughType=search
     
  7. darich

    darich TPF Noob!

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    I have a set of extension tubes too (Kenko 12,20,36mm).
    I've found that with certain focal lengths the point of focus is so close it's inside the lens and focussing is impossible. The autofocus only works with wide apertures though....from memory i think it's 3.5 or wider.
    As Jonk mentioned....the DOF is wafer thin
     
  8. JonK

    JonK I want MORE!!

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    yep those are the ones woodsac...unfortunately they've raised the price about 30 or 40 dollars since I bought mine about 5 yrs. back.
    jo...that shot is dew on a piece of metal

    just play with them and you may be surprised what cool shots you come out with.
     
  9. woodsac

    woodsac TPF Noob!

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    Good point! Any time I'm using all three tubes, and sometimes a combination of two, I automatically switch to MF. With the 50mm open to f/1.8 with all three tubes, your image is pretty much unrecognizeable. I have yet to get a bug to sit still long enough to use that combo :p
     
  10. JonK

    JonK I want MORE!!

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    i find it almost pointless to use AF with the tubes...much easier fine-tuning with MF...they even sell focussing rails to mount to your lens in order to super-fine-tune in micromillimetres(?) when shooting this close
     
  11. woodsac

    woodsac TPF Noob!

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    I don't use the tubes a lot, but I've been using them more and more. This could be useful. Thanks Jon :thumbup:
    *jumps over to B&H to look around some more*
     
  12. jocose

    jocose TPF Noob!

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    Hey, thanks guys...actually my film cam is all manual anyway (which fortunately for me, by bro-in-law still bought a kickass 50mm prime 1.8 that's all mine now :) and that works just fine with the auto in my digi!).

    I'm not afraid of manual focus, and if the DOF is supposed to be that shallow, then it's all good...I was just worried that I was doing something wrong ;)

    Anyway, as I said, I'm saddly sans D70s right now (long story), but I'm playing with film. Hopefully, I'll get the digi back by the weekend...but then I'll be shooting my other sister's wedding (otherwise, my trusty PowerShot will be excited to see the outside of the camera bag again).

    Eitherway, I will have some macros up lickity split!

    Thanks again.

    Oh, and I saw those tubes you linked to at the local shop (same price), but it's a little out of my price range at the moment...but if I get them, I'll probably put my current ones back on eBay and try to recoup some of the money I spent on them...see, I keep telling JonMikal that I'm too new to this photography stuff to be playing on eBay...but I have them, so I will make them work!
     

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