Use of Extension Tube with 24-70 AF-S … can it be done?

Discussion in 'Other Cool Gear, Camera Bags, Camera Straps' started by Wail, Sep 13, 2008.

  1. Wail

    Wail

    784
    Aug 14, 2007
    Saudi Arabia
    I’ve tried to use the above lens with my PK13 ET, it seems to fit fine, but when I take a picture the image comes out just black .. nothing there other than a whole black picture.

    My initial thoughts were that the ET would work with any lens with the only issue being the focus point!

    Anyone have any experience on this? Or could someone refer me to a web site / book that’s really good on ET.

    Thanks for any feedback.
     
  2. gvk

    gvk

    388
    Jun 17, 2005
    Mystic, CT
    The 24-70 mm f/2.8 is a G-type lens with no aperture ring. Aperture must be set by the camera via the electrical contacts on the lens. Nikon's tubes, including the PK-11A, PK-12 and PK-13, do not have these electrical contacts, therefore, the aperture spring in the lens will close down to minimum aperture during exposure, likely resulting in massive underexposure as you observed. These Nikon tubes will work ok with lenses that have aperture rings, but without AF and will only meter as non-CPU lenses when using the tubes.

    Some extension tubes, such as the Kenko's, have electrical contacts that connect the camera's control signals to the lens thus allowing full aperture control, metering and AF with G-type lenses.
     
  3. I had recently tried an extension tube on my 80-200 and lost my focusing (Kenko tubes) and wondered if you can't use them on zooms. I did not try going significantly further/closer to see if I was simply outside the focus range.....
     
  4. gvk

    gvk

    388
    Jun 17, 2005
    Mystic, CT
    Focus range is restricted when using extension tubes. For example, I have successfully used AF with Kenko tubes on a 70-200 mm VR. With the lens set at 200 mm and infinity focus, and with the Kenko 36 mm tube (mine is actually about 35.6 mm) attached, the lens focuses at about 1.4 m and a magnification of around 1:5.6. These magnification and distance, coincidentally, are nearly the same as when using the lens without tubes, but at minimum focus setting. At minimum focus using the same 36 mm tube and zoom setting, the magnification is about 1:2.8 at a distance of just under 1 m. Thus the allowable range of focus is only a bit over 0.4 m with the 36 mm extension tube. Also note that when using tubes, changing the focal length on a zoom lens also affects the allowable focus distance range, in addition to changing the magnification.

    I sometimes used this combination (with or without a TC-14E) when chasing butterflies. I now more often use a 200 mm Micro that allows continuous focus from infinity to 1:1, or a 300 mm f/2.8 that gets to about 1:3.4 magnification at somewhat longer distance (over 1.5 m) with the Keno 36 mm tube. AF can useful for rough focus even for close-up work, especially with these AF-S lenses that allow direct manual override adjustment.
     
  5. Wail

    Wail

    784
    Aug 14, 2007
    Saudi Arabia
    Gerry,

    Thank you for the clarification. I knew that the G series lenses lacks the apperture ring, but I thought there may be a work-around this issue.

    Also, I thought one of the advantages of the extension tubes is to reduce the minimum focusing distance, and thought that this could be done with any lens. Again, learnd the hard way .. this isn't possible with all lenses.

    Bottom line, I guess it is prime time I ordered the Kenko set of tubes. Funny that Nikon's set don't offer autofocus and metering! One would think for the price they sell for, the Nikon should offer all functionality.

    Again, thank you for the clarificaiton ... very much needed and appreciated.
     
  6. gvk

    gvk

    388
    Jun 17, 2005
    Mystic, CT
    Yes, by extending the lens away from the image plane, tubes reduce minimum focusing distance, but they also greatly reduce the maximum focusing distance, and decrease the amount of light reaching the focal plane (bellows effect) as magnification increases. Extension tubes can be used with most lenses, but some perform better than others outside of their normal range of operation. :smile: The extension required to achieve a given magnification is proportional to focal length. Therefore, any given tube length will be more effective with shorter focal lengths. However, even moderate extensions can sometimes be useful with longer lenses to achieve closer focus, as I mentioned in my previous post regarding the 70-200 mm VR and 300 mm f/2.8.

    The Nikon tubes are relatively old designs that preceded modern AF and G lenses by many years. Nikon has not released updated designs containing the electrical contacts that are needed to provide compatibility with these new lenses. Kenko tubes have the required electrical contacts, but are less robust, and can also result in vignetting when used in combination to achieve higher magnification, particularly for FX sensors or 35 mm film.

    I have tried using Kenko extension tubes with the 24-70 mm f/2.8. Small to moderate extension is useful in the longer focal length range (50-70 mm) to achieve closer focus. However, with increasing extension length or at smaller focal length image quality suffers with edge sharpness degradation and lateral chromatic aberration. Here is a link to a Nikonians post with some comments about using the 24-70 mm f/2.8 with Kenko tubes.
     
  7. Wail

    Wail

    784
    Aug 14, 2007
    Saudi Arabia
    Gerry,

    Thank you, again, for a wonderful reply and for the link. Very useful information there .. great read.