Need to get closer with 105

Discussion in 'Nikon' started by tim_eastman, May 15, 2016.

  1. I am setting up for slide copying with my D7000, 105 micro and a PS4. I need to get about 2 1/2" - 3'' closer than the minimum focusing distance will allow. I am trying to determine which extension tube will get me there and the math for figuring it out is over my head. Any educated tips would be welcomed!
  2. The formula for a simple lens is
    1/d + 1/d' = 1/F
    Where d and d' are the distance from the center of the lens to the subject and film plane respectively, and F is the focal length. If you use an extension tube, add that to the distance to the film plane. That distance includes the position of the focusing helix.
    It would be hard to achieve exactly 3" (or whatever) closer range, but with the range afforded by the focusing helix, you can bracket the distance. Instead of d and d', you would substitute d +h+x and d'-3 (all in inches), where h is the focusing extension, and solve for x.
    It gets more complicated with a compound lens, where the distances are to the front and rear nodes respectively, and the positions of the nodes can vary with focus. The diaphragm is usually close to one of the nodes. For a telephoto or inverse-telephoto, the relative position of the nodes can be reversed. Lenses with internal focusing often vary the focal length to reduce the extension needed at close range (e.g., Nikon 105/2.8 AFD). Is this sounding like fun?
    Use the simplified formula, which will work well enough, most of the time.
    NOTE: If you want a 1:1 copy of a slide, the slide needs to be further from the lens, which will require extension tube(s) with 52 mm threads. If it is an older lens which only achieves 1:2 magnification, you will also need an extension tube between the lens and camera. Nikon makes/made a set of "K" extension tubes which fit in front of the lens, also to invert the lens for extreme magnification. Is the D7000 an APS-C sensor, then you need 1.5:1 magnification, not 1:1. Magnification is approximately d/d'.
    I suggest you buy a used 55/2.8 AIS Micro-Nikkor (1:2 max), a Nikon PK13 automatic extension tube (for 1:1), and a Nikon ES-1 slide holder. You will still need the 52 mm front end extension rings for a DX camera.
  3. You asked a wonky question, and I gave a wonky answer to the best of my ability (which can be excessively wonky). Sometimes it's better to tell someone what they need, rather than what they ask for, and this is one of those instances.
    Somebody on the internet has already done this and assembled all the right equipment. I referenced that source in a previous post on in the "Digital Darkroom" forum. We had a nice thread on slide copying in lieu of using an unobtanium scanner.
  4. If I correctly understand your questio , you need to extend the 105mm Micro-Nikkor to be a 2:1 (2x lifesize) macro lens so
    that an an approximately 24x36 mm film frame fills the 16x24mm sensor of the D7000. If you want to maintain autofocus and TTL metering your best bet will be to use either a two- element diopter or a reversed wide angle lens on the front of your 105mm Micro-Nikkor.
  5. You need LESS magnification to fill a 16x24 mm sensor. The magnification ratio does not depend on the sensor. 1:1 is always 1:1. For APS-C cameras, you need 1:1.5 for slide copying (less than unity). That also means more distance between the lens and the slide holder. (I reversed the ratio in my previous post.)
  6. It would help if we knew exactly which Micro-Nikkor we were dealing with Tim. The 105mm AF micro-Nikkors focus to 1:1 unaided, so I assume you've got an older MF 105mm micro-Nikkor that only focuses to 1:2.
    The theroretical formula to obtain lens extension from magnification is: Extension = F x (1+m)
    In this case you need a magnification of ~0.7x, which means a tube of around 73mm would be needed with the lens focused at infinity. With the lens focused at 1:2 the tube length would only need to be around 20mm. So any tube between 20mm and 74mm in length should do the job. The recommended Nikon tube is a PN-11 to enable the 105mm MF micro-Nikkor to reach lifesize magnification.
    However, the PS4 may not be able to provide sufficient distance between the front of the lens and the slide. It's really designed for copying 35mm slides to full-frame (24mm x 36mm) at around a 1:1 RR.
  7. ShunCheung

    ShunCheung Administrator

    If we are talking about an older 105mm macro lens that only goes to 1:2, it is simpler to find a newer macro lens such as the 105mm/f2.8 AF macro from the late 1980's, which really isn't all that new any more. I have that lens and it goes to 1:1.
  8. I found a source for 52mm 1 1/2" spacer rings. They have male and female threads and I can screw three together to the front of the 105 ( 2.8, 1:1 ) to get me far enough away to focus. They will attach to the bellows on the PS-4. Of course I was totally wrong on the extension tubes!
  9. I have a full set of Nikon AIS extension rings in addition to my PK-13. A 3 ring set, PK-11,PK-12 and PK-13 can be found on Ebay for around $75 in good shape. Mount them all together with a body cap on one and a rear element cap on the other and stuff them in your gear bag. They take up about the same amount of room as a 55mm lens.

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