Delivery time on Kenko m4/3 extension tubes

Discussion in 'Open Discussion' started by iGonzoid, May 18, 2012.

  1. iGonzoid

    iGonzoid Mu-43 Veteran

    247
    Feb 6, 2011
    Tasmania, Australia
    I have just ordered from B&H the Kenko 10 & 16mm auto-capable extensions set for m4/3, which was out of stock at the time of order. Anybody know how long it might take for them to be in stock again? And has anyone used this recently released gear yet. I aim to use it mainly on my 45mm Macro Elmarit f2.8 —how many stops of light are lost with the respective and combined rings? Thanks, iGonzoid.
     
  2. LeeOsenton

    LeeOsenton Mu-43 Button Clicker

    297
    Jun 25, 2010
    Hayes, Virginia, U.S.A.
    Lee Osenton
    I just bought the 45mm macro and am only beginning to work with this lens. Macro photography is a new world to me and I am already struggling with the unbelievably thin depth of field. I am not ready for extension tubes yet!

    I have been reading about the techniques and equipment used for macro photography. It is my understanding that there is no light loss since they are just hollow tubes with no optical elements inside them. The tubes move the lens farther from the sensor and this causes greater magnification. I think the formula is: Length of Tube / Focal Length of Lens = Additional Magnification.

    So, using the 45mm macro with 1:1 magnification we get:

    10mm (short kenko) / 45mm (lens length) = .22 (magnification factor) + 1 (base magnification = 1.22:1 Magnification
    16mm (long kenko) / 45mm (lens length) = .35 (magnification factor) + 1 (base magnification = 1.35:1 Magnification
    26mm (stacked kenkos) / 45mm (lens length) = .58 (magnification factor) + 1 (base magnification = 1.58:1 Magnification

    Following the math, the magnification increases with extension tube length. However, depth of field will decrease so greater precision and lighting will be key to getting good shots.
    I think a lightbox may be necessary for all but the most experienced macro shooters. Are you planning to build / buy one or just wing it in the wild? I searched the web and found many how-to guides with some being very inexpensive and others more involved. I have not checked out the Kenko tubes, but assume they have electrical connections that will allow the 45mm to work as normal?

    Lee
     
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  3. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    There is a loss of light with increasing extension from infinity. I t starts becoming noticeable at around 1:4. We used to need charts; measure with a light meter and compensate exposure based on magnification ratio. TTL metering eliminated the need for charts but also made it less obvious that the phenomenon was occurring.

    I don't have a chart at hand but I remember this. At 1:2, 1 stop; at 1:1, 2 stops. Using the 45/2.8 at 1:1 the light reaching the sensor at f/2.8 is equivalent to f/5.6 at infinity. For this purpose any further than 1:10 is infinity.

    This occurs because the intensity of a light source decreases as an inverse square to increasing distance. Move your light from 5 feet to 10 feet and you've increased the distance by a factor of 2. 2 squared is 4. The inverse is 1/4 the light, 2 stops. The lens acts as a light source projecting onto the sensor. A 45mm lens is 45mm from the sensor at infinity. At 1:1 it's 90mm from the sensor twice the distance, 1/4 the intensity, 2 stops difference.

    All that being said, you can still rely on the camera's light meter. You just get a dimmer viewfinder or grainier evf.

    Fred
     
  4. LeeOsenton

    LeeOsenton Mu-43 Button Clicker

    297
    Jun 25, 2010
    Hayes, Virginia, U.S.A.
    Lee Osenton
    Forgot my question to B&H. I am going to build a 24"x24"x24" lightbox from inexpensive materials. The top and front will be open and I want to add a light source to either side. I have read that incandescent bulbs are preferred, but there are CFL bulbs that produce comparable light. One brand referenced was BlueMax, but I only found the bulbs at a specialized site that I am not familiar with. Does B&H carry this type of bulb?

    Thanks,
    Lee
     
  5. G1 User

    G1 User Mu-43 Veteran

    411
    Jul 20, 2010
    Your TTL light meter will correct for any extension... Just use "Aperture Priority" mode, and have a tripod handy if needed. And if you have a Pen/OMD, the $60.00 LED Macro light will help for handheld macros.
     
  6. G1 User

    G1 User Mu-43 Veteran

    411
    Jul 20, 2010
    I believe you are refering to a Daylight corrected bulb, 5500k typically,
     
  7. LeeOsenton

    LeeOsenton Mu-43 Button Clicker

    297
    Jun 25, 2010
    Hayes, Virginia, U.S.A.
    Lee Osenton
    Fred, thanks for amplifying on the extension tubes. What you are saying makes sense. I took a statement out of context where the use of extension tubes were being compared to multipliers.
    G1User, I found the BlueMax bulbs. These bulbs are 5500k like you mentioned to give a light that is similar to daylight. The article I read discussed the color rendering index (CRI) of the bulbs; this rating is given as a percentage with higher being desirable. The article recommended bulbs with a high CRI and said that cheaper bulbs would not have a CRI rating. I am hoping to hear from someone that has tried different CFLs and can speak to the real world applicability. I know I can just use incandescent bulbs and avoid the possible pitfall, but I prefer the low power & low heat of CFL bulbs.

    Lee
     
  8. iGonzoid

    iGonzoid Mu-43 Veteran

    247
    Feb 6, 2011
    Tasmania, Australia
    Thanks all for your generous advice and computations — my maths is pretty lousy. Fortunately my order for the Kenko m4/3 extension tubes are now in stock and bound for the warehouse and shipping, so it won't be long before I can start experimenting. Much of my current macro work is done hand-held in the wild; but with the tubes I will probably be doing very studied tripod and light set-ups, or bounced flash with reflectors. Lots of experimentation lies ahead. Recently I found a three-LED lamp on a headband [rather like a doctor] which I have been using with the 45mm Macro to add light to insects in dark corners. Thanks again for all the advice. iGonzoid