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04/04/2008 10:47:24 AM · #1 |
I bought the Nikon AF-S Micro-Nikkor 60mm f/2.8G ED.
For some reason, and this may be due to lack of knowledge on the macro lenses, but when I try to bring it down to 2.8 it won't let me. It sits at whatever it's at, like 3.2F and will let me bring it up, but not down to 2.8F. When I mess around with different objects it will bring itself down to 2.8 at one point or another. Why?
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04/04/2008 10:52:44 AM · #2 |
| I didn't know that was available yet. B&H still has it listed as "coming soon." Once you figure out your problem, let us know how you like the lens! |
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04/04/2008 10:56:45 AM · #3 |
Originally posted by citymars:
I didn't know that was available yet. B&H still has it listed as "coming soon." Once you figure out your problem, let us know how you like the lens! |
It came out here in Japan last month. The older one was something I really wanted
But after playing around with the newer one, and taking a few test shots, it was clear where the extra money went. I also had points at the store to buy it, so it didn't cost me a thing.
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04/04/2008 10:58:37 AM · #4 |
| I believe with the Nikon mount the aperture ring has to be set at 2.8 before mounting the lens. (At least that's what a friend has to do for the D300) |
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04/04/2008 11:00:49 AM · #5 |
Originally posted by cpanaioti:
I believe with the Nikon mount the aperture ring has to be set at 2.8 before mounting the lens. (At least that's what a friend has to do for the D300) |
That's worth a try, but I think if the lens is mounted "incorrectly" (not as described above), you get an Err message. |
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04/04/2008 11:04:03 AM · #6 |
| At close focus distances it closes the aperture down. I don't know the mechanics of why, but the "old" 60 does the same. I haven't found it to be a problem, because at those distances, f/2.8 would put the DOF so thin that nothing would be in focus. |
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04/04/2008 11:28:39 AM · #7 |
| Just a thought: does it really close the aperture down, or is it just reporting the true aperture? I'm thinking that even if the aperture ring mechanically is at the f/2.8 position, you may only get 3.2 optically since something else is limiting the aperture at close-up distances. This would be due to the very divergent light from close-up sources hitting the edge of some lens etc. |
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04/04/2008 11:32:52 AM · #8 |
Don't know...but so far some nice pictures nonetheless.
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04/04/2008 11:40:46 AM · #9 |
At close distances the camera compensates the reported aperture in order to get a "correct" exposure.
On old cameras you would have to figure out the compensation yourself and adjust shutter speed.
It's called the "effective" aperture.
Lots more info if you google it. |
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04/04/2008 11:43:10 AM · #10 |
Originally posted by somwhere:
The question about why or how the aperture values on a Micro-Nikkor (or any macro lens for that matter) keeps changing during focusing, especially at high magnifications, keeps cropping up... so I decided to post an explanation to this "confusing" issue to all macro lens owners & would-be owners.
(Actually this is a slightly modified re-post of my answer to a similar query on different Forum)
The answer to this query about the baffling aperture change with the macro lens is actually very simple. What you're seeing in your viewfinder is the effective aperture as opposed to the actual aperture that you set on the lens. In theory, there is a requirement for some compensation the moment you are not focusing at infinity. The amount of compensation required is dependent on the film plane/aperture distance to the focal length. In most normal lenses in normal photography, this amount of compensation is very small is often ignored because of the magnification scales involved... i.e. Effective Aperture = Actual Aperture. However, the moment you delve into photomacrography, all these compensation issues becomes very critical... i.e. Effective Aperture does not equal to Actual Aperture.
The following mathematical formula is the actual definition of Effective Aperture:
//mysite.freeserve.com/nikonians/images/EffectiveAperture.jpg
where,
A = aperture
M = subject magnification
p = pupil magnification (exit pupil diameter/entrance pupil diameter)
Looking at the mathematical definition for the effective aperture, you can see that the effective aperture is a function of both the subject magnification (M) as well as the pupil magnification (p). To be more precise:-
The subject magnification is set based on the actual reproduction magnification as indicated on the lens... i.e. the 1:M ratio. For a true life-size magnification between the actual subject and the film plane, the reproduction magnification would be 1:1. Half life-size would be 1:2. With me so far...
At whatever magnification setting, each lens will have an associated pupil magnification value. This is the ratio between the exit pupil (the inner most objective diameter or the lens element you see when you look at the back of your lens) and the entrance pupil (the outer most objective diameter or the lens element you see when the lens is mounted on your camera). The value of p is given as:
p=1 - for a normal lens.
p>1 - for a wide-angle lens.
p<1 - for a telephoto lens.
A lot of people tend to approximate p=1. This is fine if you're using say the 60mm micro-nikkor or 55mm micro-nikkor as it is effectively a normal lens, but in the case of the 105mm AF micro-nikkor, it actually falls under the p<1 case.
So, back to our equation...
//mysite.freeserve.com/nikonians/images//EffectiveAperture.jpg
If you substitute the appropriate numbers into the above equation, you'll find that the effective aperture for the 105mm at life-size 1:1 magnification is approximately equal to 5... i.e. f/A = f/5 (i.e. the f/stop number). If you try this equation out at the various magnification settings, you will find that it will give you the appropriate effective aperture conversion.
Note that most modern Nikon AF body CPUs do all these calculations for you because it knows what Nikkor lens is mounted via the electronic coupling between the lens mount and the lens. MF body and/or MF Micro-Nikkor users will need to know this to work out the appropriate effective aperture for metering purposes. |
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