Kenko Extension Tubes

[ATJ]

I'm currently using an old Nikon PK-13 (27.5mm) extension tube with my 60mm f/2.8D. It works well, but is a little frustrating as it doesn't have any CPU connections. This means I have to set the aperture using the ring on the lens and I don't get any aperture information in the viewfinder or in Exif. I also have to use manual focus, which 99% of the time is fine, but there are times where AF would be of value - like if I'm shooting with one hand only (on a monopod).

Do the Kenko tubes have CPU linkage when used with Nikon? This comment "Nikon "D" information is not transmitted because the lens is focusing closer than its programmed to focus." confused me somewhat.

Will AF work with my 60mm f/2.8D?

[gstark]

Andrew,

Which body?

And does the PK-13 have an AI coupling ring? If so, and on a D200 or better, it should be possible to set up the AI interface, although I'm not quite sure how that will work given the effect of the ring's extension on EV.

[ATJ]

D300. The AI coupling works (at least my understanding of it does - the lens is wide open until I take a photograph and it stops down to the aperture set on the aperture ring).

The PK-13 has no CPU contacts.

[gstark]

D300. The AI coupling works (at least my understanding of it does - the lens is wide open until I take a photograph and it stops down to the aperture set on the aperture ring).

That's not the AI coupling, but the stop-down control lever at work

The PK-13 has no CPU contacts.

Doesn't need 'em - the AI ring on the lens couples to the PK-13 which couples to the body to transmit the physical aperture setting into the body. In your menus, there's a setting where you can program in the lens and maximum aperture in use. That's where I'm unsure of how that works with the PK-13.

The stop-down lever holds everything open until you make your exposure, which is when the mirror box/shutter mechanisms release the lever and the lens then stops down.

[ATJ]

Excellent. Thanks! That works, with a couple of provisos: 1) 60mm is not available as a selection, so I had to choose 58mm. 2) it will only be indicating the f/stop on the aperture ring rather than the real f/stop (based on extension from tube and focusing). It is a lot better than what I had before.

I still wonder, though, if the Kenko tubes would provide even more information, such as connecting the CPU from the lens to the camera.

[gstark]

Excellent. Thanks!

Great stuff, and my pleasure.

it will only be indicating the f/stop on the aperture ring rather than the real f/stop (based on extension from tube and focusing).

That's about what I expected, but I wasn;t sure. Even so, it will be metering on the basis of actual transmitted light: it will be the read value that will be out by about a stop.

I still wonder, though, if the Kenko tubes would provide even more information, such as connecting the CPU from the lens to the camera.

If they have the contacts, then probably. But for the cost of this solution, it's probably not too bad a way to travel.

[ATJ]

Even so, it will be metering on the basis of actual transmitted light: it will be the read value that will be out by about a stop.

The camera meters perfectly. The tube will increase the f/stop by about 1 stop when the lens is on infinity, but as I focus in, the effective f/stop could be a lot larger. I just know with the bare lens focused at its closest distance, the f/32 becomes f/57 which is nearly stops. So, potentially, if I have the lens at f/16 and focus it as close as possible, I may effectively have f/45 (but I'll never know).

[latch]

I have recently bought a set of Kenko extension tubes, and they work fine with my D70 and 50mm f1.4 lens. I can set aperture values via the camera body controls (as usual), and both autofocus and autoexposure work.

I suppose it is obvious that the distance information from D lenses will be irrelevant when using extension tubes, but I don't know how to find out if it is being transmitted to the camera or not.