Sunday, June 16, 2002

Notes on using a teleconverter with an EOS camera

Some EF lenses have 7 electrical contacts ("7-pin" lenses) and some are "10-pin" lenses (typically the later Canon telephotos).

Teleconverters such as Kenko's Pro 300 (and presumably Canon's own TCs although I haven't checked one lately to be sure) have 7 pins on the camera side and 10 on the lens side (actually 11: one of the pins on the lens covers two of the "raised" ones on the camera/TC). If you attach a 10-pin lens to a TC the camera recognises the existence of the TC and reports the effective focal length and aperture of the combination. If however you attach a 7-pin lens to the TC, the camera does not recognise the presence of the TC and reports the native features of the lens.

By covering the extra 3 pins on the lens side of the TC (either by using a small extension tube which only has 7 pins or by using tape as shown in the D30/D60 Tips section on Fred Miranda's website) you can fool the camera about the TC's presence. The main reason you might want to do this is to trick the camera into autofocussing when the effective aperture is above f5.6 (or f8 on some cameras). I have done this successfully with my 100-400mm IS (a 10-pin lens) and a 1.4x Kenko on a D30, although the AF performance at f8 is nothing to write home about.

This also explains why when you stack TCs the camera does not recognise the presence of the TC closest to the camera. Keep in mind that in situations like this the camera is not able to record the complete details about the settings used in the photo.
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Saturday, June 1, 2002

Kirk SS-1 Shoulder Strap

The SS-1 uses a standard Arca-Swiss quick-release clamp to attach to the foot of a telephoto lens. In this way a lens that's detached from a camera can simply be slung over your shoulder or around your neck until you need it.

Or you might decide to use it to carry a lens with camera attached. I've been using a 100-400mm IS lens with my EOS D30 for quite a while now, and there are often times when it's dangling from my neck via the strap attached to the camera body as my hands are full of other things. The 100-400 is not a featherweight lens and this puts quite a bit of stress on the camera body around the lens mount, which has made me a little uneasy. Alleviating this was the main reason I purchased the SS-1.

I did a bit of web searching before I purchased, and only read good things about it. I was about to purchase some other equipment from Kirk Enterprises, so the decision was easy.

The "Arca-Swiss" QR system

Of course, it's not much use unless your lens has an Arca-Swiss plate on its tripod foot, such as those available from Wimberley, Kirk Enterprises, and Really Right Stuff. These plates are usually made from machined aluminium and are designed to attach securely to the lens and not rotate. Often the plate will be specifically designed for a particular lens to achieve a secure grip. Similarly, plates are available for specific camera bodies. The plate on the camera or lens is designed to slide into a clamp on a tripod head and be gripped from the sides. Some heads (such as the B-1 ballhead from the company that started it all: Arca-Swiss) come with these clamps built-in, but a variety of clamps are available to fit to existing platforms.

Because the plates are matched to the device they're supporting, they provide a better grip than systems like Manfrotto's PL-14 QR plates, which follow a one-size-fits-all philosophy. The Arca-Swiss system is used for cameras and lenses from Nikon Coolpix digicams up to large-format gear. Various plates and clamps differ in details such as their length, but they are all compatible. Many accessories are available for the Arca-Swiss system, including flash brackets that attach to the lens or camera plate at the same time as the clamp on your tripod's head. The SS-1 is yet another useful accessory in the family.

How it hangs
SS-1 +lens+bodySS-1 +lens
By way of illustration you can see here the 100-400mm lens hanging from the strap, and also with the D30 and BG-ED3 grip attached. When worn on the body the camera and lens sits differently than shown here, depending on the length of the straps and the rotation of the tripod foot. I didn't have an assistant handy when I was taking these photos to model the gear, so you'll have to take my word for it.

The clamp's knob is easy to grip and the clamp feels nice and solid when attached to the lens plate. Some lens plates have "stop screws" which can be set to stop the plate sliding out one end of a loosened clamp. This gives you extra piece of mind for when you forget to tighten the clamp, but in any case the SS-1 really does provide a solid grip.

The padded portion of the strap is curved in order to hang well on your shoulder, and the "inside" is rubberised in order to provide a good grip.


So far the SS-1 has lived up to my expectations. As I get more time in the field with it I may uncover some niggles, but it's been great so far. The D30 plus BG-ED3, 1.4TC, 100-400mm IS, and 420EX flash is the heaviest gear I'll be carrying on it for now, but it's certainly not straining at the weight.

Update after 6 months - December 2002

I've been using the SS-1 for a while now, and it's become a standard part of my gear. I hang it over my left shoulder, underneath my photo vest (sometimes also under a cardigan-style polarfleece) and leave it on all the time. When it's not carrying anything it's out of the way, and otherwise the 100-400mm lens or the camera/lens (and sometimes flash) hang from it when not being used. There's enough slack in the strap that I can pick up the camera and take a handheld shot without detaching from the strap if I need to.

I guess the bottom line is that I'm still happy.
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