M lenses and metering options

Just out of curiosity, does anyone know if adding the infofmation contacts to an M lens as in this method would allow sooper-dooper matrix or pattern metering on the *st D with the old M lenses?

I wrote Pentax, but received a canned reply stating that the lens needs to talk to the camera. DUH!! That's what this method is all about!!!

Dent Arthur Dent,
There are two ways for the lens to communicate. The first is the "old" way using the binary connections as outlined in the method you linked to.
The second way is via the digital "Data" contact where the body interrogates the lens using some kind of serial link.

I suspect the *ist-D uses just the "Data" link for matrix metering (quote taken from the small print of the site you linked to):
But it doesn't exactly say whether matrix metering in manual mode is possible... why don't you email Mark Roberts directly??

Matt

Matt, I sent off an email. We'll see if he has tried it, he uses the *st D

Well, not getting an intelligable reply from anyone, I performed some preliminary tests. The lens tested was the 50mm f/1.4 M lens.

Earliiest results are negative, even with the contact altered, the M lens seems not to be able to use Matrix metering. A 50 f/1.4 A lens has no problem at all, so it must have a ROM chip inside it to communicage with the camera.

Non-AF lenses seem only to be able to use the middle AF sensor, a red light indicates if you're in focus. Selective AF point or auto AF point seem not to be available. No great loss, the AF sensor acts like a focus-aid spot as if there was a microprisim or split image in the viewfinder.

So the camera will use all K mount lenses, but manual focus lenses can only get confirmation via the central point.

This is way better than most autofocus cameras, which are no help at all with a manual focus lens. The *st D is close to perfect.

If they just hadn't crippled the KAF mount.........

Hi,
The answer is on Robert's site if you read it carefully. As far as I am aware there is no chip or any other electronic circuit in an A lens or any of the normal AF lenses. The purpose of all but two of the pins is to indicate the maximum and minimum F stop of the lens. The matrix metering needs this to do it's computations. The 6th pin is to tell the body that the lens has been set to A mode and the camera should set the F stop for program and shutter priority modes. There is no way to make this functional on an M lens so Robert's method always tells the body that it is user set ie in manual or Aperture priority and is why you can't use a programed mode. Now with the "crippled" mount cameras, you must always set the lens to A and use the dials on the body to set aperture in an aperture priority mode and to use matrix metering. No last pin and switch, no command so you can't use a modified lens. In effect, the camera is being told the information it needs to know to use these modes but it is not being told that it should and hence it doesn't work. I rather suspect that this is what Pentax meant when they said the lens needed to communicate.

Regards
Kim

So you are saying that it's that 6th pin that makes the M lens unable to use Matrix metering on the "crippled" KAF mount?

I wonder if there's a way to fake it, than use the lens in Manual mode with Matrix metering? Interesting. Thanks for the information!

Have a look at Robert's site, he gives a diagram of the pins. If you were to put an isolated hole where the A pin is, the camera would see this as you having set the lens to A mode. This should work but you must remember to leave the lens at it's widest setting and you wouldn't be able to use it in manual or aperture priority mode on any camera that makes use of the A settting unless you can select manual and the aperture from the camera body. Still work on a K/M series though. You could try it by covering the relevent pin with a small piece of PVC tape or similiar. You would have to be carefull to make sure you didn't lose when removing the camera. Personally, I thought it would be too much effort for a small gain and perhaps bigger loss in functionality. Why not just get an A lens in the first place Better still get an incident light meter. they are much more accurate than even the matrix metering

Kim

Or use spot metering, which works fine with all lenses.

G

I'm more concened with getting the Matrix mode in manual mode. If I set it up right, I could use the lens in manual, just like I do now, but with the fancy Matrix mode.

I actually use a Sekonic incident meter for most of my work, but I thought it might be fun to try out the Matrix stuff to see if its's any good.

I don't expect much from it. I tried my one AF lens with multi-point AF, and all that happened is the lens started gyrating wildly between focus points.

Now I just leave the camera set to center point AF, it's faster and easier.