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Old Jun 22, 2007, 2:03 AM   #11
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have you set the camera to use the focus indicator when a screw mount lens is used?
custom settings "F1 with S lens used" on my ist ds
i cant try it at the moment
i only have a 400mm screwount and it is pouring down outside
so it is way too dark
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Old Jun 22, 2007, 2:40 AM   #12
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Just an observation:

With my *ist DS:

1.Auto Pict mode

2.Focus switch set to 'AF'

3.Aperture set to 'A'

Focus trap works, but if I move lens away from 'A' it does not work, as far as I can determine the 'A' setting operates the contact that is very slightly depressed on the camera body and there is not way a screw mount lens or its adapter can contact this pin, perhaps this explains the reason the metal foil works.



My next experiment was to mount my M42 50mm F1.4 with a scrap of foil to make contact with the recessed pin. Focus trap works but the camera 'assumed' the lens was set to 2.8, which it was not, maybe it always assumes the lens is 2.8 but more tests may tell.




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Old Jun 22, 2007, 3:43 AM   #13
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More experiments:

With the camera and lens as before. It seems the camera always "thinks" the aperture is set to 2.8 and that is what is written in the exif data however the exposure does seem to be right. I experimented with my M42 lens (the 50mm F1.4) indoors under tungsten light. Holding the shutter button down (while out of focus) showed the shutter speed changing as expected when I rotated the aperture ring on the lens. Slowly rotating the focus ring caused the shutter to fire.



So that seems to be the story for focus capture with a screw mount or fully manual lens all that is required is the recessed contact on the camera be grounded, the camera set for auto focus and 'Auto Pict' (I did not test other modes).

Putting the bit of tinfoil in is not something I am really happy with and Iwould like to make some sort of 'focus capture' adapter. Perhaps a teleconverter with the contact added or maybe an adapted macro ring. Hmmm, I wonder if a contact could be added to one of those flange (non-flush) type M42 adapters.


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Old Jun 25, 2007, 1:19 AM   #14
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John Hill wrote:
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So that seems to be the story for focus capture with a screw mount or fully manual lens all that is required is the recessed contact on the camera be grounded, the camera set for auto focus and 'Auto Pict' (I did not test other modes).

Putting the bit of tinfoil in is not something I am really happy with and Iwould like to make some sort of 'focus capture' adapter. Perhaps a teleconverter with the contact added or maybe an adapted macro ring. Hmmm, I wonder if a contact could be added to one of those flange (non-flush) type M42 adapters.
If by fully manual you mean a K-M.... focus trap will work fine on those (at least on K-10D) as the smooth K-M mount does ground out all the auto/F pins. My KM lenses focus trap just fine. And actually the contacts protrude slightly, not recessed... but I guess not enough to hit a flush adapted M42 lens that does not cover the entire mount, or paint too non conductive, (as most I have seen have painted black backs) etc.

So yes a bare metal flanged M42 adapter should do exactly the same thing, as its smooth and flush to the mount surface and wide enough to do that too. (As well as engage the locking pin if it has the slot for it)

And pehapes if the flush type adapted M42 lens does cover the contacts.... just sanding off the paint in that area would do the trick too.
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Old Jun 25, 2007, 2:10 AM   #15
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Hayward wrote:
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So yes a bare metal flanged M42 adapter should do exactly the same thing, as its smooth and flush to the mount surface and wide enough to do that too. (As well as engage the locking pin if it has the slot for it)

And pehapes if the M42 lens does cover the contacts.... just sanding off the paint in that area would do the trick too.
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Well no, I cant agree with you Hayward, the camera contact that is matched by the 'A' pin of the lens is below the surface of the camera mount, at least it is on my *ist DS and here is a picture of a K10, clearly showing the third pin (from the left) is depressed on it too.




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Old Jun 25, 2007, 3:46 AM   #16
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I have just done another experiment which I think concludes the identification of what is required to get focus capture with old lenses.

I took an old teleconverter and fitted a sprung ball in the position to match the depressed contact on the camera and now I have focus capture on all old lenses including the most basic, that is M42 screw mount lenses.



As far as I can understand you can get focus capture with any lens that has an 'A' setting on the aperture, otherwise you need something (tinfoil for example) to make contact with that depressed pin.
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Old Jun 25, 2007, 4:39 PM   #17
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John Hill wrote:
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Well no, I cant agree with you Hayward, the camera contact that is matched by the 'A' pin of the lens is below the surface of the camera mount, at least it is on my *ist DS and here is a picture of a K10, clearly showing the third pin (from the left) is depressed on it too.
OOPS you are right it is, all the others aren't.... but regardless a K/M lens will focus trap just fine. (again on 10Dat least, though only center point is available)

The A contact shouldn't really matter as that is exposure not focus, and it would not touch a M lens, but a M lens will ground out the other contacts and that seems to be what matters.


PS I should have realized that about the A contact, as I have an A lens that accidentally got out of A, which lifts the cnntact on the lens making it essentially an M lens, as that is the only contact on an A lens.
Still focus trapped fine but was a bit confused about exposure for a bit since the lens doesn't stop down and was still wide open.through the VF. Then took a shot and realized it was at like F22 or 16, and then figured it out. (It was a dark place, and couldn't really read the lens)


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Old Jun 25, 2007, 4:59 PM   #18
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The A contact shouldn't really matter as that is exposure not focus, and it would not touch a M lens, but a M lens will ground out the other contacts and that seems to be what matters.

Thats not what I am finding Hayward. I have no idea why the A contact is important for focus trap but all indications are that it is. Most of the other contacts are there to indicate the maximum aperture of the lens, thats why most lenses have either nothing (which seems to indicate f2.8 or a pattern of insulated dots. The lowest end contact seems to be data and somehow signals focal length but I cant see it signalling focus as as far as I know it is the camera that senses focus not the lens (someone may correct me on that detail?).

There is a table of the contact here http://www.robertstech.com/matrix.htm



Simply put, on the *ist DS, when I mount a M42 lens and set the camera to auto there is not focus trap. If I short the A contact to ground I get focus trap.

I made an 'adapater' from an old teleconverter that supports what I am saying, it has no contacts except a grounded A contact and with that on the camera I get focus trap with the most basic of lens, the M42 screw mounts. I will try and make a better one to photograph and show on here.

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Old Jun 25, 2007, 5:16 PM   #19
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John Hill wrote:
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. Most of the other contacts are there to indicate the maximum aperture of the lens
Nope, that all gets through the A contact... again all my A lenses have just the one contact.... and camera know how wide it it can open. And also out of A ring setting that lifts the A contact, foucus still traps.

Now the Focal length and all that is on the other pins, and some information for multipoint focus likely (as only centerpoint will work on a A or M lens) and other stuff.

RE-EDIT and looking at the article you mention, that explains it they are for the mult point, functions

On a A lens you must manally set the FL for for the SR as that is not reported

Could be just any of the pins needs to be grounded (though A wouldn't be on an K/M lens) And again possibly the paint on most M42's insulates the others from doing so. A ball bearing or tinfoil wad would ground the contact to the camera mount, accomplishing same thing, but not really the lens doing it, as a bare metal K/M/A would.


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Old Jun 25, 2007, 5:38 PM   #20
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Whatever..:?

Just wait until I get my pukka 'adapter' and we will have more to go on.


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