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01-26-2010, 01:46 AM   #1
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Hoya Teleconverter Question

I have an autofocus Hoya teleconverter. It has no electrical contacts. I have a Pentax K10d. Am I right in thinking that if I try to use this with a lens without an aperture ring the only way of doing so is to put the camera into AV or Green mode and the camera will then use the lens aperture wide open? I guess I also need to use manual focusing? Not sure under what circumstances the supposed "autofocus" ability of the lens could be used? Grateful for any advice.

Paul

01-26-2010, 02:02 AM   #2
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If it has no electrical contacts, I don't think it's going to be AF. Show a picture of it for clarification.
01-26-2010, 02:54 AM   #3
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As Wallaby wrote: a tc without electrical contacts can hardly be AF.

Ben
01-26-2010, 07:05 AM   #4
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Here are a couple of shots as requested:

First, mount on camera side:


This one is from mount on lens side:


It says "Hoya Auto Teleconverter" on the casing.

Paul

01-26-2010, 08:17 AM   #5
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I think the word "auto" is for auto aperture in A mode.
01-26-2010, 09:38 AM   #6
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Paul, this is unfortunately a purely manual tele converter. NO AF function and not even the electrical contacts you would need to keep all the Program-modes of a current Pentax digital SLR.

Ben
01-26-2010, 12:43 PM   #7
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QuoteOriginally posted by mcjm78 Quote
I think the word "auto" is for auto aperture in A mode.
Not even "A" mount. Straight K mount form the 70's
Features and Operation of the Original K-Mount
Auto referring to metering wide open and "automatically' closing the lens down to the shooting aperture.
Automatic-Diaphragm Lenses

These are the "standard" lenses, and unless otherwise specified, it is assumed that every lens uses an automatic diaphragm. Lenses in this category have an additional lever that allows the body to open their diaphragms wider than dictated by the aperture ring. In particular, the body keeps the diaphragm fully open at all times except in the short moment of making a photo. The operating procedure is thus reduced to:

1. Compose and focus without worrying about the selected f-stop. Since the body keeps the lens diaphragm fully open, the image in the viewfinder is as bright as possible and the DOF is minimal.
2. Choose an aperture value that will produce the desired DOF. To see the actual DOF, press the DOF preview lever on the body. If the body does not have such a lever, examine the DOF scales on the lens. If the lens does not have such a scale, calculate the DOF range or look it up in a table.
3. Calculate and set the desired shutter speed (or let the camera body do it, if in Av mode).
4. Trip the shutter.

Even though DOF preview requires an extra action, the overall convenience is significantly improved.

to the OP, sorry no AF ect.......
01-26-2010, 04:16 PM   #8
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Many thanks to everyone. That has clarified things a lot for me. Thanks especially for that link Jeffkrol; it was very informative. Originally bought this 3x teleconverter to have a bit of fun rather than serious photography hoping to use it with my DA*300 and also for occasional long distance shots across lakes as I do a bit of wildlife photography. It is unusable with the DA 300. It is a lesson in ensuring I have a good understanding of the complications of the varying Pentax mounts down the ages before jumping into a purchase. I have managed to use it with my Sigma 70-300DL in manual and Av mode and now I understand why. The optics seem pretty good for a 3x TC. I guess it should be possible to use with some automatic lenses but I presume you could only shoot wide open which would limit the IQ that could be achieved?

Paul

01-29-2010, 10:04 AM   #9
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I correct myself. I've now retried the Hoya 3x TC with my DA*300 and it does work. When I tried it before it must have been something to do with either the order I assembled everything or the programme mode I had the camera in. I took a quick shot earlier. The overall scene with another lens at 70 mm first:



With the Hoya TC and DA300 focusing on the top of the pole for the parasol:



This was only a quick shot to retry the combination to see if I could get them to work. It was hand held with a cushion for supporting the lens/camera. I had the camera and lens in manual focus and the camera in Av mode. Light is poor today so with the loss of F stops as well shutter speed was slow, about 1/30th. I had to use some -exposure compensation as well as the first image was overexposed. Still, though the IQ is not great on this occasion, the result gives me some encouragement to try the combination on a tripod on a bright day. May possibly give me some mileage for the occasional long shot across a reservoir or lake. I guess though that the lens will only be used by the camera wide open F4 (with 3 stops loss) and as the DA300 doesn't have an aperture ring there isn't much I can do about that and this will limit the potential IQ I can achieve with the combination?

Paul

Last edited by channeler; 01-29-2010 at 10:19 AM.
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