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08-13-2010, 03:51 AM   #1
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Catch-in focus with Tamron SP AF 90mm 2.8 Di Macro

Hi,

I was wondering if you could tell me if it is possible to use catch-in focus on the Pentax K20D with the Tamron 90mm lens.

The K20D manual states if the camera is set to AF.S and it is used with a "DA or FA lens that has a AF and MF setting on the lens" - with the lens set to A, you can use catch in focus.

Does this mean this applies only to pentax lenses (DA and FA) or is it that they just don't like to advertise 3rd party lenses, but that it would work equally well on any lens that has an AF/MF switch?

The tamron is discussed at the end of this forum:
https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/51036-how-use...tch-focus.html

This seems to suggest that it doesn't work with the Tamron - unless you cover over one of the pins. Have I understood that right?

Similarly, the manual to the Tamron 90 states that btoh camera and lens should be set to AF or both should be set to MF. Thus, it seems to imply that you should not have the camera set to AF, while the lens is set to MF. Is that right?

Also, it states that "when focusing ring is set in the manual focus position while the camera is set in AF mode, the focusing right rotates as if it were in autofocus mode. Turning of the focusing ring in this instance may cause damage to the lens and/or the camera body."

But when it says the ring will move, does this mean it will autofocus as normal, or does it just mean it will move, but without focusing?

Does it mean that you shouldn't use this combination of settings, or only that if you do you need to make sure you don't turn the focusing ring?

Any information on this would be appreciated.

Thanks

Rob

P.S. Is there a B&H store in the UK?

08-13-2010, 06:24 AM   #2
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Location: New York
Posts: 863
Hello,

I called Tamron and they received your E-Mail. They are working on this and will respond to you directly. I will get a CC of the response and when I do, I will post it here.

C h u c k C a p r i o l a
Live Chat and E-Mail Sales Manager B&H Photo-Video

Thank you, we appreciate your business.
*** Peace on Earth ***
08-16-2010, 10:06 AM   #3
B&H Photo Specialist
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Join Date: May 2010
Location: New York
Posts: 863
As promised;

Hi Rob,

I spoke with our head technician regarding your issue. He is not familiar with that feature of Pentax cameras, and is therefore not comfortable approving use of the lens in MF mode while the camera is set to AF mode. He stands by the manual's recommendation that the lens and camera always be set to the same mode.

Please let me know if you have any questions!


Regards,

Customer Service
Tamron USA, Inc.
10 Austin Blvd.
Commack, NY 11725
631-858-8400


Chuck

08-16-2010, 10:22 AM   #4
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I don't currently own the Tamron 90 (I used to), but from what I remember you would not be able to use catch-in-focus with the Tamron 90 without covering a pin. Basically the camera body has to think the lens is MF. With a DA* lens, turning the AF/MF switch to MF does this. On the Tamron 90, moving the focusing ring to MF doesn't (as far as I know) change how the body "sees" the lens. It just engages/disengages the AF clutch.

So if you have the body set to AF and the Tamron set to AF, the AF will work properly and the focus ring does no turn.

If you have the body set to AF and the Tamron set to MF, the AF will work, but the focus ring will turn and potentially put more stress on the lens/AF motor. I forgot once or twice to switch the focus ring back to AF from MF and there were no ill effects. Whether or not doing this long term would be an issue is another question.

If you have the body set to MF and the lens set to MF, the lens will function as a manual focus lens. But as I stated earlier, I believe the body still think the lens is AF so catch-in-focus won't work. Covering a pin may change that, but I can't say for sure as I've never tried.

Finally, if you have the body set to MF and the lens set to AF, you won't be able to focus as the turning the focus ring in this mode will have no effect on the focus. No harm will come to the lens or body, it's just not a very useful combination to have the body/lens in

Hope that all made sense. If someone reads this and I made a mistake in my explaination, please post a reply and correct me as I'm pretty sure what I wrote is correct, but don't want to spread misinformation if I am incorrect.

QuoteOriginally posted by rob_k20d Quote
Hi,

I was wondering if you could tell me if it is possible to use catch-in focus on the Pentax K20D with the Tamron 90mm lens.

The K20D manual states if the camera is set to AF.S and it is used with a "DA or FA lens that has a AF and MF setting on the lens" - with the lens set to A, you can use catch in focus.

Does this mean this applies only to pentax lenses (DA and FA) or is it that they just don't like to advertise 3rd party lenses, but that it would work equally well on any lens that has an AF/MF switch?

The tamron is discussed at the end of this forum:
https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/51036-how-use...tch-focus.html

This seems to suggest that it doesn't work with the Tamron - unless you cover over one of the pins. Have I understood that right?

Similarly, the manual to the Tamron 90 states that btoh camera and lens should be set to AF or both should be set to MF. Thus, it seems to imply that you should not have the camera set to AF, while the lens is set to MF. Is that right?

Also, it states that "when focusing ring is set in the manual focus position while the camera is set in AF mode, the focusing right rotates as if it were in autofocus mode. Turning of the focusing ring in this instance may cause damage to the lens and/or the camera body."

But when it says the ring will move, does this mean it will autofocus as normal, or does it just mean it will move, but without focusing?

Does it mean that you shouldn't use this combination of settings, or only that if you do you need to make sure you don't turn the focusing ring?

Any information on this would be appreciated.

Thanks

Rob

P.S. Is there a B&H store in the UK?


08-17-2010, 01:17 AM   #5
Senior Member




Join Date: Aug 2010
Location: Leeds
Posts: 152
Original Poster
Thanks

Thanks a lot for these responses - very helpful.

Rob
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