Teleconverter & Focal length

Bart · 04-17-2009, 12:16 PM

I'm posting this in the beginners corner since I'm cleary a beginner regarding teleconverters.
Last year I got a tc but up till now, I didn't use it very much and only with an 'A' lens (due to a variety of reasons).
So, when mounting the A lens + the tc, the camera asks for the focal length - no problem there.
Some days ago, I tried it out for the first time with a FA lens. Of course the camera didn't ask for a focal length and the lens being FA, I thought nothing of it.
Or rather, I assumed the focal length in the exif would be multiplied by the factor of the tc (1,7) but of course, it wasn't

.

Now, how do you best deal with this phenomenon?

Last edited by Bart; 04-18-2009 at 02:53 AM.

SOldBear · 04-17-2009, 12:54 PM

I don't think there is away to deal with this, at least with the TCs I've seen and with the K10D.

You see, the TC has "pass through" electrical connections. There is no data manipulation. The body reads the data, including the data of focal length, from the lens. The body doesn't know there is the TC in between.

The K10D does not allow the user to input focal length of the lens if the data (even incorrect) are already available.

Is there any TC that massages the data from the lens before passing to the body?

Bart · 04-18-2009, 03:04 AM

Originally posted by SOldBear

...The body doesn't know there is the TC in between.
The K10D does not allow the user to input focal length of the lens if the data (even incorrect) are already available...

Bummer.
I suppose there is nothing to be found in the exif data about the tc neither?

flyer · 04-18-2009, 04:21 AM

You can try a piece of tape on the contact that feeds the focal length.

Marc Sabatella · 04-18-2009, 10:37 AM

FWIW, the worst that happens when SR focal length is too low is that it doesn't work quite as effectively as it otherwise would. Still better than nothing.

Bart · 04-18-2009, 11:19 AM

Well, thanks for the replies, people.

Blocking the contacts seems indeed to be a solution but a bit too much fiddling for me.

The sr will indeed be better than nothing. It's better to have the focal length set too low than too high, isn't it.

I was more thinking about the distinction between the fl of the lens "as is" and with tc as a selection parameter, in LR for instance.

By the way, SOldBear said the K10D doesn't allow to change the fl when it is available from the lens. Does this mean you can do this on the K20D?

SOldBear · 04-18-2009, 11:47 AM

Originally posted by Bart

By the way, SOldBear said the K10D doesn't allow to change the fl when it is available from the lens. Does this mean you can do this on the K20D?

No, it just means I can't do it on my K10D, and I don't know about the K20D.

Bart · 04-18-2009, 12:37 PM

Originally posted by SOldBear

No, it just means I can't do it on my K10D, and I don't know about the K20D.

This was just curiosity on my part: I also have the K10D.
If it had been available on the K20D, then it would certainly be available on a future model as well.
And it is not possible on the K20D either: I just checked the on-line manual.

04-17-2009, 12:16 PM	#1
Bart Pentaxian Join Date: May 2007 Location: WW community of Pentax users Photos: Gallery \| Albums Posts: 2,646	Teleconverter & Focal length I'm posting this in the beginners corner since I'm cleary a beginner regarding teleconverters. Last year I got a tc but up till now, I didn't use it very much and only with an 'A' lens (due to a variety of reasons). So, when mounting the A lens + the tc, the camera asks for the focal length - no problem there. Some days ago, I tried it out for the first time with a FA lens. Of course the camera didn't ask for a focal length and the lens being FA, I thought nothing of it. Or rather, I assumed the focal length in the exif would be multiplied by the factor of the tc (1,7) but of course, it wasn't . Now, how do you best deal with this phenomenon? Last edited by Bart; 04-18-2009 at 02:53 AM.

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04-17-2009, 12:54 PM	#2
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	I don't think there is away to deal with this, at least with the TCs I've seen and with the K10D. You see, the TC has "pass through" electrical connections. There is no data manipulation. The body reads the data, including the data of focal length, from the lens. The body doesn't know there is the TC in between. The K10D does not allow the user to input focal length of the lens if the data (even incorrect) are already available. Is there any TC that massages the data from the lens before passing to the body?

04-18-2009, 03:04 AM	#3
Bart Pentaxian Join Date: May 2007 Location: WW community of Pentax users Photos: Gallery \| Albums Posts: 2,646 Original Poster	Originally posted by SOldBear ...The body doesn't know there is the TC in between. The K10D does not allow the user to input focal length of the lens if the data (even incorrect) are already available... Bummer. I suppose there is nothing to be found in the exif data about the tc neither?

04-18-2009, 04:21 AM	#4
flyer Veteran Member Join Date: Jan 2008 Location: Ste-Anne des Plaines, Qc., Canada Posts: 2,013	You can try a piece of tape on the contact that feeds the focal length.

04-18-2009, 10:37 AM	#5
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	FWIW, the worst that happens when SR focal length is too low is that it doesn't work quite as effectively as it otherwise would. Still better than nothing.

04-18-2009, 11:19 AM	#6
Bart Pentaxian Join Date: May 2007 Location: WW community of Pentax users Photos: Gallery \| Albums Posts: 2,646 Original Poster	Well, thanks for the replies, people. Blocking the contacts seems indeed to be a solution but a bit too much fiddling for me. The sr will indeed be better than nothing. It's better to have the focal length set too low than too high, isn't it. I was more thinking about the distinction between the fl of the lens "as is" and with tc as a selection parameter, in LR for instance. By the way, SOldBear said the K10D doesn't allow to change the fl when it is available from the lens. Does this mean you can do this on the K20D?

04-18-2009, 11:47 AM	#7
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by Bart By the way, SOldBear said the K10D doesn't allow to change the fl when it is available from the lens. Does this mean you can do this on the K20D? No, it just means I can't do it on my K10D, and I don't know about the K20D.

04-18-2009, 12:37 PM	#8
Bart Pentaxian Join Date: May 2007 Location: WW community of Pentax users Photos: Gallery \| Albums Posts: 2,646 Original Poster	Originally posted by SOldBear No, it just means I can't do it on my K10D, and I don't know about the K20D. This was just curiosity on my part: I also have the K10D. If it had been available on the K20D, then it would certainly be available on a future model as well. And it is not possible on the K20D either: I just checked the on-line manual.