Quick question about extension tubes.

Buddha Jones · 07-08-2009, 07:42 PM

To make a 50mm Macro go from 1:2 to 1:1, do I need 50mm worth of tubes?

X Man · 07-08-2009, 07:56 PM

Yes. ...and 10 char...

*EDIT* Err, wait. You said it's already @ 1:2 didn't you? My bad. I've got no idea. Maybe half that, or less would do it. You'll have to wait a sec for someone who knows, you know. Math. ;-)

*EDIT2* Ooh, ooh! I was right, I was right... Half that will do it. So, 25mm of "tubage" should get you to 1:1 according to the Lord Google.

Regards,
Mike

Buddha Jones · 07-08-2009, 08:50 PM

I googled it and only got more confused.... but that is what I thought I read as well but wanted to make sure.

**gofour3** · 07-08-2009, 09:40 PM

Use a #3 Pentax Auto Extension tube, which is 26mm or a Manual tube #3 which is 28.5mm.

Phil.

**Canada_Rockies** · 07-09-2009, 09:54 AM

Originally posted by Buddha Jones

To make a 50mm Macro go from 1:2 to 1:1, do I need 50mm worth of tubes?

Buddha, to take a 1:2 lens to 1:1, you need additional extension of half the focal length of the lens. 1:1 means that the lens has extension of exactly the same amount as the lens' focal length. If the lens already has enough extension to get to 1:2, it has half its focal length in the focusing helical, and you need another half.

My M 100mm macro uses a 50mm tube to switch the range to between 1:2 and 1:1 from infinity to 1:2.

**gofour3** · 07-09-2009, 02:00 PM

Originally posted by Canada_Rockies

Buddha, to take a 1:2 lens to 1:1, you need additional extension of half the focal length of the lens. 1:1 means that the lens has extension of exactly the same amount as the lens' focal length. If the lens already has enough extension to get to 1:2, it has half its focal length in the focusing helical, and you need another half.

My M 100mm macro uses a 50mm tube to switch the range to between 1:2 and 1:1 from infinity to 1:2.

Yep I also have a Pentax 50mm extension tube for my K100/4 macro and it does the trick.

Pentax does not make a 25mm tube for the 50mm macro, so you need to get the set and use the #3 tube, in either the auto or manual version.

Phil.

07-08-2009, 07:42 PM	#1
Buddha Jones Veteran Member Join Date: Sep 2006 Location: Charlotte, NC Photos: Gallery Posts: 2,591	Quick question about extension tubes. To make a 50mm Macro go from 1:2 to 1:1, do I need 50mm worth of tubes?

07-08-2009, 07:56 PM	#2
X Man Veteran Member Join Date: Aug 2008 Location: Maine Photos: Gallery Posts: 478	Yes. ...and 10 char... EDIT Err, wait. You said it's already @ 1:2 didn't you? My bad. I've got no idea. Maybe half that, or less would do it. You'll have to wait a sec for someone who knows, you know. Math. ;-) EDIT2 Ooh, ooh! I was right, I was right... Half that will do it. So, 25mm of "tubage" should get you to 1:1 according to the Lord Google. Regards, Mike Last edited by X Man; 07-08-2009 at 08:04 PM.

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07-08-2009, 08:50 PM	#3
Buddha Jones Veteran Member Join Date: Sep 2006 Location: Charlotte, NC Photos: Gallery Posts: 2,591 Original Poster	I googled it and only got more confused.... but that is what I thought I read as well but wanted to make sure.

07-08-2009, 09:40 PM	#4
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 5,293	Use a #3 Pentax Auto Extension tube, which is 26mm or a Manual tube #3 which is 28.5mm. Phil.

07-09-2009, 09:54 AM	#5
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 9,402	Originally posted by Buddha Jones To make a 50mm Macro go from 1:2 to 1:1, do I need 50mm worth of tubes? Buddha, to take a 1:2 lens to 1:1, you need additional extension of half the focal length of the lens. 1:1 means that the lens has extension of exactly the same amount as the lens' focal length. If the lens already has enough extension to get to 1:2, it has half its focal length in the focusing helical, and you need another half. My M 100mm macro uses a 50mm tube to switch the range to between 1:2 and 1:1 from infinity to 1:2.

07-09-2009, 02:00 PM	#6
gofour3 Site Supporter Join Date: Oct 2008 Location: Vancouver, Canada Posts: 5,293	Originally posted by Canada_Rockies Buddha, to take a 1:2 lens to 1:1, you need additional extension of half the focal length of the lens. 1:1 means that the lens has extension of exactly the same amount as the lens' focal length. If the lens already has enough extension to get to 1:2, it has half its focal length in the focusing helical, and you need another half. My M 100mm macro uses a 50mm tube to switch the range to between 1:2 and 1:1 from infinity to 1:2. Yep I also have a Pentax 50mm extension tube for my K100/4 macro and it does the trick. Pentax does not make a 25mm tube for the 50mm macro, so you need to get the set and use the #3 tube, in either the auto or manual version. Phil.