Macro confusion.......

**gsrokmix** · 11-26-2009, 07:49 PM

Hi,

I am confused a little. In order to be able to achieve a 1:1 size using extension tubes on my K20:

1) Do I have to use a macro focusing lens with the tubes (like a Macro Takumar), or any prime like the 1.4 50mm?

2) If i want to use a 100mm lens with tubes do I have to stack 100mm worth of tubes (ie. 2 full sets or 6 tubes) behind the lens to get the 1:1?

I've read quite a bit on this but am unsure of the above.

Thanks!

George

**Ash** · 11-26-2009, 07:55 PM

Think of it this way:
Using a 50mm lens, 50mm of extension tubes doubles its native magnification.
Don't know what the highest magnification is for the 50/1.4, but let's say it's 1:4, then 50mm of tubes would make it 1:2.
Indeed, 100mm of tubing is necessary to convert a 100mm 1:2 macro to a 1:1 macro.

Peter Zack · 11-26-2009, 08:27 PM

Ash sorry but you have that somewhat wrong and that's why there's confusion about this subject. It does not matter what the lens magnifies at if it's a normal lens (non macro). If it's macro, then you get a double effect with tubes added.
So to get 1:1 with a 50mm add 50mm of extension. To get a 100mm lens at 1:1, then add 100mm of extension. So with any lens, just add the same length of the lenses focal length in extension tubes to get a 1:1 ratio.

If the 100mm is 1:2 macro on it's own. Then you are making it 1:1 with a 100mm extension and then if you extend it to it's macro ability, it's now a 1.5 :1 (or 1.5x life sized) but in the real world, when you extend a 100mm macro lens with tubes and then it's own macro extension, the front edge of the lens is so close to the subject, you can hardly get any light in there.

To be sure I just double checked my old Honeywell book that discusses adding a lens to a bellows.

**gsrokmix** · 11-26-2009, 08:44 PM

Aahhhh, thanks to you both. So I can actually get 1:1 w/ my 50mm & tubes. That's exciting! What kind of magnification would I get if I reversed mounted my 50 or say stacked it with my 28mm?

Thanks again!

George

Peter Zack · 11-26-2009, 08:47 PM

Have a look at this. it's a tad more complex than a simple answer:

Macro Math

**Ash** · 11-26-2009, 08:53 PM

Right Peter - I did know that, but explained it poorly and too simplistically.
Thanks for clarifying it.

**gsrokmix** · 11-26-2009, 09:33 PM

Thank you for your link Peter. The information in your article cleared up a lot for me. I have a much better understanding now!

Thanks!

George

11-26-2009, 07:49 PM	#1
gsrokmix Site Supporter Join Date: Oct 2009 Location: CT Photos: Albums Posts: 515	Macro confusion....... Hi, I am confused a little. In order to be able to achieve a 1:1 size using extension tubes on my K20: 1) Do I have to use a macro focusing lens with the tubes (like a Macro Takumar), or any prime like the 1.4 50mm? 2) If i want to use a 100mm lens with tubes do I have to stack 100mm worth of tubes (ie. 2 full sets or 6 tubes) behind the lens to get the 1:1? I've read quite a bit on this but am unsure of the above. Thanks! George

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
SDHC Confusion!	CeeDee	Pentax Camera and Field Accessories	9	03-13-2010 10:08 AM
confusion about KM criticism	FHPhotographer	Pentax DSLR Discussion	2	03-08-2009 01:52 PM
Lens confusion	desertwalker	Troubleshooting and Beginner Help	4	02-06-2009 09:03 AM
K100D Macro mode confusion	BobG	Pentax DSLR Discussion	10	02-21-2007 08:01 AM
F stop confusion!	slip	Pentax SLR Lens Discussion	5	12-20-2006 04:42 PM

11-26-2009, 07:55 PM	#2
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Think of it this way: Using a 50mm lens, 50mm of extension tubes doubles its native magnification. Don't know what the highest magnification is for the 50/1.4, but let's say it's 1:4, then 50mm of tubes would make it 1:2. Indeed, 100mm of tubing is necessary to convert a 100mm 1:2 macro to a 1:1 macro.

11-26-2009, 08:27 PM	#3
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	Ash sorry but you have that somewhat wrong and that's why there's confusion about this subject. It does not matter what the lens magnifies at if it's a normal lens (non macro). If it's macro, then you get a double effect with tubes added. So to get 1:1 with a 50mm add 50mm of extension. To get a 100mm lens at 1:1, then add 100mm of extension. So with any lens, just add the same length of the lenses focal length in extension tubes to get a 1:1 ratio. If the 100mm is 1:2 macro on it's own. Then you are making it 1:1 with a 100mm extension and then if you extend it to it's macro ability, it's now a 1.5 :1 (or 1.5x life sized) but in the real world, when you extend a 100mm macro lens with tubes and then it's own macro extension, the front edge of the lens is so close to the subject, you can hardly get any light in there. To be sure I just double checked my old Honeywell book that discusses adding a lens to a bellows.

11-26-2009, 08:44 PM	#4
gsrokmix Site Supporter Join Date: Oct 2009 Location: CT Photos: Albums Posts: 515 Original Poster	Aahhhh, thanks to you both. So I can actually get 1:1 w/ my 50mm & tubes. That's exciting! What kind of magnification would I get if I reversed mounted my 50 or say stacked it with my 28mm? Thanks again! George

11-26-2009, 08:47 PM	#5
Peter Zack Pentaxian Moderator Emeritus Join Date: May 2007 Location: Edmonton Alberta, Canada Photos: Gallery \| Albums Posts: 10,643	Have a look at this. it's a tad more complex than a simple answer: Macro Math

11-26-2009, 08:53 PM	#6
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Right Peter - I did know that, but explained it poorly and too simplistically. Thanks for clarifying it.

11-26-2009, 09:33 PM	#7
gsrokmix Site Supporter Join Date: Oct 2009 Location: CT Photos: Albums Posts: 515 Original Poster	Thank you for your link Peter. The information in your article cleared up a lot for me. I have a much better understanding now! Thanks! George