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Photography Question 
Sherri McGee
 

Macro Lens Vs. Extension Tubes


I struggle with depth of field with my macro lens. I have a 100mm macro lens and a set of Kenko extension tubes. Can someone tell me the difference between the two? Is one easier to use? Can I get better DOF with the extension tubes? I really struggle with macro shots. Trying to get the tripod set up just right is impossible. When I use the extension tubes, do they only work at one distance vs. the macro lens that I can focus?


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3/16/2005 5:25:29 AM

 
Robert Hambley
rlhambleyphotography.com
  OK, here is my experience and knowledge of macros and extension tubes.
Macro lenses let you focus at closer distances than regular lenses. Extension tubes increase the size of the image on the sensor (or film) without the use of glass by increasing the distance from the lens to the sensor. An extension tube reduces the minimal focus distance, and the depth of field is reduced (but increasing the f-stop will help give control over the depth of field).
A little hint I found on another thread on BP, when doing macro: set the camera up on the tripod. Set the background, then move the subject into position, sliding it back and forth until it is in focus and position. This is sometimes easier than adjusting the tripod.
Hope this helps and Good Luck.


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3/16/2005 8:18:22 AM

 
Michael H. Cothran   There is no real difference. A true "macro" lens simply has a "built-in extension tube." Look at the back of your macro - see all that space in there?
The optical rule is this: the farther you space your lens from the film plane, the closer you can focus. Thus, the purpose of extension tubes is to do just that - extend your lens farther from the film plane. Your macro lens does the same thing, only it does it internally with its built-in helicoid - and it has a whopping helicoid system inside - look how long it gets when you focus from infinity down to 1:2 or
1:1. Aside from this is the fact that true macro lenses are optically designed to provide the best imaging in the closer ranges, usually about 1:10, while "normal" type lenses are optically designed to provide optimum quality about 10-15 feet away. Macro lenses also have a flat focusing plane - ideal for stamps and other flat surfaces, while regular lenses all have curved focusing planes.
You CAN use your extension tubes in conjunction with your macro lens to get even closer. I own some MF macros from the 1970s that only focused to 1:2, but came supplied with a dedicated extension tube that, when mounted, would get you down to 1:1.
As far as DOF is concerned, it makes no difference whether you are using an extension tube or just the macro lens. On the same lens, at any given focusing ratio, your DOF will be the same.
Michael H. Cothran
www.mhcphoto.net


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3/16/2005 4:00:00 PM

 
Bob Cammarata
BetterPhoto Member Since: 7/17/2003
cammphoto.com
  One thing I've found helpful when trying to focus on a macro subject is to set my lens to the minimum focus distance before getting into place. Then, while looking through the viewfinder, I'll ease into position until I see the subject pop into focus.
With the tripod firmly mounted, I'll lean the camera forward or backward just enough to assure tack-sharp focus on a critical part of the image ... then take the shot.
This can be done with macro lenses or extension tubes (or a combination of both), but keep in mind that light loss, subject and/or camera movement, and a lack of DOF will be your biggest challenges.
I wouldn't recommend moving the subject back and forth unless it is firmly anchored on something stationary or some movement will likely register.


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3/16/2005 5:46:41 PM

 
Robert Hambley
rlhambleyphotography.com
  Greetings,
Bob's suggestion is better. I only move the subject back and forth when I have control over its exact position. For this I use the 'PLAMP'. It is a plant clamp, that can hold the stem.
Good Luck!


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3/17/2005 8:09:47 AM

 
Sherri McGee   Thanks everyone. I spent several hours in my yard this week practicing macro.


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3/18/2005 3:10:10 PM

 
Allen M. Aisenstein
BetterPhoto Member Since: 3/3/2005
 
 
 
Depth of field is of particular importance when shooting things like flowers and insects. Increase DOF with small apertures (f22 and smaller). This will require more light which could be provided with a flash or just a slower shutter speed. I consider a tripod manditory for maximum DOF and sharpness.


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3/23/2005 7:09:35 AM

 
Allen M. Aisenstein
BetterPhoto Member Since: 3/3/2005
 
 
 
Depth of field is of particular importance when shooting things like flowers and insects. Increase DOF with small apertures (f22 and smaller). This will require more light which could be provided with a flash or just a slower shutter speed. I consider a tripod manditory for maximum DOF and sharpness.


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3/23/2005 7:16:09 AM

 
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