I like using this lens at approximately 200mm for macros because I get a better dof than at 300mm. Problem is, the focus distance is 39". Would Kenco tubes help and if so, how much closer could I get?
Thnax
jackprks Goldmember  1,299 posts Joined Jun 2007 Location: Michigan City, IN More info | Aug 31, 2007 11:03 | #1 I like using this lens at approximately 200mm for macros because I get a better dof than at 300mm. Problem is, the focus distance is 39". Would Kenco tubes help and if so, how much closer could I get? JACK Photos http://www.flickr.com/photos/parksplace
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LordV Macro Photo-Lord of the Year 2006  More info | Aug 31, 2007 11:14 | #2 jackprks wrote in post #3834038  I like using this lens at approximately 200mm for macros because I get a better dof than at 300mm. Problem is, the focus distance is 39". Would Kenco tubes help and if so, how much closer could I get? Thnax Yes tubes will help- a full set of kenkos or Jessops ext tubes will get you to just about 1:1 at 70mm. Although your comment re DOF worries me as that is directly linked to magnification, so the higher the magnification, the lower the DOF. http://www.flickr.com/photos/lordv/
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Aug 31, 2007 11:43 | #3 LordV wrote in post #3834095 Yes tubes will help- a full set of kenkos or Jessops ext tubes will get you to just about 1:1 at 70mm. Although your comment re DOF worries me as that is directly linked to magnification, so the higher the magnification, the lower the DOF. Brian V. This lens @ 200mm the dof is .6 inch, at 300mm is .25 inch. More than twice the dof 200 over 300. All at a distance of 39 inches. JACK Photos http://www.flickr.com/photos/parksplace
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PhotoFranz Goldmember  1,639 posts Likes: 2 Joined Jan 2007 Location: Chicago, Illinois More info | Aug 31, 2007 11:47 | #4 Isn't the DOF highly dependent on the aperature too? .6" at 300mm at what f-stop? http://www.flickr.com/photos/photofranz/
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eccles Goldmember  2,948 posts Joined Jun 2006 Location: Bristol, UK More info | Aug 31, 2007 11:56 | #5 The reason you're getting lower DOF at 300mm is the magnification is greater. Using tubes to get closer won't help your DOF, but it'll help keep your shots steadier if you shoot at shorter zoom settings.
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I used f11 for this example. I have ordered the Kenko tubes from B&H just a few minutes ago. All the threads I have read about them are in praise of them. I don't know much about macro but am learning, mainly from looking at and reading posts in this forum. I understand dof as a function of aperature and magnification but because I have to stay back 39 inches, I have used both 200mm and 300mm and found that (especially hand held) that 200mm is better for me. Of course I have to crop a lot and that is the reason I ordered the tubes. JACK Photos http://www.flickr.com/photos/parksplace
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