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08-29-2007, 05:02 AM   #1
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What closeup lens required to make the Tamron 28-75/f2.8 do macro at 1:1?

Hi

The Tamron 28-75/f2.8 can do closeup at 1:1.39. What closeup lens (+2, +3, etc) is required to make it do say 1:2 or 1:1?

Is this possible at all?

Thanks

08-29-2007, 05:46 AM   #2
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The Tamron's built in "macro" ratio is 1:3.9 so I'd guess that a 2+ gives you about 1:2 and a 4+ gives you about 1:1. But the filter size is large on this lens at ø67. So if you can find these sized diopters they could be expensive. Plus these add on filters aren't the greatest for image quality etc. Why not consider a set of extension tubes? They will cost the same or less and you get the full image quality of this great lens. Also you can use the extension tubes on any lens you own now or in the future.
08-29-2007, 05:59 AM   #3
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How does a 2+ closeup lens make the 1:3.9 lens go 1:2? I would like to know the maths of how to calculate this.

Thanks
08-29-2007, 06:20 AM   #4
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I don't know the math, but I know how diopters work :-)

A +x diopter makes any lens' focus distance 1/x meter (eg. a +2 gives a working distance of 1/2m, a +4 gives 1/4m, etc) irrespective of the lens' focal lenth. The resulting magnification is calculated from that distance, and the lens' focal length.

08-29-2007, 06:58 AM   #5
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If you are going for closeup filters then get the nikon or canon ones, not the cheap 1 element filters.

I believe the Nikon is only available in 2 different filter sizes, but the canon one is available in several.

I have the Nikon filter and I also had some cheap... I think they were hoya.. closeup filters which I gave away when I sold a camera I had before because they were no good, but I kept the Nikon filter.
08-29-2007, 09:08 AM   #6
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For canon u mean the 250D and 500D filter?
08-29-2007, 11:18 AM   #7
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Yep, just bought a 500D filter for a friend of mine who wanted it for his 50-200.
The Nikon ones should be equally good though, but the 500D can be had in many sizes, up to 77mm. The Nikon I believe is 62mm and 52mm
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