Qn on Closeup filter

[zh3ng]

Hi CS bros,

I read through the closeup filter thread, but I don't know how to do the calculations.

I currently have a sigma 70-300mm macro. the macro working distance from lens front to subject is 0.95m

So if I get a Closeup+4 filter, what will be the new macro working distance? Which means how close can I go up to my subject?

At the moment, with my lens front range at 0.95m, it's very hard to take closeup subjects to get a bigger macro view. So i'm thinking what closeup filter range i should get to go up to at least below 0.5m or to 0.25m.

Thanks in advance.

 

[windwaver]

+2.9 29cm
+1.6 39cm
+4.5 19cm
+8 10cm

 

[Entertainer]

+2.9 29cm
+1.6 39cm
+4.5 19cm
+8 10cm

may i know how did u calculate this? is there a formula? thanks!

 

[FIR]

Sigma 70-300 can do 1:2 half lifesize, which magnifying power do I need to get 1:1?
Is it +1 power?