Sigma 17-70mm DC Macro lens + Extension tube

[subha]

I have a Sigma 17-70mm DC Macro lens. It's magnification factor is 1:2.3, which

is as close as one can get to life size.

 

Now what extension tube size should i use to increase magnification to 1:1 and

beyond. 12mm? 25mm? or 36mm? or a combination of extension tubes and 2x tele

converter

 

- EOM

[mark u]

You are not usefully going to be able to get to life size and larger magnifications with that lens. Put the money you were thinking of spending on tubes and TC into a proper macro lens instead - you'll be pleased you did.

[subha]

i already have a 2x tele convertor, and have access to extension tubes (kenko set) : 12mm, 20mm, and 36mm. I did play with it briefly and i can use them individually and still be able to do auto focus

[mark u]

Then play with them and see, putting the tubes on the lens and the TC behind. However, I don't think image quality will be great. You can measure the magnification you get by photographing a ruler.