Ping Rockyc2 re 1.4 extender

[Ron Lacey]

You were quite correct my Canon Extender couldn't be directly mated to my Sigma 180mm macro so I looked for a workaround which was to mate a 25mm extension tube onto the extender then the lens could be mated with the extension:D . I was curious to see how much magnification I could get with this gear so I did some test shots.

The posted photos are 20D full frame resized.

The first photo below is a tape measure taken with my Sigma 180mm macro alone at it's closest focus, as you can see the width of the image on the tape is pretty close to the 22.5mm width of the 20D sensor so this shot is 1:1, the advertised macro capability of this lens.

The second shot is with the 180mm plus a Canon 25mm extension tube and is about 16mm wide or around 1.4:1.

With the extension tube I could mate up the Canon 1.4X extender. With this combination the frame is just over 11mm wide or close to 2:1 or double life size in the third shot (followup message). The cool thing is I was able to achieve 2:1 while still maintaining the same distance from my sujbect as with the bare lens, about 10 inches from the front lens element.

Anyway thanks for pushing me into this, now I just need to find some bugs:D .

[Ron Lacey]

The 25mm extension tube plus 1.4X extender shot.

[rockyc2]

Glad it worked out, Ron. You need sme of my Bugs? Hahaha! I got plenty. Now go have fun with your 180.:-)
Rocky

[Ballen Photo]

This sounds like a good little Bug getter Ron. I'm thinking that by using the TC in conjunction with your macro settup, that you actually increase your working distance to subect. Is this true? Thanks for posting this. :D
-Bruce

[Ron Lacey]

This sounds like a good little Bug getter Ron. I'm thinking that by using the TC in conjunction with your macro settup, that you actually increase your working distance to subect. Is this true? Thanks for posting this. :D
-Bruce

Yes at a given magnification it should increase the working distance or at the same working distance give you a greater magnification. For instance, with my macro lens alone I could achieve 1:1 at a working distance of 9 inches from the front lens element. When I added the extension tube and the TC I could achieve 1:1 at a distance of 14 inches from the front lens element or I could achieve 2:1 at the same 9 inches. On the down side you will lose 2 stops through the combination of an extension tube and a 1.4X TC.

[Ballen Photo]

Yes at a given magnification it should increase the working distance or at the same working distance give you a greater magnification. For instance, with my macro lens alone I could achieve 1:1 at a working distance of 9 inches from the front lens element. When I added the extension tube and the TC I could achieve 1:1 at a distance of 14 inches from the front lens element or I could achieve 2:1 at the same 9 inches. On the down side you will lose 2 stops through the combination of an extension tube and a 1.4X TC.
Thanks Ron, This would make shooting venomous spiders a little safer. ;) :D
About loosing two stops of light, I was aware of loosing 1 stop with the 1.4x, and 2 stops with the 2x, but I wasn't sure about the extension tubes, as there are no optics in them, but this makes sense when I think about the tubes actually extending the barrel length of the lens, forcing the beam of light entering and actually making it to the sensor to be narrower. Big DOH on My part. :rolleyes: ;)
-Bruce

[Ron Lacey]

this makes sense when I think about the tubes actually extending the barrel length of the lens, forcing the beam of light entering and actually making it to the sensor to be narrower.

LOL yes I guess you want all the working room you can get with venomous critters :D. Yes you're correct lengthening the barrel affects the amount of light reaching the focal plane, if memory serves you lose 1/2 stop in effective aperture for every 12mm of extension.

[Ballen Photo]

LOL yes I guess you want all the working room you can get with venomous critters :D. Yes you're correct lengthening the barrel affects the amount of light reaching the focal plane, if memory serves you lose 1/2 stop in effective aperture for every 12mm of extension.
Good info Ron. Thanks. :D
-Bruce