Extension Tube Math?

gregpphoto wrote in post #7495283
And as to the OP saying that "why should I pay for metal, theres no optics" I agree. I bought some ebay hong kong extention tubes, $9 with shipping. It's metal, and doesn't allow lens to camera commo, what could it possibly do? I see no need to spend $100 or more on hollow aluminum tubes.

Depends if you want full use of your AF lenses, or if you want to manual focus and lose aperture control. I like the electronics pass through, one less think to worry about and I can let the camera do what I intended it to do. Might as well buy reversing rings if you don't want AF tubes, even cheaper than cheap tubes.

Ever want some fun if you have a 100-400L? Plug in all 3 tubes, then add the 1.4x TC and see how you like your 400mm macro lens!

TeamSpeed wrote in post #7495337
Depends if you want full use of your AF lenses, or if you want to manual focus and lose aperture control. I like the electronics pass through, one less think to worry about and I can let the camera do what I intended it to do. Might as well buy reversing rings if you don't want AF tubes, even cheaper than cheap tubes.

Ever want some fun if you have a 100-400L? Plug in all 3 tubes, then add the 1.4x TC and see how you like your 400mm macro lens!

That is a great point. All depends on your usages I guess.

Cheaper than tubes? But you'd need a bunch of rings to get up to 55mm in length, as one set of $9 tubes gives me.

foxbat wrote in post #7357957
The formula for magnification is here:

http://www.peterforsel​l.com/macro.html

Great link! I just did the math on a whole bunch of setups.

40mm lens reversed - 4x
40mm w/ 35mm stacked and reversed - 1.1x

One set of 55mm tubes, 70-200 at 200mm, 35mm reversed, is 7.2x! Two sets of ext. tubes, becomes 9.3x.

Oh, and if you had an extension tube aprox. one light second long (~180,000 mi) with a 40mm lens at the end, you'd get about 7.1 trillion x. That's what I want.

gregpphoto wrote in post #7495597
Cheaper than tubes? But you'd need a bunch of rings to get up to 55mm in length, as one set of $9 tubes gives me.

Hopefully you looked a bit more into what a reversing ring does, it appears maybe you have.

TeamSpeed wrote in post #7497102
Might as well buy reversing rings if you don't want AF tubes, even cheaper than cheap tubes... Hopefully you looked a bit more into what a reversing ring does, it appears maybe you have.

A reversing ring lets one lens attach backwards to another lens. How does that replace extension tubes? Besides, I'm going to use ext. tubes in conjunction w/ the reversing ring, going from 3.7x reversed to 7.2x reversed, all because of some nine-dolla tubes ya'll!

Man, talk about reviving an old thread.

Here's an online calculator:

http://home.comcast.ne​t …e_Close-up_Calculator.htm

and a chart for various Canon lenses and extension tubes and close-up combinations:

http://www.bobatkins.c​om …graphy/eosfaq/c​loseup.htm

gregpphoto wrote in post #7502978
A reversing ring lets one lens attach backwards to another lens. How does that replace extension tubes? Besides, I'm going to use ext. tubes in conjunction w/ the reversing ring, going from 3.7x reversed to 7.2x reversed, all because of some nine-dolla tubes ya'll!

A reversing ring turns a telephoto or zoom lens into a high-powered, albeit tedious, macro lens. If you flip the Canon kit lens 18-55 around, you get a killer super macro lens, even more magnification than the tubes give you depending on your settings. My reversing ring mounted to the body, not to another lens.

This was done with a reversed kit lens, at a pretty good working distance. I could have gone closer to really fill the sensor, but the fly would have flown off.

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TeamSpeed wrote in post #7503231
A reversing ring turns a telephoto or zoom lens into a high-powered, albeit tedious, macro lens. If you flip the Canon kit lens 18-55 around, you get a killer super macro lens, even more magnification than the tubes give you depending on your settings. My reversing ring mounted to the body, not to another lens.

That's what I do currently, flip a lens around. But by flipping it and adding extension tubes, I can almost double my magnification.

gregpphoto wrote in post #7505725
That's what I do currently, flip a lens around. But by flipping it and adding extension tubes, I can almost double my magnification.

Yup... or just all 3 tubes on a dedicated 1:1 macro lens too, but at that point, the dragonflies get a little scared! Just add a 1.4x TC to the whole combo as well.

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I've used them mostly on my Nikon F. They're fairly sharp stopped down & you don't have to lose auto exposure. Problem is that you'll be working VERY close to the subject. This is a copy of a slide using the +10 diopter one:

Stopping down before shooting can be a PITA. I took these with the 85mm f/1.8 on the cam with a 50mm f/1.4 Nikkor reversed on the front & it worked fairly well.
Frost - Close up this time.

In this video, he used a 50mm reversed on 105: ProPhotoLife macro photography trick

Lens reversing, which one to use?

the post is excellent.. tube math..
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Do extension tubes work with the 18-55mm kit lens?

kskitt wrote in post #9432596
Do extension tubes work with the 18-55mm kit lens?

Yes, they will work. Just make sure to use the latest ones that are compatible with EF-S lenses. The older Canon and Kenko ones will not work. The Canon II and tne Kenko (not sure on model) will work fine.