Stupid question

[agspecialties]

What is the difference between an extension tube and a reversing ring? I am just getting into macro photography and have bought a canon 100mm F2.8 macro lens with a set of extension tubes. Then tonight i found a reversing ring. Just trying to figure out if i should get one of those? They are cheap enough.

 

[Designer]

If you think it is a stupid question, then you must already know the answer.

 

[AaronLLockhart]

Agreed with designer. They are two completely separate ball parks. For you to think that the question was stupid before asking, would imply that you already know the difference.

 

[sm4him]

Doesn't imply anything of the sort, imo. It could also--very likely--suggest that the OP has a nagging suspicion that they SHOULD know the answer, but they are admitting they don't.

I don't, either. At least, not so I could explain it to someone else. Seems like they both accomplish basically the same thing, just different tools for doing it. I'll be interested to hear the answer, from someone who knows.

 

[Dao]

With the reverse ring, you can mount a lens in front of another lens.

i.e. A reverse ring screw mount to the front of a 50mm lens. Then on the other side of the reverse ring is screw mounted to another lens such as your telephoto zoom lens in the front so that the front of the lenses are facing each other. Now mount the telephoto lens to your camera and use the 50mm lens as a macro filter.

 

[Overread]

They are two very different tools:

Extension tubes: these increase the distance between the lens and the camera body and, as a result, reduce the minimum focusing distance of the lens and also remove its infinity focusing. The result is you can focus closer and get a more magnified photo at the cost of now not being able to shoot further off subjects with the tubes added.
The rough maths for extension tubes is:
(length of extension tubes in mm - divided by - focal length of the lens) + base magnification of the lens at the set focus point = magnification :1

For example a 100mm macro lens at its closest focusing point with a 50mm length of extension tubes would be:
(50/100)+1 = magnification:1
0.5+1 =1.5:1

Remember a macro lens gives you 1:1 magnification already.


2) Reversing ring; this lets you reverse one lens onto another via the screw filter threads on the front of the lens. Generally you always mount the heavier, longer focal length lens to the camera and the lighter, smaller focal length lens in front (This not only puts less strain on the filter threads, but also gives you the most magnification possible).
Note, like extension tubes, you will focus closer than normal, but again lose infinity focusing.

The rough maths for this is:
Focal length of the lens on the camera body - divided by - focal length of the reversed lens = magnification :1

Eg 100mm lens with a 50mm reversed onto it would give:
100/50 = 2:1

I'm unsure if base magnifiaction of either lens affects the results or not


Reversing rings typically can let you get the most magnification gain for the cheapest cost, eg a 70-300mm lens with a 50mm f1.8 would give you a possible range of between:

70/50 = 1.4:1 magnification
300/50 = 6:1 magnification