Modifying Macro Tube into Teleconverter?

[Eire35]

So, my question is more complicated than just a mod. I would like to add a piece of glass in the Macro Tube mount to act as a tele-converter. I have a genuine screw mount 3x tele-converter that otherwise is of no use with my current setup, but I figured it might be viable to gently attach it to the tubes mounting bracket. From what I understand, a macro tube and a tele-converter are the same thing accept for the glass lenses, correct me if i'm off. Please weigh in on your thoughts.

Thanks

 

[robbins.photo]

So, my question is more complicated than just a mod. I would like to add a piece of glass in the Macro Tube mount to act as a tele-converter. I have a genuine screw mount 3x tele-converter that otherwise is of no use with my current setup, but I figured it might be viable to gently attach it to the tubes mounting bracket. From what I understand, a macro tube and a tele-converter are the same thing accept for the glass lenses, correct me if i'm off. Please weigh in on your thoughts.

Thanks

Not sure how well that would work. I would imagine the glass portion of the tc would have to be a precise distance from both the lens and the sensor in order to work properly. Otherwise I think your probably looking at introducing distortion.

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[Overread]

Well they are the same thing in that they fit between the lens and the camera body - but otherwise they are totally different internally.

Macro tubes are just a tube; they've got no internal mounting points for lenses; so they won't actually take optics inside of them. You'd have to do a LOT of work to try and make the glass fit inside at all and by whcih point it would be easier just to experiment changing the mount attachments on the teleconverter rather than trying to modify the extension tube to take glass.

And as said you'd have to spend ages adjusting the optics so that the'd line up correctly. A good quality extension tube will have several glass elements at set distances from each other and from the lens and sensor. You'd have to adjust each element again relative to each other and the sensor and lens to acheive the same effect. That means you'd not only have to have a setup that allows you to adjust the positions but also an understanding to how to effectivly adjust optics to balance them.

 

[petrochemist]

A 3x TC is unlikely to be any good on the correct lens mounts let alone after adapting. AFAIK nobody makes 3x converters any more, and most photographers/manufacturers stick to 1.4x though there are some good 2x or 1.7x converters.

As above if the positioning of the lenses is critical distance to your sensor & to the lens will both have to be correct to a small fraction of a millimeter. I doubt your extension tubes are even roughly the right length for your glass. If your lenses aren't designed to have the same rear flange distance the correct position for the glass would be different than the converter was designed for...

If you remove the glass from a TC you will be left with an empty tube with mounts at either end - in other words an extension tube. Going the other way from an empty tube to a TC is a very different matter!

 

[480sparky]

This is like asking if a bicycle can be converted into a motorcycle by adding a 2-cylinder 4-stroke engine.

I remember back in the 70s and 80s I had an extension tube/TC unit. It was a typical 2x TC but the optics were mounted on a bayonet mount so they could be removed, leaving me with a simple extension tube.

 

[Eire35]

I understand that the lens in the Tele-converter makes the difference between the 2 techs. I managed to remove the outer shell of the 3x keeping just the lens elements inside their case with the screw mount and made a simple non-destructive mod to the macro tube mount bracket and the tele-converter screws in nicely, my only issue is that when using my 70-300mm telephoto I still get a macro shot when not zoomed, roughly a clear macro at 10 feet. At night I cannot tell if im getting any extension in distance because when zoomed its blurred, I can discern shapes of the building but not with clarity. For example I direct the lens (not zoomed) towards a porch light thats a few hundred feet away, say the distance of buildings across from each other across a street and I see a clear image of the whole porch but when I attach the tube and Tele-converter it magnifies so that the porch light is now the main object in view but not in focus as that distance. Now that its Day ill retest and see.

Thanks.