2X converters

[calmwater]

This may seem like a dumb question. If you add a 2X converter to a 150mm lens it (effectively) becomes a 300mm. (2x by 150=300) Question.-If you added a second 2X converter to that would that change it to 450mm (2x by 150=300 by 2x=150 by 3 == 450) or would it change it to 600mm? (2x by150=300 by 2x-600)

 

[480sparky40 39]

It would be three things.

1. Effective focal length: 600mm
2. 4 full stops of light loss.
3. Totally crap for image quality.

Oh, wait.... 4 things.

4. Unable to autofocus 99% of the time. And a viewfinder so dim you'd be lucky to even manually focus.

 

[Derrel]

600, and substandard image quality.

 

[Original katomi]

Very dark, loss of 4 or 5 f stops and you are opening up a window to problems with the contacts between lens converters and camera.

 

[zombiesniper114 13]

Not to mention if you buy 2 QUALITY converters you're already into the 300mm f4 range that will give you a better final image.

 

[Soocom1]

What's being missed here however is that the mechanism of the teleconverter is taking an image of a very specific circle size post rear element and altering it, in this case TWICE!

That alone is cause to not do such.

Because I have done it, I wind up with a horrible looking tunnel.

I say bite the bullet and buy an old Vivitar 1000mm TP tube lens and call it a day...

 

[Strodav]

As you can see from the other posts, it's a bad idea. Just to pile on, teleconverters are only compatible with specific lenses. You should only buy a known compatible teleconverter from the lens manufacturer. An incompatible teleconverter might have the front element of the teleconverter come in contact with the rear element of the lens. Not a good thing, so I'm thinking two teleconverters might crunch into each other as well.

 

[cgw117 142]

They're cheap and plentiful, especially the really bad ones, so try it with 2 2x TCs and promise to post the results, OK?

 

[Derrel]

A 500mm f/8 preset long focus lens or a used 500/8 mirror lens might give better Optical quality at about the same effective F – stop and for around $100 in price.

 

[photoflyer]

That reminds me of Junior High. This was a long time ago and the screw mount on my Pentax enabled a buddy and me to stack a 2x on a 3X on a 135 F 3.5.

We had no idea about what this did to the aperture. We only knew that the viewfinder was very dark.

 

[480sparky40 39]

That reminds me of Junior High. This was a long time ago and the screw mount on my Pentax enabled a buddy and me to stack a 2x on a 3X on a 135 F 3.5.

We had no idea about what this did to the aperture. We only knew that the viewfinder was very dark.

Mathematically.... f/20.

 

[Original katomi]

Post 10
F stop .. view finder well . midnight in a coal cellar Comes to mind

 

[calmwater]

Okay. Question answered. I was aware of all the pitfalls of doing such a thing and really didn't have any intention to try, but..since it seems to be of interest, maybe I will just try a shot and see what the result is. Don't know what I'd shoot but I'll find an example. Just for the fun of it and see.

 

[Derrel]

Nikkor 500mm f/8 mirror lens, circa 1974, $130. Nikon D610 in Dx mode, estimated 15 feet. Summer 2017.

 

[Rickbb66 4]

Way back in the day I put a 2x on a 200/f4 and shot Tri-X pan push processed to 3200ASA for a rock concert. I got images and even made some 11x14 prints. You could almost tell who the people on stage were.

As others have said, its not really something you will be happy with.