An experiment

[Ron Evers]

I have often read that you loose IQ if you use a tele-converter so I wanted to see for myself. I used a Vivitar series 1, 70-210/3.5 & a Vivitar 2x converter for the experiment on my Panasonic G1. I set a tripod up on our balcony & shot the bird bath in the back yard with a salmon tin sitting in it. The ISO was set @ 100 & I used f5.6 for the shots.


1. Lens set ~ FL 200, no converter, 1/1600s

2. Lens set ~ FL 100 with 2x converter to equal FL 200, 1/400s

There is definitely a loss of light & IQ with the converter in this simple trial. However it looks as though the converter shot has a greater DOF.

 

[Ron Evers]

Bump, I thought some would find this interesting.

 

[LaFoto]

Yes, I find this interesting, though the odd bird in the bird bath would be nice to see, too. Maybe you could drain it, pour in some seeds, and take bird pics with the tele-converter (or without)?!

 

[Village Idiot]

Bump, I thought some would find this interesting.

Bump, nah, if it would have been of a resolution chart or something of that nature with concrete proof, then maybe.

 

[Ron Evers]

Yes, I find this interesting, though the odd bird in the bird bath would be nice to see, too. Maybe you could drain it, pour in some seeds, and take bird pics with the tele-converter (or without)?!

Here are a couple birds for you Corinna.

 

[bazooka]

I think just changing the FL from 100 to 200 is going to vary your IQ. I would retest using the same FL on both shots. From looking at the website where you can compare charts shot with all the different canon lenses at different Aperture and FL, I see a big difference in sharpness between the 1.4 and 2.0 convertors, let alone 2.0 and none. However, I agree that looking at a real shot instead of a chart does make a difference.

 

[TiaS]

Thanks for this. I am thinking about getting one of these. Do they loose quality the more strength you go?

 

[Ron Evers]

Thanks for this. I am thinking about getting one of these. Do they loose quality the more strength you go?

I assume they do (I only have a 2x) but I was pleased that there was not a huge degradation in this experiment.

 

[Ron Evers]

I think just changing the FL from 100 to 200 is going to vary your IQ. I would retest using the same FL on both shots. From looking at the website where you can compare charts shot with all the different canon lenses at different Aperture and FL, I see a big difference in sharpness between the 1.4 and 2.0 convertors, let alone 2.0 and none. However, I agree that looking at a real shot instead of a chart does make a difference.

I expect that the FL 100 is the sweet spot for this lens being pretty much in the middle of the zoom range. However, if both shots were @ 200 & one with the 2x converter it would be very difficult to compare image quality with the converter image having half the field of view. Well that was my thinking @ least.

 

[Village Idiot]

Thanks for this. I am thinking about getting one of these. Do they loose quality the more strength you go?

Along with increasing the aperture. A 1.4x increases by one stop and a 2x increases it by 2, iirc.

That means an f/2.8 lens would have a max aperture of f/4 with a 1.4 x and f/5.6 with a 2x I believe.