more sigma 70-300 w/2x tele extender

[MiniChris]

The first image is a sparrow in a Martin house at approximately 100 feet. The second image is a close up of the bird...both images have been heavily sharpened. at 100 feet, 300x2 at 250mm (500mm) extension, it's not as sharp as I would have liked. 5.6 @ 1/200 200 ISO

[jeeperman]

Interesting comparison Chris. How does the first one fair if it is cropped to equal the second. And at what focl length was #1.....full 300mm?

[MiniChris]

It was at 250mm (X 2) so I guess a 500 equivilent...I should note however, there was a fairly stiff breeze blowing and the pole house sits up about 30'. I am going to set up my 100 foot tape tomorrow and shoot a series at differnt f/stops per each 20' on the 300 lens, then reset at do the same with the 2x tele extender and see how the same items fare at the same distances, focal lengths, etc...it will be a long and tedious test, but before I shuck out any dinero, I want to know what I am getting.

[jeeperman]

Right on, sounds like a good test to see where things excel and/or decline. Look forward to seeing it.

[Geoff F]

From my experience of shooting wildlife, etc, the answer is simple. If you want to get to 500 mm (or thereabouts) you need a lens which is designed for that size, and with a matching price I'm afraid.

Suitable prime lenses, like 300 or 400 mm will take a converter fairly well, including a x2.

A few of the really good zooms will work successfully with x2 but even these are normally better with just a x1.4.

But fitting any converter to a budget/mid price zoom gives disappointing results. I've tried it many times with a x1.4 and always ditched the results.

And to get a Canon x1.4 converter to fit a Canon 70-300 lens I even added a 12 mm extension tube between the converter and lens to make a 'spacer' so that the two would physically fit together.

This lost infinity focus but even at shorter distances I was disappointed with the results.

[MiniChris]

I'm processing some shots I took out at the state park today..not terribly bad, but certainly not stellar, either. I think Geoff is right in his assesment of getting what you pay for...I think I am going to start saving my pennies. Below was taken with just the 70-300 at 300mm f/9 at 1/500 ISO 320...it's okay, but certainly not prime time. I was about 100' away.

[Geoff F]

Yes Chris, I have found that if you are pushing a lens beyond it's designed limitations, you can get away with quite a lot when using the best settings for that lens and with ideal light; and still obtain a reasonable result.

The problems occur once you try to stretch those limiting factors a little bit too far.