Extender Lens

[Marty31]

I have a Canon 7d mk11 and love wildlife photography. Among my lenses I have a Tamron 150-600mm, but it is really heavy and bulky to carry around, especially when travelling abroad.
I have been thinking of getting an extender to use with my Sigma 18-250 lens and was just wondering if anyone has any experience of using them and if it is something I should consider, or not.

 

[480sparky41 40]

Kit and Superzoom lenses tend to be quite slow in terms of aperture to begin with. Adding a teleconverter (I'm assuming that's what you're referring to here) will make it even slower.

As a general rule, this class of lens is also isn't as sharp and might be slower to focus. Adding a TC will compound these issues. Plus, you may lose autofocus altogether.

Remember, the more a lens tries to do, the less it does everything as well. Teleconverters will magnify each imperfection.

 

[benhasajeep47 46]

I don't mind using tele-extenders. Thing is you need to buy good ones. The cheaper ones are just that! Even the best ones still degrade your pictures some. But they are still useable. The cheap extenders are not! Anything you put on a lens will degrade it's quality.

Now the problem is you Sigma 18-250 is a slow lens. Not sure of the AF on the 7D buy you very well may not get AF with a 1.4x extender, or possibly just the center AF point. With a 2x extender you will loose AF. A 1.4x extender costs you 1 stop of light. A 2x extender will cost you 2 stops of light!

Your Sigma is f/6.3 at long end. With a 1.4x on it. You are now around f/9. Most AF will not work above f/8 on very good cameras, and f/5.6 on lesser models.

And 1.4x you will only be gaining 100mm. It's probably not worth it for your lenses!