I have had my camera and 70-300mm sigma lens for about 4 days now, and have noticed 300mm isn't as zoomed in as I thought.. So I looked around, and found some extenders, I am mainly looking at either the sigma 1.4x or 2x extenders.. ($190 or $230) I just have a few questions...
They're generally refered to as teleconverters, you may find that to be a better Google term in the future...
1) I was just wondering, if these really work, and if they are worth the money...
Yes, teleconverters work, but as with all things, there are trade-offs (otherwise you'd see lenses go up to half the focal lengths they do.)
Worth the money depends a lot on the specific application...
2) If I get a sigma extender, will it work with canon lens'?
You should get one for whatever lens mount you have. In general, just like lenses the more you spend the better the quality...
3) Will the extender work with macro lens'?
Teleconverters work like extension tubes for macro photography. I don't think they affect the working distance though.
4) When I buy one, I will be buying from 47th Street Photo, are they trustworthy? Amazons feedback for them is 94% positive, with over 21k reviews... Will I be charged tax when buying from 47th street photo? (they are based in New York and I live in California)
I only buy from B&H, Adorama, KEH, Calumet or Ace Photo, so I have no idea what anyone outside of those are.
Ok, now for the trade-offs-
1. Light.
A 1.4x teleconverter is generally going to take a full stop of light. A 2x teleconverter is going to take 2 stops of light. That means that on a lens that's f//4, you're going to be at f/5.6 or f/8- many modern cameras don't like to autofocus past f/5.6. If your lens is f/2.8 @300mm, then you'll be at f/4 or f/5.8, if it's slower than 2.8 you'll probably only want to go with the 1.4x.
2. Quality.
Extra glass adds distortion to the image. Personally, I only shoot with 1.4x or 1.7x converters with extra-sharp glass to start with. I don't like the quality a 2x converter gives me in generally-- even though I may get acceptable shots from time-to-time. This is somewhat subjective and you'll have to decide what you like. I've see shots with 2x converters that the photographer thought was great that I thought sucked bigtime- so obviously my standards are different than others' may be.
After comparing the prices, I would say 2x extender is a better buy...
Please suggest\comment on this, to help me decide which is a better buy, and if an extender is even worth it...
Can someone maybe post a before, and after extender pictures? Like, get a lens, zoom it out all the way, take a pic... put the extender on, and take the same pic... (1.4x and\or 2x)
Also, in general the lens manufacturers make teleconverters that are best used with their lenses (though you can use them with other lenses in a pinch.) With Nikon there are 4-5 different converters for different focal length lenses. You could use a Canon or Nikon telecoverter with a Sigma lens that would fit the respective mount, but the Sigma converter would probably be better matched to the glass. In terms of generic 3rd party TCs, I really like the Kenko 1.4x (which was also branded by Tamron at one point) though these days I tend to shoot with Nikon converters on a Nikon 400.
Comparison pictures really don't help much without a lot of work, because in general, you're changing both focal length and aperture, so both field of view and depth of field change- you'd really want to be able to matrix out the different possibilities. In general though, TCs are thought of as a compromise and the more magnification, the more degradation and light lost, so you need to decide if you need a 420mm lens or a 600mm lens and if you can shoot at whatever aperture that's going to give you.
If your lens is the 70-300 f/4-5.6, you're going to have f/8 with a 1.4x converter and f/11 with the 2x. Neither of those is especially good, but I'd say f/11 is probably bordering on useless for most things. Also, don't forget you're going to need heavy support if you're shooting past 1/focal length.
