Cfalk From , joined Dec 1969, posts, RR:
Reply 1, posted (13 years 3 months 1 week 4 days 8 hours ago) and read 1774 times:
Stationary pics are probably your best bet. Remember to stop down your lens significantly. From what I have seen, vignetting will show up much easier with a teleconverter than a normal lens. I'd say any f-stop larger than 9.5 or even 11 should be avoided to prevent vignetting.
For those who don't know, vignetting is when the corners go dark, and is pretty typical of long lenses at wide-open aperture. Here's a sample of mine.
AndyEastMids From United Kingdom, joined Jan 2001, 1014 posts, RR: 2
Reply 3, posted (13 years 3 months 1 week 4 days 7 hours ago) and read 1765 times:
Like Charles says, stop down a fair bit.
The only other tip I could give you is this: because the converter adds very little size and weight to your camera and lens combination, you will be tempted (at least in the early days) to use it in the same way as your 70-210 lens on its own. No matter what you do, a 420mm lens needs much more careful handling than a 210mm lens if the results are not to be blurred / shaken. Be cautious in using the lens + converter and you should be OK, and do not use the converter for the sake of it.
Ckw From UK - England, joined Aug 2010, 730 posts, RR: 16
Reply 5, posted (13 years 3 months 1 week 4 days 6 hours ago) and read 1749 times:
A lot depends on the quality of the convertor - I bought the best I could afford (2nd hand!) and have been very pleased with the results. I found stopping down 1 stop was sufficient to avoid vignetting - your milage may vary. I've just uploaded some pics taken on the Heathrow 27L approach using a Canon 1.4x or a Canon 2x convertor with a 300mm lens - have a look if they get accepted.
One bonus you get with a convertor is that your close-focus distance remains the same, so in effect you increase the macro capability of your lens, which has some creative possibilities. One downside is that your depth of field is significantly reduced.
In practice, the fact that you're losing 2 stops to the convertor, plus at least one more to avoid vignetting and provide a little depth of field means that you will need to shot at an effective f11 (assuming your prime lens is f4) ... do you have a good tripod?