converters

[hairybeast]

anybody out there use converters, I have a 2x convertor which i get good photos with of inanimate subjects, but anything that moves photos are slightly blurred, any tips would be much appreciated. I always use a tri pod.

[AdrianW]

The problem with teleconverters is that they effectively reduce the amount of light available to the film/sensor, a 1.4x by 1 stop, and a 2x by 2 stops.

So, if you have an f4 lens, it becomes an effective f8. Not a major problem, except that it means you lose 2 stops of shutter speed in the process. Slower shutter speeds obviously mean that the subject has more of a chance to move during the shot.

If you're using a digital SLR, probably the best solution is to increase the ISO by two notches to compensate, i.e. if you normally shoot at ISO100, try shooting at ISO400. That will counter the effect on shutter speed, albeit at a penalty of increased noise levels.

At the end of the day, there's no such thing as a free lunch, teleconverters are useful, but they're not magic ;)

Also it's worth remembering that AF doesn't work reliably in low light, but I don't think that's your issue, bearing in mind you say that static shots are sharp.

[hairybeast]

cheers Adrian, going away for a long weekend on Thursday, going to take it with me and give it a real go.

[cjmm]

Hi again Alan,

It seems we are cross posting... :-)!!!

I agree with what Adrian said, and would only add that (following his expample of f4 + 2xTC = f8) your camera will not autofocus, and you will have to go with manual focus. (That could cause the blurr).

If I am not mistaken, Canons (exept for the 1D series)stop auto-focusing with lenses not brighter than f5.6.

In the case of TCs, I know that there is a way around (have read about it, but never tried myself) which is taping one of the pins on the TC (the one that 'tells' the camera the lens' available maximum aperture).

Hope this helps,
Regards,
Carlos

[hairybeast]

cheers again Carlos, thing is i very rarely use auto focus for any shots, except when watching the grandchildren and you need to be quick to get that all important shot.

[hairybeast]

Hi thanks for the advice, been away for weekend, got some quite good shots of a kingfisher using the 2x converter but still not as good as I would of liked and not as sharp as I have seen of birds of Treknature. Come to the conclusion there is a problem with my manaul focussing, not spot on all the time, my lens 75-300 usm, Carlos you have already said the IQ is not the best and my conveter is not the best make Vivitar, loveing to barter i got it thrown in when I got a new camera and lens some nine years ago (dosnt time fly). think Like my eyes, my lens and converter? definately need upgrading. Up to now it looks like the Sigma 50-500mm £599 gbp and maybe a sigma converter 2x £129. Would have to use MF with the converter. Any comments would be appreciated, o and yes the details of a good book to improve my "very Basic" knowledge

[AdrianW]

To be honest teleconverters are one area where penny-pinching is a bad idea.

I have the Sigma 1.4x EX (non DG), and it appears to cause quite a large drop in image quality.

In my rough test (using a solid tripod and MLU on a test chart) I used the 70-300 IS (non DO) and the 200 f2.8 L/II both with and without the Sigma TC.

By itself the 200 easily beat the 70-300 (@200) in image quality terms at all apertures.

When comparing the 70-300 (@280) with the 200 + Sigma 1.4x EX however, the 70-300 won quite easily.

Recently as a result of discussions I'd had both here and elsewhere I bought the Canon 1.4x II. With the Canon 1.4x II in the tables are turned and the 200 beats the 70-300 (@280).

The only thing to be wary of is that the front element of the Canon 1.4x II protrudes quite far from the front of the teleconverter, which makes it incompatible with many lenses (see here for more info.

To a certain extent fieldcraft is more important than hardware, as is luck ;)

If you're still interested in the Sigma 1.4x EX tc, I'm prepared to sell it for 70 quid (+post) if you're interested, that's about half the RRP of the current model.