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02-07-2007, 04:49 PM   #1
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Info on using 2x adaptor

I've just had a few weeks off on holiday. Went into a camera shop in a mall and ended up buying a Sigma 70-200/2.8 EX APO and a Sigma TC 2x EX APO (I'm at work so the details may be slightly wrong). They were about 50% new price and in mint condition. Lens is something like this.

Love the 2.8ness of the zoom, but get a bit of a sore arm carrying it.

With the 2x on the camera this turns into a constant 5.6, or so I've learnt here. But how come I can still dial in 2.8 when in Av mode? What aperture is it really using?

It's great having the 35mm equiv of a 210-600mm lens!


Last edited by Arpe; 02-09-2007 at 01:40 AM.
02-07-2007, 05:30 PM   #2
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In a sense you still have the 2.8 aperture. When you move the effective objective plane of a lens further from the focal plane-the sensor or film you get a larger image. The glass in the converter helps to refocus this image but you are still making a photo with 1.4 or 2 times less light--and that's where the change in f-stop comes into play---it's an equivalence thing.
02-07-2007, 05:34 PM   #3
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first off, congrats...

QuoteOriginally posted by Arpe Quote
I've just had a few weeks off on holiday. Went into a camera shop in a mall and ended up buying a Sigms 70-200/2.8 EX APO and a Sigma TC 2x EX APO (I'm at work so the details may be slightly wrong). They were about 50% new price and in mint condition. Lens is something like this.

Love the 2.8ness of the zoom, but get a bit of a sore arm carrying it.

With the 2x on the camera this turns into a constant 5.6, or so I've learnt here. But how come I can still dial in 2.8 when in Av mode? What aperture is it really using?

It's great having the 35mm equiv of a 210-600mm lens!
I've heard good things about this lens. You've already discovered the side effect of fast glass - weight...

If you plan to use it a lot, you may wish to consider a monopod. I use my FA* 80-200/2.8 with my K10D and have no issues slinging it around. My bigger glass is another matter altogether...

Generally I'll do the monopod thing if the lighting is going to reduce the shutter speed too much. The biggest benefit is brighter images through the viewfinder - no question!

You are correct about the aperture - that's the miminum (5.6), although the viewfinder shows otherwise.

Just a clarification: you are referencing the field of view (FOV), not the actual focal length you realize with the 2X TC. It's still a 140-400 with the 2X TC. The sensor crop of 1.5x is simply the effect on the FOV. (If you were aware of this, my apologies!)

Enjoy and post some images soon!

Cheers,
Marc
02-08-2007, 01:48 AM   #4
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Thanks guys, helps a bit, but still confused! I think I'll just put it in the "don't worry about it and just get on with it" basket! As far as bokeh goes when using the 2x, will it be the same as using f2.8, or will it be like f5.6?

Marc, I'm aware of the FOV thing, but I still get that equivalent result! I've got a tripod, bought for video really but it'll do. Not sure if I can afford a monopod yet. I'll have to see if they come long enough for me, I'm 1.96m (6'5").

As for images, I took 420 while away, a helluva lot for me. So I'll slowly get through them, and if any are worthy I'll post.

02-08-2007, 01:52 AM   #5
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By the way, I just read on the Sigma site that the 2x TC should be attached to the lens first, then all that attached to the camera. Ooops. Oh well i was just playing at this stage anyway.
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