2x converters

[Davi]

Other than increasing the Fstop, what are the major disadvantages of 2x converters?

I'm thinking why spend a fortune on a lens I'll not get *that* much use out of (300mm + ) when I could spend £1k on a good quality 70-200 F2.8 and get a 2x for the odd occasion I want something longer.

Or am I missing something really fundamental that's leaving me looking like a prat for asking?

[itsnotarace]

Image quality suffers, simple as that really

Stick to 1.7x at the most, 1.4x is better

[tog]

If you get a decent lens, and used it with a quality converter, the results will be fine. Technically slightly less sharp than a 400mm prime, but of perfectly acceptable quality for most people, most of the time. And a decent 70-200 will be sharper than a 100-400, so on those occasions when you don't need a 400mm, you come out better off as well.

[S47]

2x convertors need careful matching to the lens you gonna use it with - simple as that.
I bought 3 Canon 2x convertors to go with my Canon 400 F2.8IS after testing each with the lens I kept the best and sold the other 2 on ebay, the differences between the 3 supposedly identical convertors was remarkable.
The effort is really worth it with a lens as good as the 400 F2.8 IS. with the 2x convertor fitted I have a 800 F5.6 which is fantastic to use at full aperture

[d1d215]

the less glass there are in the lens, the better. but anyway - a converter pluss a good lens is a way to go.

[Snapper7]

1.4 is normally a good option, where as a 2x is normally a get you out of the mire situation IMHO.

[smack]

S47 said:

The effort is really worth it with a lens as good as the 400 F2.8 IS. with the 2x convertor fitted I have a 800 F5.6 which is fantastic to use at full aperture

I have even stacked the 400 and got very good results.

[smack]

I did a bunch of test shots years ago to compare what quality I would lose. All the shots are wide open, apart from the 400mm. I think the crane was about 500m away.

300mm @ f2.8


300mm + 1.4TC @ f4.0


300mm + 2.0TC @ f5.6


400mm @ f5.6 (not sure why took this test shot, I think it is my prime, and not the 70-200+2TC, but not sure why I didn't shoot it wide open??)


300mm + 1.4TC + 2.0TC @ f5.6

[Pete Baraka]

There's something that's been puzzling me about converters - I hope one of you might be able to enlighten me! I understand if I add a x1.4 converter then I'll lose one stop of light i.e. the lens set at f2.8 will mean camera exposure settings at f4... but what will be the change to depth of field? Assuming I'm photographing an object 30 metres away and it doesn't fill the frame with a 200mm lens fitted, so I fit the x1.4 and the effective focal length becomes 280mm. If the lens aperture was set at f2.8 both times, does the depth of field shrink or grow or stay the same when I add the converter?

Pete

[Davi]

Must admit I'd not thought of a smaller converter - no reason why a 1.7 wouldn't do the job, I was only really looking for 300mm for the time being.

Also looking at another tack - replacing the d60 with a d90, which opens up a wealth of lenses which are much cheaper - I reckon I could make up the difference in price to upgrade with just one lens!