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2x convertor

brrttpaul 4 205 United Kingdom
23 Mar 2014 12:32PM
Hi, was after some advice on convertors and cropping. 99% of my photos I crop (birds). I am watching some birds at the moment but dont want to get to close, I use a 300mm sigma 2.8 even through this they are too far away, so I was wondering on the cropping and convertor. When I use the crop tool in lightroom i do it freehand if I cropped at 50% would that be equivalent to a 300 lens with a 2x convertor? I realise I will lose 2 f stops with a convertor but I am looking for an example between a 300 and a 600 to get some idea.
Thx in advance

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richmowil Plus
6 307 1 England
23 Mar 2014 1:51PM
The sigma imaging web site has a lens simulator that will show you the difference in angle of view between lenses and also can take into account what sensor you are using!! I am not sure if it shows the effect of a convertor but its worth a look!! Hope this helps!!
brrttpaul 4 205 United Kingdom
23 Mar 2014 2:08PM
it certainly does rich thankyou
gary_d Plus
7 576 13 Wales
23 Mar 2014 5:52PM
When you crop by 50% that is effectively the amount of pixels you are losing, there is no substitute for getting closer to your subject.
brrttpaul 4 205 United Kingdom
23 Mar 2014 6:47PM
i totally agree but you wont get closer to these unless you can fly lol, not at the moment anyway
mikehit Plus
6 8.0k 13 United Kingdom
24 Mar 2014 9:09AM
I have seen much discussion on different forums on the merits of using a 1.4xtc and cropping as opposed to using a 2x tc - many experience long-lens users seem to prefer the former due to the greater image degradation of the 2x tc.
tomcat Plus
10 6.4k 15 United Kingdom
24 Mar 2014 7:22PM
Would like to know what the bird species is that you are after
brrttpaul 4 205 United Kingdom
25 Mar 2014 7:51PM
Mainly raptors, kites, buzzards, peregrines, but also kingfishers, I think the best thing is for me to put a photo in the gallery of peregrine its not a very good picture as I said I,m just too far away, cant get any closer to these as they are protected.
Overread 7 4.0k 19 England
25 Mar 2014 9:35PM
Sigma 120-300mm f2.8 is one of the few zooms that can take a 2*TC and retain a usable level of image quality. Sure a straight 500mm or 600mm prime will beat it no question; but they'll also be 3 - 4 maybe more times its cost.

Drop the aperture down to f7.1 and you should not only have a good depth of field but also a good degree of sharpness in the shots. About the same as you'd expect from a 100-400mm or a 70-200mm f2.8 IS L M2 with 2*TC.
brrttpaul 4 205 United Kingdom
26 Mar 2014 5:51PM
its a 300mm prime not zoom. I do try and knock it down 2 stops but I still need good light to get the shutter speed up. its a puzzle I am enjoying if I,m honest
mikehit Plus
6 8.0k 13 United Kingdom
27 Mar 2014 2:55PM
Regards the focal length used for the shot of the peregrine on your portfolio, I really don't think there is much you can do - imagine the bird being twice as big in the frame (=600mm lens) which is still shorter than the post it is sitting on and I think you will still be asking the same question. Mind you, f2.8 is pretty tight and I would go with Overread's comment on trying a narrower aperture.

This of course brings the question of shutter speed that you also mention - I see the peregrine was shot with ISO200 and I think the 3100 should be able to manage at least ISO800; and if that is not enough have you tried underexposing by one stop (or even 2), then recovering the shadow in post-processing? I have found this works fairly well with my Canon 7D to give that extra bit of shutter speed where it is needed and the 3100 could probably cope as well.
brrttpaul 4 205 United Kingdom
27 Mar 2014 6:21PM
thx for the advice, I will take that on board as I said I think its a matter of tinkering here and there and seeing whats best thx again

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