x1.4 and x2 canon converters stacked
Discussion
Tried stacking these 2 canon converters yesterday and expected to get f8 as minimum aperture but ended up with f5.6 and autofocus still working increadably well.
Images were of OK quality but purple fringing was massivly increased with high contrast edges. I will try to post some up later.
Any one any clues why still got F5.6 and not f8 as 1.4x converter results in 1 stop of light loss and 2x causes 2 stops loss. If it was that it did not recognise the 1.4 on there I would have expected underexposure but this was not the case.
Images were of OK quality but purple fringing was massivly increased with high contrast edges. I will try to post some up later.
Any one any clues why still got F5.6 and not f8 as 1.4x converter results in 1 stop of light loss and 2x causes 2 stops loss. If it was that it did not recognise the 1.4 on there I would have expected underexposure but this was not the case.
If you were shooting wide-open (i.e. what the camera was telling you was f5.6), I wouldn't expect it to mis-expose. The camera would be receiving the same amount of light when metering as it would be when exposing.
Assuming you were using an f2.8 lens, a 1.4x and 2x teleconverter will result in wide-open being f8; there's no getting around that. The camera obviously just isn't capable of realising that you're using more than one teleconverter.
Assuming you were using an f2.8 lens, a 1.4x and 2x teleconverter will result in wide-open being f8; there's no getting around that. The camera obviously just isn't capable of realising that you're using more than one teleconverter.
SamHH said:
Assuming you were using an f2.8 lens, a 1.4x and 2x teleconverter will result in wide-open being f8; there's no getting around that. The camera obviously just isn't capable of realising that you're using more than one teleconverter.
Good point - try shooting with the extenders the other way around ie; 2x on body & 1.4x on lense.....see if the camera still returns f8?4hero said:
What lenses are you guys using? I borrowed a x1.4 to try with the 100-400 and really struggled for focus (even manually).
The AF will be reduced to the centre AF point depending on your body. But from reports on forums, some folk can't get that combo to work.As for lenses 70-200/300/400/600
I was using a 2.8 70-200L IS.
Was shooting with +2/3 stop compensation as shooting with sky as background. This was the same as BeeJay who was using a 300mm 2.8 with 2x extender and using same compensation. If anything his were slightly darker.
Autofocus worked amazingly well with very few OOF shots.
Body was 5D Mk2
Was shooting with +2/3 stop compensation as shooting with sky as background. This was the same as BeeJay who was using a 300mm 2.8 with 2x extender and using same compensation. If anything his were slightly darker.
Autofocus worked amazingly well with very few OOF shots.
Body was 5D Mk2
It doesn't actually matter that the lens stack is telling the camera body F5.6. The metering is based on the actual lighting and will compensate even when it is being lied to be the lens.
The F-stop indication will allow or dis-allow the AF function. AF is disabled when the lens reports an apeature smaller than F5.6 (smaller hole = bigger f-stop number). I believe the trigger pooint if F8 for the centre focus point on the 1D models. Some of the longer Sigma lenses are F6.3 at the long end but report F5.6 to the body - AF works and the exposure is correct throughout the folcal length range.
As a side note, EOS Magazine did some options around getting to 400mm a while back, an off shoot theard on their forum concluded that stacking convertors was bad news and that doing a manual crop gavce better image quality.
The F-stop indication will allow or dis-allow the AF function. AF is disabled when the lens reports an apeature smaller than F5.6 (smaller hole = bigger f-stop number). I believe the trigger pooint if F8 for the centre focus point on the 1D models. Some of the longer Sigma lenses are F6.3 at the long end but report F5.6 to the body - AF works and the exposure is correct throughout the folcal length range.
As a side note, EOS Magazine did some options around getting to 400mm a while back, an off shoot theard on their forum concluded that stacking convertors was bad news and that doing a manual crop gavce better image quality.
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