Sigma 300 F2.8

CarlEvans

CarlEvans

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Carl
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Hello everyone.

I have a canon 500d body and I just purchased a sigma 300 F2.8 with 1.4 and 2x converters. With the 2x converter my F stop is 5.6 at its largest making a 600mm F5.6 plus my cropped sensor if im correct.

My question is..... i stacked the the 1.4 and the 2x converters and my F stop stayed the same (5.6) and auto focus still worked. is this right?

I thought it would end up with a smaller apature?
 
I got the canon version and canon TCs. When I stacked the TCs on my 20D I still retained autofocus because I think that it only reports the 1st TC. However the actual light getting to the sensor will still be like losing 3 f-stops so you need reasonable light to get a decent shot and the lens will be prone to focus hunting, well that's what I experienced. You might have problems with the sigma 300 prime as its not as sharp as the sigma 120-300mm can be a tad soft wide open.
 
pete.rush said:
I got the canon version and canon TCs. When I stacked the TCs on my 20D I still retained autofocus because I think that it only reports the 1st TC. However the actual light getting to the sensor will still be like losing 3 f-stops so you need reasonable light to get a decent shot and the lens will be prone to focus hunting, well that's what I experienced. You might have problems with the sigma 300 prime as its not as sharp as the sigma 120-300mm can be a tad soft wide open.
Click to expand...

Thanks. I don't think ill have to many problems personally (being fairly new to photography in the past year) but i know what you mean. Maybe in time ill notice more and more. :thumbs:

Cheers again.

Edit... i had the 1.4 then the 2x converter and it read 5.6 surely if it was only reading the 1st TC then it wouldn't be 5.6 right?
 
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The T/C connected to the lens detects the f stop of the lens a passes the I formation through to the body, when you stack them the T/C between the body and the T@C connected to the lens I'd effective transparent electronically, but optical losses are still present so you have to manually compensate for the extra stop.
 
chubster1969 said:
The T/C connected to the lens detects the f stop of the lens a passes the I formation through to the body, when you stack them the T/C between the body and the T@C connected to the lens I'd effective transparent electronically, but optical losses are still present so you have to manually compensate for the extra stop.
Click to expand...

I understand that there would still be loss of light with stacked TC's but I had the 1.4 on the body then the 2x. If the 2x converter is transparent Electronically then why was my body reading a 5.6 Fstop and not the Fstop of the 1.4 :thinking:
 
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