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Taped Contacts - 1.4 X

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Author Topic: Taped Contacts - 1.4 X  (Read 367 times)
JohnC
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« on: June 22, 2009, 10:55:16 pm »

Brian & Paul.

To test what you've suggested might be the case I tried this. I hope it was the correct way to determine whether the camera is only fooled into thinking that the lens is at f5.6 with the extender when it should be at f8 (at 400mm in the case of my lens)
I found that to do this  without introducing other factors I had to have the priority in Av thus controlling the shutter speed.

Photo 1. With the taped  extender. f5.6   gave 1/80sec.

          2. f.5.6 without the extender.................1/160 sec.

          3. Without the extender at f8 (what you think it might actually be)..1/80 sec.

So the shutter speed for f5.6  (with the extender) and f8 (the real f8 without the extender) is the same which suggests to me that the f5.6 in the first photo with the extender is infact f8 even though it's reading f5.6.           

What do you think ? Have I got this test right ? I mean have I carried it  out correctly to get the result I was wanting- ie. to find out if f5.6 with the ext. really is f5.6. ?

It now appears that you are right.
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