Strange behaviour of Tamron 28-75 F2.8 and canon 430EX

kelvin8x · 25th February 2009

Hi bros, I have a good and sharp copy of Tamron 28-75 even at F2.8. Normal condition focussing no issue (back, or front) and always spot on. Recently, I shot more indoor at F2.8 with the Canon 430EX and found pix is not sharp. Did the test and found this strange behavior:

1. Tamron + 430EX with AF assist beam from the flash is ON : back focus
2. Tamron + 430EX with AF assist beam is OFF: focus is spot on and pix is sharp as expected
3. Test 430EX with AF assist beam is ON with my other canon lens like 70-200 F4: no problem, focus spot on.

Have any bros encountered this problem before? Very strange as from test 3 it seems that my 430EX is fine. From test 2 and without flash my Tamron lens is fine too. It only has problem when the AF assist beam is ON. Very funny. Think i read about the thread in which someone also has that problem (not exactly the same combo but Tamron and Canon Flash) but last time I didn't see any conclusion and solution for it.

Any bros got any clues about it. Thanks.

25th February 2009	#1
kelvin8x Member Join Date: Aug 2006 Posts: 131	Strange behaviour of Tamron 28-75 F2.8 and canon 430EX Hi bros, I have a good and sharp copy of Tamron 28-75 even at F2.8. Normal condition focussing no issue (back, or front) and always spot on. Recently, I shot more indoor at F2.8 with the Canon 430EX and found pix is not sharp. Did the test and found this strange behavior: 1. Tamron + 430EX with AF assist beam from the flash is ON : back focus 2. Tamron + 430EX with AF assist beam is OFF: focus is spot on and pix is sharp as expected 3. Test 430EX with AF assist beam is ON with my other canon lens like 70-200 F4: no problem, focus spot on. Have any bros encountered this problem before? Very strange as from test 3 it seems that my 430EX is fine. From test 2 and without flash my Tamron lens is fine too. It only has problem when the AF assist beam is ON. Very funny. Think i read about the thread in which someone also has that problem (not exactly the same combo but Tamron and Canon Flash) but last time I didn't see any conclusion and solution for it. Any bros got any clues about it. Thanks.