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Archive 2013 · 5DIII Does Auto Focus >5.6 if using Live View
  
 
ratsnest74
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p.1 #1 · 5DIII Does Auto Focus >5.6 if using Live View


I was playing my 5D III and new Canon 1.4 and 2x Mark III teles, I wanted to stack them and check the image quality and was using live view to attempt accurate manual focus when I realized it was successfully focusing on its own to my shock and surprise and happiness. Has anyone else found this to be true? Granted it would have to be a static subject, in bright sunlight with some contrast.

I was using in this order: 5DIII>1.4>Kenko 12mm extension tube>2x>100-400L at 400mm.

Would the extension tube cost another stop of light? I couldnt get the two teles to connect without the extension tube, I guess Canon did this intentionally?

So by my count, even though EXIF info says 800mm f11, I was at 400mmx1.4x2=1120mm at 5.6+1+1+2 = f22

here are some examples:







power pole at 1120mm using autofocus via liveview, uncropped, jpeg out of camera, no postprocessing

  Canon EOS 5D Mark III    800mm    f/16.0    1/1000s    6400 ISO    0.0 EV  







power pole at 1120mm using autofocus via liveview, uncropped, jpeg out of camera, no postprocessing

  Canon EOS 5D Mark III    800mm    f/11.0    1/4000s    6400 ISO    0.0 EV  







100% crop of above photo

  Canon EOS 5D Mark III    EF100-400mm f/4.5-5.6L IS USM +2x III lens    800mm    f/16.0    1/1000s    6400 ISO    0.0 EV  







100% crop of above

  Canon EOS 5D Mark III    EF100-400mm f/4.5-5.6L IS USM +2x III lens    800mm    f/11.0    1/4000s    6400 ISO    0.0 EV  




Jan 20, 2013 at 06:56 PM
RobDickinson
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p.1 #2 · 5DIII Does Auto Focus >5.6 if using Live View


Live view uses contrast AF which doesnt care about the aperture.


Jan 20, 2013 at 07:09 PM
ratsnest74
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p.1 #3 · 5DIII Does Auto Focus >5.6 if using Live View


Im wondering why I never heard about this before, makes autofocus >f5.6 not that big of an issue


Jan 20, 2013 at 07:26 PM
RobDickinson
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p.1 #4 · 5DIII Does Auto Focus >5.6 if using Live View


Because CDAF is slow and wont track moving targets?

Its tricky to use when at 5 or 10 zoom, mostly only useful for static stuff on tripod, when you could just as well manual focus.



Jan 20, 2013 at 07:28 PM
mitesh
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p.1 #5 · 5DIII Does Auto Focus >5.6 if using Live View


RobDickinson wrote:
....mostly only useful for static stuff on tripod, when you could just as well manual focus.


Exactly.



Jan 20, 2013 at 07:34 PM
ratsnest74
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p.1 #6 · 5DIII Does Auto Focus >5.6 if using Live View


its definitely easier and faster to use LV Autofocus vs LV Manual focus as the Canon moved the zoom button to the left side from the right on my 50D. Aside from that, sure it wont track moving subjects, that is why autofocus and expensive fast large glass comes into play, but many birds and other wildlife are virtually static while feeding, etc so this is a handy method indeed, just cant believe I never read about it previously


Jan 20, 2013 at 07:46 PM
Ian.Dobinson
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p.1 #7 · 5DIII Does Auto Focus >5.6 if using Live View


in your example you go Body>1.4>Tube>2x>lens that will give you a reading of f8 which the camera (at this point in time) wont allow to AF using the phase detection. of course your real F number is 11 (plus a bit for the tube i think)
but if you can co Body>2x>tube>1.4>Lens then your reported fstop will be 5.6 and the camera can attempt to AF using Phase detect . of course it may not get a great lock on anything thats not stationary or in good ligtht.

This is because ONLY the TC that is connected to the LENS is ever reported .

Please note that if the 5D3 system is anything like as picky as my 7D system you may find there are points that wont AF at all. on my 7D @ f11 the middle point wont AF but all the others work fine, and focus quicker than the same combo ever manages in Live view AF



Jan 20, 2013 at 08:18 PM
ratsnest74
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p.1 #8 · 5DIII Does Auto Focus >5.6 if using Live View


Body>1.4>Tube>2x>lens actually gave me a reading of 800mm at f11. It was reading the 2x TC for some reason. So if I reversed it perhaps it would read f8


Jan 20, 2013 at 11:49 PM
mitesh
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p.1 #9 · 5DIII Does Auto Focus >5.6 if using Live View


ratsnest74 wrote:
Body>1.4>Tube>2x>lens actually gave me a reading of 800mm at f11. It was reading the 2x TC for some reason. So if I reversed it perhaps it would read f8


That's precisely what Ian was saying. Since you had the 2x attached to the lens, it reported f/11.

Ian.Dobinson wrote:
This is because ONLY the TC that is connected to the LENS is ever reported .




Jan 20, 2013 at 11:54 PM
Monito
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p.1 #10 · 5DIII Does Auto Focus >5.6 if using Live View


A 12 mm extension tube on that combo is almost nothing, and will not cost you a stop.

What is your reasoning for the exact order you used? I'd put the extension tube next to the lens because all it does is extend the focusing, just like lens elements extending out as the lens focuses closer (in simplistic terms). Why put it between the tele-extenders?



Jan 21, 2013 at 12:13 AM
 

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RobDickinson
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p.1 #11 · 5DIII Does Auto Focus >5.6 if using Live View


I assume he is using the tube so he can use two mkIII tele's together


Jan 21, 2013 at 12:23 AM
Monito
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p.1 #12 · 5DIII Does Auto Focus >5.6 if using Live View


RobDickinson wrote:
I assume he is using the tube so he can use two mkIII tele's together


Ah, thanks. You reminded me I read something about that being an issue.



Jan 21, 2013 at 12:25 AM
ratsnest74
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p.1 #13 · 5DIII Does Auto Focus >5.6 if using Live View


No, it reported the TC which was not against the lens but was after the tube. And used the tube only so I could put both TCs on the lens. Not sure why it only reported the TC that was second?


Jan 21, 2013 at 02:44 AM
Ian.Dobinson
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p.1 #14 · 5DIII Does Auto Focus >5.6 if using Live View


ratsnest74 wrote:
No, it reported the TC which was not against the lens but was after the tube. And used the tube only so I could put both TCs on the lens. Not sure why it only reported the TC that was second?



No it didn't. Sorry I made a slight error in my post. For some reason I was thinking the original lens was f4 . (I may have had the 500/4 on my mind , :doh

Anyway in your setup you go

Body>1.4>tube>2x>lens which is a total drop of 3 stops . So if all was reported you would see 1120mm f16

As I explained earlier only the TC that's mounted to the lens ever gets reported. If you look at both ends of the TC you will notice the female side has 3extra contacts compared to the male side which mounts to the body.. Also look at the mount of a TC compliant lens compared with a normal lens and you will see extra contacts on the TC compliant one .
Now look at the contacts in the body and you can see it has just the normal contacts .

So from that you can see the TC tells the lens of its presence (via those 3 extra contacts) but the TC can't know there is a TC behind it (and also a tube has no extra contacts) .


Also I will revise what I said about switching the combo round to get phase AF. Doing that will report f8 so until the new fw comes out the body will still not try to phase detect AF . And even after the f8 fw I would be surprised if it could ever manage to get a lock with a true f16 . (Although its always worth a try to see how far the envelope can be pushed )
So yeah carry on with the contrast detect . and sorry for the earlier confusion


Also a quick question. With the short tube in place how far can you focus to? I'm assuming you loose infinity?



Jan 21, 2013 at 08:00 AM
ratsnest74
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p.1 #15 · 5DIII Does Auto Focus >5.6 if using Live View


Ian.Dobinson wrote:
No it didn't. Sorry I made a slight error in my post. For some reason I was thinking the original lens was f4 . (I may have had the 500/4 on my mind , :doh

Anyway in your setup you go

Body>1.4>tube>2x>lens which is a total drop of 3 stops . So if all was reported you would see 1120mm f16

As I explained earlier only the TC that's mounted to the lens ever gets reported. If you look at both ends of the TC you will notice the female side has 3extra contacts compared to the male side which mounts to
...Show more

Thanks for the info, I hope they do come uot with f8 campabilties, but until then, Im just happy LV autofocus works!





Jan 21, 2013 at 04:12 PM
ratsnest74
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p.1 #16 · 5DIII Does Auto Focus >5.6 if using Live View


Aww, loosing infinity may be the reason I wasnt able to get a sharp moon shot, I was wondering why. Its not bad but certainly not as sharp as these telephone pole shots are,. Is there another way to stack TCs to shoot the moon or am I stuck with the 2x TC only?


Jan 21, 2013 at 04:13 PM
ratsnest74
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p.1 #17 · 5DIII Does Auto Focus >5.6 if using Live View


Moon shot with same set up + a monopod, perhaps the tube is why I couldnt get it sharp? How else can I get TCs to stack?






  Canon EOS 5D Mark III    800mm    f/16.0    1/400s    3200 ISO    0.0 EV  




Jan 21, 2013 at 04:19 PM
abqnmusa
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p.1 #18 · 5DIII Does Auto Focus >5.6 if using Live View


5D III with current firmware will autofocus at F8 with a non-reporting TC

http://www.fredmiranda.com/forum/topic/1172620/0?keyword=f8#11177672

http://www.fredmiranda.com/forum/topic/1138371/0?keyword=f8#10865045

http://www.fredmiranda.com/forum/topic/1126462/0?keyword=f8#10755580




Jan 21, 2013 at 05:06 PM
mitesh
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p.1 #19 · 5DIII Does Auto Focus >5.6 if using Live View


I think the lack of sharpness on the moon shot has more to do with stacked TCs than poor focus due to the tube.


Jan 21, 2013 at 06:58 PM
ratsnest74
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p.1 #20 · 5DIII Does Auto Focus >5.6 if using Live View


mitesh wrote:
I think the lack of sharpness on the moon shot has more to do with stacked TCs than poor focus due to the tube.


One might guess that but Ive done this before on my 50D and it was sharper, but that was without a tube and using a Canon II 2x TC and a Sigma 2x TC, a combo that I would think would produce inferior results vs this 1.4 III and 2x III TC combo. In additional, the daytime shots of the telephone pole looks pretty sharp to me until its 100%, even then its ok.

Im going to remove the tube and revers the TCs and see if I get better results.



Jan 21, 2013 at 08:19 PM
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