7D does Auto focus with converters.

cosmix3

cosmix3

David Sullivan
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Stuart
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Hi,

Was having a mess around while packing up kit on the Donna Nook trip, myself, Cobra and mrgubby went on, decided to have a play around with teleconverters, the 7D and the 100-400L, had stacked Cobras Canon 2X and mrgubbys 1.4 Sigma on the camera, for some reason the Sigma wasn't seen by the camera and did not effect aperture or show in Exif (not sure if it should have), I was setting up a shot using Live View and manual focus to see what IQ was like, as I started to press the shutter I noticed that the Auto Focus confirmed on the screen by making the focus box green and heard a beep from the camera, now I did not think this could be Auto Focus with the converters as I was only getting F11, so I put the lens out of focus and half pressed the shutter, and to my shock, the camera Auto Focused and locked on target, this was also seen by Cobra and mrgubby, I checked if it would work through the View Finder, and it did not even try,

Don't know why it works but it does, and a 2X is now on my shopping list in the near future. I would like to stress this is not a wind up and I am planning to contact a member on here to see if he can test his to see if it works. Hope this is one thing Canon don't fix in a future firm ware.

Here is one of the shots taken with the 2X and 1.4X as I say the Camera did not see the 1.4. This sign must have been about 1/2 mile away, no PP other than raw conversion (Elements standard Sharpening), just re-sized.

IMG_3267.jpg
 
I find that whenever I have used stacked converters the 1.4x often doesn't report, on my Tokina 300mm neither of my Kenko Pro300 DG converters report.

Quite noticeable the lack of contrast in the scene though!
 
cosmix3 said:
this was also seen by Cobra and mrgubby, I checked if it would work through the View Finder, and it did not even try,
Click to expand...

And you really want to "use me" as a witness after THIS? :razz: :D
 
cosmix3 said:
this was also seen by Cobra and mrgubby, I checked if it would work through the View Finder, and it did not even try,
Click to expand...

In all honesty, I can say that all the above is 100% true /\


EdBray said:
Quite noticeable the lack of contrast in the scene though!
Click to expand...

Actually I am surprised at the quality,
now that I see the image on the PC.
It was quite a miserable grey day at the time .
 
Did you try it with just the 2x Stuart? I reckon it wouldn't have worked and it was adding the non-reporting 1.4 that confused things.

I'll try my 2x and 300 f/4 sometime when I get the chance but I think I've tried it before and I don't think it worked.

If it doesn't know the converter is there then it will try and focus. Doesn't mean it will be that reproducable though...
 
grumpybadger said:
Did you try it with just the 2x Stuart? I reckon it wouldn't have worked and it was adding the non-reporting 1.4 that confused things.

I'll try my 2x and 300 f/4 sometime when I get the chance but I think I've tried it before and I don't think it worked.

If it doesn't know the converter is there then it will try and focus. Doesn't mean it will be that reproducable though...
Click to expand...

Yep, tried with the 2X only and it focused and locked inside the caravan, did struggle a bit with faces inside though, but worked even without the 1.4 in the mix. and when the 1.4 was on it did see the 2X.
 
EdBray said:
I find that whenever I have used stacked converters the 1.4x often doesn't report, on my Tokina 300mm neither of my Kenko Pro300 DG converters report.

Quite noticeable the lack of contrast in the scene though!
Click to expand...

Was a dull day and have not done any PP on the shot at all.

Thmaga said:
Its not bad for 1800mm though surely ?
Click to expand...

Not quite 1800, was 1120 but am still impressed.
 
cosmix3 said:
Yep, tried with the 2X only and it focused and locked inside the caravan, did struggle a bit with faces inside though, but worked even without the 1.4 in the mix. and when the 1.4 was on it did see the 2X.
Click to expand...

I agree that also happened BUT if you post the ****ing picture
I will have your balls for breakfast :D
 
There's no trickery or anything sinister or unusual going on here....

Part 1....two extenders and one not being reported.
The extender reports to the lens, not the body.....look at the pins on the extender and you'll see an extra two on the front end...these are the ones that tell the lens that an extender is installed. The lens then modifies the parameters (FL and aperture) that it reports to the body. The extender nearest the body will not have any contact with the second extender as the second extender has not contacts for the pins to mate with.

Part 2....AF at f/11
This will work in Liveview mode just as it did on the 50D and probably the 5D2 (I haven't tried on the 5D2). Liveview AF works by contrast detection as opposed to the more accurate phase detection of normal AF. Phase detection requires a larger max aperture to achieve accurate focus.....the achieved focus will be better than contrast detection when the aperture conditions have been fullfilled.

HTH

Bob

PS...Chris, would that be ketchup or HP?
 
Canon Bob said:
There's no trickery or anything sinister or unusual going on here....

Part 1....two extenders and one not being reported.
The extender reports to the lens, not the body.....look at the pins on the extender and you'll see an extra two on the front end...these are the ones that tell the lens that an extender is installed. The lens then modifies the parameters (FL and aperture) that it reports to the body. The extender nearest the body will not have any contact with the second extender as the second extender has not contacts for the pins to mate with.

Part 2....AF at f/11
This will work in Liveview mode just as it did on the 50D and probably the 5D2 (I haven't tried on the 5D2). Liveview AF works by contrast detection as opposed to the more accurate phase detection of normal AF. Phase detection requires a larger max aperture to achieve accurate focus.....the achieved focus will be better than contrast detection when the aperture conditions have been fullfilled.

HTH

Bob


PS...Chris, would that be ketchup or HP?
Click to expand...

Clever b****r :thumbs:
 
cosmix3 said:
After we clubbed together Saturday night, had to have the Duck again tonight. :)
Click to expand...

fur-enough ;)

I am not sure whether some are missing the point that it
only Worked in live view
and not through the eye piece, :shrug:
 
Off to have a look into this Bob, think I get what you mean, need to do some reading I think. :)

Canon Bob said:
There's no trickery or anything sinister or unusual going on here....

Part 1....two extenders and one not being reported.
The extender reports to the lens, not the body.....look at the pins on the extender and you'll see an extra two on the front end...these are the ones that tell the lens that an extender is installed. The lens then modifies the parameters (FL and aperture) that it reports to the body. The extender nearest the body will not have any contact with the second extender as the second extender has not contacts for the pins to mate with.

Part 2....AF at f/11
This will work in Liveview mode just as it did on the 50D and probably the 5D2 (I haven't tried on the 5D2). Liveview AF works by contrast detection as opposed to the more accurate phase detection of normal AF. Phase detection requires a larger max aperture to achieve accurate focus.....the achieved focus will be better than contrast detection when the aperture conditions have been fullfilled.

HTH

Bob

PS...Chris, would that be ketchup or HP?
Click to expand...
 
Yep - 7D works in Live View with either converter or with both stacked. Very surprised I must say. Potentially useful, although I don't see it being too useful for birds?

This is at 1120mm - can't be bad!

4125943569_0cfdbdeaf1_o.jpg


Page wasn't flat btw.
 
Broadly speaking, phase-detect needs a low f/number with a physically wide aperture to work well and doesn't need much light, contrast-detect just needs bright ambient light regardless of aperture. Very roughly.

Looked at another way, phase-detect works in low light with a decent f/number, whereas contrast detect will struggle in very low light regardless of aperture.

Phase-detect compares two images coming from either side of the lens aperture and when the physical dimension gets too small, ie at high f/numbers, they are not sufficiently distinguished for it make out a difference. Contrast detect uses only one image and just knows that when contrast is highest within the sensing zone, focus is optimum.

I think contrast-detect is the way forward, if it can get faster and more sensitive. It seems to be getting quite good in the Panasonic GF1 which is probably its toughest test to date as these new EVIL cameras cannot use phase-detect. Contrast-detect can also work form any area of the image, not just designated points in the frame.
 
I have to confess, I missed the 'live view' bit, as my Tokina 300mm f2.8 autofocussed on both my 5D Mk2 and 7D with both Kenko Pro300 DG converters 'through the viewfinder'.

This gave a rather unwieldy 840mm f8 and although the AF was slower it did work.
 
Won't all the images with the stacked converters be slightly lacking anyway, due to the circle of confusion caused by the smaller effective aperture/diffraction?
 
???
But the circle of confusion would be more of a problem for the 7d, due to the smaller photosite size than the 5dmkII (or am I missing something from your other topic?)
 
coldpenguin said:
???
But the circle of confusion would be more of a problem for the 7d, due to the smaller photosite size than the 5dmkII (or am I missing something from your other topic?)
Click to expand...

Not sure what effect that would have in practise.

Here is a quick shot of the same roof taken on the 7D with the Tokina 300mm f2.8 and Kenko 2x and 1.4x converters stacked. Giving an 840mm lens (1344mm FF AOV equiv) taken wide open at f8. It was very, very windy.

roof.jpg


100% Crop

roof100.jpg
 
cosmix3 said:
After we clubbed together Saturday night, had to have the Duck again tonight. :)
Click to expand...

Seals and clubbing in the same thread?! :eek: :nono:
 
EdBray said:
Not sure what effect that would have in practise.

Here is a quick shot of the same roof taken on the 7D with the Tokina 300mm f2.8 and Kenko 2x and 1.4x converters stacked. Giving an 840mm lens (1344mm FF AOV equiv) taken wide open at f8. It was very, very windy.
Click to expand...

Yeah, Ok, I would be happy with that!
 
Nod said:
Seals and clubbing in the same thread?! :eek: :nono:
Click to expand...

Yep we took a few pictures of the seals then when (night) clubbing :thumbs: :D
 
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