• Please use real names.

    Greetings to all who have registered to OPF and those guests taking a look around. Please use real names. Registrations with fictitious names will not be processed. REAL NAMES ONLY will be processed

    Firstname Lastname

    Register

    We are a courteous and supportive community. No need to hide behind an alia. If you have a genuine need for privacy/secrecy then let me know!
  • Welcome to the new site. Here's a thread about the update where you can post your feedback, ask questions or spot those nasty bugs!

5D Mrk II and f8 lens autofocus?

Asher Kelman

OPF Owner/Editor-in-Chief
I am planning to use a Canon 2x multiplier on an 400 mm 5.6 and wonder whether there's a firmware update that allows for AF or does one need to use a non canon extender?

Magic Lantern doesn't add this functionality as far as I can fathom.

Asher
 
I am planning to use a Canon 2x multiplier on an 400 mm 5.6 and wonder whether there's a firmware update that allows for AF or does one need to use a non canon extender?

Magic Lantern doesn't add this functionality as far as I can fathom.

Asher
I'm sorry Asher... f5.6 sensitivity is the minimum that Canon AF systems can recognise if a lens is used on them. If you try a Leitz R lens for example on a Canon, via an adapter fitted with a chip for AF assistance, you'll find that AF confirmation can only work if the lens is used at f5.6 or wider....
This means that the AF system has the sensitivity to focus TTL only if available light is of f5.6 or wider... Note that the focusing on dedicated lenses is done through full aperture since the lens has automatic aperture (the aperture closes to the correct value only after the shutter is activated).
Now if one uses a TC on an f5.6 lens, the lens max aperture is below the f5.6 sensitivity limit since the AF "sees" the whole system as a lens... This is not a matter of firmware upgrade to correct... it's simply a matter of AF sensitivity! Nikon cameras where the same up to the last generation... now the D800 and D4 can AF at f8 too... the D600 is less sensitive, it also needs at least f5.6 like the Canons do.
 

Asher Kelman

OPF Owner/Editor-in-Chief
I'm sorry Asher... f5.6 sensitivity is the minimum that Canon AF systems can recognise if a lens is used on them. If you try a Leitz R lens for example on a Canon, via an adapter fitted with a chip for AF assistance, you'll find that AF confirmation can only work if the lens is used at f5.6 or wider....
This means that the AF system has the sensitivity to focus TTL only if available light is of f5.6 or wider... Note that the focusing on dedicated lenses is done through full aperture since the lens has automatic aperture (the aperture closes to the correct value only after the shutter is activated).
Now if one uses a TC on an f5.6 lens, the lens max aperture is below the f5.6 sensitivity limit since the AF "sees" the whole system as a lens... This is not a matter of firmware upgrade to correct... it's simply a matter of AF sensitivity! Nikon cameras where the same up to the last generation... now the D800 and D4 can AF at f8 too... the D600 is less sensitive, it also needs at least f5.6 like the Canons do.


Thanks for the reply! Is it really a necessary limitation? There's firmware for the 5D Mark III which does allow AF at f8 so it's seems feasible for the 5D Mark II. Also, reports suggest that using 3rd party extenders allow the camera to ignore that limitation of f 5.6.

Asher
 
Thanks for the reply! Is it really a necessary limitation? There's firmware for the 5D Mark III which does allow AF at f8 so it's seems feasible for the 5D Mark II. Also, reports suggest that using 3rd party extenders allow the camera to ignore that limitation of f 5.6.

Asher
Diminishing the limitation is one thing, making the camera able to work is another... In previous Nikons you don't have the limitation put in software, Nikon just mentions that AF won't work at f8 and smaller, ...yet IT DOES WORK if light is very good... but it is close to useless as hunting and inaccuracy increases by much and speed is much slower...
I suspect that Canon has set the limit to f5.6 to avoid having customers using it and then blaming Canon for the results... So, I guess that if you manage to exclude the limitation, it will be the same case... it will be able to work when light is very good, but the results will be worst than using MF..., just my 2 cents...
I am sure that Canon would have let the ability operative if the AF was capable to perform adequately, it's a good selling point Asher.
 

Doug Kerr

Well-known member
Hi, Asher,

Thanks for the reply! Is it really a necessary limitation? There's firmware for the 5D Mark III which does allow AF at f8 so it's seems feasible for the 5D Mark II. Also, reports suggest that using 3rd party extenders allow the camera to ignore that limitation of f 5.6.
Traditional Canon focal length extenders (I don't know about the latest ones) advise the lens (not the body) that they are in place, and this makes the lens (if of an extender-aware model) report to the body (right through the extender) the properties of the new lens that has been formed by adding the extender elements (including the greater f-number of its smaller maximum aperture).

Simple third-party extenders do not have provision for advising the lens of their presence. Thus the lens reports to the body (right through the extender) its normal properties (not taking into account he extender elements, about which the lens is unaware). Thus the lens reports an erroneous f-number for the maximum aperture of the new lens, one which may allow the body to activate AF.

How the AF will perform in the face of this is another matter altogether.

Best regards,

Doug
 

Jerome Marot

Well-known member
Simple third-party extenders do not have provision for advising the lens of their presence.

I don't think third party extenders with AF won't report the new aperture. They need electronic communication or nothing will work on the Canon mount which is 100% electric.
 
I don't think third party extenders with AF won't report the new aperture. They need electronic communication or nothing will work on the Canon mount which is 100% electric.
It will work Jerome... only the exif data will be wrong... (it will record the aperture of the lens as if the TC wasn't attached), still the exposure will be correct since the metering is measuring TTL light.

This (what Doug says) doesn't apply to all third party converters, it's true with many of them though...
 

Doug Kerr

Well-known member
Hi, Jerome,

I don't think third party extenders with AF won't report the new aperture. They need electronic communication or nothing will work on the Canon mount which is 100% electric.

Traditional Canon focal length converters are completely passive. They have no electronics. All the regular mount leads just pass right through.

But the lenses can only deal with two magnifications of an extender: 1.4X and 2.0X.

AF of course operates with either kind of extender in place. The extender itself is not involved.

I assume there are third party extenders that operate just like the Canon traditional ones, but maybe not.

Best regards,

Doug
 

Jerome Marot

Well-known member
A more complete explanation of the system is shown here:

All L series primes 135mm or longer, the 400mm DO, the 70–200mm zooms, the 100–400mm zoom, and the 50mm Compact Macro have three additional communication pins. These additional pins are shorted by the Canon Extender EF adapters and the Life-Size Converter EF to indicate to the lens the change in focal length so that it is able to report the correct focal length and aperture to the camera body when mounted on a teleconverter. The lens also reduces autofocus speed when a teleconverter is attached to improve autofocus accuracy.

So indeed the converter have no electronics and the lens can only differentiate between 3 different types of converters (3 contacts can only carry 2 bits of information).

I did not know Canon used such a system. I am used to other mounts where the converter have electronics.
 

Doug Kerr

Well-known member
Hi, Jerome,

So indeed the converter have no electronics and the lens can only differentiate between 3 different types of converters (3 contacts can only carry 2 bits of information).

Yes. The first pin(9) is the common. A closure from it to the third pin (11) means "this is an extender you are coupled to". A closure to the second pin (10) means "this extender is 1.4x"; otherwise it is 2.0x.

Thus, there are only three meaningful states.

These pins are of course on the "toward the lens" face of the extender.

Only "extender-aware" EF lenses have the pads to contact those pins.

Best regards,

Doug
 

Jerome Marot

Well-known member
Hi, Jerome,



Yes. The first pin(9) is the common. A closure from it to the third pin (11) means "this is an extender you are coupled to". A closure to the second pin (10) means "this extender is 1.4x"; otherwise it is 2.0x.

Thus, there are only three meaningful states.

These pins are of course on the "toward the lens" face of the extender.

Only "extender-aware" EF lenses have the pads to contact those pins.

Best regards,

Doug

There are 4 meaningful states:
-no converter
-x2 converter
-x1.4 converter
-macro adapter.
 
This is totally irrelevant actually.... I am with Nikon for 32 years now, ....the last 20 years, I've been many times tempted to change for Canon (Eos)... the only thing that kept me for doing so, was purely the mount... but if they won't consider bringing the aperture ring back, I may be thinking about getting a divorce once more... It's funny that my old AI-s glass has mattered for me more than using my C645 glass on Canon via a Conorus adapter... it would have saved me a lot of money too... Heck, even my Nex mount videocameras can have full automatic compatibility with Canon glass... I guess I am a bit stubborn to still use MF on everything wider than 35mm and still never use the camera's metering or any of the auto exposure modes.
 

Doug Kerr

Well-known member
Hi, Jerome,

There are 4 meaningful states:
-no converter
-x2 converter
-x1.4 converter
-macro adapter.

What is a macro adapter? Is that the thing that makes the 50mm macro go to 1:1 image magnfication?

Does it have the three "extra" pins. Didn't know that.

I assume it has continuity from pin 9 to 10.

Thanks.

Best regards,

Doug
 
Top