# F/8 Autofocusing impressions



## tron (May 16, 2013)

Now that 5DMkIII has been upgraded to support f/8 autofocusing have you tried using it? Of course this question applies equally to 1D series owners too.

1: Do you find AF practical/fast/accurate ?
2: How is the quality retained? 

Well, I know that the latter is NOT f/8 autofocusing related but now that this feature is available it may invite more and more people to try using it (instead of just watching the excellent the-digital-picture site). Apart from the new generation super telephotos that can probably handle the version III teleconverters well, how smaller/cheaper Canon lens/teleconverter combinations work? (for example EF300MM f/4 with 2X, EF100-400mm with 1.4X, EF400mm f/5.6 with 1.4X)

I am thinking mostly Canon lenses with Canon II or III series teleconverters but feel free to comment on any camera/lens/teleconverter combination you want regarding autofocusing and quality issues.


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## RLPhoto (May 16, 2013)

This is something I'd like to know also.


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## FallsGuy (May 16, 2013)

A little help with a qualifier:
I recently rented a 5D III for the purpose of examining the F8 focus with a 100-400 when paired with a 1.4 III tc.
Subjectively, it worked well. The af was not perceptibly slower than "normal" in decent light. The picture quality was good but was affected. Because of some bad weather and a personal emergency, I was unable to use Reikan's focal to really dial it in. Overall, I would not buy a 5D III for the F8 but it certainly is useful. Btw, the 5D III was very impressive with its autofocus but I am sure you already know that. 
I normally shoot, birds mostly, with a 7D.


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## CarlTN (May 16, 2013)

The 1D4 I rented last fall, seemed a bit slower to AF with a series 2 2x TC mounted to the 300 f/4. It achieved accurate enough autofocus for me, though, and the AF speed was not what I would call "slow".

I have no doubt the 5D3 could achieve similar or superior AF speed and accuracy, especially when coupled to a series 3 TC on a series 2 supertele.


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## neuroanatomist (May 16, 2013)

I've used my 1D X with a 600/4 II and 2xIII to track birds in flight, sometimes handheld. It does fine. However, when shooting small birds in thickets (branches in front of and behind subject), where the bare 600 II locks onto the bird easily, with the 2x it hunts a bit - in that situation, it behaves a lot like the bare 100-400L.


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## wickidwombat (May 17, 2013)

i've only tested my 300f4L and 2x mk3 TC didnt test tracking

AF speed is quick if it doesnt have to rack the whole focus range using the limiter makes a difference
accuracy seems good and ability to lock in really low light seems good too much better than even fast glass with the previous firmware so far AF in general seems to have got a big boost


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## WillThompson (May 17, 2013)

neuroanatomist said:


> I've used my 1D X with a 600/4 II and 2xIII to track birds in flight, sometimes handheld. It does fine. However, when shooting small birds in thickets (branches in front of and behind subject), where the bare 600 II locks onto the bird easily, with the 2x it hunts a bit - in that situation, it behaves a lot like the bare 100-400L.



Did you use spot single point or regular single point focus for this test?

Thanks, Will T.


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## Rienzphotoz (May 17, 2013)

I haven't used f/8 yet on my 5D MK III coz in order to to use f/8 to AF I first need to buy a tele-convertor :-\ ... its funny that for almost a year, there been so many people who were cribbing about not having f/8 AF function on 5D MK III, but hardly anyone is talking about what it is like having f/8 capability, now that it is available. Hope this thread has more entries of people who have tried out the f/8 AF.


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## RAKAMRAK (May 17, 2013)

Rienzphotoz said:


> I haven't used f/8 yet on my 5D MK III coz in order to to use f/8 to AF I first need to buy a tele-convertor :-\ ... its funny that for almost a year, there been so many people who were cribbing about not having f/8 AF function on 5D MK III, but hardly anyone is talking about what it is like having f/8 capability, now that it is available. Hope this thread has more entries of people who have tried out the f/8 AF.



Interesting observations  Either everyone is busy taking photos with f/8 lenses and have no time to write anything on the forum. Or it was just gear craving. Let's wait and see...


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## Kernuak (May 17, 2013)

RAKAMRAK said:


> Rienzphotoz said:
> 
> 
> > I haven't used f/8 yet on my 5D MK III coz in order to to use f/8 to AF I first need to buy a tele-convertor :-\ ... its funny that for almost a year, there been so many people who were cribbing about not having f/8 AF function on 5D MK III, but hardly anyone is talking about what it is like having f/8 capability, now that it is available. Hope this thread has more entries of people who have tried out the f/8 AF.
> ...


When I went to a 5D MkIII CPS event at Focus on Imaging last year a couple of days after its release, someone asked the rep the question about lack of f/8 focus. The rep responded with a question "how often do you use it and is the IQ good enough (on the previous 1D series). The person asking the question admitted that it was rarely and the IQ wasn't really as good, so that seems to bear out RAKAMRAK's observation.


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## nubu (May 17, 2013)

I'm quite happy with the now possible EF500/4 IS L + EX2XIII combo on my 5DIII. Did a lot of of wildlife pics at dusk and down and had no problems with focus both in central single point as well as extended mode. I prefer the first to pinpoint the focus. It is slower than without but perfectly ok with stationary objects that one is for with 1000mm anyway. I also found the focus help from the 600 flash now much better in low light situation! Thank you Canon!


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## eddiemrg (May 17, 2013)

Excuse me, can anyone explain me what is F8 autofocus and why is so important?
Thanks!


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## nubu (May 17, 2013)

Very simple: Lenses with a maximum aperture of LESS then 5.6 did NOT autofocus before the firmware update for the 5DIII. This also holds for lens+teleconverter combinations leading to maximum apertures of less than 5.6. e.g. my 500/4 lens turns into a 1000/8 lens when combined with a 2x converter. Before we had to focus manually them or do some "taping contact" things leading to suboptimal results....


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## eddiemrg (May 17, 2013)

okay... is the same for the 7D?


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## skinkfoot (May 17, 2013)

I shot a lot with the 5d mk iii and taped pins on a 1.4 ii/400 f5.6 combo, and I was pretty impressed with this combo, with the new firmware I removed the tape and expected not much difference. What I found was the focus speed felt a little bit slower, but, locking on quicker and more accurately. No more jerky hunting. 

As far as the image quality goes, you still pay a price, but, when I am further than 6m(20ft) and I am in good light the extender combo is better than cropping, anything closer the bare lens and cropping are better.

Its always hard to decide if I should mount the extender or not, It is capable of BIF but. not as fast. If I knew that I was going to take pictures of stationary birds it would be okay. If I could afford it, I would preorder the 200-400 but that is not an option(My Wife clarified that for me).


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## neuroanatomist (May 17, 2013)

WillThompson said:


> neuroanatomist said:
> 
> 
> > I've used my 1D X with a 600/4 II and 2xIII to track birds in flight, sometimes handheld. It does fine. However, when shooting small birds in thickets (branches in front of and behind subject), where the bare 600 II locks onto the bird easily, with the 2x it hunts a bit - in that situation, it behaves a lot like the bare 100-400L.
> ...



I've tried both, spot AF does not offer a significant improvement. It certainly does help for birds in thickets without the TC in place, though.



eddiemrg said:


> okay... is the same for the 7D?



The 7D cannot autofocus with an f/8 combo.


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## tron (May 17, 2013)

skinkfoot said:


> If I could afford it, I would preorder the 200-400 but that is not an option(My Wife clarified that for me).


Does she have the same hard feelings for EF500 f/4L IS II ? ;D


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## miah (May 17, 2013)

Someone please explain this f/8 brouhaha to me: my 5D3 + Kenko 1.4x tele-extender + 400 & 70-300 auto-focus (at f/8, pre-firmware update) all day long. I just downloaded the firmware update and will install it later today, but I've been auto-focusing just fine at f/8 for some time. Am I missing something?


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## tron (May 17, 2013)

miah said:


> Someone please explain this f/8 brouhaha to me: my 5D3 + Kenko 1.4x tele-extender + 400 & 70-300 auto-focus (at f/8, pre-firmware update) all day long. I just downloaded the firmware update and will install it later today, but I've been auto-focusing just fine at f/8 for some time. Am I missing something?



You are missing ... Canon teleconverters which report the correct maximum aperture to camera.

When you put kenco with your say 400 f/5.6 lens does it report it as having a maximum f/8 aperture? I guess not! It still reports it as f/5.6!

You have effectively a 1.4X400 = 560mm f/8 lens but the camera thinks it is connected to a f/5.6 maximum aperture lens and tries to autofocus!


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## East Wind Photography (May 17, 2013)

Tried it with my 600 F4 and didnt like the IQ. So I put the 2XIII in with my 70-200L IS II where it will stay. F8 AF was what I expected. Slower than without and IQ did not meet my QA!


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## Tom W (May 17, 2013)

I haven't given it a good full test yet, but I am enjoying backyard bird photography with the 5D3, 100-400 and the 1.4X II. Focus is reasonably quick, and it is pretty accurate. The image quality is decent, not on par with the big primes, but definitely not bad either. Occasionally, I find some weird pattern to the bokeh, but I think that's more a fault of the 100-400 than anything.

The true test will come with using some of the bigger glass and teleconverter combinations to see how it works for very long distance shooting. I've found, though, that stacking teleconverters does take its toll on IQ so that the results will be slightly less than optimal.

I'm really considering a 500/4 II in the future - somewhat light, and compatible with the 1.4X or the 2X teleconverters to give a variety of very long lens capability without the heft of the 400/2.8.


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## JPAZ (May 17, 2013)

I don't like being an "early adopter" (although this firmware update is not exactly a totally new thing), but reading these comments has convinced me to go ahead and install it.


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## miah (May 17, 2013)

tron said:


> miah said:
> 
> 
> > Someone please explain this f/8 brouhaha to me: my 5D3 + Kenko 1.4x tele-extender + 400 & 70-300 auto-focus (at f/8, pre-firmware update) all day long. I just downloaded the firmware update and will install it later today, but I've been auto-focusing just fine at f/8 for some time. Am I missing something?
> ...



When my Kenko is attached to my EF 400 f/5.6 lens, the 5D3 tells me that the max aperture available is f/8. It auto-focuses just fine (I used it that way between my last post and this post). The EXIF data in Lightroom lists the lens as the EF 400 f/5.6, but the images display the correct EXIF data: f/8. So, *tron*, maybe I'm still not seeing something, but this all jives.


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## tron (May 17, 2013)

miah said:


> tron said:
> 
> 
> > miah said:
> ...


That's interesting for Kenko! However, everyone who had Canon teleconverters could not have this option!

So as I said before it wasn't possible with Canon teleconverters...


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## tron (May 18, 2013)

JPAZ said:


> I don't like being an "early adopter" (although this firmware update is not exactly a totally new thing), but reading these comments has convinced me to go ahead and install it.


Firmware seems fine  Just read the instructions. The part at the end that says to remove the battery for a few seconds seems new to me. I remember members of this forum mentioning the same thing for the 7D upgrade but I do not remember this instruction for the 5DMkII firmware updates. 

(Or there was and I simply omitted it and I didn't know it!! )


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## Sella174 (May 18, 2013)

tron said:


> ... everyone who had Canon tele-converters could not have this option!



Smells like Canon is doing this on purpose ... because what I can't understand is if the 6D can AF down to -3EV, then it should also be able to AF with an f/11 lens (in bright daylight, that is).


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## neuroanatomist (May 18, 2013)

Sella174 said:


> ...because what I can't understand is if the 6D can AF down to -3EV, then it should also be able to AF with an f/11 lens (in bright daylight, that is).



Because it doesn't work that way. The f/5.6 limit isn't all about the amount of light, it's about the incoming rays being phase-separated with enough resolution to determine focus. An f/2.8 point has a physically wider baseline (separation between the two sensor lines) on the AF sensor than an f/5.6 point.


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## dougkerr (May 18, 2013)

Sella174 said:


> tron said:
> 
> 
> > ... everyone who had Canon tele-converters could not have this option!
> ...



The AF aperture limit issue that we normally discuss does not evolve light levels. It is based on optical-geometric considerations.

An AF detector is like a rangefinder, with two sensors looking at the scene through two "virtual sub apertures" located on opposite edges of the real exit pupil.

To attain a certain accuracy, these sub-apertures must be located a certain distance apart. This distance is like the "baseline length" of a classical rangefinder (I do not mean "rangefinder camera").

The distance between the two sub apertures is built into the optical system of each AF detector pair. If they are farther apart than the diameter of the exit pupil for the maximum aperture of the lens in place, then no light passes to the detector pairs and AF fails. (So typically the Canon cameras block any attempt when the aperture is not "suitable").

But of course the whole situation is more complex than that, and their are various steps that can be taken to "cheat around" the optical-geometric limitations.

Some of the principles are described here:

http://dougkerr.net/pumpkin/articles/Split_Prism.pdf

Best regards,

Doug


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## Click (May 18, 2013)

Thanks Doug. Interesting read.


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## Sella174 (May 18, 2013)

OK, and now for my next dumb assumption ... at f/11 the focus needs to be less accurate than at f/2.8 due to the greater depth of field (front & back) of the former over the latter.


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## neuroanatomist (May 18, 2013)

Further to what Doug stated, it's always been possible to 'trick' Canon's f/5.6 AF points into focusing with an f/8 max aperture, with pin taping or a TC that doesn't properly report. Canon did not allow the functionality because it wasn't completely reliable. Their recent firmware, possible coupled with higher density line sensors on the 1D X/5DIII (which is how the past 1-series bodies achieved f/8 AF), allowed them to enable it with confidence. 

I also suspect they built the capability into the 1D X/5DIII sensor, but left it disabled in firmware until later. 



Sella174 said:


> OK, and now for my next dumb assumption ... at f/11 the focus needs to be less accurate than at f/2.8 due to the greater depth of field (front & back) of the former over the latter.



Correct. The smaller the baseline of the sensor, the less accurate. But, the narrower the selected/available the aperture, the deeper the DoF and the more inaccuracy tolerable in terms of focus.


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## Tom W (May 18, 2013)

neuroanatomist said:


> Further to what Doug stated, it's always been possible to 'trick' Canon's f/5.6 AF points into focusing with an f/8 max aperture, with pin taping or a TC that doesn't properly report. Canon did not allow the functionality because it wasn't completely reliable. Their recent firmware, possible coupled with higher density line sensors on the 1D X/5DIII (which is how the past 1-series bodies achieved f/8 AF), allowed them to enable it with confidence.


For the record, utilizing stacked teleconverters or third-party telecons (like the Kenko), I have been able to reliably autofocus with great results on the 5D3 (center region AF points), fair results (center point only) on the 5D2 and 5D, and "hit-and-miss" with the 7D.

Basically, the results I got with the 5D3 were so good that I was surprised that Canon hadn't included f/8 AF on that body right from the start. Perhaps they needed to iron out some issues first, I don't know.


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## tron (May 19, 2013)

Tom W said:


> I was surprised that Canon hadn't included f/8 AF on that body right from the start. Perhaps they needed to iron out some issues first, I don't know.


+1 Same with the 1DX. As it was replacing 1D4 (at least!) it was very strange that they omitted this feature initially.


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## tron (May 20, 2013)

Finally I found time to test my 5D3 with a 300mm f/4 (non-iS) lens with EF2X II teleconverter.
The test was inside my house and not much light.

It worked fine


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## tron (May 20, 2013)

tron said:


> Finally I found time to test my 5D3 with a 300mm f/4 (non-iS) lens with EF2X II teleconverter.
> The test was inside my house and not much light.
> 
> It worked fine


More information about "not much light"

Shutter: 1/50 Aperture: f/8 ISO: 25600

According to an EV calculator I found it worked fine to 3.6EV.

Next step would probably be to use half the lights I used...


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## AlanF (May 20, 2013)

miah said:


> Someone please explain this f/8 brouhaha to me: my 5D3 + Kenko 1.4x tele-extender + 400 & 70-300 auto-focus (at f/8, pre-firmware update) all day long. I just downloaded the firmware update and will install it later today, but I've been auto-focusing just fine at f/8 for some time. Am I missing something?



The Kenko locks up the 5DIII when used with the latest generation telephotos, and you have to remove the battery to restart.


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## miah (May 20, 2013)

AlanF said:


> miah said:
> 
> 
> > Someone please explain this f/8 brouhaha to me: my 5D3 + Kenko 1.4x tele-extender + 400 & 70-300 auto-focus (at f/8, pre-firmware update) all day long. I just downloaded the firmware update and will install it later today, but I've been auto-focusing just fine at f/8 for some time. Am I missing something?
> ...



I found this to be true ONLY when AFMA is enabled. Otherwise, Kenko TC's autofocus fine at f/8 and did so prior to the 5D3 firmware update.


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## neuroanatomist (May 20, 2013)

miah said:


> AlanF said:
> 
> 
> > miah said:
> ...



My car runs fine, except when I try to back up while turning - then the steering wheel locks up. But otherwise, it works fine. Maybe that fits some people's definition of 'works fine' - not mine. 

But hey, if locking up with AFMA means the Kenko TC 'works' then you could also say the Canon 1.4x 'works' with the 70-300L. If you zoom the lens out to the 250-300mm range, the 1.4x TC can be mounted. It will AF on the 5DIII, you can AFMA the combo, and your camera won't lock up. Retracting the zoom will bump the rear lens element into the rubber ring on the TC, long as you keep the zoom extended, it 'works' just fine.


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## miah (May 20, 2013)

neuroanatomist said:


> My car runs fine, except when I try to back up while turning - then the steering wheel locks up. But otherwise, it works fine. Maybe that fits some people's definition of 'works fine' - not mine.
> 
> But hey, if locking up with AFMA means the Kenko TC 'works' then you could also say the Canon 1.4x 'works' with the 70-300L. If you zoom the lens out to the 250-300mm range, the 1.4x TC can be mounted. It will AF on the 5DIII, you can AFMA the combo, and your camera won't lock up. Retracting the zoom will bump the rear lens element into the rubber ring on the TC, long as you keep the zoom extended, it 'works' just fine.



Touche, Neuro, I clearly should have said it works fine--provided AFMA is not required. As stated in my other thread, I'm not happy about not being able to AFMA the lens + Kenko TC combo (although I'm still playing with possible work-arounds). That said, I'm getting well auto-focused shots from my various lenses + Kenko TC combos, including at f/8, and they are quite sharp.


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## Tom W (May 20, 2013)

miah said:


> AlanF said:
> 
> 
> > The Kenko locks up the 5DIII when used with the latest generation telephotos, and you have to remove the battery to restart.
> ...



Agreed - I had that issue prior to the new firmware also. Could not micro-adjust the Kenko-lens combination because the camera would lock up. The solution was to delete the MA setting for that lens and not use AFMA with my Kenko (which I only used for F/8 AF situations anyway).


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## tron (May 20, 2013)

That's the problem with 3rd party manufacturers. I have a nice Tokina ATX-28-70 f/2.8 which stopped working since my analog days Canon 50E. It continues to work fine on the old 6xx series and my EOS1n though!

Regarding teleconverters however I guess Canon could have done better.

Even if not regarding the f/5.6 constraint at least regarding the design that limits the Canon TCs use on specific few lenses.


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## Tom W (May 20, 2013)

When I bought the Kenko (which still works fine), the primary purpose was to allow AF with an f/8 combination on the 5D2. I soon bought the 5D3 and found the performance to be very good with it at f/8. 

I've also got my Canon 1.4X II and 2X teleconverters still - no need to get rid of them.

As for micro-adjustment - I just haven't taken the time to perform that function at all with the 5D3, though I probably should at least with my longest lens combinations. There are a lot of competing variables that conspire to degrade image quality when shooting with long lenses (camera shake, etc.) so having the absolute best AF precision would seem to be more critical.


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## Marsu42 (May 20, 2013)

tron said:


> That's the problem with 3rd party manufacturers.



I'd say this is the problem with *2nd* party manufacturers (I guess the 1st party is us, the customers) - it would be no surprise if Canon, Nikon or whatever changes specs and didn't open their protocols just to +1 their own equipment. Luckily, the 3rd party just got smarter and Sigma now has an usb dock for lens fw updates...


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## tron (May 20, 2013)

Marsu42 said:


> tron said:
> 
> 
> > That's the problem with 3rd party manufacturers.
> ...


That's a very welcome addition! Let the (lens manufacturers) competition begin


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## adhocphotographer (May 24, 2013)

I havn't had a chance to try this yet, but i am looking forward to!


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