October 23, 2014, 05:08:53 AM

Author Topic: F/8 Autofocusing impressions  (Read 11051 times)

neuroanatomist

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Re: F/8 Autofocusing impressions
« Reply #30 on: May 18, 2013, 01:35:42 PM »
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.

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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Re: F/8 Autofocusing impressions
« Reply #30 on: May 18, 2013, 01:35:42 PM »

Tom W

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Re: F/8 Autofocusing impressions
« Reply #31 on: May 18, 2013, 04:14:41 PM »
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.

tron

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Re: F/8 Autofocusing impressions
« Reply #32 on: May 19, 2013, 12:00:14 PM »
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.
« Last Edit: May 19, 2013, 12:25:00 PM by tron »

tron

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Re: F/8 Autofocusing impressions
« Reply #33 on: May 20, 2013, 05:21:30 AM »
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  :)


tron

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Re: F/8 Autofocusing impressions
« Reply #34 on: May 20, 2013, 06:21:12 AM »
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...

AlanF

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Re: F/8 Autofocusing impressions
« Reply #35 on: May 20, 2013, 06:23:31 AM »
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

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Re: F/8 Autofocusing impressions
« Reply #36 on: May 20, 2013, 08:24:53 AM »
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.

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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Re: F/8 Autofocusing impressions
« Reply #36 on: May 20, 2013, 08:24:53 AM »

neuroanatomist

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Re: F/8 Autofocusing impressions
« Reply #37 on: May 20, 2013, 08:58:29 AM »
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.

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.

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

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Re: F/8 Autofocusing impressions
« Reply #38 on: May 20, 2013, 10:45:58 AM »
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

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Re: F/8 Autofocusing impressions
« Reply #39 on: May 20, 2013, 12:09:51 PM »

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

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.

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).

tron

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Re: F/8 Autofocusing impressions
« Reply #40 on: May 20, 2013, 01:05:11 PM »
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.

Tom W

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Re: F/8 Autofocusing impressions
« Reply #41 on: May 20, 2013, 01:20:59 PM »
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.

Marsu42

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Re: F/8 Autofocusing impressions
« Reply #42 on: May 20, 2013, 01:40:42 PM »
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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Re: F/8 Autofocusing impressions
« Reply #42 on: May 20, 2013, 01:40:42 PM »

tron

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Re: F/8 Autofocusing impressions
« Reply #43 on: May 20, 2013, 02:12:13 PM »
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...
That's a very welcome addition! Let the (lens manufacturers) competition begin  :)

adhocphotographer

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Re: F/8 Autofocusing impressions
« Reply #44 on: May 24, 2013, 07:00:00 AM »
I havn't had a chance to try this yet, but i am looking forward to! :)
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Re: F/8 Autofocusing impressions
« Reply #44 on: May 24, 2013, 07:00:00 AM »