5D mark III manual lenses focusing

[J Michael]

I've seen reference to an AF confirmation chip that can be added to lenses like the Rokinons. See this video for installation example.

[Steve Kahn]

Interesting...

The thing about this chip is that it doesn't seem to do anything but fool Canon electronics.

I wonder if Magic Lantern could develop a hack for this that would fool the electronics without adding the chip?

[joema]

The problem is it doesn't appear to work for completely dumb nonelectronic lenses. When I use a piece of cinema glass there is no beep when I turn through the focus range at all.

Part of the AF design is a "talk back" electronic path for the lens to inform the camera it reached the requested position. The AF logic in the camera body might use this to signal the viewfinder focus confirmation light. In theory it should be possible to determine focus status using only phase detect data, with no lens talk back. That would enable focus confirmation on a manual, non-electronic lens. However the way it's currently designed that apparently doesn't work.

Since the advent of the EOS EF mount in 1987, there is only electronic signaling between camera body and lens, and only in-lens AF motors (for Canon). A non-EF lens cannot be autofocused -- there's no in-camera focus motor or mechanical screw-drive system to the lens. Thus it was likely not a design priority to provide viewfinder focus status for non-EF lenses.

The situation with DSLR video and high-end, manually-focused cinema lenses is a relatively new development which EOS system designers could not have anticipated in 1987. Also most of those users will have an external monitor, EVF, etc. It would be a small % which use manually-focused cinema glass with no focus aids and want viewfinder focus confirmation. However you are an example of one and this usage segment is increasing, so it's conceivable Canon could add that feature in the future. But I wouldn't hold my breath waiting.

[Steve Kahn]

You can buy an AF confirmation chip on eBay. These fool the camera into thinking that it is using an EF lens.

It appears that camera to lens communication is a one way street. That is it goes from camera to lens but not from lens to camera. I learned that researching the Okii follow focus watching this YouTube video.

Also, it appears that Magic Lantern can not trick the camera into thinking that the lens is there from this Magic Lantern thread.

Oh well. The chip is cheap but my worry is gluing it into place correctly. It just seems like a very rough hack. Wish it could be done via software. Wish Canon would have accounted for manual and non-Canon lenses... And, agreed. I won't hold my breath. It's quite interesting that the first people I think of when an issue such as this arises is ML and not Canon. Quite interesting.

[bumkicho]

I use Nikon to EF adapter with AF confirmation chip often. When shooting stills through viewfinder, you can half click to confirm your focus. When focused, you'll hear a beep sound from 5D3. Having said that, I think the best way is still to use a LCD viewfinder.

[maarek]

^ My method is only good if all your lenses are fully manual (no AF), as is my case
Plus, you can disable image preview if that's bothering you.

Disabling the image preview does not speed up liveview shooting at all. It's still slow as hell. Manually shooting with viewfinder = FAST (except nothing is in focus), manually shooting with liveview = SLOW because after every shot there is a 1-2 sec delay before liveview switches back on.

[J Michael]

I use Nikon to EF adapter with AF confirmation chip often. When shooting stills through viewfinder, you can half click to confirm your focus. When focused, you'll hear a beep sound from 5D3. Having said that, I think the best way is still to use a LCD viewfinder.

Interesting. I need to try that with my 800 Nikkor.

[Steve Kahn]

Disabling the image preview does not speed up liveview shooting at all. It's still slow as hell. Manually shooting with viewfinder = FAST (except nothing is in focus), manually shooting with liveview = SLOW because after every shot there is a 1-2 sec delay before liveview switches back on.

+1

I don't know how you guys even shoot stills with LiveView because it feels really odd to me. I like the ergonomics of placing my eye against the VF and shooting pictures. I don't have a loupe but really don't want to glue something on the back of my camera.

For video it would really be a nice addition to have that beep even when using an external focus peaking monitor as a bit of double check or in situations where you just don't have the monitor.

[joema]

...It appears that camera to lens communication is a one way street. That is it goes from camera to lens but not from lens to camera. I learned that researching the Okii follow focus watching this YouTube video...

Steve, I watched that video -- it was very good. He did say there's no feedback from the lens to camera -- however he was talking exclusively about the USB interface. IOW the AF command protocol exposed at the USB interface allows sending AF commands but not status readback from the lens of the transmitted command.

I was talking instead about the internal body/lens communications protocol. Canon EF lenses definitely send back a lot of data to the body. That is discussed on page 168 of this Canon whitepaper, titled "The EF Lens Concept" (33 MB .PDF): http://www.mpi-inf.mpg.de/~lintu/doc..._Work_Book.pdf

The EF lens sends over 50 different types of data back to the camera, including things like lens status, minimum aperture, focal length, and many different AF-specific items such as focus position, focus compensation amount, etc. The degree to which these are unavoidably vital for AF operation, I don't know. It would seem a DSLR could go solely by phase detect focus data. In older Nikon AF lenses which were driven by a mechanical shaft from the camera, I doubt there was any electronic readback from the lens. The camera commanded a position seek operation, read the AF sensor, and iteratively fine-tuned that.

However the fact is Canon EF lenses send a lot of data back to the camera. Without that data (as in a manual cinema lens) they have chosen to not activate the viewfinder focus confirmation. There is a detailed post by lens repair technician "yepun" about Canon's body/lens communications protocol here: http://www.dpreview.com/forums/thread/2536155?page=3

Even if the viewfinder focus confirmation worked for manual cinema lenses, you would have no lens-specific focus calibration or compensation, certainly no focus micro-adjustment. See 5D3 manual topic "AF Microadjustment". Yet the camera would be telling you "in focus", when those items were not accounted for. Note the internal light path for phase detect is different than the imaging light path. Without lens-specific compensation, the phase detect system could read good focus, then the mirror flips up and the image on the sensor could be slightly out of focus. It makes you wonder how phase detect AF ever worked on non-electronic lenses

One solution is simply staying in Live View mode and using a monitor, loupe or EVF. Your lens is manual, so there's no issue with slower contrast detect AF. All you want is the best visual indication of focus.

Canon has responsive, high-res image zoom in Live View with no aliasing. The downside is it only works when not rolling video. I think Magic Lantern enables zoomed view while rolling video. My preferred method is using a Zacuto EVF, which has several types of focus peaking. I manually focus almost all video this way and it works very well. I occasionally use it for stills, but the LCD blackout problem is really bad. It's worse for HDMI monitors and EVFs due to HDMI handshake time. Whenever the LCD blacks out the HDMI signal is cancelled and the external monitor must re-sync. For Zacuto this adds 1-2 sec to the already frustrating backpanel LCD blackout time.

Ergonomically using a loupe or EVF is great. It adds a 3rd contact point which stabilizes the camera, and the focus aids let you really nail the focus. However the LCD blackout is bad, so it's not optimal for stills. You described it correctly.

To my knowledge you haven't missed anything. There is no secret trick or solution to your situation, except maybe for replacing the optical viewfinder focus screen. I've seen favorable posts about 3rd party microprism focus screens like this supplier: http://www.focusingscreen.com/ However I have no first hand experience with it.

[Steve Kahn]

Thanks for all the great information Joema!

It seems there are issues too with changing the focusing screens. They are not intended to be switched out as is with the 5D mark ii and because so they can be difficult to change out and if not using a genuine Canon focusing screen there can be issues with focus and/or metering.

The reason I thought I must be missing something is that there is a long tradition with photographers using retero glass. My uncle passed away recently and before he did gave me all his old glass which included manual focus Nikon, Leica and Zeiss. I understand the need for AF lenses. Sometimes you have to get the picture in burst mode before it goes away. But, there are times when photography is a very slow art form. Where you don't mind taking time with focus and exposure to get the shot you want. It is a shame that Canon didn't take this into account for those photographers who shoot this way.

One can buy these AF confirmation chips on eBay but I don't love the idea of gluing them on to lenses. I've also heard that they don't always work for reasons you so adroitly stated. But they were also the sorce of my hope that ML could fool the camera because these chips do nothing but sit in the lens mount and connect with the camera AF electronics. That is they dont' control the lens. Unfortunately ML say they cannot fool the electronics.

[Samuel H]

... But, there are times when photography is a very slow art form. Where you don't mind taking time with focus and exposure to get the shot you want ...

That's the kind of photography that I like, and I think my method (loupe permanently on LCD, forget there's even an OVF in the camera) is perfect for that. It has downsides for different styles of shooting, as others have pointed out (I don't do fast shooting so I didn't even know about those problems).

I will also say that for this style of shooting I particularly like the sense that *I* am focusing, with my eye and my hand, with all the technology hidden away, relatively out of sight. It's similar to how using primes gives me a feeling of working to get the framing I want, whereas zooms let me be lazy and go with whatever is easiest and fastest.
The zoom-in for focus doesn't kill this feeling of empowerment; the red dot and beep, I haven't used them but I'm not so sure.