EOS R6 focus guide inaccuracy

Started 11 months ago | Questions
HHaapala New Member • Posts: 19
EOS R6 focus guide inaccuracy

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

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Canon EOS R6
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ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting!  That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

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VLreviews
VLreviews Regular Member • Posts: 248
Re: EOS R6 focus guide inaccuracy

Interesting. Does focus accuracy depend on the aperture used? Is it maybe more misfocused when wide open?

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OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

As far as I can see its present at f/4 as much as at f/1.7

OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting! That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

Nope, there is no microadjustment. Microadjustment specific to this "lens" would fix the issue, sure, but that indeed is not an option on R-series cameras because as you said, it shouldnt be physically possible. Maybe i could see if external software can do microadjustment on a per-lens basis?

ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy

HHaapala wrote:

ProfHankD wrote:

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting! That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

Nope, there is no microadjustment. Microadjustment specific to this "lens" would fix the issue, sure, but that indeed is not an option on R-series cameras because as you said, it shouldnt be physically possible. Maybe i could see if external software can do microadjustment on a per-lens basis?

Ok. Let's assume nothing is defective....

The dual pixel phase detection is actually a lot trickier than one might think in that the SNR between halves of a pixel is terrible and the angular separation is pretty sloppy too -- at least compared with masked pixels or a separate PDAF sensor. Canon's algorithms for processing the dual pixel data are not public, nor do any of the patents I've seen make it clear how they're doing it. It is quite possible that their processing is dependent on lens parameters obtained from that focus confirm chip.

What lens does the focus confirm chip identify as?

I would guess the issue is bad parameterization of the dual-pixel processing algorithm. For example, if the lens suffers from fairly serious SA (which many normals do) or field curvature, the correct focus point could be dramatically missed if their processing essentially targets a relatively wide aperture because the marginal rays don't come into focus at the same point as the rays closer to on-axis. Basically, the question is really how different is the lens you're using from the one the chip IDs?

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OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

HHaapala wrote:

ProfHankD wrote:

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting! That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

Nope, there is no microadjustment. Microadjustment specific to this "lens" would fix the issue, sure, but that indeed is not an option on R-series cameras because as you said, it shouldnt be physically possible. Maybe i could see if external software can do microadjustment on a per-lens basis?

Ok. Let's assume nothing is defective....

The dual pixel phase detection is actually a lot trickier than one might think in that the SNR between halves of a pixel is terrible and the angular separation is pretty sloppy too -- at least compared with masked pixels or a separate PDAF sensor. Canon's algorithms for processing the dual pixel data are not public, nor do any of the patents I've seen make it clear how they're doing it. It is quite possible that their processing is dependent on lens parameters obtained from that focus confirm chip.

What lens does the focus confirm chip identify as?

I would guess the issue is bad parameterization of the dual-pixel processing algorithm. For example, if the lens suffers from fairly serious SA (which many normals do) or field curvature, the correct focus point could be dramatically missed if their processing essentially targets a relatively wide aperture because the marginal rays don't come into focus at the same point as the rays closer to on-axis. Basically, the question is really how different is the lens you're using from the one the chip IDs?

You sound like you know a lot. But here's the kicker: camera says the attached lens is 50mm. Thats it. The lens i'm using is exactly 50mm 1.7.

OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

HHaapala wrote:

ProfHankD wrote:

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting! That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

Nope, there is no microadjustment. Microadjustment specific to this "lens" would fix the issue, sure, but that indeed is not an option on R-series cameras because as you said, it shouldnt be physically possible. Maybe i could see if external software can do microadjustment on a per-lens basis?

Ok. Let's assume nothing is defective....

The dual pixel phase detection is actually a lot trickier than one might think in that the SNR between halves of a pixel is terrible and the angular separation is pretty sloppy too -- at least compared with masked pixels or a separate PDAF sensor. Canon's algorithms for processing the dual pixel data are not public, nor do any of the patents I've seen make it clear how they're doing it. It is quite possible that their processing is dependent on lens parameters obtained from that focus confirm chip.

What lens does the focus confirm chip identify as?

I would guess the issue is bad parameterization of the dual-pixel processing algorithm. For example, if the lens suffers from fairly serious SA (which many normals do) or field curvature, the correct focus point could be dramatically missed if their processing essentially targets a relatively wide aperture because the marginal rays don't come into focus at the same point as the rays closer to on-axis. Basically, the question is really how different is the lens you're using from the one the chip IDs?

Also, theres another detail about my PK adapter. It seems as if its not quite the right focal distance. At lens infinity the focus seems to go past the infinity for the camera.

Additionally, I will test the same adapter on a different lens when i get home from deployment later this week.

rkc Forum Member • Posts: 68
Re: EOS R6 focus guide inaccuracy

FWIW I noticed exactly the same phenomenon with a chipped PK adaptor on my R5 (on a Canon EOS->RF adaptor).

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Richard

OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

rkc wrote:

FWIW I noticed exactly the same phenomenon with a chipped PK adaptor on my R5 (on a Canon EOS->RF adaptor).

Does your adaptor have proper focusing? As in actually being at infinity when lens caps at infinity etc

ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy

HHaapala wrote:

ProfHankD wrote:

HHaapala wrote:

ProfHankD wrote:

HHaapala wrote:

Hi,

I recently bought a PK-EOS adapter, and Im now using a Pentax-M 50 1.7 on my EOS R6 with that and the EF-RF adapter. The PK-EF adapter has a focus confirmation chip, meaning it gives the R6 the ability to activate the manual focus guide feature. This uses the on-sensor AF system to help with manual focusing.

But its inaccurate. The focus guide seems to work normally, but when it says focus is nailed its actually backfocused. I have no idea how this is possible, since the focus guide is on-sensor so there is no way a misalignment or such could cause this. It simply just shows up green meaning 100% perfect focus when you're actually focused behind what you're supposed to. It even clashes with the cameras own peaking. Peaking works normally, and when peaking is on top of focus guide, guide says its not hitting focus.

Very interesting! That really shouldn't be possible with main-sensor PDAF.

My guess is that the focus chip is somehow identifying as an EF lens that needs a correction for focus data it returns to the camera. Is there even a micro focus adjustment on the camera?

Nope, there is no microadjustment. Microadjustment specific to this "lens" would fix the issue, sure, but that indeed is not an option on R-series cameras because as you said, it shouldnt be physically possible. Maybe i could see if external software can do microadjustment on a per-lens basis?

Ok. Let's assume nothing is defective....

The dual pixel phase detection is actually a lot trickier than one might think in that the SNR between halves of a pixel is terrible and the angular separation is pretty sloppy too -- at least compared with masked pixels or a separate PDAF sensor. Canon's algorithms for processing the dual pixel data are not public, nor do any of the patents I've seen make it clear how they're doing it. It is quite possible that their processing is dependent on lens parameters obtained from that focus confirm chip.

What lens does the focus confirm chip identify as?

I would guess the issue is bad parameterization of the dual-pixel processing algorithm. For example, if the lens suffers from fairly serious SA (which many normals do) or field curvature, the correct focus point could be dramatically missed if their processing essentially targets a relatively wide aperture because the marginal rays don't come into focus at the same point as the rays closer to on-axis. Basically, the question is really how different is the lens you're using from the one the chip IDs?

You sound like you know a lot. But here's the kicker: camera says the attached lens is 50mm. Thats it. The lens i'm using is exactly 50mm 1.7.

Which 50mm does it think it is?

Again, this shouldn't be happening, but weird data from the adapter might trigger very strange behavior.

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rkc Forum Member • Posts: 68
Re: EOS R6 focus guide inaccuracy
1

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

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Richard

ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy
1

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

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moedius
moedius Contributing Member • Posts: 609
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

I was curious if all chipped adapters were still made by ripping the contacts off a scrap lens and gluing to adapter; the only chipped adapter I've had was like this.

After a little googling it seems like at least some seem to have non-scrap based chipping? I presume they'd still need to pick a lens ID for the camera to detect.

Might have missed it but I didn't see where OP mentions what brand adapter they have, but if its fotodiox this might be helpful?

https://www.fotodiox.info/blog/dt_articles/instruction-manual-generation-10-focus-confirmation-chip-instructions/

* i cant find a specific focal length in the adapter specs, which makes me think maybe the manual is for adjusting FL rather than microadjustments.

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ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy

moedius wrote:

I was curious if all chipped adapters were still made by ripping the contacts off a scrap lens and gluing to adapter; the only chipped adapter I've had was like this.

No; almost none are made that way.

You build a little jig to break-out the wires and snoop on the lens protocol. Then a chip is programmed to do the minimum handshakes you found necessary. It's particularly easy with the SPI lens interfaces used by most cameras (Sony E is a bit of a pain because they use a faster interface).

After a little googling it seems like at least some seem to have non-scrap based chipping? I presume they'd still need to pick a lens ID for the camera to detect.

Yes. Generally, they use something similar to a lens they snooped the protocol for.

Might have missed it but I didn't see where OP mentions what brand adapter they have, but if its fotodiox this might be helpful?

https://www.fotodiox.info/blog/dt_articles/instruction-manual-generation-10-focus-confirmation-chip-instructions/

* i cant find a specific focal length in the adapter specs, which makes me think maybe the manual is for adjusting FL rather than microadjustments.

Well, that's interesting. Perhaps the adapter is telling to body to microadjust? The body really shouldn't listen to that when using the main sensor for PD, but who knows? (Actually, the folks at Magic Lantern might know....   )

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moedius
moedius Contributing Member • Posts: 609
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

moedius wrote:

I was curious if all chipped adapters were still made by ripping the contacts off a scrap lens and gluing to adapter; the only chipped adapter I've had was like this.

No; almost none are made that way.

Unsurprising that mine was, IIRC it was an M42 to minolta AF, bought off ebay.  Was clearly homemade from an old minolta AF 50/1.7

You build a little jig to break-out the wires and snoop on the lens protocol. Then a chip is programmed to do the minimum handshakes you found necessary. It's particularly easy with the SPI lens interfaces used by most cameras (Sony E is a bit of a pain because they use a faster interface).

After a little googling it seems like at least some seem to have non-scrap based chipping? I presume they'd still need to pick a lens ID for the camera to detect.

Yes. Generally, they use something similar to a lens they snooped the protocol for.

Might have missed it but I didn't see where OP mentions what brand adapter they have, but if its fotodiox this might be helpful?

https://www.fotodiox.info/blog/dt_articles/instruction-manual-generation-10-focus-confirmation-chip-instructions/

* i cant find a specific focal length in the adapter specs, which makes me think maybe the manual is for adjusting FL rather than microadjustments.

Well, that's interesting. Perhaps the adapter is telling to body to microadjust? The body really shouldn't listen to that when using the main sensor for PD, but who knows? (Actually, the folks at Magic Lantern might know.... )

Yeah, I couldnt really wrap my head around how that would translate when everything is done in camera, but im used to not having a clue when it comes to this stuff..

Thanks for the info.

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OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

moedius wrote:

ProfHankD wrote:

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

I was curious if all chipped adapters were still made by ripping the contacts off a scrap lens and gluing to adapter; the only chipped adapter I've had was like this.

After a little googling it seems like at least some seem to have non-scrap based chipping? I presume they'd still need to pick a lens ID for the camera to detect.

Might have missed it but I didn't see where OP mentions what brand adapter they have, but if its fotodiox this might be helpful?

https://www.fotodiox.info/blog/dt_articles/instruction-manual-generation-10-focus-confirmation-chip-instructions/

* i cant find a specific focal length in the adapter specs, which makes me think maybe the manual is for adjusting FL rather than microadjustments.

Unbranded adapter i bought off of ebay.

OP HHaapala New Member • Posts: 19
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

I wonder if its possible to alter the metadata of the adapter to be better suited for the lens used?

ProfHankD
ProfHankD Veteran Member • Posts: 8,825
Re: EOS R6 focus guide inaccuracy

HHaapala wrote:

ProfHankD wrote:

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

I wonder if its possible to alter the metadata of the adapter to be better suited for the lens used?

Unless that's an advertised feature, it's not practical. You'd need to write code to run in the adapter and give the new handshakes.

 ProfHankD's gear list:ProfHankD's gear list
Canon PowerShot SX530 Olympus TG-860 Sony a7R II Canon EOS 5D Mark IV Sony a6500 +32 more
rkc Forum Member • Posts: 68
Re: EOS R6 focus guide inaccuracy

ProfHankD wrote:

rkc wrote:

Yes, it seems to be focusing to infinity correctly.

I just double checked and it looks like I had misremembered slightly - the chipped adaptor I have that is behaving oddly is a C/Y adaptor not a PK one. I just tried it with a few different lenses and it reports "correct" focus in all cases when focused behind where it should be. It's not just a bit out either - it's enough to be very obvious that it has got it wrong.

My adaptor reports that the lens is f/1.4 - which none of the lenses I have tried actually are. I don't know whether that is is any part of the problem. It does seem as though the error is greater the more the lens is stopped down.

I checked in exiftool and it does seem to be reporting some rather weird values for the lens type:

Lens Type : Canon EF 35-80mm f/4-5.6

Max Focal Length : 65535 mm

Min Focal Length : 1 mm

Focal Units : 1/mm

Max Aperture : 1.4

Min Aperture : 1.4

Focal Length : 50.0 mm

One of the lenses I tried WAS 50mm, but other than that all the info is wrong.

Most main-sensor-based PD algorithms I know would use the aperture as a parameter, and it's quite possible they are tuning for f/1.4 marginal rays that don't exist when using an f/1.7 lens. If so, it would probably get worse when stopped down, and that's what you're seeing, so that's my guess. That actually bodes poorly for chipped use of adapted lenses in general, because chips generally report a fixed (maximum) aperture, so stopping the lens down would just make the PD data garbage.

The Canon EF 35-80mm f/4-5.6 is NOT a good lens. In fact, it's one of the poorer kit zooms with fully plastic build, a slow limited zoom range, and various optical issues. It is possible they'd be trying to correct for it, but if so, raw captures shouldn't be affected when processed by straight dcraw (or any other raw tool that doesn't apply corrections).

There is a slim possibility that the disagreement about the 1-65535mm with the 35-80mm causes the lens to be flagged as "fake" and is deliberately messed-up as an effort by Canon to discourage fakes -- sort-of like some Sonys refuse to work with batteries that don't ID themself as Sony made. However, I'm not aware of Canon doing that.

As luck would have it, I just got another chipped adaptor - M42 this time, which means I was able to test it with a F/1.4 lens.

I still see the exact same behaviour as with the prior adapter / slower lenses. Even with the lens wide open, the confirmation is considerably out from where it should be.

This chip is reporting the same weird settings via exiftool as the C/Y one. Both are unbranded and of unknown origin via eBay, free with lenses that I bought.

The other downside of using (these) chipped adaptors on the R5 is that it restricts the burst rate when using them, compared to when using an unchipped adaptor - presumably because the identified 35-80mm does not have a fast aperture.

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Richard

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