AF Point Selection Oddity on 5D MkIII with 100mm Macro

[Kernuak]

I've found an oddity with the AF on the 5D MkIII. For a couple of weeks, I've been scratching my head over how I would select the outer points when using single point focus. After playing around this afternoon, I have found that if I select only the 41 most sensitive points, I can only select the central 21 points when using single point, single spot, or expanded, but if I switch to zone, I can select the outer zones. Switching to all 61 points or 9/14 points allows me to choose any point. Trying it out with other lenses (all in group A as opposed to group C for the 100mm macro), I can select any point I wish in any selection mode, including 61 points. I then tried another group C combination, the 300mm L IS iwth 1.4x extender. Again, I didn't have any problems with selecting any point I wished, so it isn't as simple as applying only to certain lens groups. From all of my lenses that are f/2.8 or wider maximimum aperture (I didn't try either the 24-105 or 17-40), it is only with the 100mm macro in 41 point mode where I can't select the outer 20 points and doesn't affect zone AF. I may have mised it, but I couldn't find any reference to the phenomenom in either the 5D MkIII manual or the 1D X AF guide. It isn't really a major issue, as most of the time, I would be using manual focus for macro work and I would be inclined to use the 135mm for the little portrait work I do.

 

[Loswr]

You don't explicitly state (as far as I can tell) which 100mm Marco lens you have. While the 100mm f/2.8L macro is a Group C lens, the 100mm f/2.8 non-L USM macro is a Group E lens. The behavior you describe sounds like a Group E lens. Do you have the non-L macro?

 

[Kernuak]

I do have the non-L lens and maybe I looked at the wrong list. It would explain why it was different to all the other lenses, but it's probably worth otheres being aware that it behaves differently for single/expanded point and zone.

 

[Richard Lane]

Yes, the 100mm f/2.8L IS Macro is group C and the 100mm f/2.8 non-L Macro is Group E. So, the combo is functioning properly.

 

[Kernuak]

Yes, the 100mm f/2.8L IS Macro is group C and the 100mm f/2.8 non-L Macro is Group E. So, the combo is functioning properly.

I just had another look. The EF 100mm f/2.8 Macro and EF 100 f/2.8L Macro IS USM are both in groups C, but the EF 100mm f/2.8 Macro USM is in group E, so that's where the confusion is. However, it still doesn't state that it behaves differently between the 41 point selection and all the other modes. In 61 point, 14 point and 9 point, it is possible to select a single AF point (or any of the options surrounding the point) for any of the points, it is only when in 41 point mode that only the 21 point centre points are selectable. To me that is illogical, it should be the same for all of them for any given lens. The outer points don't suddenly become less sensitive just because you choose the most sensitive 41 points, particularly as they are selectable for teh various zones.

 

[Loswr]

the 41 point selection mode

There is no such mode. The setting you are thinking of is called "only cross type AF points" and with a group E lens, only the 21 center points act as cross type AF points, so that's all you can select. See p.98 of the manual. Granted, the graphic icon for the mode shows 41 points, because that's how many crosses there are - but not all of them are available with all lenses.

All 61 points are available with a Group E lens, but 40 of them are lines, not crosses. So in all other modes (auto, 15, 9, expansion, zone) they are all available. It's only when you restrict selection to cross-type that you're limited to 21.

I suppose you're thinking it's '41 point mode' because with your other lenses, you get 41 points because those lenses are Group C or higher. Mount a typical f/5.6 lens and it will behave like your 100mm non-L USM macro.

Mystery solved?

 

[Richard Lane]

...it still doesn't state that it behaves differently between the 41 point selection and all the other modes. In 61 point, 14 point and 9 point, it is possible to select a single AF point (or any of the options surrounding the point) for any of the points, it is only when in 41 point mode that only the 21 point centre points are selectable. To me that is illogical, it should be the same for all of them for any given lens. The outer points don't suddenly become less sensitive just because you choose the most sensitive 41 points, particularly as they are selectable for teh various zones.

The Guide does actually state what you're asking. Pg.36-39 below:

http://cpn.canon-europe.com/files/education/technical/eos_1d_x_explained/AF_guide_EOS-1DX_eng.pdf

Take a look at the AF Guide, and right next to or below the Group A through Group E Charts it does state that, AF focusing is possible with all 61 points and All AF area selection modes are available. Group F & G states that, All 61 points is not possible, however All AF Area modes are available.

15 point and 9 Point don't use the far outer points anyway, so that's why they are not selectable in single manual AF point selection. However, the outer points are available in 61 All AF Points and All AF Area Modes as stated above in Group A-E.

I hope that helps clarify it.

Rich

 

[Kernuak]

the 41 point selection

There is no such mode. The setting you are thinking of is called "only cross type AF points" and with a group E lens, only the 21 center points act as cross type AF points, so that's all you can select.

That's the mode I meant and granted it is only 21 points on group E lenses, but I was trying to be clearer, unsuccessfully. I know camera manufacturers have a lot to learn when writing manuals that make sense when reading them, but it would only take a sentence to actually state that single point (and others) are not available, instead of stating "All of the area selection modes are selectable". In fact, it would be clearer if they used "Only the..." instead of "All of the...". In fact, when the manual describes each of the modes, the section is titled "AF Area Selection Modes", then describes spot, single point and expanded point in that section, so the whole section is rather confusing. The confusion lies around the fact that it behaves differently for zone and single point (with or without expansion). While I can see to some degree why zone AF is going to increase the chances of a successful AF, it is still slightly illogical that the outer 20 cross points (on other lenses) are selectable when switching to zone AF for group E lenses. I think knowledge of that in itself is useful to know. It's also interesting that it is the only f/2.8 lens listed in group E, all the others are in groups A, B or C. I'm intrigued now, why that lens is different, as it can't be down to age, considering the non-USM is in group C.

 

[Kernuak]

The Guide does actually state what you're asking. Pg.36-39 below:

Take a look at the AF Guide, and right next to or below the Group A through Group E Charts it does state that, AF focusing is possible with all 61 points and All AF area selection modes are available. Group F & G states that, All 61 points is not possible, however All AF Area modes are available.

Rich

Thanks, I did miss the diagram when I looked through the guide, however, the way it is worded is clumsy (the same as in the manual). If the manual didn't refer to the single points in the AF area selection section, then it would make more sense to read.

however All AF Area modes are available.

Suggests that the zone should only select from those 21 points, but it also allows selection of zones in the outer 20 high sensitivity points, even though it states that group E lenses don't have access to them.
Sometimes knowing too much can result in reading manuals in less detail and it probably highlights that as much as anything else. I do have a tendency to experiment rather than follow instructions .

 

[Richard Lane]

I agree, Manuals Suck!

Lets go out and shoot, I've actually spent more time with the manual than shooting this bad-boy!

 

[Loswr]

...it is still slightly illogical that the outer 20 cross points (on other lenses) are selectable when switching to zone AF for group E lenses.

No, the outer cross-type points are not selectable with a group E lens in any mode. The points are selectable, just not as cross-type points.

I don't think the manual is confusing, but I acknowledge that the AF system is complex, so the manual is somewhat complex. All of the AF area selection modes are available - the modes are described on p.75 - single (regular and spot), expansion (4 and 8 points), zone, and auto. 'Only cross type' isn't a mode, it's a customization option described in the customization section. If you read the notes on that section (p.99), you'll see that it states that even with settings other than 61 points (i.e., only cross-type, 15, 9), expansion and zone selection are possible. So, everything you're describing seems consistent with the manual.

 

[Kernuak]

...it is still slightly illogical that the outer 20 cross points (on other lenses) are selectable when switching to zone AF for group E lenses.

No, the outer cross-type points are not selectable with a group E lens in any mode. The points are selectable, just not as cross-type points.

I'm not saying they are cross type with a group E lens, that is why I had "on other lenses" in brackets, I'm saying they are selectable with zone AF, but they are not selectable with single point (or any of the point expansion modes). To me, logic dictates they should be selectable in all modes or none. If that was the case, the manual wouldn't be confusing at all (at least not in that section anyway).

I agree, Manuals Suck!

Lets go out and shoot, I've actually spent more time with the manual than shooting this bad-boy!

I'm in agreement there. I'm actually going on a themed portrait shoot tomorrow at a heritage railway, out of my comfort zone, which was why I was playing around in the first place . Had it not been for the preparation, I proably would never have found out.

 

[LetTheRightLensIn]

...it is still slightly illogical that the outer 20 cross points (on other lenses) are selectable when switching to zone AF for group E lenses.

No, the outer cross-type points are not selectable with a group E lens in any mode. The points are selectable, just not as cross-type points.

I'm not saying they are cross type with a group E lens, that is why I had "on other lenses" in brackets, I'm saying they are selectable with zone AF, but they are not selectable with single point (or any of the point expansion modes). To me, logic dictates they should be selectable in all modes or none. If that was the case, the manual wouldn't be confusing at all (at least not in that section anyway).

I agree, Manuals Suck!

Lets go out and shoot, I've actually spent more time with the manual than shooting this bad-boy!

I'm in agreement there. I'm actually going on a themed portrait shoot tomorrow at a heritage railway, out of my comfort zone, which was why I was playing around in the first place . Had it not been for the preparation, I proably would never have found out.

See pages 98-99, you probably have it locked to not let you chose non-cross type points for single point mode, so it locks with the E lens out of the outer points but that setting has no bearing on auto and zone modes and stuff. Everything is working as it should. If it let you select every point for every lens even when set to only let you chose cross-type then the latter function would be nonsensical.

 

[Kernuak]

Thanks, yes I do, it was one of the first things I did. I think the key sentence is the second one under "Selectable AF Point". "In the case of automatic AF point selection, all 61 AF points will remain active, regardless of the setting. I was considering only only all points as automatic AF, but I suppose in zone AF, it is still choosing a point automatically, it is just that it has been limited to the nine adjacent ones, whereas in AF point expansion, you have chosen the centre point, but allowed the other eight to kick in if the centre point can't obtain a lock. I think the two mistakes I made were, being a bit slow initially (even though I noticed before when I looked at the list) working out that the non-L USM macro was in group E and then not thinking about automatic AF points in zone AF. I got there in the end with some help, hopefully this thread will help someone else too.
I'm intrigued though why the 100mm macro USM is the only f/2,8 lens in group E, when even the older non-USM macro is in group C. I notice it's even worse with the 180mm macro, as it is in group G with or without the 1.4x extender.

 

[nonac]

To all, don't read this post, it is extremely difficult to even understand, let put into practice. Instead, go take pictures!

 

[LetTheRightLensIn]

I'm intrigued though why the 100mm macro USM is the only f/2,8 lens in group E, when even the older non-USM macro is in group C. I notice it's even worse with the 180mm macro, as it is in group G with or without the 1.4x extender.

Yeah it is odd. Glad I upgraded to L.

Maybe it is to sell more L versions. ;D ;D

If not then maybe something about the internal baffles and how it heads into macro mode as a non-extending lens, maybe the larger elements in the L get around this. The older non-USM uses an extended barrel type macro design. It is interesting that even the 100L is one of the few lenses faster than f/4 that does not get the central point to work as a super precision double cross point. Gotta be something to do with the way macro lenses are designed. Once you are at 1:1 I think they act more like f/5.6 in how much light they let in even when set to f/2.8 too, not sure where they decided to class the AF rating for it, at normal distance or macro.

 

[Kernuak]

I'm intrigued though why the 100mm macro USM is the only f/2,8 lens in group E, when even the older non-USM macro is in group C. I notice it's even worse with the 180mm macro, as it is in group G with or without the 1.4x extender.

Yeah it is odd. Glad I upgraded to L.

Maybe it is to sell more L versions. ;D ;D

If not then maybe something about the internal baffles and how it heads into macro mode as a non-extending lens, maybe the larger elements in the L get around this. The older non-USM uses an extended barrel type macro design. It is interesting that even the 100L is one of the few lenses faster than f/4 that does not get the central point to work as a super precision double cross point. Gotta be something to do with the way macro lenses are designed. Once you are at 1:1 I think they act more like f/5.6 in how much light they let in even when set to f/2.8 too, not sure where they decided to class the AF rating for it, at normal distance or macro.

Could be something like that, certainly you're losing around two stops at 1:1. I know some of that is due to light loss within the lens, due to the design and physics, as well as some light loss from being in your own light . Also, there is no way anyone would be daft enough to want to use zone AF for macro work, so they could have left them selectable for non-macro work, considering it also makes a useful portrait lens among other things.