90D usable AF points depending on lens used

[Philippe Lang]

Hi,

I came accross an interesting document (https://gdlp01.c-wss.com/gds/8/0300036248/02/eos90d-si2-en.pdf) that gives details about the different AF points that are available on the camera, and which ones are usable depending on the lens used.

Lenses in group A are the only ones that are able to use the center AF point in "dual cross-type AF mode" apparently. The EF 400mm f2.8 is able to do that, but the EF 500mm f4 is not, according to their list.

I didn't know this, and I'm wondering if there is a way to know in which group are my Sigma lenses: 18-35 f1.8 Art, 70-200 f2.8 Sport, 150-600 Contemporary, 500 f4 Sport.

Doe anyone have an idea?

 

[jvc1]

Hi,

I came accross an interesting document (https://gdlp01.c-wss.com/gds/8/0300036248/02/eos90d-si2-en.pdf) that gives details about the different AF points that are available on the camera, and which ones are usable depending on the lens used.

Lenses in group A are the only ones that are able to use the center AF point in "dual cross-type AF mode" apparently. The EF 400mm f2.8 is able to do that, but the EF 500mm f4 is not, according to their list.

I didn't know this, and I'm wondering if there is a way to know in which group are my Sigma lenses: 18-35 f1.8 Art, 70-200 f2.8 Sport, 150-600 Contemporary, 500 f4 Sport.

Doe anyone have an idea?

As you already have those lenses, put them on and see what AF points you have.

 

[Philippe Lang]

As you already have those lenses, put them on and see what AF points you have.

The 90D does not report if an AF point works in dual-cross-type, cross-type only, or even vertical / horizontal mode only. I'm not even sure the AF point if disabled if not used at all...

 

[cnyphotoguy]

I'm not even sure the AF point if disabled if not used at all...

I don't own a lens in class D to verify...but as I recall the 10-18mm falls into this category and the outside AF points either wont display in the OVF or on screen (or may flash) to indicate they cannot be used.

Agree though when an AF point is active I'm note sure that you can effectively tell what the functional level of the point is. I would reach out to Sigma, unlikely Canon is testing third party lenses.

 

[Sue Anne Rush]

Thank you for this information.

 

[Philippe Lang]

I'm not even sure the AF point if disabled if not used at all...

I don't own a lens in class D to verify...but as I recall the 10-18mm falls into this category and the outside AF points either wont display in the OVF or on screen (or may flash) to indicate they cannot be used.

Agree though when an AF point is active I'm note sure that you can effectively tell what the functional level of the point is. I would reach out to Sigma, unlikely Canon is testing third party lenses.

I'll try to contact Sigma. I have just seen the Canon 70-200 2.8 (all versions) are in class A: hopefully the Sigma equivalent lens is in class A as well...

 

[Philippe Lang]

Thank you for this information.

You are welcome: an interesting piece of information, there not much information on this subject, which is really important...

 

[Philippe Lang]

I've been playing with my 90D and Sigma 18-35 f/1.8 Art, Sigma 70-200 f/2.8 Sport and Canon 100mm Macro USM (referenced in group E by Canon), in order to see if the central AF point is used as a dual cross-type or simple cross-type. Apparently, with a lens up to f/2.8, there's a chance it is used as a dual cross-type.

I have configured my 90D with 9 points AF & AI SERVO. Every AF square gets bigger when the focus is detected. I have drawn a thin vertical line on a sheet of paper, and moved the 9 AF points from left to right and back with 3 different angles: 0, 90 and 45.

Although this method is not precise at all, it's really interesting to see the difference at 45 degrees between the Sigma lenses and the old Canon 100mm Macro lens. With the Canon lens, 95% of the time no AF point fires. With the Sigma lenses, 95% of the time only the central AF point fires. In all other directions, all AF points fire at some point.

I'm tempted to think that dual cross-type is not reserved to Canon lenses, and that all bright lenses up to f/2.8 are candidates, even if built by 3rd party manufacturers like Sigma.

Final note: with the Canon lens / group E, AF focus points blink when selecting the AF points configuration. This is warning that not all AF points can be used.

 

[RedFox88]

This is in the user manual and should only apply to Canon lenses. 3rd party lens makers reverse engineer autofocus to make it work in Canon cameras.