Focus function for EOS M3 / M10

c_joerg

1240

Re: Focus function for EOS M3 / M10

« Reply #20 on: 18 / April / 2019, 13:50:20 »

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Quote from: Ant on 15 / April / 2019, 13:27:09

The variable at 0x00244916(0x00244918) is updated regularly only with my Canon lenses.
You can check its behaviour with your lenses.

I can confirm this for my lenses:
EF 100mm f/2.8 Macro USM
EF-S 55-250mm IS STM
EF-M 11-22mm IS STM

Quote from: Ant on 15 / April / 2019, 13:27:09

With my Sigma lens this variable is updated only when I take photo or switch play/rec mode.

I have only Canon lenses and a manual Walimex lens.
The values from the variables (Subject Distance Near / Far) are the same as Focus Distance Upper / Lower from EXIF.

But are these values being the same as Near / Far limit from DOF? The values don’t change when I change aperture…

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pigeonhill

1126

Re: Focus function for EOS M3 / M10

« Reply #21 on: 18 / April / 2019, 14:43:00 »

Just watching with interest.

IMHO subject distance upper and lower ad NOT the DoF limits, ie near and far.

As you say, it’s ‘just’ the Canon upper and lower reporting around focus.

But I’m only watching ;-)

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c_joerg

1240

Re: Focus function for EOS M3 / M10

« Reply #22 on: 18 / April / 2019, 15:52:45 »

Quote from: pigeonhill on 18 / April / 2019, 14:43:00

Just watching with interest.

And I’m the post with failing if the smallest step is used

On the M3 I have also a parameter with which I can control the speed of focus.

Quote from: pigeonhill on 18 / April / 2019, 14:43:00

IMHO subject distance upper and lower ad NOT the DoF limits, ie near and far.
As you say, it’s ‘just’ the Canon upper and lower reporting around focus.

Yes of course…
Here is an example with my EF 100mm f/2.8 Macro USM; f2.8

Value on focus Scale: 31cm
Focus Distance Lower / Upper: 31/32cm
DOF Near / Far limit: 31/31cm

Value on focus Scale: 100cm
Focus Distance Lower / Upper: 95/114cm
DOF Near / Far limit: 99.5/100.5cm

Value on focus Scale: 300cm
Focus Distance Lower / Upper: 286/378cm
DOF Near / Far limit: 295.4/ 304.7cm

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pigeonhill

1126

Re: Focus function for EOS M3 / M10

« Reply #23 on: 18 / April / 2019, 16:46:45 »

I think you are getting in a knot because you are using a macro lens where the DoF happens to be close to the upper and lower limits.

On a non macro lens you wouldn’t have that confusion, unless you were indeed at or towards the macro end.

If only Canon ‘just’ reported focus ;-)

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c_joerg

1240

Re: Focus function for EOS M3 / M10

« Reply #24 on: 18 / April / 2019, 18:04:55 »

Quote from: pigeonhill on 18 / April / 2019, 16:46:45

On a non macro lens you wouldn’t have that confusion, unless you were indeed at or towards the macro end.

OK...

EF 24mm f/2.8 IS USM

Value on focus Scale: 100cm
Focus Distance Lower / Upper: 89/111cm
DOF Near / Far limit: 91.7/110cm

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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
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pigeonhill

1126

Re: Focus function for EOS M3 / M10

« Reply #25 on: 19 / April / 2019, 00:49:25 »

And at, say, f/10 or higher ?

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c_joerg

1240

Re: Focus function for EOS M3 / M10

« Reply #26 on: 19 / April / 2019, 02:58:12 »

Quote from: pigeonhill on 19 / April / 2019, 00:49:25

And at, say, f/10 or higher ?

That makes no difference. The values only seemed to represent the open aperture.
Here are some infos:
https://photo.stackexchange.com/questions/105977/what-is-focus-distance-lower-upper-and-how-is-it-different-from-depth-of-field
https://www.dpreview.com/forums/post/51962463

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M100 100a, M3 121a, G9x II (1.00c), 2*G1x (101a,100e), S110 (103a), SX50 (100c), SX230 (101a), S45,
Flickr https://www.flickr.com/photos/136329431@N06/albums
YouTube https://www.youtube.com/channel/UCrTH0tHy9OYTVDzWIvXEMlw/videos?shelf_id=0&view=0&sort=dd

pigeonhill

1126

Re: Focus function for EOS M3 / M10

« Reply #27 on: 19 / April / 2019, 03:03:36 »

I meant the DoF change

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c_joerg

1240

Re: Focus function for EOS M3 / M10

« Reply #28 on: 24 / April / 2019, 07:50:44 »

I experimented a bit with the following lenses:

EF 50mm f1.8 STM
EF 100mm f/2.8 Macro USM,
EF-M 11-22mm IS STM,
EF-S 55-250mm IS STM,

The lenses have different focus steps increments. I expected that too:

EF 50mm => approximately 4100
EF 100mm => approximately 2560
EF-M 11-22 => 250 (11mm) – 530 (22mm)
EF-S 55-250mm => 2050 (55mm) – 4800 (250mm)

The number of lower / upper focus distance also varies

EF 50mm => 15 steps
EF 100mm => 26 steps
EF-M 11-22 => 29 steps
EF-S 55-250mm => 31 steps

I find it interesting that with all 4 lenses have the same maximum lower focus distance

Focus Distance Lower max : 8191cm
Focus Distance Upper max : 65535 cm => inf

I guess these are all values from a table which are read out depending on the step size of the motors.

Interesting thing about the EF 100mm f / 2.8 Macro USM was that the lower focus distance jumped back at the