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KaiAdin:AF Assist Lamp

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Auto Focus Assist Lamp Pattern for the Canon Speedlite 580ex II in the EOS 40d

This page and the accompanying hand-drawn diagrams, were quickly drawn up to note down the observations made with the Canon Speedlite 580ex II on the Canon EOS 40d when using the Red AF Assist Lamps.




Auto AF Point Selection


- In Auto AF point selection the vertical line (centre) and inner horizontal (left) AF Assist Lamps light up, covering all 9 AF points in the EOS 40d. All of points are cross type.

Centre, Top or Bottom AF Point Manually Selected


- When selecting either the top, bottom or centre AF points, only the Vertical Line (centre) AF assist lamp lights up.

Other AF Points Selected


- If any of the other AF points apart from the top, bottom, and centre AF points are selected, the Inner Horizontal and Outer Horizontal AF Assist Lamps light up. With the Inner (left) lamp projecting the inner 3 rows (rows 2,3 & 4) and the Outer (right lamp) projecting rows 1, 5 and 6.


I did these tests with 40d Firmware 1.0.8, currently (Jan 2009) there has been a firmware update (1.1.1) which apparently changes the minimum brightness that is needed before the AF assist pattern on the speedlite activates. I never really tested how dim it needed to be before the pattern was used, and I don't think it affects the behavior above.

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This page was last modified on 6 September 2011, at 05:14.
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