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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

EF 300/f2.8 L IS USM II + 2x II + 2x III extenders (1 Viewer)


Well-known member
Experimenting stacking two 2x extenders (II and III version) and trying to photograph the moon using 7D MkII.

ISO1000, 1/125, f11. Camera doesn't recognize the other extender and autofocus doesn't work.

Regards, Juhani


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Here is another try a couple of nights ago with less stopped down aperture and lower ISO.

ISO100, 1/160, f9.

Quite low temperature (about -15 C degree) so it took some time for the objective to cool down when brought outside, before that, image quality was terrible.

It's very difficult to manually focus at this focal length as one needs to magnify the screen at least 5x and even the slightest turn of the focusing wheel introduces vibrations...

Regards, Juhani


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Set your lens during daylight @ infinity
I'm afraid that daylight won't help as you anyway have to find the sharpest point by manually turning the focusing wheel (remember that my combination has 1920 mm focal length when using 1.6x crop sensor) and you still need to magnify the backscreen view by 5x or 10x to see the precise focus point.

Maybe using fine marker and make marks to the focusing ring and objective body when the sharpest point is found, that at least the next time I don't have to do focusing all over again?

Regards, Juhani

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