Originally Posted by
Nodda Duma
The only concern would be the difference in ambient temperature between when you set focus and when you takes a shot.
The change in temperature will cause a focus shift due to thermal expansion coefficient of the camera material and change in index of the glass. How much shift is acceptable depends on the depth of focus of the lens vs how much the focus shifts due to temperature. The amount of focus shift due to temperature depends on the details of the optical design itself...there's no real correlation with the speed of an optic except for the larger depth of focus for a slower lens. You can try John's suggestion and it'll probably work out fine, but if you runs into focus issues when you think you've set it just right then it might be explained by the temperature drop from day to night.
I used to run into this problem in astrophotography, where as the temperature dropped during the night I'd have to readjust focus from shot-to-shot (for a telescope running at f/6.3).
Regards,
Jason
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