Optics combination (1 Viewer)

[Farnboro John]

I've run into a problem with the latest iteration of my night photography rig.

The camera is a Canon 7d with a 500mm f4 on the front. The whole is set up for my eyesight, so when I look through I see the picture in focus. So far so normal.

Behind the camera I have a 1X nightscope looking straight through the camera viewfinder. The nightscope has a diopter adjustment and a focus wheel.

This evening by way of starting off on the right foot I focused the camera on a wall using autofocus, then adjusted the nightscope so the autofocused image was in focus to my eye.

In my mind, that should mean that if I refocus the camera lens manually then if the image looks in focus it should be in focus, but the system has other ideas. It generally focuses beyond the subject.

Any able physicists out there who can tell me whether I'm way off beam with the whole plan or just executing it poorly?

All advice welcome.

Cheers

John

 

[Farnboro John]

Cracked it now, nothing wrong with the concept, just the execution.

John

 

[AndyMc]

I'm intrigued.
What are you photographing at night that you can't see with the naked eye? Or am I way off the mark :h?:

 

[Farnboro John]

I'm intrigued.
What are you photographing at night that you can't see with the naked eye? Or am I way off the mark :h?:

Badgers, Mink, Owls, Foxes.... the place really changes when the sun goes down.

The point really is to be as passive as possible, most mammals will put up with a red light but that won't let you autofocus beyond about 50 feet and doesn't give me at least enough light to focus manually further than that. With the nightscope, which "sees" red light like daylight, manual TTL focusing is no problem - once you find the right adjustment of the various optical elements so that what is presented to your eye by the night scope is how the camera lens is focusing.

See Mink below, taken at night manually focusing as it swam past about fifty feet away, red light illumination,cloudy night, no urban lighting.

John