How do I take this shot?

[macandal]

I took this photograph with my dSLR, Canon xTI. It was a 6-minute exposure.



I want to do the same thing, but this time I want to use my 4x5 camera. I'm using Ektar 100 film. I understand that I can't simply use the same time I used for the digital exposure if I'm using film, right? So, what or how should I calculate what my time should be? Oh, and how do I focus to infinity with my 4x5 (that's what I did with my digital exposure)? Thanks.

[Light Guru]

What you are wanting to learn is Reciprocity Failure. Each different type of film has different reciprocity characteristics. If you have an iPhone there is a app called reciprocity timer that will calculate it for you.

[vinny]

What he said.
Focus your camera during daylight hours or on the moon.

[macandal]

If you have an iPhone there is a app called reciprocity timer that will calculate it for you.

No. No iPhone.

[macandal]

What he said.
Focus your camera during daylight hours or on the moon.

No, what I want to do is set it to infinity. How do you do that?

[ROL]

No, what I want to do is set it to infinity. How do you do that?

What vinny said. Focus on infinity, on the ground glass. Are you sure you even have a 4x5 VIEW camera?

I suspect not, as this is elementary VC technique. If otherwise, read up on basic VC use, either here or in books.

[John Koehrer]

With a 150mm lens at infinity, the ground glass will be 150mm from the front of the lens board.
option 2: Focus on infinity in the daylight, measure GG to LB and set up the camera to the same measurement for your shot

[ImSoNegative]

i think ektar 100 has very good receiprocity characteristics, i think focusing in the daylight would make things much easier, that way you could make sure everything is focused front to rear. would be k ind of hard to do at night.

[welly]

No, what I want to do is set it to infinity. How do you do that?

During the day, find something way, way in the distance and focus on that. Mark your camera with a spot indicating that position or don't touch your camera until later on.

[Leigh]

With a 150mm lens at infinity, the ground glass will be 150mm from the front of the lens board.

Not necessarily true.

The lensboard will be in front of the film by a distance equal to the Flange Focal Length of the lens in use.
For the eleven 150mm lenses in my database the Flange Focal Length varies from 132mm to 171mm.

None has an FFL that actually equals 150mm; the closest is 149mm, and only for one lens.

- Leigh